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ANIMAL AND PLANT HEALTH INSPECTION SERVICE • UNITED STATES DEPARTMENT OF AGRICULTURE

AGRICULTURE HANDBOOK NO. 48 5

PREFACE

The primary purpose of this manual is to

serve as a training aid and provide basic information on ticks and tick-borne diseases for

veterinarians and animal health technicians

directly or indirectly involved in tick surveillance, control, and eradication activities. It is

not intended to be a definitive work on ticks of

veterinary importance.

Veterinary Services is especially grateful to

the many persons whose works have been consulted in the preparation of this manual. Without freely drawing on their publications, this

manual could not have been compiled. Some of

the principal contemporary researchers include Harry Hoogstraal, Jane Walker, Gertrud

Theiler, C. N. Smith, E. C. Loomis, Glen Kohls,

Carleton M. Clifford, W. 0. Neitz, M. N. Kaiser,

and P. R. Wilkinson. Earlier tick researchers

include W. A. Hooker, F. C. Bishopp, H. P.

Wood, W. D. Hunter, R. A. Cooley, and G. H. F.

Nuttall.

A section on ticks, intended as the first part of

a contemplated field manual on veterinary

entomology for personnel of the Animal Disease

Eradication Division, was initially compiled by

Gerald Diamant, Robert K. Strickland, and the

late W. G. Bruce. The section on ticks was

issued in June 1961 and slightly revised in

August 1961.

The section on ticks was revised by Gerald

Diamant and Robert K. Strickland and issued

in June 1965 as The Manual on Livestock

Ticks for Animal Disease Eradication Division

personnel, ARS 91-49.

The present revision has been prepared by

Robert K. Strickland, Robert R. Gerrish, James

L. Hourrigan, and Glen O. Schubert.

Document Delivery Services Branch

USDA, National Agricuitural Libran/

Nal BIdg. ^

10301 Baltimore Blvd.

Beltsville, MD 20705-2351

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price $2.40

Stock Number 001-000-03461-8 / Catalog No. A 1.76:485

CONTENTS

Page

List of illustrations vi

I. Introduction 1

II. Ticks and tick-borne diseases 1

Protozoal diseases 2

Bovine Piroplasmosis 2

Equine Piroplasmosis 2

Canine Piroplasmosis 3

The Theilerioses 3

Bovine Anaplasmosis 3

Rickettsial and Rickettsial-like diseases 4

Rocky Mountain spotted fever of man 4

Q Fever 4

Canine Ehrlichiosis 4

Bovine and Ovine Ehrlichiosis 4

Heartwater 5

Bacterial diseases 5

Tularemia 5

Spirochetosis of livestock and poultry 5

The relapsing fevers of man 5

Brucellosis 6

Viral diseases 6

Nairobi sheep disease 6

Louping 111 6

Colorado tick fever 6

III. Tick paralysis and Toxicosis 6

IV. Ticks as pests 7

V. Classification and description of ticks 8

VI. Biology and behavior 10

VII. Control and eradication 14

VIII. Regulations on importing and interstate movements of ticks.. 15

IX. Identification 15

X. The key and hov^ to use it 16

Terms used in the key 16

XL Key to families of ticks 20

Family Ixodidae 20

Morphological characteristics of the Family 20

Key to developmental stages of Family Ixodidae 21

Key to Genera of adults of Family Ixodidae 21

General comments 21

Genus Amblyomma 21

Morphological characteristics of the Genus 21

Key to males of the United States. 22

Key to females of the United States 22

General comments 22

Genus Aponomma 23

111
CONTENTS—Con.

Page

Morphological characteristics of the Genus 23

The species of Aponomma 23

General comments 24

Genus Boophilus 24

Morphological characteristics of the Genus 24

Key to the males of North America 24

Key to the females of North America 24

General comments 24

Genus Dermacentor 24

Morphological characteristics of the Genus 24

Key to the adults of the United States 25

General comments 25

Genus Haemaphysalis 26

Morphological characteristics of the Genus 26

Key to the adults of the United States 26

General comments 26

Genus Hyalomma 27

Morphological characteristics of the Genus 27

The species of Hyalomma 27

General comments 27

Genus Ixodes 27

Morphological characteristics of the Genus 27

The species of Ixodes 27

General comments 27

Genus Margaropus 28

Morphological characteristics of the Genus 28

The species of Margaropus 28

General comments 28

Genus Rhipicentor 28

Morphological characteristics qf the Genus 28

The species of Rhipicentor 28

General comments 28

Genus Rhipicephalus 28

Morphological characteristics of the Genus 28

The species of Rhipicephalus 28

General comments 28

Family Argasidae 29

Morphological characteristics of the Family 29

Key to developmental stages of Family Argasidae 29

Key to Genera of Family Argasidae 29

General comments 29

Genus Argas 29

Morphological characteristics of the Genus 29

The species of Argas 30

General comments 30

Genus Ornithodoros 30

Morphological characteristics of the Genus 30

Key to the adults mqst commonly found on livestock

in the United States 30

General comments 30
CONTENTS—Con.

Page

Genus Otobius 31

Morphological characteristics of the Genus 31

Key to the nymphs 31

Key to the adults ^ 31

General comments 31

XII. Collecting and preserving ticks 31

XIII. Hosts, distribution and diseases transmitted by selected ticks

Hard ticks (Ixodidae) 33

Soft ticks (Argasidae) 35

XIV. Life history summaries of selected ticks of veterinary

importance 36

Amblyomma americanum (Linnaeus), the Lone Star tick.. 36

Amblyomma cajennense (Fabricius), the Cayenne tick 37

Amblyomma hebraeum Koch, the Bont tick 37

Amblyomma maculatum Koch, the Gulf Coast tick 38

Amblyomma variegatum (Fabricius), the Tropical

Bont tick 39

Argas versions (Oken), the Fowl tick 40

Boophilus annulatns (Say), the Cattle Fever tick 41

Boophilus decoloratus (Koch), the Blue tick 42

Boophilits microplus (Canestrini), the Tropical

Cattle tick 43

Dermacentor albipictus (Packard), the Winter Tick 44

Dermacentor andersoni Stiles (Synonym, Dermacentor

venustus Banks), the Rocky Mountain wood tick 44

Dermacentor nitens Neumann (Synonym, Anocentor

nitens (Neumann), the Tropical Horse tick 45

Dermacentor occidentalis Marx, the Pacific Coast tick 46

Dermacentor variabilis (Say), the American dog tick 46

Haemaphysalis leachi leachi^^ (Audouin), the

Yellow dog tick 47

Haemaphysalis leoprispalustris (Packard), the

Rabbit tick 48

Hyalomma marginatum Koch, the Mediterranean

Hyalomma 48

Ixodes ricinus (Linnaeus), the European Castor

Bean tick 49

Ixodes scapularis (Say), the Black-legged tick 50

Ornithodoros coriaceus Koch, the Pajaroello tick 51

Otobius megnini (Dugès), the Spinose ear tick 51

Rhipicephalus appendiculatus Neumann, the

Brown ear tick 52

Rhipicephalus evertsi evertsi Neumann, the

Red-legged tick 53

Rhipicephalus pulchellus Gerstacker, the Zebra tick 54

Rhipicephalus sanguineus (Latreille), the

Brown Dog tick 55

XV. Checklist of the ticks of the United States 56

XVI. References , 59
LIST OF ILLUSTRATIONS

Page

Hypothetical hard ticks 66

Hypothetical soft ticks 67

Dorsal view of the scuta and capitula of some female

hard ticks 68

Schematic life cycles and disease transmission of ticks :

Type I 69

Type II , 70

Type III 71

Type IV 72

Type V 73

Ornithodoros turicata:

male 74

female 75

nymph 76

Otohius megnini:

male 77

female 78

nymph 79

Amblyomma americanum:

male 80

female 81

nymph 82

Amblyomma cajennense:

male 83

female 84

nymph 85

Amblyomma imitator:

male 86

female 87

Amblyomma Tnaculatum:

male 88

female 89

nymph 90

Boophilus annulatus:

male 91

unengorged female 92

partially engorged female 93

engorged nymph 94

Boophilus micropliis:

male 95

female 96

partially engorged female 97

Dermacentor albipictus:

male 98

female 99

nymph 100
LIST OF ILLUSTRATIONS—Continued

Page

Dermacentor andersoni:

male 101

female 102

nymph 103

Dermacentor nigrolineatus:

male 104

female 105

Dermacentor nitens:

male 106

female 107

nymph 108

Dermacentor occidentalis:

male 109

female 110

nymph Ill

Dermacentor variabilis:

male 112

female 113

nymph 114

Haemaphysalis leporispaliistris:

male 115

female 116

nymph 117

Ixodes scapularis:

male 118

partially engorged female 119

Rhipicephaliis sanguineus:

male 120

unengorged female 121

nymph 122

May 1976

VIF

TICKS OF VETERINARY IMPORTANCE

I. INTRODUCTION

The threat of the introduction of ticks and

tick-borne diseases into the United States is

probably as great today as at any time in

our history. The United States is no longer

protected by the dual barrier of time and

space. Modern transportation has increased the

chances of survival of ticks and other external

parasites on animals in transit. Today it is possible to load animals on swift ocean vessels in

Africa, Asia, and Europe, and in a few days

have them unloaded at one of our ports of

entry. With air transportation — and more

animals are being shipped by air each year—departure to arrival is measured in hours rather

than days.

In earlier days, during the long, slow voyages

of sailing ships, the infected animals often died

or recovered during the voyage so that upon

arrival they were not often a threat to the

domestic livestock. The ticks usually completed

engorgement, dropped from the host, and were

washed overboard before arrival at the port of

entry.

Since the end of World War II, the importation of exotic animals by zoological gardens,

animal dealers, and individuals has created a

potentially dangerous situation. Too often these

exotic animals are infested with economically

important species of ticks. For example, some

species found on animals at air, land, and

ocean ports of entry and on animals already

in zoological compounds include Amblyomma

hebraeum, A, pomposum, A. variegatum,

Boophilus annulatus, B. decoloratus, B. microplus, Ixodes ricinus, Rhipicephalus appendiculatiis, R. bursa, R. evertsi, R. simus, Hyalomma

marginatum, and H. truncatum. Many other

species of equal or unknown economic importance have also been detected.

Ticks are of importance to man and his

animals for two reasons : they are all parasitic

and many are important transmitters of diseases

to both man and lower animals. Ticks are the

most important vectors of a variety of disease

agents to domesticated animals and are second

only to mosquitoes as transmitters of diseases

to man. Ticks harbor protozoa, viruses, bacteria,

rickettsia, and toxins, and transmit these

organisms to man and animals.

Ticks are able to survive adverse conditions

and transmit diseases for a number of reasons :

they have a heavy, protective, chitinous covering ; can withstand long periods of starvation ;

have a wide host range ; deposit large numbers

of eggs; are relatively free from natural

enemies; and are tenacious bloodsuckers.

Ticks act not only as vectors but also serve

as reservoirs of certain infectious agents.

Mammals and birds are the principal hosts of

ticks, but reptiles and even amphibians are

parasitized by them.

Despite their lack of wings, ticks have become

widely distributed throughout the world. This

dispersion is attributed to the movement of

their many hosts. About 10 percent of the approximately 800 known species of ticks are

established in the United States. Of the 80 or so

species found in the United States, about 20 are

of some veterinary importance. A check list of

the ticks found in the United States is included

in the manual (see page 56).

II. TICK AND TICK-BORNE DISEASES

Since ticks are the most important vectors of

disease agents affecting livestock, it is desirable

to have some general knowledge of the diseases,

the ticks which transmit them, and the geographical areas of the world where they *are

known to be established. This manual introduces some of the economically important ticks

and tick-borne diseases, not only of the United

States but also of other areas of the world.

Detailed information on the diseases, tick
vectors, and distribution may be found in the

published papers cited in the references.

The tick-borne diseases are usually recognized as being in one of the following groups :

protozoal, rickettsial, bacterial, and viral. Ticks

also produce tick paralysis, tick toxicosis, and

serve as serious bloodsucking external pests.

PROTOZOAL DISEASES

Bovine Piroplasmosis

(Bovine Babesiosis, Cattle Tick Fever,

Texas Fever, Redwater, Splenetic Fever)

In the New World bovine piroplasmosis,

commonly called cattle fever, is produced by

Babesia bigemina and B. argentina, protozoan

parasites of the red blood cells. As the protozoans multiply they destroy the red blood corpuscles and thereby cause hemoglobinuria and

anemia. This is accompanied by a rise in body

temperature, depression, loss of appetite and

body weight. The animal finally goes into a

coma and dies. In severe outbreaks mortality

may approach 90 percent. When ticks feed on an

infected animal, the ingested protozoa pass into

the reproductive organs of the female tick and

thence into the eggs. Larvae, or seed ticks,

emerging from these infected eggs thus become

carriers and capable of transmitting the disease

organisms to susceptible hosts. This is known

as transovarian transmission — transmitting

disease organisms from an infected female

through the egg to the offspring.

Prior to the successful cattle fever tick

eradication program, Boophilus annulatiis and

B. microplus were the most important external

parasites of cattle in the United States. These

were the only ticks involved in the transmission

of bovine piroplasmosis in North America. An

all-out eradication program was initiated by the

U. S. Department of Agriculture in 1906. By

1943 the Boophilits ticks had been eradicated

from the United States except for a narrow

buffer zone along the Texas-Mexico border.

This buffer zone was placed under Federal and

State quarantine since reinfestations occur and

an active surveillance and control program is

required to prevent spread of Boophilus ticks

into free areas.

Eradication is difficult because the cattle

fever tick can withstand long periods of starvation—a single pair can produce several thousand offsprings in less than a year, and it

parasitizes horses, mules, and deer as well as

cattle.

In addition to Babesia bigemina and B.

argentina there are three other species of

Babesia affecting cattle throughout the world.

These other Babesia are transmitted by one or

more species of Ixodes, Rhipicephalns, and

Boophilus.

Equine Piroplasmosis

This disease, also called horse tick fever or

babesiosis, affects horses, mules, donkeys, and

zebras. In horses the disease is characterized by

fever, anemia, icterus, and often circulatory

and respiratory distress. There are two recognized types of equine piroplasmosis.

In the United States the type of equine

piroplasmosis most frequently encountered is

caused by Babesia caballi and is known to be

transmitted by Dermacentor nitens. Other ticks

are involved in the transmission in other areas

of the world. The distribution of J?. caballi

includes all or parts of southern Europe, Asia,

Russia, Africa, West Indies, Central America,

South America, and southern Florida.

The second type of equine piroplasmosis is

produced by Babesia equi (=Nuttallia equi)

and is regarded as being more pathogenic than

the type caused by B. caballi. It has been reported from all or parts of southern Europe,

Russia, Africa, South America and Asia, and

southern Florida.

The tropical horse tick, D. nitens, is the only

proven natural vector of B. caballi in the

United States. It is also a suspected vector of

B, equi in the West Indies and Florida. The only

other tick presently established in the United

States known to be capable of experimentally

transmitting either type of equine piroplasmosis is Rhipicephalns sanguineus. Fortunately,

R. sanguineus does not commonly feed on

equines in the United States. Throughout

the world several species of Dermacentor,

Hyalomma and Rhipicephalns have been incriminated in the transmission of both types of

equine piroplasmosis.
Canine Piroplasmosis

(Canine Babesiosis, Biliary Fever, Malignant

Jaundice)

In the United States the brown dog tick,

Rhipicephalus sanguineits, is the vector of

canine piroplasmosis, caused by the protozoan

Babesia canis. This tick is found throughout

most of the world and is probably the most

widely distributed of all species of ticks. It is

well adapted to the climate of southern United

States. The brown dog tick can pass its entire

life cycle indoors, making it a very annoying

pest in kennels and homes. Although it is basically a tropical or subtropical species and unable

to survive outdoors throughout the winter in

the northern States, the advent of central heating in homes and kennels has enabled this tick

to become a common pest throughout the year

as far north as Connecticut and New York.

Parasitization of the blood cells by J5. canis

causes fever, inappetance, incoordination, and

anemia in affected canines. Dogs that recover

may carry the organism in the blood for a year

or more, eventually lose the infection, and

become susceptible again.

The Theilerioses

There are several diseases caused by protozoal

parasites of the genus Theileria. The organisms

in the genus Theileria differ from Babesia in

the following respects :

(1) They do not destroy the red blood cells,

although they invade them during the

acute phase of the disease.

(2) There is no multiplication of the organism

in the red blood cells.

(3) Multiplication of the organism occurs in

the lymphocytes and the endothelial cells

of the lymph nodes, spleen, and liver.

(4) There is no transovarial transmission of

the organism; transmission is stage to

stage by 2-~host and 3-host ticks.

The most important of the theilerioses is East

Coast fever of cattle which is a serious problem

in eastern and central Africa. This disease was

once prevalent in South Africa, but reportedly

it has now been eradicated. The causative agent

is Theileria parva and the primary vector is

Rhipicephalus appendiculatus. The mortality

rate may be very high, often reaching 90 to

100 percent in susceptible animals.

In the Mediterranean coastal area and the

Middle East a disease of cattle similar to East

Coast fever is caused by T. annulata. Several

species of Hyalomma ticks are involved in the

transmission. The mortality varies from 10 to

90 percent, depending on the geographical area.

Two other species, T, lawrencei and T, mutans,

are transmitted to cattle by several species of

Rhipicephaliis in parts of Africa. At least two

species of Theileria have been reported from

sheep and goats throughout the world. Benign

strains of Theileria spp. have been reported

from cattle and deer in the United States.

Bovine Anaplasmosis

(Gallsickness)

Anaplasmosis was long believed identical with

bovine piroplasmosis. It was distinguished as a

separate entity in 1910, when the disease and

its anaplasma bodies were found in bovines

free of cattle fever. The precise nature of the

pathogenic organism that causes anaplasmosis

is not known. Many scientists believe the

organism is a protozoan, others theorize that it

is a virus, or a rickettsia, or a microorganism

belonging to a group of as yet unrecognized

and unclassified biological position. This microorganism, Anaplasma marginale, multiplies in

the red blood cells, and death of the host may

result from severe anemia.

While not the sole mechanisms of spread,

transmission studies have incriminated numerous species of ticks in the dissemination of

anaplasmosis. Anaplasma marginale, like the

causative agent of cattle fever, may be transmitted from one generation of ticks to the next.

The suspected .tick vectors of primary importance in this type of transmission in North

America are the Rocky Mountain wood tick,

Dermacentor andersoni (=D. venustus), and

B, microphis.

Stage-to-stage transmission in the same generation has been recorded for the winter tick,

D. albipictus; the American dog tick, D, variabilis; the black-legged tick, Ixodes scapularis;

the brown dog tick, Rhipicephalus sanguineus;

and the fowl tick, Argas persicus.
RICKETTSIAL AND RICKETTSIAL-LIKE

DISEASES

Rocky Mountain Spotted Fever of Man

This disease, caused by an infection of

Rickettsia rickettsi, is characterized by chills,

high fever, pains in muscles and joints, and

eruptions of livid spots on the skin. Dermacentor

andersoni, the Rocky Mountain wood tick, is

the principal vector in the mountainous regions

of the Western United States and in the

southern parts of British Columbia, Alberta,

and Saskatchewan in Canada. The mortality

may vary from 20 to 80 percent in untreated

cases.

The Rocky Mountain wood tick is a 3-host

tick and the life cycle is usually completed in

2 years. Small mammals serve as hosts for the

larvae and nymphs. The adult ticks require

large mammals, preferably cattle, horses, deer,

and elk to complete their development. Man is

an accidental host. Animals of intermediate size

such as rabbits and badgers may serve as hosts

for all three stages of the tick. The causative

agent of Rocky Mountain spotted fever may be

transferred by ticks via the egg to successive

generations. The rickettsia is maintained in

nature in a cycle between immature ticks and

a variety of small wild mammals.

The American dog tick, Dermacentor variabilis, is responsible for the spread of Rocky

Mountain spotted fever in Eastern United

States, particularly Maryland, Virginia, and

North Carolina.

Three additional species of ticks that are

known to transmit Rocky Mountain spotted

fever in the United States are Amblyomma

americanum, Haemaphysalis leporispaliistris,

and Dermacentor parumapertus. Since the distribution of A, americanum lies within that of

Dermacentor variabilis, the exact role of A.

americanum as a vector of Rocky Mountain

spotted fever in man is not known. The other

two species, H. leporispalustris and D. parumapertus, are not found on man and are involved

primarily as reservoirs and vectors of the

disease in nature among wildlife, especially

rabbits and hares.

Amblyomma cajennense and Rhipicephalus

sanguineus have been reported as vectors of

Rocky Mountain spotted fever in Mexico, but so

far there is no evidence to incriminate them as

vectors in the United States.

In southern Europe, Africa, and Asia, a

related disease, boutonneuse fever (Marseilles

fever, tick typhus), caused by Rickettsia conori,

is often a problem in humans. Two important

vectors include the cosmopolitan Rhipicephalus

sanguineus and Haemaphysalis leachi of western, central and southern Africa. Other ticks

have been incriminated in the transmission, and

a variety of ticks and small mammals are

involved in maintaining the infection in nature.

Q Fever

(Query Fever)

This ubiquitous disease, caused by Coxiella

burneti, has been associated with many species

of ticks. It is primarily a respiratory infection

in man, and although it may be transmitted by

the "bite" of an infected tick, transmission

usually occurs as the result of the inhalation of

dust or droplets contaminated directly or indirectly by infected cattle, sheep, and goats.

Man may also be infected by the inhalation of

the organism in dried tick feces or by the

ingestion of contaminated milk. Infection is

usually not apparent in livestock. The reservoirs in nature are ticks and a variety of small

wild mammals.

Canine Ehrliehiosis

(Malignant Canine Rickettsiosis)

This is a septicémie disease of canines which

is caused by Ehrlichia canis with Rhipicephalus

sanguineus as the primary vector. The infective

agent is transmitted by all three stages of the

tick as well as through the egg to the next

generation. Mortality rates as high as 90 percent have been reported. Canine ehrliehiosis has

been reported from the United States, France,

Africa, Syria, India, and the West Indies. It

probably occurs in most areas which have

established populations of R. sanguineus.

Bovine and Ovine Ehrliehiosis

(Benign Bovine and Ovine Rickettsiosis)

Cattle and sheep each have a benign form of

ehrliehiosis caused respectively by Ehrlichia

bovis and E, ovina. Bovine ehrliehiosis is common in South Africa where the vectors are

Hy&kmvma spp. The disease has also been reported from the United States. Ovine ehrliehiosis
has been reported from Africa and Australia.

In South Africa, Rhipicephalvs evertsi is the

vector ; where as in north Africa (Tunisia and

Algeria) the vector is -R. bursa.

Heartwater

This rickettsial-like disease, caused by

Cowdria ruminantium, affects sheep, goats, and

cattle, but all ruminants may carry the causative agent, some without showing apparent

clinical signs of disease. Heartwater has been

observed in Africa for at least 100 years and its

transmission by ticks has been known for some

70 years. The principal vectors are Amblyomma

hebraeum in South Africa, A. variegatum in

west, central, and east Africa; and A. lepidum

in the Sudan. Amblyomma gemma and A.

pomposum have also been incriminated. The

disease agent is not transovarially transmitted.

The ticks become infected during the larval and

nymphal stages and transmit the causative

agent during one of the subsequent stages.

Mortality in heartwater varies from 50 to 90

percent. Losses are highest in sheep, goats, and

imported cattle. Persian and Africander sheep

are more resistant, and mortality is approximately 6 percent.

BACTERIAL DISEASES

Tularemia

(Rabbit Fever)

Tularemia, primarily a disease of rabbits and

rodents, is caused by Francisella tularensis,

Man often acquires the disease by direct contact when dressing diseased rabbits but may

also be infected by tick bites or by contact with

iirfected tick feces. In. addition t© ticks, bloodsucking arthropods, such as the deer fly

(Chrysops spp.), may be of importance in the

spread of this disease. There are reports of

serious outbreaks of tularemia in sheep pastured on land with heavy infestations of the

Rocky Mountain wood tick, Dermxicentor andersoni. In the United States, the principal

vectors of the disease among rabbits and

rodents, in nature, are several species of

Dermacentor, and Haemaphysalis leporispalustris. Reportedly, Amblyomma americanum

transmits tularemia to hunting dogs in

Arkansas.

Man and domestic animals are not involved

in the natural disease cycle of tularemia and

become infected only when they accidentally

enter into it. The mortality in man is approximately 6 percent.

Spirochetosis of Livestock and Poultry

In South Africa, spirochetosis has been reported from cattle, sheep, goats, and horses. The

causal agent, Borrelia theileri, is transovarially

transmitted by Boophilus decoloratus and

Rhipicephalus evertsi, and produces a mild

febrile disease.

Avian spirochetosis is a highly fatal disease

of turkeys, pheasants, doves, and pigeons, and

is reported in many countries throughout the

world, including the United States. Transmission of the infective agent, Borrelia anserina

is by several soft ticks of the genus Argas.

The Relapsing Fevers of Man

In the United States, tick-borne relapsing

fever of man is transmitted by at least four

species of soft ticks of the genus Ornithodoros.

The disease is reported in limited areas of 13

Southwestern and Western States. There are

several species of Borrelia involved and apparently each tick carries its own species or

strain of the organism.

Like other species of Borrelia, the spirochetes

are transmitted through the egg to the larval

tick. Reservoirs of the disease include the

rodent hosts and Ornithodoros ticks. Reportedly

the Borrelia may remain infective in starved

ticks for as long as 5 years.

Man comes into contact with the disease when

frequenting caves and other areas where the

ticks and their rodent hosts live. Transmission

is affected by the "bite" of some species of

Ornithodoros or by the contamination of the

wound or skin with tick excretions in other

species. The mortality is generally 5 percent or

less, except in very young, old, or debilitated

persons.

There are also endemic foci of tick-borne

relapsing fevers reported from Mexico, Central

America, South America, Europe, Asia, and

Africa. In Africa, which probably has one of

the highest incidences of tick-borne relapsing

fever, Ornithodoros moubata is the primary
vector. This tick usually feeds at night and

remains hidden during the day in the earth

walls and floors of native houses. It is often

detected by the presence of excreta marks on

the outside of cracks and crevices in the mud

walls.

Brucellosis

Although ticks are not known to be involved

in the epidemiology of brucellosis in the United

States, there are reports incriminating them as

possible vectors and reservoirs of brucellosis in

livestock in other areas of the world. In Russia,

several species of ticks have reportedly been

found naturally infected as well as being

experimentally infected with Brucella abortus

and B. melitensis. In Mexico, Tovar reports

ñnding Boophilus annulatus naturally infected

with Brucella abortus; he was also successful

in experimentally transmitting Brucella by

allowing infected ticks to feed on normal guinea

pigs. However, until the importance of ticks as

vectors of brucellosis is clarified, care should be

taken in assigning them a definite role in the

epidemiology of this disease. Ticks may play

little, if any, role in the maintenance and

transmission of brucellosis in the United States.

VIRAL DISEASES

Nairobi Sheep Disease

Nairobi sheep disease is an infectious, noncontagious viral disease of sheep and goats in

eastern and central Africa. The primary vector

is Rhipicephalus appendiculatv^, but Amblyomma variegatum and several other species of

Rhipicephalus are also involved in the transmission of the disease. Transovarial transmission

is known to occur in R. appendiculatus; reportedly the virus can survive for about 21/2

years in the adult stage of the tick. Mortality is

invariably high in the native Masai sheep

although it rarely exceeds 40 percent in

Merinos or Merino crosses.

Louping III

Louping ill is a tick-borne virus disease of

sheep transmitted by Ixodes ricinus. The

disease is characterized by fever, nervous signs,

ataxia, and paralysis. Cattle are occasionally

infected ; horses, pigs, and man are suspectible

to a lesser extent. The disease is reported from

Great Britain and Ireland. Mortality in sheep

averages about 10 percent on farms where the

disease recurs from year to year, but may be

very high in sheep flocks encountering the

disease for the first time.

Colorado Tick Fever

This is the most common human tick-borne

disease in western United States. It is characterized by a sudden onset, aching in the muscles,

headache, malaise, chills, a diphasic fever, and

a marked leucopenia. There is usually an

absence of the rash commonly associated with

Rocky Mountain spotted fever. Although

temporarily incapacitating, the rate of recovery

is usually very high.

The primary vector of the virus of Colorado

tick fever is Dermacentor andersoni. Other

ticks found naturally infected are D. occidentalis, D. parumapertus, Otobius lagophihis, and

Haemaphysalis leporispalustris. Small mammals

and immature ticks, especially D. andersoni,

maintain a reservoir of infection in nature.

III. TICK PARALYSIS AND TOXICOSIS

Tick Paralysis

Man, domesticated animals, and birds are

subject to tick paralysis in North America,

Europe, Africa, and Australia. While the true

nature of the casual agents is not known, they

paralysis that usually leads to incoordination

and collapse within 4 to 7 days of attachment

and feeding of the tick. In many instances, the

symptoms subside if ticks are removed from

aniiÄ^s before ipÄi*€kj^is hae^ pi^egresfi^d toe

act like neurotoxins producing an ascending far. If the ticks are not removed, the infested
man or animal dies. Studies with these toxins

indicate that they cannot be transferred from

affected animals to healthy ones. Although tick

paralysis is primarily produced by the engorging females, the immatures of Ixodes holocyclus

and Argas persicus can also produce paralysis.

The tick most frequently involved in tick

paralysis in North America is the Rocky

Mountain wood tick, Dermacentor andersoni.

Serious livestock losses have been reported

from western Montana, Idaho, Oregon, and

British Columbia. Most human cases are in

children under 7 years of age, and a mortality

rate of about 12 percent has been reported. In

the Eastern and Southern United States

Dermacentor variabilis, Amblyomma americanum, and A. maculatum also produce tick

paralysis in man and dogs. Infestation with

only one tick may produce paralysis in a sheep,

dog, or human. Infestation with many ticks is

usually required to produce paralysis in cattle—

which seem more resistant. In South Africa,

Ixodes rubicundus produces a type of tick

paralysis very similar to the paralysis produced

by Dermacentor andersoni in North America.

Australian tick paralysis is produced by /.

holocycltts.

Tick Toxicosis

There are several forms of tick-borne toxicosis which are distinct from tick paralysis.

Evidence indicates that these conditions are

caused by toxins produced by some species or

strains of ticks. As with tick paralysis, the

tick-borne toxicoses cannot be transmitted by

contact with affected animals, nor can they be

transmitted by blood inoculations from affected

to susceptible animals.

Sweating sickness is one of these toxicoses,

and it differs from the others in that it is the

only one in which the affected animals exhibit

a profuse, moist eczema and hyperemia of the

visible mucous membranes. Thiö is primarily a

disease of calves less than a year old. Mortality

varies from 30 to 70 percent. The tick involved

in Africa is Hyalomma truncatum. The clinical

disease has also been reported from southern

India and Ceylon.

In South Africa, another distinct tick toxicosis, which is caused by a leukocytropic toxin,

is conveyed by Rhipicephalus appendiculattis.

At least two other mild, non-fatal toxicoses of

cattle, sheep, and pigs have also been observed

in Africa. In Australia, very heavy infestations

of Boophilus microplus on cattle were reportedly

capable of producing clinical signs and

pathological changes suggestive of tick-borne

toxicosis.

IV. TICKS AS PESTS

As well as acting as vectors of diseaseproducing organisms, ticks may cause considerable mechanical injury, producing wounds

susceptible to secondary bacterial invasion or

screwworm infestation. Ticks also devour large

quantities of blood. Severe infestations can

cause anemia, loss of weight, and even death.

Other losses on domestic animals, attributable

to heavy infestations of ticks, include those

caused by "tick worry" and hide damage.

Undoubtedly, the classic example of heavy

tick infestation was reported in 1911 from

South Africa where Sir Arnold Theiler, the

distinguished veterinarian, collected half the

Boophilus decoloratus from a horse which had

died of acute anemia ; the ticks removed from

the horse weighed 14 pounds.
V. CLASSIFICATION AND DESCRIPTION OF TICKS

Ticks belong to the class Arachnida and are

related to scorpions and spiders. Ticks and

mites belong to the order Acariña and are

closely related. The order includes two families

of ticks : the hard ticks, Ixodidae, which have

a scutum ; and the so-called soft ticks, Argasidae, which lack a scutum (see classification

chart page 91). Ticks are not insects.

Ticks are differentiated from adult insects by

certain well-defined characteristics. The adult

insect has three body segments :

• Head with eyes and antennae.

• Thorax with six legs, two pairs of spiracles,

and usually one or two pairs of wings.

• Abdomen with genitalia and usually eight

pairs of spiracles.

Ticks are small, wingless, bloodsucking

parasites that have :

• Fused head and thorax.

• Eyes, when present, small and simple.

• Mouth parts set off from the body as a

false head or capitulum consisting of a

characteristic hypostome armed with longitudinal rows of recurved *'teeth" or denticles, highly specialized chelicerae with

apical cutting digits, and palps; but no

antennae or mandibles.

• Body wall of argasids leathery. In ixodids,

a hard chitinized shield (scutum) covers

the back of the male ; in the female, nymph,

and larva, only a small shield is present

dorsally behind the capitulum, the rest of

the body wall being extensible, allowing

the tick to enlarge greatly during feeding.

• Adults and nymphs with eight legs ; larvae

or seed ticks with six legs.

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VI. BIOLOGY AND BEHAVIOR

There are four stages in the life cycle of the

tick: the egg, the 6-legged larva or seed tick,

the 8-legged nymph, and the adult (male and

female). Transition from one stage to the next

is made by one or more moltings (shedding of

the cuticle). The steps in tick development are

not particularly restricted to seasons. Species

adaptation, temperature, moisture, and availability of host animals influence their duration.

The number of generations may vary from

three or» four a year in the 1-host species such

as the tropical cattle tick, Boophilus microplus,

to one a year in the Argasidae—or even one

every 2 or 3 years in some 3-host species, such

as the Rocky Mountain wood tick, Dermacentor

andersoni.

Hard ticks are often referred to as being 1-,

2-, or 3-host ticks :

The 1-host ticks spend their entire developmental period, from young larvae to

mature adults, on one animal. Example :

The cattle fever tick, Boophilus annulatus.

The 2-host ticks attach as larvae and complete development through the nymphal

stage. The replete nymph then drops

from the host, molts to the adult stage,

and later seeks a second host to complete

development. Example: The red-legged

tick, Rhipicephaliis evertsi.

The 3-host tick feed to repletion as larvae

on one animal, drop to the ground, and

molt to the nymphal stage; as nymphs,

attach to another animal and engorge,

and again leave the animal to molt ; and

finally, as adults, feed on a third animal.

Example: The American dog tick, Dermacentor variabilis.

The above designations do not usually apply

to soft ticks since their feeding habits are quite

different from those of the hard ticks. Soft ticks

could be referred to as multihost ticks. Some

soft ticks, such as Ornithodoros coriaceus, may

have as many as seven nymphal stages with

each stage feeding briefly. The female Argos

persicus may feed as many as seven times and

deposit a small batch of eggs following each

feeding. Generally, the larval stage of soft

ticks may attach and feed on the host »for

several days, but the nymph and adult normally

feed for 30 minutes up to 2 hours, leave the

host, and return to a protected area away from

the host. The spinose ear tick, Otohins megnini,

is an exception and could be called a 1-host

tick.

Mating

Mating may take place on or off the host and

during or after engorgement. With Argasidae,

for example, copulation takes place after the

adults have fed and left the host. With Ixodidae,

Population usually occurs on the host, after

which the females appear to engorge more

rapidly.

After mating and engorgement the female

drops from the host and crawls to a protected

place to oviposit. Under favorable climatic conditions, oviposition may begin within 2 days or,

in cold weather, may be delayed for weeks or

even months.

Oviposition and Incubation

The gravid female hard tick readies herself

for egg-laying by bending the capitulum downwards so that it lies along the ventral surface

of the body near the genital opening. A vesicle,

the Gene's organ, is everted from between the

basis capituli and scutum. The Gene's organ,

which enlarges into two lobes, contains glands

that secrete a waxy material. As the eggs are

extruded from the genital aperture, they are

received by these extended lobes and coated with

the waxy secretion. This protects the eggs from

dehydration and enables them to form an

adherent mass.

While female hard ticks engorge only once

and die shortly after the completion of oviposition, most soft tick females engorge a number

of times and oviposit after each feeding. The

number of eggs laid by ticks vary by species.

For example. Argos persicus lays as many as

seven batches of eggs; the number of eggs is

usually 150 to 250 per batch up to the fourth

batch but declines to less than half that number

with the last two batches produced. On the

other hand, Boophilus microplus lays a single

batch of approximately 4,500 eggs. Although

well above the average for hard ticks, one

female Amblyommo nuttolli reportedly deposited 22,891 eggs in a single "sitting."

10
The incubation period is primarily determined

by temperature. In the hard ticks this may

range from about 2 weeks up to almost 7

months. In tropical or subtropical areas, the

incubation period is usually relatively short and

constant. However, in areas with a temperate

climate, the incubation period may be only 2 or

3 weeks if the eggs are produced in the summer,

or may be prolonged for many weeks or months

if the eggs are layed in the autumn or early

winter. For instance, the Boophilus annidatus

female, which drops from the host in September, may deposit eggs which do not hatch until

the following March.

Larva

Following hatching, the larvae, or seed ticks,

usually remain clustered near the place of

emergence. This is a protective measure to prevent desiccation and to insure survival. Larvae

seldom feed within a week after hatching.

When they are ready to feed they are often

found awaiting a host upon blades of grass,

small trees, or bushes. Upon the approach of a

suitable host, the larvae are alerted by their

sensory organs and become very active and

attempt to crawl upon the animal. Larvae seem

to be stimulated most strongly by carbon

dioxide and odors, but vibrations, air currents,

interrupted light, warmth, and moisture are

factors which alert the tick to the presence of a

host. Having found a host, the larvae may

quickly seek out their favored site for attachment, or may wander over the host for several

days before finding a suitable place to feed.

Some species attach almost exclusively in the

ear of the host; some prefer areas where the

skin is comparatively thin ; while others attach

almost any place on the host.

The larvae feed, and when engorged, most

species of hard ticks drop from the host to

molt. They make their way to some protected

area and become quiescent. Depending upon

temperature and humidity, molting to the

nymphal stage may take from 5 days to several

weeks or longer. The engorged larvae of 1-host

ticks remain on the host and molt after a short

quiescent period.

Nymph

The activities and habits of nymphs are

similar to those of the larvae, except that in

most species nymphs tend to live longer. In

those species that molt upon the host, molting

takes place following engorgement and a short

resting period. In those species that leave the

host, the molt may occur within 2 weeks or

may be delayed for several months. All hard

ticks have only one nymphal stage, but all soft

ticks undergo several nymphal molts, ranging

from two to seven, with an average of three.

Adult

In those species that molt on the host, the

adult female merely crawls from the nymphal

skin and re-attaches at another site. The male

sheds the nymphal skin, re-attaches and feeds

for a short time, then seeks a mate.

The behavior of adults of those species that

leave the host as nymphs to molt are similar to

those of the larvae and nymphs, except that the

unfed adult is usually capable of surviving

much longer without a blood meal than either

the nymph or larva.

Copulation of hard ticks usually occurs on

the host ; it generally precedes female engorgement and apparently inñuences the rapidity of

its completion. Female hard ticks may engorge

and drop within a few days of attachment or

remain on the host for 30 days or longer.

Apparently the females which remain attached

for long periods fail to find mates. Males frequently remain upon the host much longer and

thereby ensure ready mates for virgin females.

In contrast, mating of soft ticks occurs away

from the host—on the ground or in a protected

area.

Feeding Habits

Ticks are obligatory parasites and require

tissue fluids and blood for development. In

feeding, most ticks attach to a preferred part

of the host. Some favor the dewlap, shoulders,

and the region between the legs. The tropical

horse tick, Dermcicentor nitens, prefers the ear

but attaches to other parts of the body. The

spinose ear tick, Otobitts megnini, attaches only

deep in the external ear. The red-legged tick,

RhipicephaltLs evertsi, feeds deep in the ear in

its larval and nymphal stages and under the

base of the tail or between the hind legs as an

adult.

11
Ticks attach by cutting through the skin of

the host with the digits of the chelicerae and

anchor by inserting the hypostome into the

wound. The rapidity of feeding varies considerably in different species and in different

stages of the same species. Feeding in female

hard ticks is usually a gradual process until

the final day of feeding; then the body rapidly

fills with blood. Most female hard ticks feed on

the host for 7 to 12 days and under certain

conditions longer—but rarely less than 5 da^s

for complete engorgement. New cuticle is developed during the slow feeding in order to

accommodate the large volume of blood ingested.

Hard tick larvae and nymphs usually feed for

shorter periods than females. Male hard ticks

become only slightly distended ; they are intermittent feeders and may remain on the host for

weeks or even months, as with Amblyomma

variegatum, during which time several small

blood meals are taken.

The nymphal and adult stages of soft ticks

normally complete engorgement within 30

minutes to 2 hours; whereas, the larval stage

usually feeds for periods varying from 5 to 30

days.

During attachment and feeding, salivary

secretions are Injected into the wound, apparently to aid in penetrating the host's skin

and in preventing the coagulation of blood and

body fluids so that they can be readily ingested

by the tick. The salivary secretions of some

ticks are very irritating to the host. The

pajaroello tick, Ornithodoros coriacens, produces an especially painful "bite" which may

remain inflammed for days.

From the standpoint of disease transmission

and tick control, it is important to know that

the immature stages of a particular tick species

may not feed on the same host species as do

the adults. For example, the adults of Dermacentor variabilis commonly attack livestock,

man, and dogs; whereas, the immature ticks

are almost always found on small rodents,

especially mice.

Tick Secretions and Disease

Transmission

Salivary secretions play a most important

role in the transmission of disease by serving

as a medium of transport for the causal agents.

The disease agent is usually transmitted from

the infected tick to the host via the salivary

secretions.

Soft ticks have coxal organs, sometimes

called coxal glands, which may have a role in

the spread of pathogenic microorganisms by

some species of soft ticks. The coxal organs

open between the first and second pair of legs.

Their function is to filter off excess liquids and

salts from the blood meal soon after ingestion.

Within 30 minutes, soft ticks may ingest a

volume of blood which is several times the

tick's original body weight. During feeding, the

cuticle stretches to accommodate this large

amount of fluid. The coxal organs enable the

soft tick to rapidly reduce the total intake

volume to a level which best suits its needs. In

Ornithodoros moubata the coxal discharge begins about 15 minutes after the tick has begun

to feed and may continue intermittently for

about an hour after the completion of feeding.

The spirochetes of relapsing fever pass from

the infected tick in the coxal fluid on to the

skin of the host. They may then penetrate the

intact skin or enter the wound made by the

tick. Some species of soft ticks do not excrete

coxal fluid until after they have left the host.

Hard ticks do not possess coxal organs.

Engorging ticks void excretory products

which may contain pathogenic organisms that

can enter the animal body through the tick-bite

punctures or other breaks (or wounds) in the

skin. The careless removal of ticks from the

host may result in the rupture of the tick's

body with the release of gut contents around

the wound. Tularemia may be transmitted by

both of these methods.

Tick-bite wounds predispose the host to

infections and increase susceptibility to screwworm attack.

Longevity

Many species of ticks are able to survive for

long periods without a blood meal. Nymphs

usually live longer than larvae, and adults live

longer than nymphs. The adult fowl tick has

lived without food in vacant chicken houses for

37 months and then oviposited following a

blood meal. The relapsing fever tick, Omithodoros turicata, has lived more than 3 years in

jars of sand. Unfed larvae of the red-legged

12
tick can survive for 7 months, and unfed adults

for 14 months. The unfed adults of Dermacentor

variabilis have been observed to survive up to

1,053 days under outdoor conditions in eastern

United States. Under experimental conditions,

the larval stage of D, variabilis may live more

than a year without food; the nymphal stage

was observed to live for 584 days without feeding. However, it should be emphasized that, in

most of these extreme instances of long survival

periods, these surviving ticks were not tested

as to their ability to feed and to carry on to

the next stage.

The longevity of some species may be greatly

prolonged by reduced temperatures in the

autumn and winter months of temperate

regions. The activity of most, but not all, ticks

is usually suspended during the cold months of

the year. For example, Boophilus annulatus is

inactive during the winter ; on the other hand,

Dermacentor albipictus is primarily active

during this period and is commonly called the

winter tick. There is considerable variation in

the longevity of Boophihis annulatus, depending

on the season of the year; unfed larvae survived as long as 246 days during cool weather

but lived from only a few days up to 100 days

during mid-summer.

Moisture is important in the longevity of

hard ticks. Its complete absence is highly destructive. On the other hand, too much moisture, particularly following a long fasting

period, permits the growth of fungi on ticks

that is often fatal.

The longevity of any one or all stages in the

life cycle of a species of tick must be taken into

consideration when formulating a control or

eradication scheme. Failure to do so may very

well result in something less than control or

eradication.

Instincts and Adaptations

Ticks are rigidly bound by instinctive behavioral patterns ; nevertheless, they have made

interesting adaptations for survival. Leaving

one host to molt, with the necessity of waiting

for a second or commonly a third host, results in

high tick mortality. This hazard has been overcome to some extent in certain species of ticks by

the development of one or more of the following : an increased resistance to heat or cold, the

ability to withstand long periods of fasting, the

capacity to produce an enormous number of

eggs, and adaptation to a wide range of hosts.

All one-host ticks, such as Boophilus spp.,

Dermacentor nitens, and D. albipictus, have

adapted themselves to molt on the host. The

elimination of the need to seek a second and

third host diminishes the threat of speciesextinction in one-host species.

Ticks have also synchronized many of their

activities with those of the host. Rabbits

generally remain inactive in their nests during the day. The rabbit tick, Haemaphysalis

leporispahistris, adjusted to the habits of its

host by leaving the rabbit during the day. Thus,

after hatching or molting, these ticks have little

difficulty in finding the host when they are

ready to attach. In addition, the larval and

nymphal stages of the rabbit tick very successfully use several species of ground-inhabiting

birds as hosts, while using rabbits as preferred

hosts for the adult stage.

The engorged larvae of the fowl tick, Argas

persicus, have made another adaptation for

survival. They are globular in shape until a few

hours before dropping; the larvae then flatten

into the typical Argas form that permits them

to crawl rapidly into protective crevices.

The nymphs and adults of Argas persicus are

nocturnal in their feeding habits. To escape

being devoured by chickens, they hide in cracks

and crevices during the day, emerge at night to

feed for 30 minutes to 2 hours on the birds, and

return to their hiding places before the fowl

become active.

Where ticks feed on the host is important in

their survival. For example, the spinose ear

tick and the tropical horse tick attach deep

inside the ear. Species of Haemaphysalis found

on quail, meadow larks, and ground-feeding

birds customarily attach to the head, from

which they are not readily dislodged.

Female hard ticks can speed up the final

phase of engorgement. The female Boophilus

microplu^ feeds leisurely, taking several days

to become about one-third engorged. Then,

within a few hours, she normally completes

engorgement and drops from the host. Possibly

this is a defensive mechanism to reduce the

chance of the engorged female being crushed

by the host or attacked by birds such as the

oxpecker and cattle egret.

13
VIL CONTROL AND ERADICATION

Natural Control

The tremendous reproductive potential of

ticks is mitigated by climate and by predators

and parasites. Without these natural controls,

tick populations build up to great numbers.

Temperature and moisture are principal

agents affecting ticks. Cold weather, particularly

prolonged cold, harms some species of ticks,

mainly by killing them outright but also by

prolonging their inactivity on the ground,

where they are more prone to attack by predators. Excessive heat, dryness, or rainfall have

an adverse effect on some species.

Wild birds, domestic fowl, rats, mice, ants,

and at least two species of parasitic wasps play

a part in the natural control of ticks.

Research and field observations of cattle indicate that purebred Brahman (Bos indiciis)

and Brahman crosses have a greater resistance

to tick infestation than the European breeds

(Bos taurus). The mechanism of such resistance

may not yet be fully understood, but the knowledge that some species or breeds are more resistant to tick infestation may be useful in

contending with tick problems.

Pasture rotation may achieve control or

eradication by starving the ticks. However, in

view of the longevity of most species, pasture

rotation without supplemental measures is

seldom practicable.

Chemical Control

The most effective method of tick control is

by the use of chemical pesticides. Since the

usual method of tick dispersion is by movement

of the host, pesticide control can be effectively

used with quarantine and regulation of animal

movements. The combination of pesticides and

quarantine is essential in an eradication effort.

Treatment of tick-infested premises, where extensive acreages are not involved, may also be

included with other control measures.

Chemical control involves the use of pesticidal sprays, dips, dusts, aerosols, smears, or

systemics. The use of systemics is a comparatively new approach to pest control. A systemic

pesticide may be defined as a chemical which,

when administered to an animal as a spray, dip,

injection, bolus, drench, or feed additive, is

absorbed into the body tissues, either in its

original form or as a metabolite, and is toxic to

susceptible parasites feeding on such tissues.

Most species of ticks can be effectively controlled by the proper use of pesticides. "Effectively controlled" here means the reduction of

tick populations to the point where they are

of little or no economic importance. It differs

from eradication which resulta in the complete

annihilation of a species from a defined geographical area—as with the cattle fever tick.

A large number of pesticides are effective

against ticks. They include ronnel, crotoxyphos,

coumaphos (Co-Ral®,) ^ dioxathion (Delnav®),

toxaphene, malathion, and many others. The

pesticide of choice will be determined by

several factors, such as species of animal—cattle, horses, and swine—^the type of animal—

dairy or beef—and the cost of pesticide used.

Consideration must be given to compliance with

the Federal Food, Drug and Cosmetic Act

which regulates pesticide residues in raw agricultural products, including meat and milk. If

dipping is part of an official USDA Veterinary

Services program, only those chemicals permitted by Veterinary Services may be used.

No attempt is made here to elaborate on the

subject of pesticides and their uses. Instructions on vat management and the use of permitted pesticides for the control or eradication

of ticks and insects of concern to Veterinary

Services are issued as needed.

^ Trade names are used in this publication solely for

the purpose of providing specific information. Mention

of a trade name does not constitute a guarantee of

warranty of the product by the U. S. Department of

Agriculture or an endorsement by the Government over

other products not mentioned.

14
VIII. REGULATIONS ON IMPORTING AND

INTERSTATE MOVEMENT OF TICKS

The Animal and Plant Health Inspection

Service of the United States Department of

Agriculture has the responsibility for regulating the importation and interstate movement of

animal disease-producing agents and animal

disease vectors used in research of both human

and animal diseases. It is essential that diseaseproducing agents and vectors, including all live

ticks, are handled in a manner that does not

endanger the health of domestic livestock and

poultry.

The authority for regulating such movements

is contained in Part 122 of Title 9, U. S. Code

of Federal Regulations. The regulation states

that no organisms or vectors of such organisms

shall be imported into the United States or

transported from one State or Territory or the

District of Columbia to another State or Territory or the District of Columbia without a permit issued by the Secretary of Agriculture and

in compliance v^ith the terms thereof. As a

condition of issuance of permits, the permittee

shall agree in writing to observe the safeguards

prescribed by the Department of Agriculture

for public protection with respect to the particular importation or transportation.

Essentially then, anyone wishing to import

live ticks or receive live ticks from another

State must first obtain a permit from Veterinary

Services. Ticks preserved in 70 percent alcohol

or other preservatives are not subject to the

regulations and, therefore, may be imported or

moved interstate without a permit.

Individuals wishing to import or transport

live ticks interstate or desiring additional information on the movement of disease organisms

and vectors should direct their inquiry to :

Veterinary Services, APHIS

U. S. Department of Agriculture

Federal Building

Hyattsville^ Maryland 20782

IX. IDENTIFICATION

The accurate identification of ticks is a prerequisite to their control and eradication.

Identification is also essential to justify long,

costly eradication programs, and the imposition

of rigid quarantines.

Unfortunately there are not now, nor are

there likely to be, simplified keys or procedures

for the rapid creation of identification experts.

The identification of the numerous species of

ticks is a matter for the trained taxonomist.

Nevertheless, Veterinary Services veterinarians

and animal health technicians can become

familiar with the biology and identification of

the more common livestock ticks in the United

States.

An explanation of all characters will be found

on pages 16-20. Drawings of hypothetical ticks

showing the location of key characters appear

on pages 66-68.

IS
X. THE KEY AND HOW TO USE IT

The key to the identification of ticks presents

important characters of ticks arranged to

facilitate identification. This key is for adult

ticks only and primarily for ticks of veterinary

interest in the United States.

It will be noted that the key is arranged in

couplets, each couplet giving a choice of two

alternate characters or two alternate groups of

characters. Start with the first couplet and

proceed to the couplet indicated by the number

following the appropriate character, and so on,

until the final determination is made. For example, place the specimen under the microscope

topside (dorsum) up; focus the microscope and

adjust the light on the tick. Have the drawing

of a composite tick with parts labeled (pages

66-67) and the explanation of terms (pages

16-20) handy for ready reference.

Look at the first page of the key (page 20)

and note that the first thing to determine is

whether the specimen under the microscope is a

hard tick (Ixodidae) or soft tick (Argasidae).

Compare the characters in this couplet, then

look at the tick. For discussion purposes, let us

assume that the tick has a scutum (shield) and

the capitulum (head) is at the anterior end of

the body. Therefore, it is a hard tick (Ixodidae)

and the reference is to page 21. Next, determine

the developmental stage—larva, nymph, or

adult (male and female). Remember, the keys

in this manual are only for the identification of

the adult stages.

Again, let us assume that the tick you have

before you has eight legs and a genital aperture : it is an adult. Then, proceed to the key to

the genera of adults of the family Ixodidae on

page 21. Start with couplet 1. The important

character here is the anal groove—is it in front

of the anus, does it curve behind the anus, or

is it absent? The specimen tick has a small

groove behind the anus, so proceed as indicated

to couplet 2. Here the choice is between a palpus

with the second segment projecting conspicuously to the side or a palpus without such

projection. The tick fits into the second category, so proceed to couplet 3. Here the choice is

mainly between a hexagonal (six-sided) basis

capituli or one not six-sided. The basis capituli

on the specimen is rectangular, so proceed to

couplet 7. Look at the palps under the microscope—are they short with the second segment

not twice as long as its width ? You immediately

see that your specimen fits the first description,

therefore you identify the tick as belonging to

the genus Dermacentor. Now turn to page 24.

Check the specimen with the "Morphological

Characteristics of the Genus" under "GENUS

DERMACENTOR." If they all fit, you can be

certain you have keyed the specimen to the

correct genus. Proceed now in the same manner

through the key to the species of Dermacentor

and you will identify the tick as Dermacentor

variabilis.

Accessory shields :

Adanal shields :

Anal groove :

Anterior :

Anus:

Basis capituli :

Terms Used in the Key

Paired, projecting, sclerotized structures on venter, lateral to the adanal

shields in males of Boophiltts, Rhipicephalus and Hyalomma.

Paired, projecting, sclerotized structures on venter, lateral to the anus in

males of Boophilus, Rhipicephalus and Hyalomma.

Semicircular groove curving around the anus in some genera of Ixodidae

(hard ticks) ; in Ixodes curving in front, in other genera curving behind

or absent.

Toward the head end.

Posterior opening of the alimentary tract, situated on the median line

posterior to the last pair of legs.

Basal portion of capitulum on which the mouth parts are attached. May

be of various shapes: hexagonal, rectangular, subrectangular or subtriangular in hard ticks and always attached to anterior of body. In soft

ticks, located ventrally in adult and engorged nymph, anteriorly in larva.

16
Camerostome :

Capitulum :

Caudal process :

Cervical grooves :

Cheeks :

Chelicerae

(sing- Chelicera)

Chitin :

Chitinized :

Chitinous tubercles :

Cornu (pi. cornua) ;

Coxae :

(sing. Coxa)

Coxal organs :

Cuticule, or cuticula :

Denticles :

Dentition :

Dimorphism :

Distal :

Dorsal :

Dorsal humps :

Cavity or depression in which the capitulum of soft ticks is situated.

Usually not well-defined in engorged specimens.

Anterior movable portion of body of hard ticks, including basis capituli,

palps, hypostome, and chelicerae of hard ticks. Located ventrally in adult

and engorged nymph of soft ticks, anteriorly in larvae.

Distinct projection arising from median posterior end of the body in

males of some species of Boophilus, Rhipicephalits, and Margaropus.

Pair of grooves in the scutum extending posteriorly from the inner angles

of the scapulae. May be continuous or interrupted, shallow or deep, faint

or absent.

Paired flaps at the sides of the camerostome in some species of soft ticks.

Paired structures lying dorsally to hypostome which complete the cylindrical mouth parts that are inserted when the tick feeds.

The hard parts of the tick body formed from a colorless secretion produced by the epidermis.

Filled in with or hardened by chitin.

Small, chitinized, rounded lobes on the posterointernal angle of the festoons of Amblyomma cajennense and sometimes A. maculatum.

Small projections extending from the dorsal, posterolateral angles of

the basis capituli.

Small, sclerotized plates on the venter representing the first segment of

the leg to which the trochanters are movably attached. From anterior

to posterior, the coxae are designated by Roman numerals I, II, III, and

IV. Bifid coxae are those that are cleft, divided, or forked.

Called coxal glands by some authors and are present in members of the

family Argasidae but absent in members of the family Ixodidae. The

external openings of the coxal organs are located between coxae I and II.

Outer covering of a tick. Also called the integument.

Small, recurved projections or **teeth" on the ventral side of the hypostome. (See dentition.)

Refers to the presence of denticles on the ventral side of the hypostome.

The numerical arrangement of the files or rows of denticles is expressed

by the dentition formula. Thus, dentition 3/3 means that there are three

longitudinal rows of denticles on each side of the median line of the

hypostome.

Difference in form, color, etc., between individuals of the same species,

more particularly between sexes.

Farthest from the point of attachment or origin.

Pertaining to the back or top of the body.

Protuberances on the dorsal surface of the segments of the legs, but not

including the subapical dorsal protuberance.

Dorsal prolongation : The posterodorsal extension of the spiracular plate.

17
Dorsum :

Emargination :

Engorged :

Festoons:

Files:

Genital aperture :

Goblets :

Hexagonal :

Hood:

Hypostome :

Inornate :

Integument :

Lateral :

Lateral groove :

Legs :

Macula :

Mammillate :

18

The entire dorsal surface of the body.

Anterior indentation or cutout place in the scutum between the scapulae

that receives the basis capituli.

Enlargement or distention of a tick follov^ing a blood meal. Since the

scutum is short in the larva, nymph, and female hard tick (covering about

half the dorsal surface in the unfed specimen), the body is capable of

pronounced distention. As the body fills with blood, the relative size of

the scutum is reduced. In a fully engorged female hard tick, the scutum

may appear only as a small plate on the anterior of the body. In the soft

tick, the scutum is absent and both sexes may become enlarged, although

not usually to the extent of the engorged female hard tick.

Uniform rectangular areas, separated by distinct grooves, located on the

posterior margin of most genera of the hard ticks. Very distinct areas

in unengorged specimens, but may not be visible in fully engorged females.

In some species of Hyalomma, festoons may be reduced in number and

partially coalesced. Festoons are not present in Boophilus and Ixodes.

Longitudinal rows of denticles or "teeth" on the ventral surface of the

hypostome.

External opening of the genital organs. Located anteriorly on the ventromedian line, posterior to the basis capituli.

Small, round structures located in the spiracular plate. They may be very

small and numerous as in Dermacentor variablis, or relatively large and

few was in D. nitens.

Having six sides.

Anterior projection of the integument on some soft-bodied ticks.

Median ventral structure of the mouth parts that lies parallel to and

between the palps and is immovably attached to the basis capituli. It

bears recurved "teeth" or denticles. (See dentition.)

Absence of a color pattern on the scutum.

Outer covering or cuticle of the tick's body.

Toward the side.

The groove running along the sides of the scutum in both sexes—may be

continuous or interrupted.

Segmented appendages of which nymphs an^^adults have four pairs and

larvae have three pairs.

From anterior to posterior the legs are identified by Roman numerals I,

II, III, and IV. The segments from the proximal (next to the body) to

the distal end are called coxa, trochanter, femur, tibia, metatarsus, and

tarsus.

Large sclerotized structure located in the spiracular plate of adult ticks.

It may be of variable size, shape, and location.

With nipplelike protuberances or processes.
Marginal groove :

Medial :

Median :

Morphological :

Ornamentation:

Ornate :

Palps or palpi

(sing, palpus)

Periphery :

Poröse areas :

Posterior :

Protuberance :

Proximal :

Punctuations :

Scapulae

(sing, scapula)

Sclerotized :

Segment :

Scutum :

Spiracular plates :

In females, the groove which runs along the sides of the body starting

near the posterolateral border of the scutum.

Toward the median axis of the body.

The longitudinal axis that divides the body.

Pertaining to form or structure.

Enamel-like color pattern that is superimposed on the base color of the

integument in hard ticks. When present, this color pattern may be white

to dirty white in Dermacentor or may be an intense copper or bronze

color with touches of yellow or green in some Amblyomma.

Definite color pattern superimposed on the base of the integument in hard

ticks. (See ornamentation.)

Paired articulated appendages located anterolaterally upon the basis

capituli and lying parallel with the hypostome. Four distinct segments

are present in soft ticks. In all hard ticks the fourth segment is reduced

to a small hair-crowned papilla lying in a cuplike depression of segment

3. The sequence of numbering of the segments is indicated by Arabic

numerals 1, 2, 3, and 4: 1 being the proximal segment (closest to the

basis capituli).

Circumference or outer margin.

A pair of pitted areas, usually depressed and oval, on the dorsal surface

of the basis capituli; present in all adult female hard ticks; absent in

male and immature stages.

Toward the rear end.

Any elevation above the surface.

Nearest to the point of attachment or origin.

Pits in the surface of the cuticle, frequently present on the scutum and

sometimes present on the basis capituli of some of the hard ticks. The

pits may be deep or shallow, small or large.

Anterior angles or "shoulders'' of the scutum that project on either side

of the emarginalion.

Hardened in definite areas by deposition or formation of organic or inorganic substances in the cutícula (termed sclerotin).

Distinct articulated entity of a palpus or a leg.

The sclerotized dorsal plate posterior to the capitulum in hard ticks.

It covers almost the entire dorsal surface in the male, about half the

dorsal surface in the unengorged female. (See engorged.)

Paired plates located ventrolaterally and posterior to coxa IV in hard

ticks; may be oval, rounded, or comma-shaped. In the soft ticks the

spiracular plates are located ventrolaterally and opposite coxa IV and

are usually round or oval. They are the external evidence of the respiratory

system.

19
Spurs :

Subanal shields :

Subapical dorsal

protuberance :

Subterminal :

Sutural line :

Tampan :

Venter :

Ventral :

Ventral cornua :

Ventral plaques :

Ventral scutes :

Coxal spurs are projections from the posterior surface or posterior margin of the coxae; may be rounded or pointed, small or large. Projections

on the median side are called internal spurs ; those on the lateral side are

called external spurs. Metatarsal spurs are small, pointed projections on

the distal end of the metatarsus. Spurs may also be found on the palps

of some species.

Paired, projecting sclerotized structures on venter posterior to the

adanal and accessory shields in males of Hyalomma.

The subterminal protuberance present on the tarsus of some species of

soft ticks. It should be distinguished from the dorsal humps which are

present on the tarsus and metatarsus.

Before the end, or not quite attaining the end.

Distinct line around the outer margin separating dorsal and ventral

surfaces in Argas ticks.

A South African term referring to soft ticks, especially Omithodoros

and Argas.

Entire ventral or underside of the body.

Pertaining to the underside of the body.

Very small projections arising from the posterolateral angles of the

ventral surface of the basis capituli.

Small, non-projecting sclerotized plates on the venter immediately anterior to the festoons in the males of some species of Amblyomma.

Chitinous thickenings of the ventral surface of the festoons of Amblyomma. They may be distinct, protruding, faint, or absent.

XI. KEY TO FAMILIES OF TICKS

Scutum present, short in female, long in

male. Capitulum at anterior

of body in all stages. .Family Ixodidae, p. 21

Scutum absent. Capitulum on underside of

body in nymphs and adults,

anterior in larvae... Family Argasidae, p. 29

Family Ixodidae

Morphological Characteristics

of the Family

The family Ixodidae, the so-called "hard

ticks," includes those ticks that have a scutum.

Sexual dimorphism is pronounced, the dorsum

of the male is almost completely covered by the

scutum, and the body is incapable of becoming

greatly enlarged; whereas, the dorsum of the

female is only partially covered by the scutum

and the body is capable of considerable enlargement. The scutum of the engorged female appears as only a small shield posterior to the

capitulum. Poröse areas are present on the

basis capituli of the female, absent on the basis

capüttü of the male. The capitulum is always

anterior and visible dorsally. The spiracular

20
plates are located posterior and somewhat

lateral to coxa IV.

Key to Development Stages of

Family ixodidae

1. Six legs present Larvae

Eight legs present 2

2. Genital aperture not present (undeveloped). Scutum similar to the female

type but basis capituli does not have

poröse areas Nymphs

Genital aperture present. Scutum of

male or female type. Basis capituli of

female with poröse areas Adults

Key to Genera of Adult of Family

Ixodidae

1. Anal groove distinct and curves around

the anus in front. Inornate. Eyes absent.

Festoons absent Genus Ixodes, p. 27

Anal groove located behind the anus or

is absent. Ornate or inórate.

Eyes present or absent. Festoons present

or absent 2

2. Second segment of palps projects beyond

the lateral margin of the basis capituli.

Eyes absent.. .Genus Haemaphysalts, p. 26

Second segment of palps not projecting

beyond the lateral margin of the basis

capituli. Eyes usually present .3

3. Basis capituli hexagonal (six-sided).^

Usually inornate 4

Basis capituli not hexagonal dorsally.

Ornate or inornate 7

4. Festoons present. Spiracular plate

comma-shaped or subtriangular. Coxae

I deeply cleft 5

iPestoefis ^bs^it. Spir^acular plate mral.

Coxae I not deeply cleft in female 6

5. Males with adanal shields and usually

accessory shields. Coxae IV of male of

normal size. Segment 1 of palps without

dorsal spur.... Genus Rhipicephalus, p. 28

Males without adanal and accessory

shields. Coxae IV of male greatly enlarged. Segment 1 of palps with dorsal

spur Genus Rhipicentor, p. 28

^An African species, Rhipicephalus pulchellus, not

presently established in the United States, is one common exception; the male has a rectangular basis capituli and both sexes are ornate.

6. Palps very short, compressed and ridged

dorsally and laterally. Males with normal

legs Genus Boophilus, p. 24

Palps short, but not ridged dorsally and

laterally. Males with massive, beady

leg segments Genus Margaropus, p. 28

7. Palps short, second segment not twice as

long as wide. Basis capituli rectangular

dorsally Genus Dermacentor, p. 25

Palps long, second segment twice as long

as wide. Basis capituli of variable form,

usually subtriangular or subrectangular

dorsally 8

8. Eyes absent. (Reptile

parasites Genus Aponomma, p. 23

Eyes present 9

9. Scutum usually ornate.^ Festoons well

developed. Males without adanal shields,

accessory shields and subanal

shields Genus Amblyomma, p. 22

Scutum inornate. Festoons poorly

developed (often coalesced). Males

with adanal shields, accessory shields,

usually subanal

shields Genus Hyalomma, p. 27

General Comments

The family Ixodidae is represented in

North America by seven genera: Amblyomma,

Aponommu, Boophilus, Dermacentor, Haernxjirphysalis, Ixodes, and Rhipicephalus. Additional

genera found in other areas of the world include Cosmiomma, Hyalomma, Margaropus,

and Rhipicentor. The principal hosts of the

hard ticks are mammals, reptiles, amphibians,

and birds. Generally, only those species known

to be of economic importance as pests of livestock are stressed in this manual. (See charts,

pp. 33-34.)

GENUS AMBLYOMMA

Morphological Characteristics

of the Genus

Palps long, segment 2 at least twice as long

as wide. Generally ornate. Eyes and festoons

present. Basis capituli of variable form, usually

subtriangular or subrectangular dorsally.

Adanal shields absent in the male, but small

ventral plaques may be present ventrally in

' Amblyomma inornatum lacks ornamentation.

21
front of the festoons. Ventral scutes may be

present and extend beyond posterior margin of

the festoons of the male. Spiracular plates subtriangular or comma-shaped.

Key to the Males of the

United States

1. Scutum inornate Amblyomma inornatum

Scutum ornate 2

2. Coxa I with the internal spur

moderately long 3

Coxa I with the internal spur

short or insignificant ^ 4

3. Scutum with abundant ornate markings,

more or less radiating from the center ;

markings most prevalent in central and

anterior area of

scutum Amblyomma cajennense or

A. imitator "^

Scutum with sparse ornate markings,

usually four or more symmetrically

isolated patches ; central area of scutum

without ornate

markings Amblyomma americanum

4. Coxae II, III, and IV each

with one spur Amblyomma maculatum

Coxae II, III, and IV each with two spurs. .5

5. Coxa IV with the external spur distinctly

longer than the

internal spur Amblyomma dissimile

Coxa IV with both spurs very short

(internal spur may be difficult

to see) Amblyomma tuberculatmn

Key to the Females of the

United States

1. Scutum inornate... ,Amblyom7na inornatum

Scutum ornate '\ 2

2. Coxa I with the external spur distinctly

longer than the internal spur 3

Coxa I with external and internal spurs

approximately but not exactly equal 6

3. Scutum with scant ornamentation,

usually limited to a distinct spot near the

posterior end .Amblyomma americanum

* Differentiation between the male A. cajennense and

A, imitator is difficult. The male A. imitator is usually

paler, narrower, and smaller. See Kohls' original description of A. imitator for additional information on

the separation of the two species.

Scutum with abundant ornamentation in

an extensive pattern 4

4. Coxa I with the internal spur very short

or insignificant Amblyomma maculatum

Coxa I with the internal spur about half

the length of the external spur 5

5. Festoons with chitinous tubercles at

posterointernal

angle Amblyomma cajennense

Festoons without chitinous

tubercles Amblyomma imitator

6. Coxa IV with the external spur longer

than the internal spur (often difficult to

see or may be absent). Common on

snakes and iguanas imported from South

America Amblyomma dissimile

Coxa IV with the internal and external

spurs very small and about equal.

Found on the gopher-tortoise in the

coastal plain of Southeastern United

States Amblyomma tuberculatum

General Comments

The genus Amblyomma is represented in the

United States by at least seven species, four of

which are commonly found on livestock. Those

found on livestock include A. americanum, A.

cajennense, A. imitator, and A. maculatum.

Their distribution is limited usually to the

southeastern or southwestern coastal States.

The long mouth parts and the color pattern on

the scutum are distinctive characters which aid

in recognition of Amblyomma attacking livestock in the United States. Two species, A.

dissimile, the iguana tick, and A. tuberculatum,

the gopher-tortoise tick, as larvae and nymphs,

have attached to and engorged upon bovines.

Adults, however, usually attach only to reptiles

and amphibians. The engorged adult A. tuberculatum may be almost an inch in length.

Another species, A. inornatum, has been collected from dog, cow, coyote, deer, and rabbit in

southern Texas.

Amblyomma americanum, the lone star tick,

so named because of the conspicuous ornate

spot on the posterior of the female scutum, is

one of the more economically important species.

The long mouth parts and great abundance

of this tick make it an especially annoying

pest of livestock. The wound produced predisposes livestock to attack by the screwworm

fly, Cocb^iomyia hominivorax.

22
The lone star tick is also important from

the public health standpoint because it is

capable of transmitting tularemia, Rocky Mountain spotted fever, and Q fever; and it produces

tick paralysis in man and dogs.

The lone star tick is more widely distributed

in the United States than the other Amblyomma

species. It is commonly found from Texas north

to Missouri and eastward to the Atlantic coast.

A. americanum is a 3-host tick. It may be

active from early spring to late fall and all

stages attack livestock and man.

Amblyomma cajennense, the Cayenne tick,

has limited distribution in the United States,

being confined to a few counties in southern

Texas. In tropical Central and South America,

this species has been reported abundant, active

the year round and of definite economic importance as a livestock pest. It is a known

vector of Rocky Mountain spotted fever in

Mexico, Panama, Colombia, and Brazil. A.

cajennense is a S-host tick.

Amblyomma imitator was, until 1958, confused with A. cajennense. The species has been

recorded from man and a variety of domestic

and wild animals in southern Texas, Mexico,

and Central America. Its definitive distribution,

life history, and economic importance have not

yet been determined.

Amblyomma maculatum, the Gulf Coast tick,

is an important pest of livestock. The adults

are usually found in clusters in the external ear

where they produce an intense inflammation.

Tick bites predispose the ear to attack by the

screwworm fly. The Gulf Coast tick is found

in those States bordering the Gulf of Mexico

and along the Atlantic Coast of South Carolina,

Georgia, and Florida. This species is rather

exacting in its environmental requirements,

usually preferring areas of high rainfall, temperature, and humidity. It is seldom found in

great number more than 100 to 150 miles from

the coast.^ Livestock are attacked principally

during the late summer and early fall. A,

maculatum is a 3-host tick. The larva and

nymph generally feed on birds and small

mammals, while the adult prefers livestock.

^Established infestations of A, maculatum of livestock have been reported from at least 15 counties in

OJclahorna.

In Africa members of the genus Amblyomma

are frequently called bont ticks. The word

**bont" is of Afrikaans origin and refers to the

presence of brightly colored patterns on thé

scutum and the white-banded legs. This is an

economically important group of ticks in Africa.

Five species frequently found on livestock are

A. hebraeum, A. variegatum, A. gemma, A.

pomposum, and A. lepidum.

Amblyomma variegatum, the tropical bont

tick, was found on cattle on St. Croix, U. S.

Virgin Islands, in August 1967. Subsequently,

A. variegatum was also collected from sheep,

goats, dogs, horses, and mongooses. An eradication program started in late 1967 was completed by May 1970. In June 1974, A. variegatum

was found established in Puerto Rico. See

page 39.

The tropical bont tick was first reported m

the Western Hemisphere (Antigua) in 1895.

Apparently it had been introduced 30 to 40

years previously with cattle imported from

Senegal, located on the west coast of Africa at

about the same latitude as Antigua. It spread

to St. Kitts and Guadeloupe, but it was not

known to exist in the U. S. Virgin Islands

before August 1967. The tropical bont tick is a

serious pest of domestic livestock and has a

broad host range. It is a known vector of the

virus of Nairobi sheep disease and also transmits the agent which causes heartwater in

cattle, sheep, and goats. Neither disease was

found in the U. S. Virgin Islands.

Amblyomma hebraeum, the South African

bont tick, has been reported on several occasions

in the United States on rhinoceroses imported

from South Africa. This is a 3-host tick that

transmits the agent which causes heartwater in

cattle, sheep, and goats.

GENUS APONOMMA

Morphological Characteristics

of the Genus

Palps long, segment 2 at least twice as long

as wide. Ornate or inornate. Eyes absent.

Festoons present. Basis capituli rectangular or

subrectangular dorsally.

The Species of Aponomma

No key to the species of Aponomma is included in this manual.

23
General Comments

The genus Aponomma closely resembles the

genus Amblyomma except that Aponomma is

smaller in size, broadly oval, and does not have

eyes. This genus is found almost exclusively on

reptiles and is of no known veterinary or medical importance. Only one species, Aponommxi

elaphensis Price, is known to be established in

the United States; it is reported from the

Trans-Pecos rat snake in the Big Bend National

Park, Texas. Other species are occasionally

found on snakes and lizards imported from

Africa and South America.

GENUS BOOPHILUS

Morphological Characteristics

of the Genus

Very short, compressed palps, ridged dorsally and laterally. Basis capituli hexagonal dorsally. Eyes present. Inornate. Festoons absent.

Spiracular plate rounded or oval. Male with

adanal shields and accessory shields. Anal

groove indistinct or absent in female, faint in

male. Caudal process present or absent in male.

Key to the Males of North America

With caudal process at posterior extremity

of body B. microplus

Without caudal process B. annulatus

Key to the Females of North America "

With internal and external spurs of coxa I

broadly rounded and wider than long. Coxae II

and III with external spurs broadly rounded

and wider than long. Coxa IV with or without

a very small external spur.. Boophilus microplus

Internal spur of coxa I absent, external spur

broadly rounded and wider than long. Coxae

II, III and IV without external

spurs B. annulatus

General Comments

Ticks of the genus Boophilus have been

eradicated from the United States—except for

a small, narrow quarantine zone along the

'Females of some populations are very difficult to

separate due to morphological variation. Accurate

identification is best accomplished with male specimens.

Texas-Mexico border. Periodic reinfestations in

the quarantine zone occur from adjacent

heavily infested areas of Mexico.

The cattle fever tick, B. annulatus, was

formerly the most common and most economically important tick attacking livestock, particularly cattle, in the Southern States. As a

vector of Babesia bigemina, the causative agent

of bovine piroplasmosis (cattle fever), this tick

and the disease it transmits cost the livestock

industry an estimated $100 million annually

prior to the start of the Tick Eradication

Program in 1906.

Boophilus microplus, the tropical cattle tick,

was also once established in the United States.

It is closely related to J5. annulatus, and the

females are sometimes difficult to differentiate.

Both species are 1-host ticks that prefer

similar hosts, and both species are vectors of

piroplasmosis and anaplasmosis. As the name

implies, the tropical cattle tick prefers a

tropical or subtropical climate. In the United

States, in the past, it was reported most frequently from Florida and extreme southern

Texas. The tropical cattle tick is very prevalent

in the more humid and hotter parts of the West

Indies, Central America, Mexico, South America, Australia, Africa, and the Orient.

Boophilus decoloratus, an African species

closely related to B. microplus, has been found

on wild animals from Africa held in quarantine

before being released for entry into the United

States. In South Africa this is one of the

commonest species parasitizing cattle and less

frequently horses. The biology and disease relationships are similar to those of B. microplus.

GENUS DERMACENTOR

Morphological Characteristics

of the Genus

Basis capituli rectangular dorsally. Eyes and

festoons present. Palps short, broad, or moderate. Coxae I to IV of males increase progressively in size; in all species coxa IV is the

largest. Male without ventral plates or shields.

Coxa I bifid in both sexes. Spiracular plates

sub-oval or comma-shaped. Usually ornate.

24
Key to the Adults of the United States

1. Spurs on coxa I widely divergent 2

Spurs on coxa I not divergent or only

slightly divergent 4

2. Scutum inornate. Spiracular plate without dorsal prolongation and with few

(usually 4-10), large, isolated goblets.

Seven festoons present (not distinct on

engorged female) Dermacentor rdtens

(=Anocentor nitens)

Scutum ornate. Spiracular plate with

dorsal prolongation and with many

small or medium sized goblets. Eleven

festoons present 3

3. Scutum with large, deep punctations.

Cervical grooves of female deep and

extend nearly half the length of scutum.

(Primarily a rabbit tick of the Southwestern United States and adjacent area

of Mexico) . .. .Dermacentor parumapertus

Scutum with the punctations shallow

and moderate in size. Cervical grooves

of female deep and short, scarcely more

than pits. Found on peccary (javelina)

in Texas and Mexico Dermacentor halli

4. Spiracular plate without dorsal prolongation ^ and with goblets of medium

size and number 5

Spiracular plate with dorsal prolongation

and with goblets many or of moderate

numbers 6

5. Scutum and legs profusely

covered with white

ornamentation Dermacentor albipictus

Scutum without white or with very little

white ornamentation. Common on deer

in Southeastern United States

of America Dermacentor nigrolineatus

6. Cornua long, especially in the male

(found along Pacific Coast of California

and Oregon) Dermacentor occidentalis

Cornua short or of moderate length 7

^ The frame of the spiracular plate of some specimens

of D. albipictus is occasionally formed to resemble a

partially developed dorsal prolongation. When such a

specimen is encountered, one may possibly identify it

as D, hunteri with this key. However, the dorsal prolongation is very definite in D. hunteri.

7. Spiracular plate with goblets very small

and numerous (like grains

of sand) Dermacentor variabilis

Spiracular plate with goblets moderate

in size and number 8

8. The larger punctations on scutum very

large and deep Dermacentor andersoni

(=D. venustus)

The larger punctations on scutum moderate in size and depth. From bighorn

sheep in Arizona and

Mexico Dermacentor hunteri

General Comments

The genus Dermacentor comprises an important group of ticks in the United States,

particularly as vectors of disease-producing

organisms affecting man. Several of the species

are known transmitters of Rocky Mountain

spotted fever, tularemia, Colorado tick fever,

and Q fever; some species may produce tick

paralysis. Several members of this genus are

also important pests of livestock, both as disease

vectors and as bloodsucking parasites.

This genus is represented in the United

States by at least nine species, six of which

commonly attack livestock. D. andersoni (= D.

venv^tus), D. occidentalis, and D. variabilis are

3-host ticks. Dermacentor albipictus and the

closely related D, nigrolineatus, as well as D.

nitens, are 1-host ticks. The three additional

species Z>. halli, D. hunteri, and D. parumapertus

do not commonly attack livestock.

Dermacentor nitens (= Anocentor nitens),

the tropical horse tick, is an important parasite

of horses, mules, and asses in parts of Mexico,

Central America, and the West Indies. Until

about 1960, it was believed the tropical horse

tick was established in the United States only

in extreme southern Texas. Evidence now indicates that this species is also well established

in southern Florida. Dermacentor nitens is a

1-host tick. It is usually found in the ears of

horses, mules, and asses, although it has also

been found on cattle, goats, and deer. In heavy

infestations on horses, it has also been found

in the nasal diverticulae, the mane, the perineal

region, and along the ventral midline.

25
Dermacentor albipicttis, the winter tick, is an

important pest of horses, cattle, moose, elk, and

deer in the northern and western United States.

It is often abundant on range stock and, if not

controlled, may cause losses through weakened

condition or death of the host. This 1-host

tick is active during the late fall, winter, and

early spring.

Dermacentor nigrolineatus, the brown winter

tick, is closely related to D. albipictus. In fact,

some taxonomists regard D. nigrolineatus as a

variation or "form" of D. albipictus. Other

authorities regard the completely inornate D.

nigrolineatus as a valid species.

The brown winter tick is widely scattered

throughout the eastern half of the United

States, both north and south, although the incidence of this species is greater in the southeastern quarter of the country. In southwestern

Texas and New Mexico, the distribution of D.

albipictus and D, nigrolineatus may have overlapped with a crossing of the two species resulting in a fertile hybrid which is sometimes

difficult to place in either species. The preferred host for the brown winter tick in the

southeastern states is the white-tailed deer,

although it will also attack horses, mules, and

cattle. It is a l~host tick and is found on

animals only during fall, winter, and spring.

Dermacentor occidentalis, the Pacific Coast

tick, is common from Oregon to lower California. This species occurs on a variety of

domestic animals with occasional heavy infestations on deer. Adult ticks are most numerous

on hosts during the rainy season. All stages of

the tick have been reported on cattle. This is a

3-host tick.

Dermacentor variabilis, the American dog

tick, is widely distributed in the United States.

It is found in all the States east of the Rocky

Mountains, as well as in California, Washington, Idaho, and Oregon. The American dog tick

is an important vector of Rocky Mountain

spotted fever in the Eastern States. It transmits

tularemia and possibly bovine anaplasmosis

and produces tick paralysis. D. variabilis is

a 3-host tick. Although the dog is the preferred

host for the adult tick, man, as well as domestic

and wild animals, is frequently attacked. The

larva and nymph prefer small rodents, especially mice, rats, and rabbits.

Dermacentor andersoni (= D. venustus), the

Rocky Mountain wood tick, is one of the most

infamous transmitters of diseases of man in

the United States. It is a vector of Rocky

Mountain spotted fever, tularemia, Colorado

tick fever, and Q fever; and produces tick

paralysis in both man and animals. It is also

a suspected vector of anaplasmosis in cattle. This

species has been reported in 14 Northwestern

States and in three provinces of southwestern

Canada. It is a 3-host tick. The nymph and

larva feed primarily on small animals, such as

squirrels, chipmunks, and rabbits; whereas, the

adults generally attack the larger mammals—

horses, cattle, sheep, deer, and man.

GENUS HAEMAPHYSALIS

Morphological Characteristics

of the Genus

Inornate. Eyes absent. Festoons present.

Usually short conical palps with second segment projecting beyond the lateral margin of

the basis capituli which is rectangular in the

dorsal view. Usually of small size and sexual

dimorphism slight. Ventral plates or shields

absent in the male. Posterior margin of coxa

I never bifid or deeply cleft. Spiracular plates

usually rounded or comma-shaped in the male,

rounded or oval in the female.

Key to the Adults

of the United States

Ventral cornua present. Dentition of

hypostome 3/3. ,Haemaphysalis leporispalustris

Ventral cornua absent. Dentition of

hypostome 5/5 H, chordeilis

General Comments

The genus Haemaphysalis includes approximately 150 species. Only two species, H.

leporispalustris and H. chordeilis, are known to

be established in the United States. Neither is

commonly found on livestock. Both species are

3-host ticks.

Haemaphysalis leporispalustris, the rabbit

tick, is widely distributed in the United States

from Massachusetts to California. The adult

is found primarily on rabbits and groundfrequenting birds; whereas, the larva and

nymph are usually found on numerous kinds

of birds and small mammals. None of the stages

are commonly found on livestock or man. This

species may be more important than is realized.

26
Evidence indicates that the rabbit tick may be

an important factor in the spread of Rocky

Mountain spotted fever and tularemia among

wild animal reservoir hosts.

Haemaphysalis chordeilis, the bird tick, is

also widely distributed in the United States.

Birds are the preferred hosts for all stages of

the species, and livestock and man are only

rarely attacked. Several authorities have reported deaths in turkeys and wild game birds

from heavy infestations of this species.

Some important species of Haemaphysalis in

other areas of the world are H. leachi of Africa,

H. longicornis of Australia, New Zealand and

Japan; and H, bispinosa of Ceylon, Pakistan,

India, and Malaysia.

GENUS HYALOMMA

Morphological Characteristics

of the Genus

Ornamentation, if present, limited to pale

bands on legs. Eyes present. Festoons irregular,

partially coalesced. Palps long, segment 2 approximately twice as long as segment 3. Basis

capituli subtriangular dorsally. Coxa I usually

deeply cleft. The male with adanal and acces90Yy shields and usually subanal shields.

Spiracular plate usually comma-shaped.

The Species of Hyalomma

No key to the species of Hyalomma is included. All suspected specimens of Hyalomma

ticks should, without exception, be forwarded

to the Veterinary Services Laboratories for

identification or confirmation.

General Comments

Until relatively recently the taxonomic status

of the species in the genus Hyalomma was confused. However, thanks to Hoogstraal and

Kaiser, this group is now reasonably well

understood. The Hyalomma complex of species,

which at one time consisted of almost 100

species or subspecies, is now recognized as consisting of approximately two dozen or fewer

valid species.

Fortunately, the genus Hyalomma is not represented in the New World. It is distributed

throughout Asia, Africa, and southern Europe.

Adult Hyalomma ticks are primarily parasites

of domestic animals and are of considerable

economic importance in areas where they are

established. The species of this genus are especially eflScient vectors of a variety of diseaseproducing organisms of man and animals.

Hyalomma ticks are probably among the most

economically important external parasites which

attack animals.

GENUS IXODES

Morphological Characteristics

of the Genus

Anal groove distinct and curves around the

anus anteriorly, and usually uniting in a point

or arch. Inornate. Eyes and festoons absent.

Palps and basis capituli of variable form.

Spiracular plates round or oval. Venter of male

covered with seven nonprojecting, armor-like

plates. Sexual dimorphism pronounced, especially in regard to the capitulum.

The Species of Ixodes

Due to the complexity of the ticks in this

genus, no attempt has been made to present a

key for the identification of the species. It is

suggested that all Ixodes be referred to a

specialist for identification. For information on

the identification and distribution of the species

in the United States, refer to Cooley and

Kohls (1945).

General Comments

Some 200 species of the genus Ixodes are

found throughout the world. Over 30 species

have been reported in the United States. Only

two species, however, /. pacificus and /. scapularis, are commonly found on livestock in the

United States ; both are 3-host ticks. The long

mouth parts of the female Ixodes enable these

ticks to be especially painful and annoying

parasites of livestock and man.

Ixodes pacificus, the California black-legged

tick, is commonly found on domestic livestock,

deer, and man along the western coast of the

United States from Me^tico to British Columbia.

Records indicate that this species is most

abundant on livestock during the spring.

Ixodes scapularisy the black-legged tick, is

found primarily from Texas and Oklahoma

eastward to the Atlantic Ocean, but it has been

reported as far north as Minnesota and Wisconsin and as far northeast as southern Massachusetts. In the Southern States, where this

27
species is commonly found, it is abundant in

winter and early spring. This tick is not known

to naturally transmit livestock diseases ; it is a

suspected vector of anaplasmosis and tularemia.

Also, see footnote on p. 51.

Other important species of Ixodes are /.

ricinus of Europe, /. persnlcatus of parts of

Asia and parts of Europe, /. holocyclus of

Australia, and /. rubicundus of southern Africa.

GENUS MARGAROPUS

Morphological Characteristics

of the Genus

Palps short but not ridged as in Boophilus.

Basis capituli hexagonal dorsally. Eyes present.

Inornate. Festoons absent. Legs of male increase progressively in size from pair I to IV ;

the segements of leg IV greatly enlarged. Male

with adanal and sometimes accessory shields.

Spiracular plates rounded or oval in both sexes.

Anal groove absent or indistinct.

The Species of Margaropus

No key to the species is included in this

manual. See Hoogstraal (1956).

General Comments

The genus Margaropus is closely related to

Boophilus and is known to be established only

in Africa. At one time Boophilus annvlatus was

placed in the genus Margaropus, and much of

the older literature lists B. annulatus as

Margaropus annulatus.

Only two species, M. winthemi and M. reidi

are presently included in this genus. Margaropus

ivinthemi is found in southern Africa and feeds

chiefly on horses and cattle ; it is a 1-host tick

and the female resembles B. decoloratus, but is

larger. Margaropus reidi is reported only from

the giraffe in the western Sudan; the biology

and disease relations are unstudied.

GENUS RHIPICENTOR

Morphological Characteristics

of the Genus

Inornate. Eyes present. Festoons present.

Basis capituli hexagonal dorsally. Palps short;

segment 1 with a short broad dorsal spur. Coxa

I unusually long and deeply cleft. Spiracular

plates subtriangular or comma-shaped. The

male resembles Rhipicephalus dorsally, Derma^

centor ventrally; coxa IV is greatly enlarged;

adanal shields and accessory shields absent. All

coxae with a well developed antero-external

prolongation which is spurlike in coxa I. Coxal

spurs are sharper than in Rhipicephalus.

The Species of Rhipicentor

No key to the species is included in this

manual. See Theiler (1961).

General Comments

The genus Rhipicentor presently contains two

species and both are established only in Africa.

Rhipicentor hicornis has been reported from

goats, horses, cattle, dogs, and wild carnivores

in southern and central Africa. The biology

and disease relationships are unstudied, but

since it does parasitize domestic animals it is

potentially dangerous. Rhipicentor nuttalli has

been reported from hedgehogs, dogs, hyenas,

wild cats, large carnivores, and cattle in southern Africa.

GENUS RHIPICEPHALUS

Morphological Characteristics

of the Genus

Palps short and basis capituli usually hexagonal dorsally. Usually inornate. Eyes and

festoons present. Coxa I deeply cleft. Males

with adanal shields and usually accessory

shields. Spiracular plates comma-shaped. Caudal process present or absent in male.

The Species of Rhipicephalus

Due to the number, complexity, and economic

importance of the species in the genus Rhipicephalus, no key is included in this manual.

All Rhipicephalus ticks should be submitted to

the Veterinary Service Laboiatories, Beltsville,

Md., for identification or confirmation.

General Comments

The genus Rhipicephalus apparently originated in Africa where some 60 species are now

found. These ticks are especially important as

reservoirs and vectors of a variety of animal

diseases. Some of the economically important diseases transmitted or produced by

28
Rhipicephalus ticks include piroplasmosis,

anaplasmosis, theileriosis, tick toxicosis, and

spirochetosîs.

At least three species of Rhipicephalus,

namely R. evertsi, R. pulchellus, and R. appertdiculatus, are occasionally found on zoo-type

animals being held in quarantine at the USDA

Animal Import Center at Clifton, N.J. Other

important species in Africa are R. capensis, R.

pravus, and R. simus.

At the present time, R. sanguineus is the only

species of this genus established in the United

States. However, in 1960 R. evertsi, the redlegged tick, was found on a variety of zoo

animals in two wild animal compounds in

Florida and a game farm in New York. Based

on the degree of infestation and number of

animals infested, the red-legged tick had been

established in one of the zoological compounds

in Florida for approximately 2 or 8 years.

Following an intensive eradication program,

the red-legged tick was eliminated from the

United States by 1961.

Family Argasidae

Morphological Characteristics

of the Family

The family Argasidae, "soft ticks," consists

of those ticks that lack a scutum. Sexual

dimorphism is not marked ; the males closely

resemble the females. Poröse areas are absent.

The capitulum of the nymphs and adults is

always ventral and not visible dorsally, except

for the distal end of the palps, which sometimes

project beyond the anterior margin of the

body. The capitulum is anterior in the larvae.

The spiracular plates usually are located

anterior to coxa IV.

Key to Development Stages

of Fam^ily Argasidae

1. Six legs present Larvae

Eight legs present 2

2. Genital aperture undeveloped; in large

nymphs may appear as a small

depression Nymphs

Genital aperture well developed.. Adults

Key to Genera of Family Argasidae

1. Margin of body thin and acute with a

definite sutural line separating the

dorsal and ventral

surfaces Genus Argas, p. 30

Margin of body thick, rounded, and

without a definite sutural line separating

the dorsal and ventral surfaces .2

2. Integument of nymph covered with

spines. Adult with granular integument

and poorly developed

hypostome Genus Otobius, p. 31

Integument of nymph and adult mammillated and without spines. Adult

with well-developed

hypostome Genus Ornithodoros, p. 30

General Comments

The family Argasidae is represented in the

United States by four genera, three of which

have been found on livestock and poultry—

Argas, Otobius, and Ornithodoros. The fourth

genus, Antricola, has been found in bat guano

and is suspected of feeding on bats.

The Argas persicns complex of species,

although not presently of much economic importance, was once a serious pest of domestic

fowl in Florida and several Southwestern

States. The spinose ear tick, Otobius megnini,

is the only soft tick commonly found on livestock in the United States. Ticks of the genus

Ornithodoros are not usually important parasites of livestock, although several species are

important vectors of the spirochetes of relapsing

fever in man. The principal host of the soft

ticks include birds, rodents, and bats—occasionally livestock and man. (See chart on p. 35).

The South Africans commonly refer to most

soft ticks as tampans, but this term has not

gained acceptance in the United States.

GENUS ARGAS

Morphological Characteristics

of the Genus

Body distinctly flattened with dorsal and

ventral surfaces approximately equal in area.

Margin of body flattened and composed of radial

striae or quadrangular plates. Sutural line

29
present. Integument leathery, minutely wrinkled

in folds, often intermingled with small, rounded

"buttons," each with a pit on top and often

bearing a hair in the pit. Eyes absent. Sexes

similar. Nymphs and adults similar.

The Species of Argas

Due to the complexity of this genus, no key

is included to separate the species of Argas.

See Kohls ei aï (1970).

General Comtnenis

It has been found that the ticks commonly

identified as Argas persicus in the United

States actually represent a complex of species.

The true A. persicus, an Old World species, is

apparently rather rare in the New World. The

common Argas species found in the United

States are A. radiatns and A. sanchezi; a fourth

species. A, miniatus, may also occur, but definite

proof of its presence is still lacking. These four

closely related species have been reported from

domestic poultry in the New World. Argas

radiatns and A. sanchezi have also been found

on various wild birds. Three additional species,

A. brevipes, A. cooleyi, and A. giganteus, have

been reported from or associated with wild

birds in the western United States. The genus

Argas is of little economic importance as pests

of livestock in the United States.

GENUS ORNITHODOROS

Morphological Characteristics

of the Genus

Capitulum either subterminal or distant from

anterior margin. Hypostome well developed and

essentially alike in both adult sexes and in

nymphs. Integument with discs and mammillae

commingling in a variety of patterns. Hood,

camerostome, and checks present or absent.

Eyes present or absent. Dorsal humps and

subapical dorsal protuberances on legs progressively more prominent in successive nymphal

stages. Body more or less flattened but strongly

convex dorsally when distended. Integumental

pattern continuous over sides from dorsal to

ventral surfaces.

Key to the Adults

Most Commonly Found on Livestock

in the United States

1. Cheeks present Ornithodoros talaje

Cheeks absent 2

2. Eyes present (on sides of body above

second and third coxae). Tarsus IV

with prominent subapical dorsal protuberance. (Reported from Pacific

Coast of California and

Mexico) Ornithodoros coriaceus

Eyes absent. Tarsus of leg IV without

subapical dorsal

protuberance Ornithodoros turicata

General Comments

This genus is well represented in the United

States, especially in the Southwestern and

Western States, with some 15 species being

reported. Several species occasionally attack

livestock, but generally Ornithodoros ticks are

not a problem as pests of domesticated animals.

This genus is primarily significant as the vector

of spirochetes of relapsing fever in man.

Ornithodoros turicata, the relapsing fever

tick, and 0. talaje, which has no common name,

occasionally attack domestic animals in the

United States. These species have been reported

from the Southwestern States and Florida.

They are not known to be vectors of livestock

diseases, but are vectors of relapsing fever in

man in the Southwestern States.

O. coriaceus, the pajaroello tick, has been

taken from cattle and deer in California and

the Pacific Coast region of Mexico. It readily

attacks man and its venomous "bite" is said to

be very painful. This tick, however, is not

known to be a disease vector.

In other areas of the world, particularly

Africa and Asia, Ornithodoros ticks are important as reservoirs and vectors of diseaseproducing organisms of man and animals. Some

of these species are O. erraticus of northern

Africa, Portugal, and Spain, O. tholozani of

central Asia, O. savignyi of Africa and Asia,

and the O. moubata species complex of Africa.

30
GENUS OTOBIUS

Morphological Characteristics of the Genus

Integument of nymph covered with spines.

Integument of adult granulated. Sexes similar.

Capitulum distant from the anterior margin in

adults, near the margin in nymphs. Hood and

eyes absent. Hypostome well developed in

nymphs, vestigial in adults.

Key to the Nymphs

Integument with numerous heavy spines

anteriorly and lighter spines posteriorly.

Dentition of hypostome 4/4. Spiracles

conical O. megnini

Integument with numerous spines all of

one size. Dentition of hypostome 3/3.

Spiracles convex O. lagophilm

Key to the Adults ^

Pits on dorsal surface of body separated

by a distance of two or more times the

diameter of one pit Otohius megnini

Pits on the dorsal surface of body separated by a distance of the diameter or

less of one pit O. lagophilus

General Comments

The genus Otohius presently contains only

two species, 0. megnini and O. lagophilits, both

of which are found in the United States. The

spinose ear tick, O. megnini, is a common and

important pest in the Southwestern States. It

is primarily reported from livestock, particularly cattle and horses, although other domestic

and wild animals are attacked. The larval and

nymphal stages are found in the ears. The

nymph is easily recognizable by the spines on

the integument and the violin-like shape of the

body. The adult stage of O. megnini differs

from the nymphal stages in that the integument

lacks spines ; the hypostome is poorly developed,

and it does not feed.

The spinose ear tick is the only species of

Otobiiis reported from livestock. Otohius lagophilus is found on rabbits in the western United

States, Mexico, and Alberta, Canada. Like 0.

megnini, the adults of 0. lagophilus are not

parasitic.

• The adults are not parasitic and are not likely to be

found on animals.

XII. COLLECTING AND PRESERVING TICKS

Finding ticks on an animal often requires

careful examination of all parts of the animal.

Some species of ticks, such as the spinose ear

tick, tropical horse tick, and the larval and

nymphal stages of the red-legged tick, are

almost always attached in the ear of the host.

Other species prefer the thin skin between the

hind legs, under the base of the tail, or on the

brisket. Some ticks have been collected from

the eyelids and the tongues of animals. In inspecting an animal for ticks, use the fingers as

well as the eyes, for often a tick that cannot

be seen may be felt. If possible, watch a trained

tick inspector at work and note how carefully

he moves his fingers over an animal.

Female ticks, ordinarily much larger than the

males, are easy to find. Careful scrutiny of the

area near the female tick frequently will also

reveal a tiny male tick.

Remove ticks from the host carefully so as

not to break off the capitulum (false head) —

especially in removing ticks with long mouth31
parts such as Ixodes and Amblyomma species.

Forceps are useful to grasp the tick near the

head end and "tease" it off. Ticks with short

mouthparts, as in the cattle fever tick, are

readily removed without injury.

Ticks often may be collected from grass and

other vegetation, where they are awaiting a

host, by dragging a flannel cloth over the area.

This procedure is referred to as "dragging" or

"flagging" for ticks. The drag is made by

attaching one end of the flannel cloth (about

30" X 60") to a piece of wood, such as a

broomstick, to which a strong cord is attached

for a towline.

For use in brush or scrub, Stampa's modification of the drag or flag is recommended. The

drag is cut into tails, slightly weighted, so that

they will fall between the higher twigs and

come into contact with the inner parts of the

brush where the ticks are often found.

Blood tubes or screwcap vials are satisfactory

containers for tick specimens. Cattle fever ticks

and other disease vectors should be put in vials

containing a preserving fluid before removal

from an infested property. Tick specimens can

be preserved in 70 percent isopropyl alcohol

(rubbing alcohol).

Ticks from different species of hosts should

never be mixed. For example, ticks collected

from cattle should not be mixed with ticks

collected from horses, even when collected on

the same farm or ranch.

Any additional information is valuable in

determining the distribution of a species of

tick. For example, "Four ticks were collected

from inside ear and two ticks from between

hind legs of a young Hereford cow. Animal

pastured in dense woodland and only 1 in herd

of 20 found to be infested. This animal was

purchased about 1 month ago from Paul Cannon

at Coleman, Texas."

Where to Submit Ticks for Identification or

Confirmation—All suspected cattle fever ticks

and other exotic species should be forwarded

for confirmation and cataloging through the

area Veterinarian in Charge to ;

Veterinary Services Laboratories

APHIS, USDA

Parasitology Laboratory

Bldg. 322, BARC-East

Beltsville, Maryland 20705

Each tick or group of ticks collected from

an animal should be properly labeled, and if

possible, should always include at least the

following information :

(1) Type animal from which specimen (s) taken Cow, Hereford

(2) Geographical location where ticks are collected

(city, county, and State).

Hamlin, Jones County, Texas

(3) Owner's name and address ^ D. W. Scott

(4) Number of specimens 7 ticks

(5) Collector's name B. F. Hall

(6) Date collected October 21, 1974

" This may not always be the same as (2).

32
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35
XIV. LIFE HISTORY SUMMARIES OF SELECTED TICKS

OF VETERINARY IMPORTANCE

The data presented in each of the following

life history summaries was collected from a

number of sources. The intent is to present a

picture of possible tick development for selected

species of ticks. A tick may not necessarily

complete all stages of the life cycle within the

period of time given in the life history summary. The life history summaries indicate the

wide range of variation which may be possible with a given species of tick. This information was obtained in the laboratory or under

simulated field conditions and does not necessarily indicate the rate of development under

natural field conditions.

Assuming that the relative humidity and

precipitation are adequate for survival, temperature is the most important factor affecting

the length of the life cycle. Generally, the

parasitic period for each species is relatively

constant in length, but the nonparasitic period

is often highly variable. The lower the temperature is, the longer it takes a tick to go

through the nonparasitic period. For instance,

the life cycle of Haemaphysalis leporispalustris

can be expected to take longer in northern

Pennsylvania than in southern Texas.

Anthlyomma americanum (Linnaeus),

the Lone Star tick

DISTRIBUTION

This tick is distributed from central and

eastern Texas, north into Missouri, and east in

a broad belt to the Atlantic coast. It has also

been reported in Mexico, Guatemala, Guyana,

and French Guiana.

HOSTS

This species has a wide host range. The

adults are commonly found on large mammals

such as cattle, horses, deer, and dogs. Although

the larvae and nymphs attach to the same

hosts as the adults, they prefer to feed on

birds and small mammals. All three parasitic

stages attack man.

LOCATION ON HOST

On livestock, all stages of this tick prefer

attachment to thin-skinned areas such as the

ears, dewlap, escutcheon, axillary region, and

inguinal region ; however, in heavy infestations

they may be found attached all over the body.

SEASONAL ACTIVITY

The Lone Star tick is most commonly found

on livestock in the spring and summer. In the

lower Southern States all parasitic stages have

been taken on hosts throughout the year.

LIFE CYCLE SUMMARY

The following life history information is

adapted from Hooker, Bishopp, and Wood:

Amblyomma americanum is a 3-host tick.

The female lays up to 8,300 eggs

Preoviposition period 5-13 days

Oviposition period 7-23 days

Incubation of eggs 23-117 days

Larvae engorge 3-9 days

Larvae molt 8-26 days

Nymphs engorge 3-8 days

Nymphs molt 13-46 days

Females engorge 9-24 days

Unfed larvae survive up to 279 days

Unfed nymphs survive up to 476 days

Unfed adults survive up to 430 days

ECONOMIC IMPORTANCE

The long mouth parts, capable of deep penetration, make the bite of this tick painful to

man and animals. Suppurating sores form at

the site of attachment inside the ears and

attract screwworms. Chickens are killed by

massive infestations of tick larvae.

Amblyomma americanum is a carrier of the

rickettsia, Coxiella burneti, causative agent of

Q fever. Man and animals are infected by the

feeding of ticks or by inhalation of contaminated dusts and infected tick feces. This tick

is also a vector to man of Rocky Mountain

spotted fever and tularemia. In the Eastern and

Soirtbeni Statei^ A. americanum reportedly

causes tick paralysis in man and in dogs.

36
Amblyomma cajennense (Fabricius),

the Cayenne tick

DISTRIBUTION

In the United States, A, cajennense is limited

to several counties in southern Texas. This

species is widespread throughout Mexico and

Central America and is also found in the Caribbean area and in parts of South America. The

tick derives its name from the locality, Cayenne,

French Guiana, in v^hich it v^as first collected.

HOSTS

All stages of this species attach to man as

well as to livestock. Adults occur in great abundance on horses, mules, donkeys, cattle, dogs,

and a variety of other animals. In many parts

of tropical America, the larvae and nymphs

are extremely abundant and aggressive in

attacking man.

LOCATION ON HOST

Adult ticks prefer to attach between the legs

or on the abdomen. However, in the equine, all

stages of the tick are frequently found inside

the ears and in other natural cavities, as well

as on the flanks, withers, mane, and tail.

In cattle, the tick may be found attached to

any part of the body. This species also has

been found attached to the tongues of young

calves.

SEASONAL ACTIVITY

All stages are found on hosts throughout the

year in areas where this species is established.

LIFE CYCLE SUMMARY

The following life history information is

adapted from Hooker, Bishopp, and Wood :

Amblyomma cajennense is a 3-host tick.

The female lays up to 7,700 eggs

Preoviposition period 9-20 days

Oviposition period average 19.7 days

Incubation of eggs 37-154 days

Larvae engorge 3-7 days

Larvae molt approximately 10 days

Nymphs engorge 3-13 days

Nymph molt 12-105 days

Females engorge .7-12 days

Unfed larvae survive 57-386 days

Unfed nymphs survive, .more than 13.5 months

Unfed adults survive up to 466 days

ECONOMIC IMPORTANCE

Amblyomma cajennense is a very serious pest

of man and animals. In parts of South America,

it is alleged to cause great damage to cattle by

producing *'fever," weakness, and death.

This species is a vector of spotted fever in

Mexico, Panama, Colombia, and Brazil. Experimentally, this tick is capable of transmitting

brucellosis. It is also reported to be capable of

stage-to-stage transmission of Q fever and has

been experimentally infected with Trypanosoma

cruzi.

Amblyomma hebraeum. Koch,

the Bont tick

DISTRIBUTION

Amblyomma hebraeum is a native of southern

Africa. It is found in the Republic of South

Africa in the coastal areas east of Fort Elizabeth, up through Natal and Zululand into the

eastern and northern Transvaal; and in parts

of Mozambique, Botswana, and Rhodesia. It

thrives in a warm, moderately humid climate

on the veld where tall grass and trees provide

shade.

The bont tick has been found in the United

States on several occasions, either on rhinoceroses offered for entry or on rhinoceroses

which had recently been imported. For example,

in June 1966, two rhinoceroses arrived at the

port of Mobile, Ala., enroute to a zoological

garden in California. They were trucked from

Mobile prior to treatment. Veterinary Services

inspectors at Laredo, Tex., learned that the

animals had been held for feed, water, and rest

in Laredo. They collected ticks which were

later identified as A, hebraeum. Meanwhile, the

truck proceeded to El Centro, Calif., where the

rhinoroses were treated prior to proceeding

to destination. The animals were heavily infested with A. hebraeum at the time of treatment.

37
HOSTS

Cattle and antelopes are the preferred hosts

for the adult ticks but a variety of larger

domesticated and wild mammals are attacked.

The larvae and nymphs also feed on the larger

mammals as well as on a number of smaller

ones, particularly wild hares. The immature

stages frequently feed on ground birds and

even reptiles.

LOCATION ON HOST

The adults prefer bare areas of the body,

especially under the tail, on the genitals, teats,

udder, and in the groins and axillae. They are

also found on the dewlap, brisket, and undersides of the abdomen. Larvae and nymphs

attach anywhere on the body.

SEASONAL ACTIVITY

In South Africa, the adults are most abundant on hosts during the late summer and

autumn months.

LIFE CYCLE SUMMARY

The following information is adapted from

Lounsbury and from Nuttall :

Amblyomma hebraeum is a 3-host tick.

The female

lays 10,000-20,000 eggs

Preoviposition period 2-11 weeks

Oviposition period 3-9 weeks

Incubation of eggs 11 weeks-6 months

Larvae engorge 4-9 days

Larvae molt 16 days-3 months

Nymphs engorge 4-8 days

Nymphs molt 18 days-11 weeks

Females engorge 6-10 days

Total 147 days-409 days

Unfed larvae survive up to 346 days

Unfed nymphs survive up to 250 days

Unfed adults survive more than 660 days

In South Africa, at least 9 months are required to complete the life cycle under natural

conditions; in exceptional circumstances 2

years or more may be required. Normally, however, one generation is completed each year.

ECONOMIC IMPORTANCE

The bont tick is a vector of Cowdria ruminantium, causative agent of heartwater in cattle,

sheep, and goats. Rickettsia conori, which produces boutonneuse fever (tick typhus), has

been isolated from this species and it is apparently a vector in the South African veld.

The long mouth parts of A. hebraeum enable

it to produce deep-seated, painful wounds which

often become infected and lead to abscess

formation and infestation with blowfly larvae.

When these ticks occur on the legs and between

the toes of cattle and sheep, they may cause

sores that result in lameness.

Amblyomma maculatum Koch,

the Gulf Coast tick

DISTRIBUTION

In the United States, thi« tick is found primarily in the Southern States bordering the

Gulf of Mexico and along the Atlantic coast. It

is seldom established more than 200 miles

inland. However, Veterinary Services personnel

have found established infestations on sheep

and cattle in several counties in northeastern

Oklahoma. The tick has also been reported

from Mexico and several countries in northern

South America (Colombia, Ecuador, Venezuela) .

HOSTS

The larvae and nymphs engorge primarily on

ground-inhabiting birds, although they are also

found on small mammals. Sheep, mules, horses,

cattle, dogs, and deer are common hosts for

adult ticks. Man is sometimes attacked by the

adults.

LOCATION ON HOST

The larvae and nymphs are found primarily

on the head and neck of birds, and on the head

and ears of small mammals. The adults prefer

to attach to the head, particularly the ears, of

larger mammals, but in heavy infestations may

also%e found efi other areas.^ the^ body.

38
SEASONAL ACTIVITY

The imature stages are found on birds

throughout the year but are most abundant in

the spring and summer. The adults are found on

livestock in the greatest numbers during the

late summer and early fall.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood ; and Bishopp and

Hixon:

Amblyomma maculatum is a 3-host tick.

The female lays up to 18,000 eggs

Preoviposition period 3-9 days

Oviposition period 13-75 days

Incubation of the eggs 21-142 days

Larvae engorge 3-7 days

Larvae molt 7-121 days

Nymphs engorge 5-11 days

Nymphs molt 17-71 days

Females engorge. 14-18 days

Unfed larvae survive up to 179 days

Unfed nymphs survive somewhat longer

than larvae

Unfed adults survive up to 411 days

Due to the limited seasonal activity of the

adult stage, the Gulf Coast tick probably completes one life cycle per year under normal

conditions.

ECONOMIC IMPORTANCE

The Gulf Coast tick has been incriminated as

a producer of tick paralysis in man and dogs in

the Southeastern United States.

This tick causes "tick worry" to domestic

animals and massive infestations result in

great loss of blood, debilitation, and even death.

Heavy infestation of the ears often results in

the development of a condition suitable for

attack by the screwworm, Cochliomyia hominiVOTUX.

Amblyomma variegatum (Fabrîcîus),

the Tropical Bont tick

DISTRIBUTION

The tropical bont tick is a native of Africa

and is widely distributed in Eastern, Central,

and Western Africa. It was introduced into the

West Indies in the mid-to-late 1800's on cattle

imported from Senegal and is now well

established on St. Kitts, Guadeloupe, and

Antigua.

In September 1967, A, variegatum was found

established on St. Croix, U.S. Virgin Islands.

An extensive program of inspection, dipping,

and ground spraying was carried out, and by

May 1970, the tropical bont tick had been

eliminated from St. Croix.

In June 1974, A. variegatum was confirmed

as being established in Puerto Rico. Subsequent

investigations revealed the presence of the tropical bont tick on at least 26 premises in the area

of Cidra and Cayey, some 25 miles south of

San Juan.

HOSTS

The common hosts for adult ticks include

cattle, sheep, horses, goats, antelopes, camels,

and a long list of large wild mammals. Man

has also been reported as a host for the adult

stage. Nymphs feed on a great variety of

mammals of medium and large size, occasionally

including man. Birds are frequently attacked

by the nymphs. The larvae may feed on any of

these hosts but prefer smaller mammals and

birds.

LOCATION ON HOST

The adult ticks are commonly found on the

lower part of the dewlap, brisket, axillae,

abdomen, groins, escutcheon, udder, and external genitalia of the male. They may also be

found on or near the vulva, under the tail, and

in the interdigital cleft. The immature stages

are more likely to attach anywhere on the host.

119
SEASONAL ACTIVITY

The following information is taken from

Hoogstraal (1956) and applies to the Sudan:

"Adults appear towards the end of the dry

season, first males and then females. Populations increase in numbers and remain high

through the rainy season and decrease rapidly

in the dry season, although a few specimens

may be found even then. Larvae and nymphs

gradually become more numerous in the dry

season, and while some nymphs are found

during the rains they are scarce."

LIFE CYCLE SUMMARY

The following information is adapted chieñy

from Walker in Hoogstraal :

Amblyomma variegatum is a 3-host tick.

The female

lays approximately 10,000-12,000 eggs

Preoviposition period 12 days

Oviposition to hatching 53 days

Larval prefeeding period 7 days

Larva feeds 5 days

Premolting period 14 days

Nymphal prefeeding period 7 days

Nymph feeds 5 days

Premolting period 19 days

Adult prefeeding period 7 days

Female feeds 12 days

Total 141 dayö

In areas with one rainy season each year,

only one life cycle is completed per year; in

areas with two rainy periods, two generations

may be expected each year.

ECONOMIC IMPORTANCE

Amblyomma variegatum is a common vector

of Cowdria ruminantium which produces heartwater in cattle, sheep, and goats. This species

is also a vector of Nairobi sheep disease.

Apparently A, variegatum plays a role in the

natural spread of dermatophilosis (bovine

streptothricosis), which is generally accepted

to be produced by Dermatophilus congolensis,

Epidemiological evidence indicates that there is

a relationship between the tropical bont tick

and the development of the disease. In the

laboratory, dermatophilosis has been transmitted from cattle to rabbits by adults of A.

variegatum.

The bite of the adult tropical bont tick is

especially serious since the mouth parts penetrate very deep, resulting in the formation of

wounds and abscesses. Severe lameness may be

caused by the attachment of the ticks in the

interdigital clefts. A definite reduction in the

value of hides and skins is caused by heavy

infestations of A. variegatum.

In some areas the larvae are a serious pest of

man and attach on the legs and around the

waist. Larvae reportedly may burrow under the

skin and cause intense irritation and inflammation. The causative agents of Q fever, caused

by Coxiella bumeti, and boutonneuse fever

(tick typhus), caused by Rickettsia conori, have

been isolated from A. variegatum.

Argas persicus (Oken), the Fowl tick

DISTRIBUTION

Argas persicus is primarily an Old World

species. Careful study ^^ of specimens from the

New World believed to be A. persicus showed

that this tick plus three other closely related

but distinct, valid species are present. The other

species are A. radiatus reported from Florida,

Iowa, Texas, and Mexico; A. sanchezi reported

from Arizona, California, Nevada, New Mexico,

Texas, Utah, and Mexico; and A. miniatus

reported from Panama, Trinidad, Colombia,

Brazil, and possibly the United States (Georgia). Apparently A. persicus is rather rare in

the New World with very limited collections

reported from Maryland, Pennsylvania, Georgia, California, and Paraguay.

In this manual the name Argas persicus

group is used collectively when referring to the

above-named species, although it is recognized

that A. persicus is probably not the common

species encountered in the United States. There

is confusion regarding the validity of older

published material on the distribution, hosts,

identification, and biology of the Argas ticks.

Quite likely many of the older published references to A. persicus in the Southwestern

United States were misidentifications of A.

radiatus and A. sanchezi. All conditions being

equal, the biology of these species is probably

very similar.

'« See Kohls, Hoogstraal, Clifford and Kaiser (1970).

40
HOSTS

In the New World the true A. persicus and

A. miniatus have been collected only from

chickens or chicken houses. Argas radiatus, and

A. sanchezi parasitize poultry and various wild

avian hosts.

LOCATION ON HOST

The fowl tick attaches beneath the wings and

other places where feathers are sparse.

SEASONAL ACTIVITY

The fowl tick occurs in greatest abundance

on birds during the warmer, drier seasons of

the year.

LIFE CYCLE SUMMARY

The following information is chiefly adapted

from Hooker, Bishopp, and Wood :

Argas persicus is a multihost tick.

The female may lay as many as 874 eggs

during her entire life. These are produced in as

many as seven batches with a blood meal proceeding each batch of eggs. The maximum

number of eggs in the first batch is 195 with a

peak of 245 eggs with the third batch. Only 47

eggs were reported from the seventh oviposition.

Preoviposition period. .2 days to several months

Oviposition period in summer usually

4 to 10 days;

Incubation of the eggs. . in summer, usually

8-11 days; in winter,

up to 107 days

Larvae engorge 2-10 days

Larvae molt 4-17 days

Nymphs (1st, 2nd, and 3rd

stage) engorge approx. 30 min.-2 hours

1st stage nymphs molt 7 to 28 days

2nd stage nymphs molt. . in summer,

11-24 days; in winter,

up to 195 days

3rd stage nymphs molt 9-12 days

Females may engorge as many as

7 times and feed each

time for approx 30 min.-2 hrs...

Unfed larvae survive in cool weather,

up to 164 days;

in mid summer,

about 60 days

Nymphs survive, .up to 509 days for 2nd stage

Unfed Adults survive, .up to 2 years and 5 mos.

(Some authors report longer periods.)

ECONOMIC IMPORTANCE

These ticks may inflict extensive skin damage

and produce large blood clots on their natural

hosts during feeding. Light infestations cause

emaciation, weakness, slow growth, and lowered

egg production. Heavy infestations cause exsanguination and death of the host. Turkeys and

newly hatched poults and chicks show the

greatest mortality. Birds are attacked more

freqeuntly during the warmer, drier seasons

of the year.

Argas persicus is the chief vector of

Borrelia anserina, causative agent of a highly

fatal spirochetosis in chickens, turkeys, pheasants, doves, and pigeons. It also transmits

Aegyptianella pullorum which produces fowl

piroplasmosis in chickens and geese.

Gothe reported tick paralysis in chickens

infested with the South African strain of A.

persicus.

The authors observed tick paralysis in a

southern Maryland flock of chickens infested

with A, persicus; 85 percent of the birds died

within 1 month of being placed in the infested

chicken house.

While A. persicus is not known to transmit

any human diseases naturally, its bite has been

reported to cause severe pain. The true A,

persicus rarely attacks man and other mammals.

Boophilus annulatus (Say),

the Cattle Fever tick

DISTRIBUTION

At the beginning of the 1900's the cattle-fever

tick was widely distributed throughout the

Southern United States. The species is now

eradicated from the United States except for

periodic introductions on illegal movements or

stray cattle from Mexico where Boophilus

annulatus is still prevalent. This species is also

found in western and central Africa, and the

Sudan. If B. calcaratus is synonomous with B,

annulatus, the range is extended to the Mediterranean basin and the Near East.

II
HOSTS

Cattle are preferred hosts ; horses are next in

preference; and sheep and goats are rarely

attacked. Under certain conditions deer may

serve as suitable hosts. Attachment to man and

dog has been reported, but neither is considered

to be a satisfactory host for the development of

B. annulatus.

LOCATION ON HOST

The cattle fever tick prefers to attach on the

dewlap, brisket, neck, axillae, abdomen, groins,

escutcheon, and the genitalia. Larvae and

nymphs may be found in the ears. In severe

infestations ticks may be found any place on

the body.

SEASONAL ACTIVITY

In the lower portion of the Southern States,

prior to eradication, all parasitic stages were

found on livestock throughout the year. However, in both the upper and lower Southern

States B, annulatus was most abundant on livestock during the spring, summer, and early fall.

LIFE CYCLE SUMMARY

The information given below is adapted from

the following sources: Hunter and Hooker;

Hooker, Bishopp, and Wood; Bishopp; and

Graybill.

Boophilus annulatus is a 1-host tick.

The female lays as many as 4,500 eggs

Preoviposition period 2-66 days

Oviposition period 6-70 days

Incubation of the eggs 19-202 days

Larvae engorge and molt 5-16 days

Nymphs engorge and molt 5-18 days

Females engorge 4-14 days

Unfed larvae survive. up to 246 days

The minimum parasitic period (from the attachment of larvae to dropping of engorged

females) is 20 days; the maximum parasitic

period is 59 days; and the average is 32 days.

The nonparasitic period (from the dropping

of the engorged female to death of the last

larva) may be as short as 28 days in the

summer or extend up to 288 days, particularly

if the engorged female drops in late summer^or

early fall.

Under very favorable conditions, particularly

in the southern part of the old cattle fever tick

infested area, as many as three or four generations of B. annulatus are possible each year.

Fewer generations are capable of being produced each year in the northern part of the old

cattle-fever tick zone because of the lower

temperature.

ECONOMIC IMPORTANCE

This tick was once the most important

external parasite of cattle in the Southern

States. It caused serious economic loss by transmitting Babesia bigemina, causal protozoan of

cattle fever (bovine piroplasmosis). The fever

not only caused death in cattle but secondary

losses also included: (1) weakened condition

and stunted growth, (2) death due to gross

tick infestation, (3) losses of potential markets

by both northern and southern cattle breeders,

(4) restriction on movement of southern cattle,

(5) lowered milk production, (6) damage to

hides and skins, (7) cost of maintaining

quarantine line and facilities, (8) expenses incurred in attempt to reduce or eliminate ticks,

and (9) infested animals predisposed to attacks

by screwworms in Texas. In 1907, the primary

and secondary losses due to Boophilus ticks in

the United States were estimated to be $100

million each year.

The cattle fever tick has been incriminated in

the transmission of bovine anaplasmosis. Experimentally, this species has transmitted, via

its eggy the spirochete, Borrelia theileri, causative agent of spirochetosis in cattle, sheep,

goats, and horses. Also, experimentally, this

species has transmitted Theileria mutans,

which causes benign bovine theileriosis.

Boophilus decoloratus (Koch),

the Blue tick

DISTRIBUTION

The blue tick is widely distributed in western,

central, eastern, and southern Africa.

HOSTS

Cattle are the chief hosts; horses are the

second preference, with sheep and goats less

frequently parasitized. Antelopes are the most

important wild hosts.

42
LOCATION OF HOST

The blue tick is commonly found on the

dewlap, brisket, neck, axillae, udder, groins,

scrotum, and escutcheon. Larvae and nymphs

are often found on the distal half of the ear

flap. In heavy infestations ticks may be

scattered over most of the body.

SEASONAL ACTIVITY

The blue tick is usually found on hosts

throughout the year, with the greatest abundance and activity occurring during the warmer

months.

LIFE CYCLE SUMMARY

The following information is adapted from

Lounsbury in Theiler and du Toit and Theiler.

BoopMlus decoloratus is a 1-host tick.

The female lays up to 2,500 eggs

Preoviposition period 6-9 days

Oviposition and incubation period... 3-6 weeks

Larvae engorge and molt 7 days

Nymphs engorge and molt 7 days

Females engorge 7-9 days

In South Africa, the engorged female usually

drops from the host 21-23 days after attaching

as the larva.

ECONOMIC IMPORTANCE

The blue tick is one of the most common ticks

attacking cattle in parts of Africa. It is an

important transmitter of the following diseases :

bovine piroplasmosis (Babesia bigemina and B.

bovis), anaplasmosis (Anaplasma marginale

and A. centrale), and spirochetosis (Borrelia

theileri) of cattle, sheep, and goats. In addition

to transmitting the above diseases, cattle are

often heavily infested with blue ticks resulting

in severe anemia, weakness, and death due to

blood loss.

Boophilus microplus (Canestrîni),

The Tropical Cattle tick

DISTRIBUTION

Boophilus microphis is found in the hotter,

more humid parts of the West Indies, Mexico,

Central America, South America, Africa.

Australia, the Orient, and Micronesia. At one

time it was also established in southern Florida

and in several counties in extreme southern

Texas.

HOSTS

Apparently B. microplus has a slightly wider

host preference than B. annnlatus. The primary

hosts for B, microplus are cattle, with horses

as the second preference. It is found more

commonly on goats, sheep, and deer than is

B, annulatus.

LOCATION ON HOST

On the primary host, this tick is commonly

found on the dewlap, brisket, neck, axillae,

groins, abdomen, escutcheon, and the genitalia.

Larvae and nymphs sometimes may be found

in the ears.

SEASONAL ACTIVITY

Larvae, nymphs, and adults may be found on

the host through the year in tropical and subtropical areas.

LIFE CYCLE SUMMARY

The following information is adapted from

several sources including Täte ; Hooker, Bishop,

and Wood ; Hitchcock ; and Legg :

Boophilus microplu^ is a 1-host tick.

The female lays as many as 4,400 eggs

Preoviposition period 2-39 days

Oviposition period 4-44 days

Incubation of the eggs 14-146 days

Larvae engorge and molt 7-12 days

Nymphs engorge and molt .5-17 days

Females engorge 5-23 days

Unfed larvae survive up to 240 days

In Puerto Rico, the minimum parasitic period

(from the attachment of larvae to dropping of

engorged females) is 18 days; the maximum

parasitic period is 37 days; but the greater

number of females engorge and drop by the

25th day. The length of the life cycle may range

from 41 to 300 days. Under favorable tropical

conditions, B. microplus may produce more

than four generations each year.

ECONOMIC IMPORTANCE

Boophilus microplus is a reported vector of

the following agents : Babesia bigemina and B.

argentina, which cause piroplasmosis in cattle.

13
Anaplasma marginale, which produces bovine

anaplasmosis ; and Theileria mutans, causative

agent of benign bovine theileriosis.

Dermacentor albipictus (Packard),

the Winter tick

DISTRIBUTION

This tick is widely but unevenly distributed

in the northern tier of States from Maine to

Oregon and throughout the Western States

south into Texas and Mexico. It is also widely

distributed in Canada.

HOSTS

The common hosts for D. albipictus include

horses, cattle, deer, elk, and moose.

LOCATION ON HOST

This tick prefers to attach on the dewlap,

brisket, abdomen, groins, and axillae but may

be found attached all over the body in heavy

infestations.

SEASONAL ACTIVITY

As the name indicates, D, albipictus is a

winter tick ; it occurs on livestock from autumn

until early spring.

LIFE CYCLE SUMMARY

The following information is adapted from

Bishopp and Wood:

Dermacentor albipictus is a 1-host tick.

The female lays as many as 4,400 eggs

Preoviposition period 7-134 days

Oviposition period 19-42 days

Incubation of the eggs 33-71 days

Larvae engorge and molt 9-20 days

Nymphs engorge and molt, .usually 9-12 days

Females engorge 8-30 days

Unfed larvae survive up to 346 days

On livestock, the parasitic period ranges from

approximately 28 to 60 days. The nonparasitic

period (from the dropping off of the engorged

female to death of last larva) ranges from 159

to at least 479 days. Under natural conditions

the winter tick produces one generation a year.

44

ECONOMIC IMPORTANCE

Heavy infestations of the winter tick inflict

severe losses among deer, elk, and moose.

Animals become weakened and often die as a

result of the parasitism. Cattle, and especially

horses, may also be seriously affected by attacks

of this tick.

Under experimental conditions D. albipictus

is a vector of Anaplasma marginale, which

produces bovine anaplasmosis.

Dermacentor andersoni Stiles

Synonym^ Dermacentor ventustus Banks,

the Rocky Mountain wood tick

DISTRIBUTION

This tick is found from the western counties

of Nebraska and the Black Hills of South

Dakota to the Cascade and Sierra Nevada

Mountains, and from northern Arizona and

northern New Mexico to British Columbia,

Alberta, and Saskatchewan, Canada.

HOSTS

Important hosts for the adult stage include

cattle, horses, deer, dogs, man, elk, and several

other large mammals. The immature stages

prefer many small mammals such as chipmunks,

ground squirrels, meadow mice, woodchucks,

and rabbits.

LOCATION ON HOST

The adults prefer to attach on the head,

neck, shoulders, dewlap, brisket, groins, and

escutcheon. Immature stages usually attach

around the head, neck, and shoulders of small

mammals.

SEASONAL ACTIVITY

Adults usually begin showing up on hosts in

February or March, reach a maximum abundance during April and May, and decline in

numbers by July. Immatures occur somewhat

later than do the adults; nymphs appear on

hosts early in April; larvae appear on hosts

early in June; and both disappear from hosts

by late summer.
LIFE CYCLE SUMMARY

The following information is adapted from

Hunter and Bishopp ; and Hooker, Bishopp, and

Wood:

Dermacentor andersoni is a S-host tick.

The female lays as many as 7,400 eggs

Preoviposition period 6-41 days

Oviposition period 15-32 days

Incubation of the eggs 15-51 days

Larvae engorge 2-8 days

Larvae molt 6-21 days

Nymphs engorge 3-9 days

Nymphs molt usually 11-19 days

Females engorge 8-17 days

Unfed larvae survive up to 117 days

Unfed nymphs survive over 300 days

Unfed adults survive up to about 600 days

The normal life cycle requires 1 or 2 years

for completion, with the 1-year cycle being

common where small mammals are abundant.

A 3-year cycle may exist at high altitude and

at the northern limits of the tick's range.

ECONOMIC IMPORTANCE

In the Northwestern United States, D,

andersoni is very important as a parasite of

man and livestock. It is the primary vector of

Rickettsia rickettsi, disease agent of Rocky

Mountain spotted fever, and it is also the chief

producer of tick paralysis in man and animals.

Other diseases transmitted or carried by this

tick include Colorado tick fever of man,

tularemia, and Q fever.

Bovine anaplasmosis is an important livestock disease suspected of being transmitted by

D. andersoni in the Northwestern States.

Causative agents of other diseases such as

canine piroplasmosis and arthropod-borne encephalitis (Western type) have been experimentally transmitted by D. andersoni, but there

is no evidence to indicate that disease transmission is a problem under natural conditions.

Dermacentor nitens Neumann

Synonym, Anocentor nitens (Neumann),

the Tropical Horse tick

DISTRIBUTION

In the United States, the tropical horse tick

is established only in southern Florida and

several counties in the extreme tip of southern

Texas. This tick is also common in Mexico,

Central America, the West Indies, and northern

South America.

HOSTS

The horse and other domesticated equines are

the preferred hosts, but it also occurs on cattle,

deer, sheep, and goats.

LOCATION ON HOST

The ears are the preferred site of attachment

for the tropical horse tick. This tick is unusual

because the larvae, nymphs, and adults all occur

in the ears. Ticks also attach in the nasal

diverticula, perianal area, groins, mane, and on

the abdomen. In heavy infestations, ticks may

be found all over the body.

SEASONAL ACTIVITY

All parasitic stages may be found on the host

throughout the year in enzootic areas.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood ; and Täte :

Dermacentor nitens is a 1-host tick.

The female lays as many as 3,400 eggs

Preoviposition period 3-15 days

Oviposition period 15-37 days

Incubation of the eggs 21-28 days

Larvae engorge and molt 8-16 days

Nymphs engorge and molt, .approx. 7-14 days

Females engorge 9-23 days

Unfed larvae survive up to 71 days

The minimum parasitic period reported is 26

days ; the maximum parasitic period is 41 days;

but the majority of the females probably

engorge and drop well before the maximum

period is reached. Under favorable tropical conditions several generations are completed each

year.

15
ECONOMIC IMPORTANCE

Dermacentor nitens is a vector of Babesia

caballi, one of the organisms which causes

equine piroplasmosis.

This tick is a serious pest of horses in tropical

and subtropical areas where it is established.

The ears may literally become filled with ticks,

molted skins, and excrement which develop a

very offensive odor. Infection and suppuration

often follow and predispose the animal to

attack by the screwworm, Cochliomyia hominivorax. Massive infestations of D. nitens can

cause anemia, loss of weight, and even death.

Dermacentor occidentalis Marx,

the Pacific Coast tick

DISTRIBUTION

As the common name implies, D. occidentalis

is confined to the Pacific Coast. It is established

in and to the west of the Cascade Range and

Sierra Nevada Mountains in Oregon and California. It has also been found in northern Baja

California, Mexico.

HOSTS

The common hosts for the adult stage include

cattle, horses, deer, dog, sheep, and man. Immature ticks are found on a variety of smaller

mammals such as chipmunks, ground squirrels,

field mice, and wood rats.

LOCATION ON HOST

The adult is the only stage commonly found

on livestock and it may be found distributed

over the host's body.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood :

Dermacentor occidentalis is a 3-host tick.

The female lays up to 4,500 eggs

Preoviposition period 4-17 days

Oviposition period approx. 14 days

Incubation of the eggs 16-38 days

Larvae engorge 3-7 days

Larvae molt 6-12 days

Nymphs engorge 4-9 days

Nymphs molt 13-22 days

Females engorge 6-17 days

Unfed larvae survive up to 124 days

Unfed nymphs survive up to 108 days

Unfed adults survive up to 359 days

ECONOMIC IMPORTANCE

This tick apparently plays a role in the

maintenance and spread of bovine anaplasmosis.

In California, it has also been found associated

with cases of tick paralysis in livestock.

Dermacentor occidentalis is capable of transmitting the causative agents of tularemia and

Rocky Mountain spotted fever, and it has been

found naturally infected with the virus of

Colorado tick fever and the rickettsia of Q

fever.

Dermacentor variabilis (Say),

the American dog tick

DISTRIBUTION

This tick is widely distributed over the

eastern half of the United States, and in parts

of California, Idaho, Oregon, Washington, and

Montana. It is also established in areas of

Canada and Mexico.

SEASONAL ACTIVITY

The larvae and nymphs are most abundant

on hosts in the spring and summer. Adults

have been taken from livestock throughout the

year but seem to reach a peak of abundance in

April and May.

HOSTS

The common hosts for the adult stage include

man, dogs, cattle, horses, deer, and many other

wild and domesticated mammals. The immature

stages engorge mainly on small rodents, especially meadow mice.

46
LOCATION ON HOST

Adults seem to prefer to attach on the neck,

dewlap, brisket, axillae, groins, genitalia, abdomen, and escutcheon. In massive infestations

they may be found all over the body. Immature

stages feed mainly around the head, neck, and

shoulders of small mammals.

SEASONAL ACTIVITY

In the Central and Northern States, adult

activity begins around mid-April, peaks in

June, and thereafter declines until September.

In the Southern States, ticks in all stages may

be found on hosts throughout the year, although

they are usually more abundant in the spring.

LIFE CYCLE SUMMARY

The following information is adapted from

Smith, Cole, and Gouck; and Bishopp and

Smith :

Dermacentor variabilis is a 3~host tick.

The female lays approximately 6,500 eggs

Preoviposition period 3-58 days

Oviposition period 14-82 days

Incubation of the eggs 2&-57 days

Larvae engorge 3-13 days

Larvae molt 6-247 days

Nymphs engorge 3-11 days

Nymphs molt 24-291 days

Females engorge 5-27 days

Unfed larvae survive up to 540 days

Unfed nymphs survive up to 584 days

Unfed adults survive up to 1,053 days

In the Southern States, the life cycle may

possibly be completed in 1 year, but in the

Northern States the 2-year cycle may be more

common.

ECONOMIC IMPORTANCE

Dermacento?' variabilis is the principal vector

of Rickettsia rickettsi, the causative organism

of Rocky Mountain spotted fever of man, from

the Mississippi Valley east to the Atlantic

Ocean and south to the Gulf of Mexico, including Texas and Oklahoma. This tick also produces tick paralysis in man and dogs.

The American dog tick transmits the disease agent of tularemia and it is partially

responsible for the maintenance of infection in

rodents in nature. Stage-to-stage, but not transovarial, transmission of bovine anaplasmosis

(Anaplasma marginale) has been demonstrated

with this tick.

Haemaphysalis leachi leachi ^^

(Audouin), the Yellow dog tick

DISTRIBUTION

The yellow dog tick is distributed throughout

the Ethiopian zoo-geographical realm, except in

desert areas receiving less than 20 inches

rainfall annually.

HOSTS

The dog is the primary host for the adults of

H, L leachi, but they may also be found on cats

and the larger wild carnivores. Immatures

usually parasitize field rodents but may feed on

domestic dogs.

LOCATION ON HOST

The neck and shoulders are the preferred

attachment sites.

SEASONAL ACTIVITY

Haemaphysalis L leachi is most abundant on

hosts during the warmer seasons of the year.

LIFE CYCLE SUMMARY

The following information is adapted from

Theiler; and Nuttall:

Haemaphysalis L leachi is a 3-host tick.

The female lays up to 4,800 eggs

Preoviposition period 3-7 days

Incubation of the eggs 26-37 days

^^ The subspecies Haemaphysalis leachi muhsami Santos Dias is also widely distributed in Africa. It is

smaller in size and prefers to feed on small carnivores,

such as mongooses, and wildcats, instead of on wild or

domestic canines. Disease relationship of H, L muhsami are unstudied.

47
Larvae engorge 2-7 days

Larvae molt about 30 days

Nymphs engorge 2-7 days

Nymphs molt 10-16 days

Females engorge 4-16 days

Egg to egg 81-120 days

Unfedlarvaemay survive. .6 months or longer

Unfed nymphs may survive.. 2 months or longer

Unfed adults may survive.. 7 months or longer

In nature, the yellow dog tick apparently

produces two generations each year.

ECONOMIC IMPORTANCE

The yellow dog tick transovarially transmits

Babesia canis (canine piroplasmosis). Like

many other ticks, it has been found naturally

infected with Coxiella burneti, which causes

Q fever.

In South Africa, urban cases of boutonneuse

fever are associated with dogs infested with

adults of H, I, leachi. Human infection is often

acquired by contamination of the skin and eyes

with Rickettsia conori from yellow dog ticks

which are crushed as they are picked off dogs.

Haemaphysalis leporispalustris

(Packard), the Rabbit tick

DISTRIBUTION

This tick is widely distributed in North

America, from Alaska and Canada southward

into Mexico. It has also been reported from

parts of Central and South America.

HOSTS

Rabbits are the preferred hosts for the adult

stage of this tick. Birds of many kinds, especially ground-inhabiting birds, and small mammals serve as hosts for the immature stages.

Veterinary Services personnel have also taken

several collections of nymphs from cattle and

deer.

LOCATION ON HOST

On rabbits, the ticks usually attach to the

ears, around the eyes, and on other parts of the

head. The favorite attachment sites on birds are

the top and back of the head and around the

eyes and ears.

SEASONAL ACTIVITY

In the Southern States, H. leporispalustris

may be found on hosts throughout the year, but

is more abundant on hosts in spring and fall.

In the Northern States, this tick is usually not

found on hosts during the winter, and is most

abundant during the spring and summer and

declines in the fall.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood; and Rohr and

Hadwen in Nuttall and Warburton :

Haemaphysalis leporispalustris is a 3-host

tick.

The female lays. up to 2,400 eggs

Preoviposition period .2-18 days

Oviposition period 3-57 days

Incubation period 22-61 days

Larvae engorge. 4-11 days

Larvae molt 18-134 days

Nymphs engorge 4-11 days

Nymphs molt 14-124 days

Females engorge 19-25 days

Unfed larvae survive up to 258 days

Unfed nymphs survive up to 342 days

Unfed adults survive up to 588 days

In the Southern States, under favorable conditions, as many as two complete life cycles

may be completed each year.

ECONOMIC IMPORTANCE

The rabbit tick rarely attacks livestock and

man. It is a common parasite of rabbits and

birds and massive infestations often weaken

and kill them.

This tick plays an especially important role

in the maintenance and spread of Rocky Mountain spotted fever and tularemia among wild

animals. Haemaphysalis leporispalustris is a

carrier of Coxiella burneti, causative agent of

Q fever.

Hyalomma marginatum Koch,

the Mediterranean Hyalomma

DISTRIBUTION

The ticks generally accepted as being

Hyalomma marginatum represent a complex of

48
several subspecies ^^ that are found in southern

Europe, southern Russia, north Africa, the

Middle East, and in scattered areas of other

parts of Africa and Asia.

HOSTS

Common hosts for the adults are cattle,

horses, sheep, goats, and camels. Nymphs also

feed on domestic animals but are more common

on small wild mammals and birds. Larvae feed

only on small animals.

LOCATION ON HOST

These ticks are commonly found in the perianal area, groins, on the genitalia and udder,

axillae, and on the brisket and dewlap.

SEASONAL ACTIVITY

The adults are found on hosts most frequently

in the spring and summer; the larvae and

nymphs are usually found on hosts in the

summer.

LIFE CYCLE SUMMARY

The following information is adapted from

Nuttall (1913).13

Hyalomma marginatum may act as a 2-host

or 3-host tick.

Female lays up to 15,500 eggs

Preoviposition period 6-12 days

Oviposition to hatching 35 days

Larval prefeeding period 7 days

Larvae feed 6 days

Larvae molt 16 days

Nymphal prefeeding period 7 days

Nymphs feed 6 days

Nymphs molt 20 days

Adult prefeeding period. 7 days

Female feeds 6 days

Total ., 116 days

Unfed larvae survive up to 345 days

Unfed nymphs survive up to 89 days

Unfed adults survive over 421 days

^* Hoogstraal and Kaiser recognize several subspecies

of H. marginatum, namely H. marginatum marginatum,

H, marginatum rufipes, H. m,arginatum isaaci^ and H.

marginatum turanicum.

'^ Hoogstraal reports that the life cycle studies of H.

aegyptium conducted by Nuttall were undertaken with

specimens now recognized as H. marginatum.

Apparently one generation is normally produced each year.

ECONOMIC IMPORTANCE

As a group, the genus Hyalomma is of considerable veterinary and medical importance as

vectors and reservoirs of disease-producing

agents. The ticks of the Hyalomma marginatum.

group are reportedly vectors of the diseaseproducing agents of bovine theileriosis (Theileria spp.), equine piroplasmosis (Babesta

caballi and B. equi), and canine piroplasmosis

(B, canis). In man, some of these ticks are

vectors of the virus of Crimean hemorrhagic

fever, Q fever (Coxiella burneti), and boutonneuse fever (Rickettsia conori) and are also

incriminated in the maintenance and spread of

brucellosis (Brucella melitensis).

Hyalomma ticks, other than the H. marginatum

group, are also involved in the transmission of

other disease-producing agents. For example,

some strains of H. truncatum are known to be

involved in the production of sweating sickness

in cattle, sheep, and goats in parts of southern

Africa. Other species of Hyalomma are reportedly able to transmit the causative agents

of bovine anaplasmosis (Anaplasma marginale)

and bovine ehrlichiosis (Ehrlichia bovis).

Ixodes ricinus (Linnaeus),

the European Castor Bean tick

DISTRIBUTION

This tick is common throughout most of

Europe, including the British Isles, and is

found in north Africa (Tunisia and Algeria)

and limited areas of Asia. Contrary to earlier

reports, this tick has never been established in

North America.

HOSTS

Common hosts for the adults include sheep,

cattle, dogs, horses, and deer ; immatures have

been reported from various birds and even

lizards.

LOCATION ON HOST

This tick prefers to attach on areas where

the hair is short or the skin is bare, such as the

face, ears, axillae, groins, and escutcheon.

19
SEASONAL ACTIVITY

In northern areas this species is found on

hosts in the summer. In milder temperate

regions of Eurasia it may have two activity

periods, spring and autumn. In Algeria and

Tunisia it is a winter tick.

LIFE CYCLE SUMMARY

The following information is adapted from

Nuttall (1911):

Ixodes ricinus is a 3-host tick.

The female lays up to 3,000 eggs

Preoviposition period 8-27 days

Oviposition and incubation of

the eggs 42-252 days

Larval prefeeding period 10-570 days

Larvae engorge 3-6 days

Larvae molt 28-140 days

Nymphal prefeeding period 10-540 days

Nymphs engorge 3-5 days

Nymphs molt 56-360 days

Adult prefeeding period 10-810 days

Females engorge 8-14 days

Total 178-2,724 days

Unfed larvae survive up to 19 months

Unfed nymphs survive up to 18 months

Unfed adults survive up to 27 months

As long as 3 years is normally required to

complete the life cycle ; the larvae feed the first

year, the nymphs the second year, and the

adults the third year. Under very favorable

conditions the life cycle may be completed in

less than 3 years.

ECONOMIC IMPORTANCE

In Europe, this species is responsible for

transmitting bovine piroplasmosis (Babesta

bovis), anaplasmosis (Anaplasma marginale),

the virus of louping ill, and tick-borne fever

(Ehrlichia phagocytophila) of cattle, sheep, and

goats. It has been found naturally infected with

the causative agent (Coxiella burneti) of Q

fever.

In Great Britain, /. ricinus is associated with

the production of tick pyemia (Staphylococcus

aureus) in young lambs. Although the ticks are

not thought to transmit the bacteria, the

wounds produced by its feeding permit the

organism to gain entrance readily into various,

parts of the body and produce abscesses.

In European Russia and parts of northern

and central Europe, /. ricinus is the vector of

the virus which causes tickborne encephalitis

in man.

Ixodes scapularis (Say),

Black-legged tick

DISTRIBUTION

This tick is common in the Southeastern

States, Texas, eastern Oklahoma, and along the

Atlantic coast to Massachusetts. Recently it

was found in Wisconsin and Minnesota. It also

extends into Mexico.

HOSTS

The adults prefer to feed on larger mammals

such as cattle, horses, deer, dogs, sheep, hogs,

and man. Larvae and nymphs feed primarily on

birds, small mammals, and occasionally lizards.

LOCATION ON HOST

The adults usually attach on the head and

neck of dogs and other larger mammals.

SEASONAL ACTIVITY

The adults are more abundant on hosts from

late fall to spring; immature stages are more

abundant on hosts in the spring and summer.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood ; and Harris :

Ixodes scapularis is a 3-host tick.

The female lays approximately 3,000 eggs

Preoviposition period 10-19 days

Incubation of the eggs 48-135 days

Larvae engorge 3-9 days

Larvae molt 22-49 days

Nymphs engorge 3-8 days

Nymphs molt 25-56 days

Females engorge 8-9 days

Unfed larvae survive more than 75 days

Unfed nymphs survive more than 60 days

Unfed adults survive undetermined

Under normal conditions, the black-legged

tick apparently completes one life cycle each

year.

50
ECONOMIC IMPORTANCE

At the present time, /. scapularis is not

known to be involved in the natural transmission of disease agents of livestock and man.^*

Experimentally, stage-to-stage transmission of

Anaplasma marginale has been reported. Ticks

have been found naturally infected with

Francisella tularensis and experimental transmission of tularemia has been reported.

Ornithodoros coriaceus Koch,

the Pajaroello tick

DISTRIBUTION

This tick occurs along the Pacific Coast of

California from Humboldt County in the north

to San Diego County in the south. It is also

believed to occur along the coast of Mexico as

far south as the State of Chiapas.

HOSTS

Common hosts are cattle and deer. It also

feeds on man and probably on a variety of

other mammals.

The female tick can lay over 2,000 eggs

in her productive life of 3 or more years.

Preoviposition period 15-55 days

Incubation of the eggs 23-40 days

Larval prefeeding period 3-7 days

Larval feeding 7-10 days

Larval molt 10-28 days

First nymphal stage does not feed

First nymphal molt 8-39 days

Second nymphal molt ^^ 14-30 days

Third nymphal molt 10-60 days

Fourth nymphal molt 16-74 days

Fifth nymphal molt 28-92 days

Sixth nymphal molt 35-114 days

Seventh nymphal molt 33-53 days

Adult feeding i« 15-30 minutes

Total days for complete cycle 202-602

Unfed adults survive for about 9 months

Fed males survive about. .3 years and 7 months

Fed females survive for more than 5 years

The length of the cycle is influenced by the

temperature and availability of hosts. Under

natural conditions there is probably one generation each year, but in many instances, a generation may take 2 years to develop.

LOCATION ON HOST

The nymphs and adults remain in protected

areas under trees in old deer- and cattle-bedding

grounds and attack livestock, wildlife, and man

when they pause in these locations. The ticks

probably feed most readily on an accessible

area, most likely the legs and ventral portions

of the body.

ECONOMIC IMPORTANCE

The pajaroello tick readily attacks man and

livestock and its venomous *'bite" is reported to

be very painful.

Although this species is not known to transmit any disease, it should not be ruled out as a

potential vector until adequate research has

been conducted.

SEASONAL ACTIVITY

In some areas this tick is active throughout

the year, but in other locations it is active only

in the warmer months.

LIFE CYCLE SUMMARY

The following information is adapted from

Loomis; Herms; and Smith.

Ornithodoros coriaceus is a multihost tick.

" Recent reports incriminate /. scapularis as a possible vector of piroplasmosis (Babesia microti) in

humans on Nantucket Island, Massachusetts. Babesia

microti is a parasite of field mice and deer mice.

Otobius megnini (Dugès),

the Spînose ear tick

DISTRIBUTION

The spinose ear tick is a native of the

Americas and is very abundant in the Southwestern and Western United States and Mexico.

It has been carried to other areas of the world

^^ Each nymphal stage, except for the first, generally

feeds for 15-30 minutes.

^®The adults normally feed several times over an

extended period and the female usually lays a batch of

eggs after each feeding.

51
in the ears of the hosts. Otobius megnini is now

established in parts of Africa, Madagascar,

India, and Hawaii, as well as in Canada

(British Columbia) and South America.

HOSTS

The larvae and nymphs are found in the ears

of many large mammals, particularly cattle,

horses, sheep, deer, goats, and dogs. There are

a few reports of human infestations.

LOCATION ON HOST

The larvae and nymphs are found deep in the

ears of the host. Adults do not have functional

mouthparts, do not feed, and are not found on

animals. Careful inspection of the ears is

essential to locate this species. The use of a

curette is needed to establish definitely that

ticks are not present.

SEASONAL ACTIVITY

Immature stages may be found on animals

throughout the year, but the injurious effects

are usually most pronounced in the winter and

spring.

LIFE CYCLE SUMMARY

The following information is chieñy adapted

from Hooker, Bishopp, and Wood :

This is an aberrant 1-host tick. Only the

larval and nymphal stages feed ; the adult stage

completes the life cycle on food obtained during

the second nymphal stage. The last molt, which

produces the adults, occurs in the environment

away from the host.

Female lays as many as 1,500 eggs

Preoviposition period usually 8-12 days

Oviposition period, .approximately 14-180 days

Incubation of the eggs 10-23 days

Larvae engorge and molt 7-12 days

Nymphs ^^ engorge and molt 31-209 days

Adults do not feed

Unfed larvae survive... approximately 80 days

Unmated females survive up to 638 days

Loomis reports that the life cycle may be

completed (in the laboratory) in 62-118 days.

Therefore, under favorable conditions, the

" The spinose ear tick has two nymphal stages.

completion of several life cycles is possible each

year.

ECONOMIC IMPORTANCE

In arid and semiarid areas of the Southwestern and Western States this species is a

serious pest of cattle and horses. By attaching

deep in the ears, it causes considerable irritation and pain. Animals become restless, shake

and rub their heads, and run about until they

become exhausted. Dairy animals produce less

milk and beef cattle often show significant loss

of weight.

The injury produced by the spinose ear tick

predisposes the host to attack by screwworms

(Cochliomyia hominivorax) and secondary bacterial invaders of the inner ear; death often

follows.

Otobius megnini has been found naturally infected with Coxiella burneti and may be an

important focus of infection for livestock.

Rhipicephalus appendiculatus

Neumann, the Brown ear tick

DISTRIBUTION

The brown ear tick is widely distributed in

parts of southern, central, and eastern Africa.

It occurs in the wetter areas and is absent in

deserts and in areas without shrub cover.

HOSTS

This is primarily a cattle tick and all parasitic stages thrive on cattle. Secondary hosts

include sheep, goats, dogs, buffalo, antelopes,

and other mammals. The immatures are reported from hares and other smaller mammals,

but prefer the same larger hosts as the adult

ticks.

LOCATION ON HOST

The following statement is from Yeoman and

Walker :

"By far the most important predilection site

for R. appendiculatus is the inside of the flap

of the ear, in particular the proximal third of

the upper edge, where the fringe of long hairs

grows. Owing to the curvature of the ear, quite

large numbers of ticks can be^ttached ^n Ihia

52
site without being visible to anyone merely

looking at the standing animal. We have known

field staff and cattle owners to deny the presence of any ear ticks but when the animals

were properly restrained and the ears were

opened ticks were found to be numerous."

This direct quotation is used because it

clearly points out the necessity and importance

of carefully examining the ears of imported

livestock and exotic animals.

In heavy infestations ticks may be found

on the head, neck, abdomen, genitalia, and

extremities.

SEASONAL ACTIVITY

In South Africa, the adults are reported to

be most abundant on hosts from November to

March; the immatures are absent on hosts

during this period. The larvae are usually most

abundant on hosts during May through July

and decline in August. The nymphs occur on

hosts from June through September and decline

in October.

LIFE CYCLE SUMMARY

The following information is adapted from

Theiler; and du Toit and Theiler:

RMpicephalus appendiculatits is a 3-host tick.

The female lays up to 5,700 eggs

Preoviposition 5-40 days

Oviposition to hatching 28 days-3 months

Larva feeds 3-7 days

Premolting period 10-49 days

Nymph feeds 3-7 days

Premolting period 10-61 days

Female feeds 4-10 days

Unfed larvae survive up to 10 months

Uaafed nymphs-suxvive.......^^^^ 15 months

Unfed adults survive up to 2 years

In areas where there is a single rainy season

each year, the brown ear tick completes one

life cycle a year. However, in areas with two

rainy seasons each year, as many as three

generations may occur within a 1-year period.

ECONOMIC IMPORTANCE

The brown ear tick is the most important tick

involved in the transmission of East Coast

fever (Theileria parva) of cattle in eastern,

central, and southern Africa. Theileria parva is

not transovarially transmitted as is Babesia

bigemina by Boophilus microplus; instead, only

trans-stadial (stage-to-stage) transmission

occurs. For instance, infection is either picked

up by the larva and transmitted to a susceptible

host by the nymph, or it is picked up by the

nymph and transmitted by the adult. Infection

is not carried through the egg to the larva of

the next generation.

Other protozoal diseases of cattle transmitted

by R, appendiculatus include Corridor disease

(T, lawrencei), benign bovine theileriosis (T.

mntans), and bovine piroplasmosis (Babesia

bigemina).

Three viral diseases of sheep are transmitted

by this tick: louping ill (experimentally),

Nairobi sheep disease, and Kisenyi sheep

disease.

In South Africa, R, appendiculatus has been

associated with the development of tick toxicosis in cattle following very heavy tick

infestations.

The wounds produced by the feeding of the

brown ear tick can become infected and develop abscesses which often result in severe

injury or even loss of the ears.

Rhipicephalus evertsi evertsi

Neumann, the Red—legged tick

DISTRIBUTION

The red-legged tick is widely distributed in

parts of eastern, western, central, and southern

Africa as well as in the mountains of Yemen

in southwestern Arabia.^^

In September 1960, R, e, evertsi was found on

a variety of wild animals confined in two

zoological compounds in Florida and on a wild

game farm in New York. Following a concerted

eradication effort, the red-legged tick was declared eradicated from the United States in

January 1962. This tick is frequently found on

zebras, antelopes, and other wild animals from

Africa which are being held in quarantine prior

to release for entry into the United States.

^® In the very dry regions of southwest Africa, the

subspecies Rhipicephalus evertsi mimeticus Donitz replaces R. e. evertsi. Both subspecies occur together in

the savannahs of western equatorial Africa.

53
HOSTS

The adults commonly occur on domesticated

equines, cattle, goats, and sheep and on wild

antelopes, zebras, and several other large game

animals. Immature stages usually feed on the

same hosts as the adult ticks, but have been

known to occur on smaller mammals such as

hares, elephant shrews, tree rats, and grass

mice.

LOCATION ON HOST

Adults prefer to attach in the peri-anal area,

under the base of the tail, and less frequently

on the teats, groins, and scrotum. Immatures

are found deep in the convolutions of the external ear. A curette should be used in examining the ears for the immature stages.

SEASONAL ACTIVITY

This tick can occur on hosts throughout the

year but is more active in the summer than in

the winter.

LIFE CYCLE SUMMARY

The following information is adapted from

Theiler; and du Toit and Theiler:

Rhipicephalus e. evertsi is a 2-host tick.

Female lays 5,000-7,000 eggs

Preoviposition period 6-24 days

Eggs hatch 4-10 weeks

Larvae and nymphs on host 10-15 days

Nymphs molt 42-56 days

Females engorge 6-10 days

Total 92-175 days

Unfed larvae survive up to 7 months

Unfed adults survive up to 14 months

ECONOMIC IMPORTANCE

Rhipicephalus e, evertsi is a very important

tick in the areas of eastern, western, central,

and southern Africa where it is established. It

is known to transmit the following diseases:

bovine piroplasmosis (Babesia bigemina),

equine piroplasmosis (B, equi), East Coast

fever (Theileri parva), benign bovine theileriosis (T, mutans), ovine theileriosis (T, ovis),

benign ovine ehrlichiosis (Ehrlichia ovina),^

and spirochetosis (Borrelia theileri) of cattle,

sheep, goats, and horses. The red-legged tick

has been incriminated in the production of tick

paralysis in sheep. Heavy infestations cause

"tick worry.*'

Rhipicephalus pulchellus Gerstacker,

the Zebra tick

DISTRIBUTION

This is an east African tick and is primarily

found from northern Tanganyika through

eastern Kenya into Ethiopia, and Somalia.

Rhipicephalus pulchellus is occasionally found

on zebras and other African animals which are

being held in quarantine at the U.S. Department of Agriculture quarantine facility for the

Port of New York at Clifton, N.J.

HOSTS

This tick is especially fond of zebras, but

likes the rhinoceros and a variety of other large

herbivores. It feeds on common domesticated

animals and readily attacks man. The larvae

and nymphs apparently feed on the same hosts

as the adults.

LOCATION ON HOST

The zebra tick is usually found on the dewlap, brisket, abdomen, axillae, groins, peri-anal

area, and in the tail switch.

SEASONAL ACTIVITY

In enzootic areas this species may be found

on the host throughout the year.

LIFE CYCLE SUMMARY

The following information is adapted from

Walker.

Rhipicephalus pulchellus is a 3-host tick.

Preoviposition period 6 days

Larvae hatch 39 days

Larvae harden i»

Larvae engorge 3 days

Larvae molt 11 days

Nymphs harden i^

Nymphs engorge 3 days

Nymphs molt 15 days

Adult harden i»

Adults engorge 11 days

^* Accurate records of time required by each stage

for hardening were not kept, by¿ this period is^ frequently accepted to be approximately 1 week.

54
ECONOMIC IMPORTANCE

The zebra tick is a vector of the virus of

Nairobi sheep disease.

Since Babesia equi is a very common parasite

in the wild zebra of eastern Africa, this tick

should remain in a suspect category as a potential vector of this protozoal disease-producing

agent of equines.

Rhipicephalus sanguineus

(Latreille), the Brown Dog tick

DISTRIBUTION

Rhipicephalus sanguineus is one of the most

widely distributed tick species in the world. It

is believed to be a native of Africa, but has

been distributed throughout the tropical and

warm-temperate parts of the world with the

migration of man and his dogs. The brown dog

tick is established in North, Central, and South

America, the West Indies, Africa, Madagascar,

the Middle East, East Indies, China, Australia,

Micronesia, southern Europe, and other areas.

HOSTS

In the United States, the brown dog tick

almost exclusively attacks dogs; when it is

found on other hosts such as horses, cattle or

man, there is usually a history of close association with dogs.

In other areas of the world, R. sanguineus

has been reported from a wide variety of

medium- and larere-size mammals and groundfeeding birds. Some of these hosts include

buffalo, camel, cat, cattle, deer, goat, horse,

sheep, lion, zebra, ground-feeding birds (ostrich,

bustard, ibis, hornbill, buzzard), hare, hedgehog, reptiles, and man. This unusually wide

host range leads one to suspect that R, sanguineus has either developed physiological races

with adaptation to particular hosts, or it consists of a complex of distinct species which are

morphologically, if not physiologically, similar

to the classical brown dog tick. In Africa, the

immature stages of R. sanguineus occur on a

wide range of small mammals.

LOCATION ON HOST

On the dog, the adult stage is commonly

found in the ears, along the nape of the neck,

and between the toes. The immatures often

attach in the long hair on the neck. In heavy

infestations, all active stages may be found

attached to the hairy parts of the body.

SEASONAL ACTIVITY

This tick is found on hosts throughout the

year in tropical or subtropical areas. In warmtemperate areas, where definite seasonal changes

occur, ticks are commonly found on hosts from

early spring until fall. Few ticks are found on

animals during the winter. The brown dog tick

is unable to survive outdoors in the Northern

States, but when provided protection in heated

houses and kennels, it is commonly found as far

north as Connecticut.

LIFE CYCLE SUMMARY

The following information is adapted from

Hooker, Bishopp, and Wood; and Nuttall in

Hoogstraal.

Rhipicehalus sanguineus is a 3-host tick.

The female lays approximately 4,000 eggs

Preoviposition period 3-83 days

Incubation of the eggs 8-67 days

Larvae engorge .3-7 days

Larvae molt 6-23 days

Nymphs engorge .4-9 days

Nymphs molt 12-129 days

Females engorge 6-50 days

Unfed larvae survive up to 253 days

Unfed nymphs survive up to 183 days

Unfed adults survive up to 568 days

Under favorable conditions, the life cycle may

be completed in 63 days ; in warm areas, several

generations may be expected each year.

ECONOMIC IMPORTANCE

The brown dog tick is an exceedingly troublesome pest of dogs, causing discomfort, blood

loss, and disease. In the United States, it is a

vector of Ehrlichia canis (—Rickettsia canis),

which causes canine ehrlichiosis, and Babesia

canis, which causes canine piroplasmosis.

The Rhipicephalus sanguineus complex is a

very eflicient vector of many disease-producing

agents. In other areas of the world, it is incriminated in the natural or experimental

transmission of many diseases of man and

animals, including boutonneuse fever (Rickettsia

conori), Rocky Mountain spotted fever (R.

55
rickettsi), spirochetosis (Borrelia theileri)

tularemia (Francisella tularensis), equine piroplasmosis (Babesia caballi and B. equi), anaplasmosis (Anaplasma marginale), Q fever (Coxiella burneti), and other diseases. See Hoogstraal

(1956) and Neitz.

The disease relationships should not be assumed to apply to R. sanguineiis, which is now

established in the United States. The U.S.

"race" of the brown dog tick is not commonly

found on hosts, other than dogs, and it is not

known to be important in the transmission of

diseases other than canine ehrlichiosis and

piroplasmosis. The United States form of R.

sanguineus may or may not be capable of

transmitting all the diseases attributed to it

throughout the world. Nevertheless, the brown

dog tick should remain in a suspect category

until the questions regarding classification and

disease transmission are resolved.

In the United States, R. sanguineus often

becomes an annoying pest in households where

dogs are kept. All active stages may be found

crawling about the walls, curtains, and furniture. The homeowner often becomes greatly

alarmed, but fortunately this tick does not

readily feed on man and is not known to

naturally transmit any disease of man in the

United States. Elimination of brown dog ticks

from premises is difficult because of the hardiness and longevity of all active stages, the ready

availability of the canine host, and the development of acaricidal-resistant strains in some

areas.

XV. CHECKLIST OF THE TICKS OF THE UNITED STATES

Scientific Name Principal Host(s)

Family Argasidae

Genus Argas Latreille :

brevipes Banks

cooleyi Kohls and Hoogstraal

giganteu^ Kohls and CliflFord

miniatus Koch

persicus (Oken)

radiatus Railliet

sanchezi Dugès

Genus Antricola Cooley and Kohls :

coprophilus (Mclntosh)

Owls, sparrow hawk, woodpecker

Cliff swallow

Several wild birds

Chicken

Chicken

Chicken, wild turkey, vulture

Chicken, dove, quail, turkey

Bats

Genus Ornithodoros Koch :

capensis Neumann

concanensis Cooley and Kohls

cooleyi Mclvor

coriaceus Koch

denmarki Kohls, Sonenshine

and Clifford

dyeri Cooley and Kohls

eremicus Cooley and Kohls

hermsi Wheeler, Herms, and Meyer

Ornithodoros kelleyi Cooley and Kohls :

parkeri Cooley

sparnus Kohls and Clifford

stageri Cooley and Kohls

Marine birds

Probably bats

Small mammals

Deer, cattle, man

Marine birds

Bats

Mice

Chipmunks, deer mice, wood rats

Bats

Various small mammals,

burrowing owl

Wood rats

Bats

56
XV. CHECKLIST OF THE TICKS

Scientific Name—Con.

Family Argasidae—Con.

talaje (Guérin-Méneville)

turicata (Dugès)

yumatensis Cooley and Kohls

Genus Otohius Banks :

lagophilus Cooley and Kohls

megnini (Dugès)

Famihj Ixodidae

Genus Amblyomma Koch :

americanum (Linnaeus)

cajennense (Fabricius)

dissimile Koch

imitator Kohls

inornatum (Banks)

maculatum Koch

tuberculatum Marx

Genus Aponomma Neumann

elaphensis Price

Genus Boophilus Curtice

annulatus^^ (Say)

micropluis^^ (Canestrini)

Genus Dermacentor

albipictus (Packard)

andersoni Stiles, syn. D.

venustus Banks

halli Mclntosh

hunteri Bishopp

nigrolineatus (Packard)

mten^ Neumann, syn.

Anocentor nitens (Neumann)

occidentalis Marx

parumapertus Neumann

variabilis (Say)

OF THE UNITED STATES—Con.

Principal Hosts (s)—Con.

Wild rodents

Various rodents, pigs,

burrowing owls

Bats

Rabbits

Livestock

Livestock, deer, birds, man

Livestock, man

Snakes, Iguana

Variety of domestic and wild

animals

Small mammals, cattle, deer

Variety of mammals and birds

Gopher-tortoise

Snake

Cattle

Cattle

Cattle, horses, deer

Variety of mammals

Peccary (Javelina)

Bighorn sheep

Cattle, horses, deer

Horses

Variety of mammals

Rabbits

Variety of mammals

' Not presently established ; occasionally introduced into Texas from Mexico.

;>v
XV. CHECKLIST OF THE TICKS OF THE UNITED STATES—Con.

Scientific Name—Con. Principal Hosts (s)—Con.

Family Ixodidae—Con.

Genus Haemaphysalis Koch

chordeilis (Packard) Birds

leporispalustris (Packard) Rabbits

Genus Ixodes Latreille

aßnis Neumann Deer, small mammals

angusties Neumann : Variety of small mammals

auritulus Neumann Birds

baergi Cooley and Kohls Cliff swallows

banksi Bishopp Small mammals

brunneits Koch Birds

californicus Banks Birds

conepati Cooley and Kohls Hog-nosed skunk

cookei Packard Small mammals

dentatus Marx Cottontail rabbit

diversifossus Neumann Raccoon

eadsi Kohls and Clifford Small rodents

hearlei Gregson Red squirrel

holdenreidi Cooley Pocket gopher

howelli Cooley and Kohls Birds

jellisoni Cooley and Kohls Mice

kingi Bishopp Small mammals

marmotae Cooley and Kohls Woodchucks

marxi Banks Squirrels

minor Neumann Birds

muris Bishopp and Smith Small rodents

neotomae Cooley Small mammals

ochotonae Gregson Pika

pacificiis Cooley and Kohls Variety of mammals

peromysci Augustson Mice

rugosus Bishopp Skunk, dog

scapularis Say Variety of mammals and birds

sculptus Neumann Ground squirrels

signatns Birula Sea birds

soricis Gregson Shrews

spinipalpis Hadwen and Nuttall Small mammals

texanus Banks Small mammals

tovari Cooley Hares

uriae White Marine birds

woodi Bishopp Wood rat

Rhipicephalus Koch :

sanguineus (Latreille) Dogs

3«
XVI. REFERENCES

ALLRED, D. M. and ROÖCOE, E. J.

1956. LIFE HISTORY OF THE TICK DERMACENTOR PARUMAPERTUS IN UTAH. Jour.

Parasitol. 42: 516-522.

ANASTOS, G.

1950. THE SCUTATE TICKS, OR IXODIDAE, OF

INDONESIA. Ent. Americana 30 (1-4) : 1-144.

ARTHUR, D. R.

1960. TICKS (A MONOGRAPH OF THE

IXODOIDEA). PART V. ON THE GENERA

DERMACENTOR, ANOCENTOR, COSMIOMMA,

BOOPHILUS, AND MARGAROPUS. Cambridge at

the Univ. Press, London, 251 pp.

1962. TICKS AND DISEASE. Pergamon Press:

Oxford, London, New York and Paris, 445 pp.

BACHA JR., W. J.

1957. THE LIFE HISTORY OF OTOBIUS

LAGOPHILUS. Jour. ParasitoL 43: 560-565.

BAKER, M. K., and DUCASSE, F. B. W.

1967. TICK INFESTATION OF LIVESTOCK IN

NATAL. I. THE PREDILECTION SITES AND

SEASONAL VARIATIONS OF CATTLE TICKS.

Jour. S. Afr. Vet. Med. Assoc. 38 (4) : 447-453.

1968. TICK INFESTATION OF LIVESTOCK IN

NATAL. THE ROLE PLAYED BY GOATS AS

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1899. THE BONT TICK: (AMBLYOMMA HEBRAEUM (KOCH). ITS LIFE HISTORY AND

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1904. REPORT OF THE GOVERNMENT ENTOMOLOGIST FOR THE YEAR 1903. Cape of

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McINTOSH, A.

1934. DISTRIBUTION OF BOOPHILUS ANNULATUS AUSTRALIS (FULLER) IN THE UNITED

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and McDUFFIE, W. C.

1956. TICKS THAT AFFECT ANIMALS AND

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1968. TICK-BORNE DISEASES OF CATTLE. Vet.

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MOREL, P. C. and VASSILIADES, G.

1962. LES RHIPICEPHALUS DU GROUPE

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1956. A CONSOLIDATION OF OUR KNOWLEDGE

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1926. TICKS (A MONOGRAPH OF THE

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1963. RECENT ADVANCES IN KNOWLEDGE OF

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64
_, COLE, M. M. and GOUCK, H. K.

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WILKINSON, P. R.

1953. OBSERVATIONS ON THE SENSORY

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1964. PASTURE SPELLING AS A CONTROL

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NATURE. Cana. Jour. Zool. 46 (4) : 677-689.

and LAWSON, J. E.

1965. DIFFERENCE OF SITES OF ATTACHMENT OF DERMACENTOR ANDERSONI STILES

TO CATTLE IN SOUTHEASTERN ALBERTA

AND IN SOUTH CENTRAL BRITISH COLUMBIA,

IN RELATION TO POSSIBLE EXISTENCE OF

GENETICALLY DIFFERENT STRAINS OF

TICKS. Cana. Jour. Zool. 43: 408-411.

WILSON, S. G.

1946. SEASONAL OCCURRENCE OF IXODIDAE

ON CATTLE IN NORTHERN PROVINCE, NYASALAND. Parasitol. 37 (3-4) : 118-125.

1953. A SURVEY OF THE DISTRIBUTION OF

THE TICK VECTORS OF EAST COAST FEVER

IN EAST AND CENTRAL AFRICA. Proc. 15.

Inter. Vet. Congr. (1) : 287-290.

YEOMAN, G. H. and WALKER, J. B.

1967. THE IXODID TICKS OF TANZANIA (A

STUDY OF THE ZOOGEOGRPAHY OF THE

IXODIDAE OF AN EAST AFRICAN COUNTRY).

Commonwealth Inst. of Ent., London, 215 pp.

65
HYPOTHETICAL MALE AND FEMALE HARD TICKS

WITH KEY MORPHOLOGICAL CHARACTERS LABELED

LEG IV

PALPUS

SEGMENT 4

SEGMENT 3

SEGMENT 2

SEGMENT 1

SCAPULA

BAèlS CAPITULI

CORNUA

CERVICAL GROOVE

EYE

LATERAL GROOVE

ORNATE MARKINGS

SPIRACULAR PLATE

DORSAL PROLONGATION

FESTOON

TIBIA

TARSUS

PULVILLUS

CLAW

HYPOSTOME

SEGMENT 4

SEGMENTS

SEGMENT 2

SEGMENT 1

BASIS CAPITULI

GENITAL APERTURE

INTERNAL SPUR

GENITAL GROOVE

EXTERNAL SPUR

ANUS

ACCESSORY SHIELD

ADANAL SHIELD

METATARSUS

DORSUM OF MALE VENTER OF MALE

PORÖSE AREA

CORNUA

LATERAL GROOVE

CERVICAL GROOVE

PUNCTATIONS

ORNATE MARKING

MARGINAL GROOVE

COXA I

INTERNAL SPUR

EXTERNAL SPUR

COXA II

COXA III

COXA IV

ANUS

SPIRACULAR PLATE

ANAL GROOVE

DORSUM OF FEMALE VENTER OF FEMALE

66
HYPOTHETICAL SOFT TICKS

WITH KEY CHARACTERS LABELED

SUBAPICAL DORSAL PROTUBERANCE

DORSUM VENTER

LATERAL VIEW

LEG

LEG II

LEG ill

LEG IV

TARSUS

METATARSUS

TIBIA

FEMUR

TROCHANTER

COXA

SUTURAL LINE

DISCS

DORSUM VENTER

67
DORSAL VIEW OF THE SCUTA AND CAPITULA OF SOME FEMALE

IXODIDAE (HARD TICKS), SHOWING CHARACTERISTICS OF THE GENERA

SEGMENT 2

BASIS CARTULI

PORÖSE AREA

- EYE

BOOPHILUS RHIPICEPHALUS HAEMAPHYSAUS

SEGMENT 2

DERMACENTOR AMBLYOMMA IXODES

68
SCHEMATIC LIFE CYCLES AND DISEASE TRANSMISSION OF TICKS

TYPE I

Adults Emerge

From Nymphal Skin

On Host l,Reattach,^s

And Mate

Engorged Fecundated Female

Drops From Host 1

x^.,^-^^ Male May Live Several More Weeks

\

\ /Oviposition Begins

Nymphs Emerge From

Larval Skin On Host

l,Reattachife

Remain When Replete

Larvae Attack Host 1

And Remain

When Replete

Female Dies

\

Larvae Hatch Out

This type has one host and is represented by Boophilus decoloratus, and Dermacentomitens.

The entire life cycle from larva to adult is spent on the same host. Feeding of the tick is

twice interrupted for molting, but the tick remains on the same host. The possibilities for

disease transmission are continuous through all the parasitic stages. Disease organisms taken

up during the parasitic period either die or may be passed transovarially to be transmitted

by the offspring of the tick.

Apparently some disease organisms, especially Babesia spp., may remain in the body of ticks

for as many as five generations, even when fed on non-infected, non-susceptible hosts.

69
SCHEMATIC LIFE CYCLES AND DISEASE TRANSMISSION OF TICKS -Con.

TYPE II

Adults Emerge From Nymphal

Skin While On Ground And

Mate Without Feeding

I

\ / Oviposition Begins

Replete Nymphs

Drop From Host 1

Second Nymphal

Stage Emerges

And Reattaches

To Host 1

Larvae Hatch

First Nymphal Stage

Emerges From Larval

Skin And Reattaches

To Host 1

Larvae Attack Host 1

And Remain When Replete

This aberrant type is found in Otobius megnini, the spinose ear tick. There is one host on

which the larval and two nymphal stages feed. The adult neither attaches nor feeds. Disease

organisms taken up by the larva and nymph either die during or after the parasitic period or

they may remain in the tick body during transformation, enter the egg and may be transmitted by the offspring.

70
SCHEMATIC LIFE CYCLES AND DISEASE TRANSMISSION OF TICKS-Con.

TYPE

Adults Attack

Host 2 and Mate

Replete Fecundated Female

Drops From Host

/ Male May Live Several More Weeks

Adults Emerge

From Nymphal Skin • While On Ground

^ Larvae Hatch Out

Replete Nymphs

Drop From Host 1

Larvae Attack Host 1

And Remam When Replete

Nymphs

Emerge

From

Larval Skin On Host 1

And Reattach

This type, found inRhipicephalus evertsi, has two hosts. The larva and nymph develop on

one host. The nymph drops when replete, molts and the adult attaches to the second host.

Disease organisms acquked by the immature stages either die or remain in the tick during

molting and may be transmitted by the adult to the second host. Disease organisms taken up

by the female either die or may be conveyed via the egg and possibly be transmitted by the

offspring.

71
SCHEMATIC LIFE CYCLES AND DISEASE TRANSMISSION OF TICKS-Con.

TYPE IV

Replete Fecundated Female

Drops From Host 3

Adults Attack

Host 3 And Mate

Adults Emerge From ^

Nymphal Skin While

On Ground

Replete Nymphs

Drop From Host 2

Nymphs Attack ^

Host 2

Nymphs Emerge From ^

Larval Skin While On

Ground

Male May Live Several More Weeks

Oviposition Begins

Female Dies

Larvae Hatch Out

Replete Larvae /

Drop From Host 1

Larvae Attack

Host 1

This type, the most common, is found in Dermacentor variabilis, Amblyomma variegatum,

and most other species of hard ticks. These are the so-called "three-host ticks". The larva

attaches, engorges, drops from the host and molts; the nymph reattaches to the same or

another host, engorges, drops from the host and molts; and finally, the adult reattaches to

the same or another host, engorges, and drops from the host. Therefore, disease organisms

taken up by the larva, if able to survive the transformation, may be transmitted to the host

of the nymph. Organisms taken up by the nymph which remain in the tick during molting

may be transmitted to the host of the adult stage. Disease organisms acquired by the adult

either may be passed transovarially to be transmitted by the offspring, or they die v^ithin the

tick without infecting the next generation.

72
SCHEMATIC LIFE CYCLES AND DISEASE TRANSMISSION OF TICKS-Con.

TYPEV

Male Lives On

Oviposition Begins

Adults Attack Several Hosts

Over A Period Of Time.

Fecundated Engorged;^^L~

Females Oviposit Each \v^\

Time

Adults Emerge After

Several Nymphal Molts

^ Larvae Hatch Out

^ Female Lives On

^ —- Larvae Attack

"^ Hostl

Replete Larva

Drops From

^ Host 1

First Nymphal

Stage Emerges

From Larval

Skin

The Several Nymphal Stages

Attack Hosts Over An

Extended Period

This type is found in various species of the soft tick genera Argas and Ornithodoros. There

is one larval host, several nymphal and several adult hosts. Only the larva remains on the

host to feed for any length of time. Both the nymph and adult are rapid and repeated feeders.

The female usually lays a small batch of eggs after each feeding. If able to survive in the tick,

disease organisms taken up by any of the parasitic stages may be transmitted to subsequent

hosts or may be passed transovarially to the offspring.

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