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DOMESTIC

RABBITS:

Diseases

and

Parasites

^.

1*

Agriculture Handbook No.490

AGRICULTURAL RESEARCH SERVICE . U.S. DEPARTMENT OF AGRICULTURE

DOMESTIC RABBITS:

DISEASES AND PARASITES

Agriculture Handbook No. 490

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE
Trade names and the names of commercial companies are used in

this publication solely to provide specific information. Mention of

a trade name or manufacturer does not constitute a guarantee or

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

nor an endorsement by the Department over other products not

mentioned.

USDA policy does not permit discrimination because of race, color,

national origin, sex, or religion. Any person who believes he or she has

been discriminated against in any USDA-related activity should write

immediately to the Secretary of Agriculture, Washington, D.C. 20250.

Washington, P.C. Issued February 1976

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

Washington, D.C. 20402—Price 65 cents. Stock Number 001-000-03480-4

Catalog Number A 1. 76:490
Precautions

Pesticides used improperly can be injurious to man, animals,

and plants. Follow the directions and heed all precautions on

the labels.

Store pesticides in original containers under lock and key—

out of the reach of children and animals—and away from food

and feed.

Apply pesticides so that they do not endanger humans, livestock, crops, beneficial insects, fish, and wildlife. Do not apply

pesticides when there is danger of drift, when honey bees or

other pollinating insects are visiting plants, or in ways that

may contaminate water or leave illegal residues.

Avoid prolonged inhalation of pesticide sprays or dusts;

wear protective clothing and equipment if specified on the

container.

If your hands become contaminated with a pesticide, do not

eat or drink until you have washed. In case a pesticide is

swallowed or gets in the eyes, follow the first aid treatment

given on the label, and get prompt medical attention. If a

pesticide is spilled on your skin or clothing, remove clothing

immediately and wash skin thoroughly.

Do not clean spray equipment or dump excess spray material near ponds, streams, or wells. Because it is difficult to

remove all traces of herbicides from equipment, do not use the

same equipment for insecticides or fungicides that you use for

herbicides.

Dispose of empty pesticide containers promptly. Have them

buried at a sanitary land-fill dump, or crush and bury them

in a level, isolated place.

NOTE : Some States have restrictions on the use of certain

pesticides. Check your State and local regulations. Also,

because registrations of pesticides are under constant review

by the Federal Environmental Protection Agency, consult your

county agricultural agent or State Extension specialist to be

sure the intended use is still registered.

m
CONTENTS

Introduction

Factors in prevention and control

Body soundness and livability

Adequate nutrition

Suitable environment

Prevention, eradication, and

control of transmissible

diseases

Sanitation program

Disinfection

Practices to maintain health

and prevent disease

Bacterial diseases

Pasteurellosis

Listeriosis

Necrobacillosis

Salmonellosis

Staphylococcosis

Spirochetosis

Tularemia

Tyzzer's disease

Viral diseases

Myxomatosis

Rabbit pox

Fibroma

Herpes virus

Rabbit papilloma

Oral papilloma

Page

1

2

2

2

2

3

4

5

6

6

6

9

10

10

11

12

13

13

14

14

15

15

15

16

17

Page

Fungal diseases 17

Parasitic diseases 19

Prevention and control 19

External parasites 19

Internal parasites 22

Nutritional diseases 26

Pregnancy toxemia 26

Vitamin A deficiency 27

Vitamin E deficiency 28

Hereditary diseases 28

Glaucoma 28

Malocclusion 28

Splay leg and ataxia 29

Miscellaneous 30

Mucoid enteritis 30

Cannibalism 31

Heat prostration 31

Broken back „ 31

Sore hocks 32

Milkweed poisoning 33

Tumors 34

Fur eating and hairballs 34

Coprophagy 34

Yellow fat 35

How to pack and ship specimens for

laboratory diagnosis 35

Shipping dead animals 35

Accompanying information 36

iv
DOMESTIC RABBITS:

DISEASES AND PARASITES

By K. W. HAGEN/ l)actcriologist, and J. R. GORHAM, veterinarian, Western Region,

Agricultural Research Service, Pullman, Wash., and R. E. FLATT, veterinarian.

Department of Veterinary Pathology, Iowa State University, Ames, loiva

INTRODUCTION

Domestication of the European

rabbit probably occurred in monasteries during the Middle Ages.

By the middle of the 17th century,

rabbits were commonly raised in

England and continental Europe.

Oryctolagus cuniculus^ one of the

more successful mammals of the

world, is both prolific and adaptable.

Most of the fancy breeds were

developed within the last 100 years,

and only since the 1900's has domestic rabbit raising been accomplished in the united States. The

first commercial colonies were

started in southern California.

Meat rationing during World War

II gave the infant industry a push.

Today, approximately 200,000 people are engaged in some phase of

the rabbit business, and animals

are produced in almost every State.

Meat processors, serving major

cities, market more than 10 million

* Deceased.

pounds annually. In medical research, more than 900,000 animals

per year are used for pharmaceutical and vaccine testing. Over the

years, the breeds have been improved from the long, rangy, lowmeat-yield type to the compact,

blocky animal of today. Production

has increased from less than 65

pounds of meat per year per doe to

a minimum of 120 pounds per doe,

and 200 pounds per doe is not unlikely for the future. Feed required

to produce 1 pound of meat has

been reduced from about 6 pounds

to 3.5 or 4 pounds.

This publication, based on years

of research by Federal and State

agencies, will provide a useful reference manual for rabbit growers.

It is designed to help ranchers recognize the more common rabbit

diseases and to know when professional advice is needed. It is not

meant to encourage rabbit growers

to diagnose and treat diseased animals without the advice of a veterinarian. There is always the pos-
2 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

sibility that an animal may be

suffering from two or more diseases

at one time.

Diseases are classified according

to major cause—bacterial, viral,

nutritional, hereditary, fungal, and

miscellaneous, including poisoning,

tumors, and vices.

FACTORS IN PREVENTION AND CONTROL

The only rabbit that will return

a profit to its owner is a healthy

one. Factors conducive to good

health include:

• Body soundness and livability

• Adequate nutrition

• Suitable environment

• Prevention, eradication, and

control of transmissible diseases

Body Soundness and

Livability

Sound, vigorous rabbits are necessary both as quality meat products and as replacement stock. The

background of animals saved for

breeding should be examined carefully so that recognizable defects

will not be perpetuated. A healthy,

mature breeder, that has a history

of several litters showing fast development, good reproduction, high

livability of the young, and relative freedom from disease, is a

better source of replacement stock

than a rabbit that has not shown

these traits. Healthy, well-framed,

well-fleshed mature does producing

litters containing from 8 to 12 live

young, with low mortality in

fryers, good feed conversion, and

high weights, should be marked as

potential sources of breeding stock.

Each individual selected for breeding should be carefully examined

for defects and for general health.

Deviations from normal should

lead to elimination. Through rigid

exercise of this practice, a profitable, high-producing herd can be

established.

Adequate Nutrition

The simplest diet sustaining good

health, growth, and reproduction is

preferred. Decline in normal health

may increase susceptibility to disease agents and cause heavy monetary loss. Slow growth and development may be as costly as disease

mortality. Finally, the rabbit must

be more than just healthy; it must

reproduce and raise young profitably.

Suitable Environment

The term "environment" includes

every factor that influences the life

of the rabbit. Some of these factors

are hutch size and location, nearness to other animals, dryness, temperature, amount of sunshine, shelter design, availability of water,

and general management. Careful

examination and control of the environment are essential for effective

disease prevention.
DOMESTIC RABBITS : DISEASES AND PARASITES

Prevention, Eradication, and

Control of Transmissible

Diseases

If disease prevention has failed

and transmissible diseases are

established in the rabbitry, heavy

mortality may lead to business failure. Pasteurellosis, ear mange, and

coccidiosis are diseases commonly

experienced by some growers.

These infectious diseases are usually introduced in two ways, by

contact or by mechanical carriers.

The adult rabbit is the most important contact carrier. An animal

may apparently recover from a disease, but still shed infectious organisms in the feces, urine, or in

droplets exhaled while breathing.

Pasteurellosis and liver coccidiosis

are important diseases spread by

contact. The grower who introduces

new stock directly to his herd or

who exhibits animals at shows and

fairs is most susceptible to disease

outbreaks. New or exhibition animals should be held in a special

isolation section of the colony until the rancher is reasonably certain

that they are disease free.

Eabbits that are carriers of disease are often not recognized because they appear healthy. Tests to

pinpoint which animals are carriers are not always practicable.

Liver coccidiosis is found when the

fryer is dressed out for market,

too late for traceback to the doe

that produced it. Bacterial cultures

of the nasal cavity may show the

presence of pasteurellosis, but the

cost of these tests usually prohibits

the grower from utilizing them.

When disease prevention has

failed, we must consider the means

available to control and eliminate

the disease. When liver coccidiosis

is involved, the adult carrier may

be freed from infection by chemotherapy, plus the establishment of

improved management practices.

In some cases, it may be necessary

to depopulate to eliminate a disease. The time between depopulation and repopulation with clean,

healthy animals depends on many

factors. Environment plays an important part in the time interval

involved.

Mechanical transmission of disease occurs when the infectious

agent is accidentally carried from

place to place. Man is the chief

offender. The grower who treats a

sick animal and then moves on to

check or count newborn young can

be an important carrier of respiratory infection and coccidiosis. Feed

salesmen, servicemen, and pickup

buyers and visitors who have made

the rounds of other rabbitries may

be sources of infection. The grower

himself should avoid visiting other

rabbitries if disease is known to

be present. These examples may be

considered extreme, yet they happen repeatedly and are definite

factors in introduction of disease.

Dogs, cats, birds, and rodents have

been incriminated in carrying diseases to rabbits and should be kept

out of the rabbitry. Insects also

should be controlled.
AGEICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

Sanitation Program

A constant sanitation program is

an important part of disease prevention. A program of cleanliness

is required to establish and maintain a safe environment in which

animals can live and reproduce.

Elimination of disease carriers is

most important.

Environmental factors must be

considered in any sanitation program. Particularly important is the

proper type of hutch and shelter

construction and its maintenance

(fig. 1). The ease of cleaning, the

supply of clean water, and the

space for I'odent-proof feed storage are important items when

building a production unit. Proper

drainage is another factor. Provision should be made for water runoff from the rabbitry area. Hutches

should be constructed so that individual units may be removed for

disinfecting. The number of animals per unit should be adjusted to

the area and the environment.

Overcrowding requires more effort

to keep the area clean, dry, and

well ventilated. Unfavorable environmental factors lower the animal's resistance to disease and facilitate the spread of infection.

Water should be fresh, clean, and

protected from contamination by

urine, fecal matter, and feeds.

Cleaning water containers frequently is important.

PN^324

FIGURE 1.—Shed construction suitable for mild climates.
DOMESTIC RABBITS : DISEASES AND PARASITES

Feed may act as a mechanical

carrier for infection when contaminated with feces. Protecting the

feed from contamination by the

use of properly designed and wellconstructed feed hoppers is necessary in any good sanitary program.

All feeders should be cleaned

periodically.

Good feed utilization and waste

removal are important in disease

prevention. Feed scattered about

the rabbitry attracts insects, mice,

rats, and birds—all potential carriers of disease. Proper storage of

bulk feed will aid the sanitation

program. In the small rabbitry or

where large quantities of bulk feed

are not stored, metal garbage cans

with tight lids are good feed-storage containers.

Disinfection

Disinfection refers to the killing

of infectious agents such as bacteria, viruses, and parasites. To

facilitate the use of disinfectants,

all equipment and other construction should be as simple and easy

to clean as possible.

Fecal matter and other organic

material protect disease-producing

bacteria, viruses, and parasites and

nullify the effectiveness of even the

most efficient disinfectants. Thorough scraping and washing should

precede disinfection. One compound should act as both cleanser

and disinfectant.

In the routine cleaning and disinfecting of pens and sheds in a

small rabbitry, ordinary lye solution is effective and economical.

One 13-ounce can of lye is enough

to make 15 gallons of cleaning and

disinfecting solution. For large

ranches, it is advisable to buy the

lye in the form of caustic soda.

Each pound makes about 20 gallons of solution, which does not

need to be heated although heating

is advisable. In addition to acting

as a disinfectant, lye cuts grease

and partly dissolves and penetrates

fecal material.

Use of lye has some disadvantages. Concentrated lye is a poison

and is destructive to aluminum

paints and clothing. The lye may be

slightly irritating to the hands and

face of the operator. Consequently,

take precautions to avoid excessive

exposure of the skin during the disinfecting process. Keep containers

of lye tightly covered.

Some ranchers use steam under

pressure to clean and disinfect pens

and equipment. When steam is

used, caked fecal material should

first be soaked with water. Use of

a good cleansing compound, followed by steam, cleans and disinfects very satisfactorily.

Sunlight is a potent disinfectant

if the equipment is very clean and

sufficient exposure time is allowed.

A cement slab exposed to the direct

rays of the sun is a good place to

disinfect movable equipment. Dry

heat in the form of a flame is effective as long as the flame is in direct

contact with the infectious agent.

Care must be taken as this procedure is a fire hazard.
AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

Practices to Maintain Health

and Prevent Disease

The successful grower observes

good sanitation and management,

feeds an adequate diet of simple

ingredients, and gives the animals

plenty of fresh water.

Daily inspection of all animals

in the herd is important. When sick

rabbits are first noticed, the grower

should immediately try to determine the cause. The following

course of action is suggested :

1. Mark or note pens that contain sick animals.

2. Isolate sick animals. It is best

if they can be kept in rooms or

buildings separate from healthy

rabbits.

3. Care for the sick animal only

after all other rahhits in the herd

have been cared for to prevent

carrying infection from sick to

healthy rabbits. Be sure to wash

hands and disinfect boots after

caring for sick animals. Clean and

disinfect any equipment moved

from the area of sick animals to

the clean animals.

4. If the cause of the trouble cannot be quickly determined, a few

typically sick rabbits should be

sent to a diagnostic laboratory.

5. Destroy all hopelessly sick

animals, and bury or burn all dead

animals. Open pits are not recommended.

6. Clean and disinfect all pens

before placing new rabbits in them.

Use a 2-percent lye solution (1

pound of lye to 51/^ gallons of

water). The solution is effective

against most viruses and bacteria.

BACTERIAL DISEASES

Pasteurellasis

Pasteurellosis is the designation

for all diseases associated with

Pasteurella^multocida. The disease

manifestations are varied and include snuffles, pneumonia, pyometra, orchitis, otitis media, conjunctivitis, subcutaneous abscesses,

and septicemia.

SNUFFLES

The mucous membranes of the

nasal sinuses become infected by

bacteria in the inspired air or by

direct contact with infected animals or contaminated objects. The

clinical disease is characterized by

a catarrhal (mucus or pus) nasal

discharge (fig. 2). The extent to

which the infection spreads into the

lower respiratory passages depends

on the virulence (invasiveness) of

the bacteria and the susceptibility

of the animal. If the disease is confined to the upper passages, the

first signs are sneezing followed by

a nasal discharge. The inner aspects

of the rabbits forepaws may be

caked with exúdate because of attempts to wipe the exúdate away

from the nose. Pasteurella bacteria

sometimes are found in the nasal

sinuses of healthy-appearing rab-
DOMESTIC RABBITS : DISEASES AND PARASITES

bits. Stress resulting from extremes of temperature, high humidity, pregnancy, and lactation

is a primary factor in the development of snuffles.

PNEUMONIA

Upper respiratory disease (snuffles) may spread to the lungs and

cause pneumonia. Eabbit mortality

surveys reveal pnemnonia to be

present in 25 percent of the animals

examined; it is the greatest single

cause of death in mature animals.

Signs of pneumonia are depression,

labored breathing, bluish eye color

in albinos, and a nasal discharge.

The body temperature is usually

above normal.

Gross lesions of the lungs appear

as red consolidated areas, sunken

purple areas, and abscesses. The

consolidated lesions are most often

in the anterior lobes of the lungs

PN-1325

FIGURE 2.—Adult showing signs of snuffles. Note discharge from nose.
8 AGRICULTURE HANDBOOK 490, U.S. DEl'T. OF AGRICULTURE

(fig. 3). A catarrhal exúdate is

found in the air passages. Abscesses

appear with thin fibrous capsules

close to the surface of the lungs.

Sometimes there are adhesions between the wall of the chest cavity

and the lungs. Good ventilation

without drafts, low humidity, and

treatment with antibiotics are recommended. Pasteurella organisms

are sensitive to oxytetracyclines,

streptomycin, sulfaquinoxaline, and

furazolidone.

PYOMETRA

Pyometra means pus in the

uterus. The walls of the uterus

usually are dilated, and the organ

is filled with pus. Affected females

will not reproduce and, therefore,

PN-1326

FIGURE 3.—Gross appearance of rabbit

lungs, showing consolidation due to

Pasteurella bacteria.

are culled and often slaughtered.

Pyometr'a results from the introduction of Pasteurella bacteria into

the uterus during mating and may

be traced to a single buck with a

chronic infection of the testicles.

Treatment of pyometra is seldom

attempted because the disease is

usually not noticed until the female is slaughtered. Successful

treatment is unlikely.

ORCHITIS

Orchitis is an infection of the

testicles of a buck. The testicle becomes enlarged and contains an

abscess. Pus can be seen when the

testicle is cut open. Sometimes infection is limited to the membranes

covering the penis, and this is

called balanoposthitis. Balanoposthitis appears as a reddening and

swelling of the membrane covering

the penis, and a white exúdate

(pus) is present on these membranes. As described above, the infection is transmitted to does by

infected bucks during breeding.

Treatment is seldom attempted;

however, balanoposthitis may be

treated by applying antibiotic ointment containing penicillin to the

penis.

OTITIS MEDIA

Middle ear infection of one or

both ears causes filling of the tympanic cavity with a purulent exúdate. If the process spreads to the

inner ear, the equilibritxm of the

animal is disturlied, and head tilt

or wryneck results (fig. 4). Although the Pasteurella organism is
DOMESTIC RABBITS: DISEASES AND PARASITES 9

PN-'Í327

FIGURE 4.—Wryneck resulting from a

middle ear infection.

sensitive to certain antibiotics,

treatment is generally not effective

because of the isolated location of

the infection.

CONJUNCTIVITIS

Conjunctivitis, or weepy eye, is

infection of the membranes that

cover the surface of the eye and

the inner part of the eyelids. The

eyelids are swollen, and white exúdate may cover the eye and surrounding fur (fig. 5). Infection of

the eye usually occurs as a result

of extension of the infection from

the nasal cavity (snuffles). Antibiotic ophthalmic ointment containing penicillin is used to treat this

form of the disease.

SUBCUTANEOUS ABSCESSES

Pasteurella may cause abscesses

in many organs, but abscesses are

especially evident when they occur

in the subcutaneous tissue. These

appear as soft swellings under the

skin. Treatment consists of opening

and draining of the abscess and

applying antibiotic ointment.

SEPTICEMIA

This disease is usually an overwhelming blood stream infection

of short duration without clinical

signs. Tissue changes are limited

to a few hemorrhagic areas on the

heart and pericardium, swelling of

the spleen, and slight congestion of

the vipper digestive tract. The lack

of clinical signs and short duration

do not allow time for suitable treatment.

Listeriosis

Listeria monocytogenes causes a

septicémie infection in young animals, a meningo-encephalitis in

adults, and metritis and fetal mortality in pregnant does.

PN-1328

FiGt:RE 5.—Conjunctivitis (weepy eye)

caused by Pasteurella iniection.
IQ AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

In septicemia, death can be sudden and without previous illness.

Generally the rabbit is depressed,

weak, has a nasal discharge, and

may have convulsions. Nervous

signs include incoordination, loss

of equilibrium, and rolling movements. These signs may persist for

several days or weeks, and complete recovery is rare. Sick pregnant animals have a purulent

metritis, lose weight, and may

abort. Survivors generally are useless for breeding because of uterine

damage and pyometra (pus within

the uterus).

The most consistent lesion at

necropsy is liver necrosis. The lesions consist of a few pinpoint foci

to almost complete studding of the

liver. The mesenteric lymph nodes

may be enlarged and reddened. In

cases of metritis, the uterine wall

is thickened, the mucous membrane

may be covered with a grayish exúdate, and the fetuses are decomposed or mummified. When infected fetuses are retained in the

uterus, a severe metritis develops.

Due to their tolerance by the rabbit and specific action, antibiotics

of the tetracycline group are the

best drugs for treating listeriosis.

Therapy should be started early

with adequate dosages. Penicillin

and erythromycin are also used. In

treating pregnant rabbits, antibiotics probably will not prevent

fetal death, and females saved by

antibiotics may be sterile as a result of the infection. The most

effective prevention of losses is

immediate isolation of diseased

pregnant animals. Pregnant females and those does that have

recently delivered young are« most

susceptible. Males and nonpregnant

females rarely contract listeriosis

by the oral route.

Necrobacillasis

Fusobacterium necrophorum in

farm animals is considered a secondary invader rather than a primary cause of disease.

Lesions first appear on the lower

lip, which becomes swollen, purplish, and painful to the touch.

Later, small abscesses are seen that

contain a thick, purulent material.

These abscesses are enclosed in a

tough, fibrous capsule, with little

tendency to rupture and drain.

When the liver and lungs become

involved, the animal becomes

emaciated and dies after several

weeks.

When the disease is recognized

and treated in its early stages, recovery is usual; when there is extensive ulcération and abscessation,

death ensues. The organism is sensitive to penicillin.

Salmonellosis

Naturally occurring Salmonella

typhimurium infections are uncommon in domestic rabbits. Salmonella organisms are easily spread by

fecal contamination, and a single

infected animal can quickly infect

a whole colony. Rabbits can also

become infected by human caretakers as the salmonella bacteria

occur in humans as well.
DOMESTIC RABBITS : DISEASES AND PARASITES 11

Infection usually takes place by

the oral route, and signs appear

after 3 to 6 days. The first signs

are listlessness, ruffled haircoat, loss

of appetite, and diarrhea. Later,

the respiration rate inci'eases, and

body temperature may rise. In the

acute form, the disease progresses

rapidly to death, whereas in the

chronic form there may be no signs

of illness other than a transient

diarrhea.

The most prominent lesions

found at necropsy are in the liver,

spleen, mesenteric lymph nodes,

lungs, and intestine. Hemorrhagic

and ulcerative changes are present

in the intestine. The liver and

spleen are usually enlarged and

contain pinpoint, pale areas of

necrosis. The lymph nodes may be

soft, hemorrhagic, and enlarged.

Surviving rabbits become carriers

and may shed bacteria in their feces

intermittently for a long time.

Streptomycin and nitrofurazone

have been used effectively against

salmonella. Animals treated with

chlortetracycline respond to the

medication, but may continue to

excrete organisms in their feces

long after treatment. Pigeons, sparrows, and wild rodents have been

shown to be reservoirs of salmonella. Feed and bedding should be

stored so as to protect them from

these possible carriers.

Staphylococcosis

StaphyJococcus aureus causes

septicémie infections as well as

abscesses in numerous organs including the subcutaneous tissue,

lungs, kidneys, and heart. This

organism is especially known for

causing infection in the breasts of

nursing does. The breasts become

swollen, hot, and may become

bluish accounting for the name

blue-breast that is sometimes used.

Cutaneous lesions in young animals appear as small abscesses and

later develop into firm caseous

nodules (fig. 6). These abscesses are

V /

/

^ <

Ä*.

PN-I329

FIGURE 6.—Cutaneous abscesses on

young rabbit caused by Staphyloeoccus.
12 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

usually found on the lower abdomen, on the inner aspects of the

forelegs, and on the lower jaw.

Small white nodules may also be

found in the lungs and heart. The

staphylococcus organism may also

cause bronchopneumonia. The lungs

appear consolidated with numerous

necrotic lesions. The bronchi and

trachea may contain a mucopurulent exúdate.

Bacteria enter the skin through

broken or abraided areas following

birth; transmission occurs from

mother to young. Staphylococci live

in the nasal passages of rabbits, and

the close contact associated with

kindling (birth) and nursing offers

opportunities for both direct contact and aerosol transmission.

Mastitis results from invasion of

the milk glands by the diseaseproducing bacteria. The glands

and teats become red and swollen

and may advance to blue-black tissues, which are feverish to the

touch. The doe may refuse to nurse

her young and generally loses her

appetite. Young from does with

mastitis should not be fostered out

to other nursing does because the

disease will be transmitted to the

doe. Mastitis may also result from

abrasions to the teats or insufficient

removal of milk when too few

young are left with the doe or when

the young are weaned too soon.

Staphylococci may be sensitive

to several antibiotics including

penicillin, tetracyclines, streptomycin, and furadantin; however,

some strains of the organism are

resistant to one or more of these

drugs, and laboratory tests may be

necessary to determine which drugs

should be used.

Spirochetosis

Spirochetosis, sometimes called

"vent disease" or rabbit syphilis, is

caused by Treponema cuniculL The

term "rabbit syphilis" is erroneous

and creates confusion with experimental human syphilis in rabbits.

Lesions of spirochetosis may resemble those of injury, fungal infection, and ectoparasites. A correct

diagnosis is important since the disease is transmitted by breeding, and

an isolated case may lead to an outbreak among the breeding stock.

Exchange of infected bucks may

spread the infection among colonies.

The first signs are usually small

blisters around the external sex

organs. Lesions involving the nose,

mouth, and ears also occur in both

sexes. They are irregular in shape,

tan-brown, and either edematous

or dry and scaly. Sometimes weeping, coalescing vesicles are found.

Facial and other lesions are usually

secondary and the result of reinfection by contact with genital-anal

lesions when the animal cleans itself. All lesions show many spirochetes by special microscopic

(dark-field) examination. Old lesions heal completely without scarring, but recovered rabbits are susceptible to later infection.

Small raw areas around the external genitals and vent caused by

irritation from urine or wet hutch

floors are frequently confused with

T, cuniculi infections. These areas
DOMESTIC RABBITS: DISEASES AND PARASITES 13

enlaige, coalesce, and may become

purulent, but when covered with

a crust these cases may be mistaken

for true vent disease. A positive

diagnosis can be made by a microscopic examination of tlie lesions.

The spread of spirochetosis can

be prevented by examining the genitals of both sexes before mating

and by eliminating rabbits with

lesions. Tlie organism is sensitive

to arsenicals and penicillin. A

single intramuscular injection of

100,000 units of penicillin is the

recommended treatment.

Tularemia

Tularemia, sometimes called rabbit fever or deer fly fever, is an infectious disease of wild animals

and man that is caused by Francisella tularensis. Tularemia can be

carried by many wild and domestic

animals, certain birds, deer flies,

and ticks. It is an important malady of wild rabbits, not the domestic ranch-raised rabbit.

Infected wild rabbits appear

sluggish in movement and are visibly sick. Yellow or white spots on

the liver or spleen are common lesions. Diagnosis is made by bacterial cultures of suspect lesions.

Domestic rabbits are susceptible to

infection with this organism under

laboratory conditions, but the disease has not been reported naturally occurring in commercial

rabbitries.

Tyzzer's Disease

Tyzzer's disease was first described in Japanese waltzing mice.

but since has been found in a variety of animals, including rabbits.

Bacillus piliformis is the causative

organism.

Signs of the acute form seen in

weanling animals are diarrhea, listlessness, lack of appetite, and dehydi'ation, followed by death in 72

hours. Lesions include necrosis in

the wall of the cecum and focal

necrosis in the liver and heart (fig.

7). The organisms are found in

cells near neci'otic areas, and the

demonstration of typical bacteria

within the cell is essential to diagnosis. Animals surviving the acute

stage may progress to adulthood,

but fail to grow at the normal rate.

Transmission of Tyzzer's disease

is by direct contact with fecal-contaminated feed and bedding. Some

form of stress, such as overcrowding or extremes in temperature, is

PN-4330

FiGiRE 7.—Tyzzer's disease. This rabbit died acutely with diarrhea. At

autopsy, focal areas of cell death

(arrows) were seen in the liver.

Photoffraph courtesy of Academic

Press and Co., New York.
14 AGRICULTURE HANDBOOK 490, U.S. DEPT. OP AGRICULTURE

necessary for initiating the condi- the disease in experimental mice,

tion in nature. The bacteria are most susceptible

Antibiotics reduce the effect of to teti'acycline and penicillin.

VIRAL DISEASES

Myxomatosis

Myxoma virus was first isolated

in South America from diseased

laboratory rabbits; the virus was

later found to be a widespread natural infection in cottontails. In

wild cottontails, it causes only mild

tumors, which regress after several

weeks; the disease is fatal only in

the very young. In contrast, the

disease can completely wipe out

some susceptible populations of domestic rabbits. Confirmed cases of

myxomatosis follow the geographical distribution of the California

brush rabbit, which is limited by

the Pacific Ocean, the Columbia

Eiver in Oregon, the CascadeSierra Nevada Mountains, and the

tip of the peninsula of lower California. Transmission of the disease

by mosquitoes led to the name

"mosquito disease." Myxomatosis is

also referred to as "big head disease" because of edema around the

eyes, ears, lips, and nose in the

early stages of the infection.

Clinical signs include lusterless

eyes with a purulent discharge and

elevated body temperature. Edema

of the ears causes them to become

heavy and pendulous (fig. 8). As

the disease progresses, edema of

the anogenital region and a nasal

discharge occur; death follows in

10 to 12 days. In the few cases that

PN^33l

FIGURE 8.—This animal, affected with

myxomatosis, shows lieavy, penflulous ears and matted eyes.

survive, widespread subcutaneous

gelatinous tumors develop all over

the body.

Rabbits dying from myxomatosis

exhibit no characteristic internal

changes by which the infection can

be definitely diagnosed. Usually,

there is congestion and consolidation of the lungs, and the spleen is

enlarged, dark red, and pulpy. The

cut surface of each edematous subcutaneous tissue is white, gelatinous, and glistening; when pressed,

clear fluid exudes. Clinical signs

and tissue examination are required

for diagnosis, which is confirmed

by inoculation of test rabbits and

virus isolation.

The virus is spread by direct contact and by biting insects, such as
DOMESTIC RABBITS : DISEASES AND PARASITES 15

mosquitoes and fleas, which act as

mechanical vectors. Control consists of prompt identification of the

disease and destruction of infected

animals. Practices that reduce mosquito populations, such as draining

or spraying breeding areas, should

be followed. Screening the entire

rabbitry is an effective but costly

solution. Antibiotics are not effective in treating sick animals, but>

an attenuated vaccine has been developed, which cohfers protection.

Rabbit Pox

The disease can occur with or

without clinical disease being

manifested. In either case, the lesions include lymphadenitis, papular nodules on the mucous membranes, and orchitis. Mortality is

highest among the unweaned

young, and may approach 75 percent. Rabbit pox virus is rarely a

cause of epizootics, but it is usually

very serious when it does occur.

Vaccination with vaccinia virus

confers immunity.

Fibrama

Eabbit fibroma virus was isolated

from nodules beneath the skin of

wild cottontail rabbits. These

fibromas (growths) were transmitted to both wild and domestic

rabbits. It was once believed that

fibroma virus only infected wild

rabbits; however, an outbreak was

recently reported in a commercial

rabbitry.

In the cottontail rabbit, fibroma

virus causes a benign tumor which

regresses within a few weeks.

Young domestic rabbits, on the

other hand, develop small subcutaneous nodules to diffuse indurations involving muscle and tendon.

The external genitalia become red

and swollen. Death is frequent in

unweaned young.

The cut surfaces of the nodules

are pale and glistening and may

have radiating white streaks. In

young animals, the tumors are

more widely spread over the body

and often coalesce. There may be

involvement of the kidneys, liver,

intestinal tract, bone marrow, and

mesentery.

The role of mosquitoes and other

insects as vectors of rabbit fibroma

virus has been established. Given

the proper environment (such as an

epizootic in wild cottontail rabbits) and an adequate mosquito

population, this viral disease could

result in significant economic loss

of young domestic rabbits.

Herpes Virus

Virus III or Herpesvirus cuniculi of rabbits exists as a latent infection in some stock lines of domestic rabbits. The virus does not

produce a natural disease, nor are

other species of animals susceptible.

A virus with characteristics of the

herpes group has been recovered

from rabbits with respiratory

signs. Its role as a pathogen has

not been elucidated, but its association with respiratory disease may

be important.
IQ AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

Another herpes virus that may

be responsible for producing

lymphoid tumors in cottontail rabbits has recently been isolated from

these rabbits.

Rabbit Papilloma

Rabbit papilloma virus was identified as the causative agent of

wartlike growth on the skin of cottontail rabbits (fig. 9). The domestic rabbit and the jackrabbit are

susceptible to experimental infection. The virus can be recovered

from lesions on cottontail rabbits,

but not from papillomas on domestic rabbits. Xaturally occurring

papillomatosis has been found in

domestic rabbits in southern California, but the vims produces no

evidence of a generalized illness.

The most common sites for papilPN^332

FIGURE 9.—Rabbit paplUonia. Scaly growths on the ear were caused by papilloma

virus.
DOMESTIC RABBITS : DISEASES AND PARASITES 17

lomas are the ears and eyelids, and

the growths vary in size and conformity. The growths are well keratinized, and the upper surfaces

are irregular and often split. The

lower portions of the growth are

pinkish and fleshy to the touch. As

the waits become older, they increase in size, become more comified, and are hard to the touch.

At this stage, they are easily

scratched off by the rabbit or

knocked off when handled. Papillomas removed in this way leave a

free-bleeding surface, which heals

without complications.

Eabbit papilloma virus is probably spread by free-flying insects

such as the mosquito; there is no

virus multiplication in insect tissue.

Transmission of the virus from

lesions of cottontail rabbits to domestic rabbits is most likely.

Oral Papilloma

Wartlike growths in the mouth,

especially on the lower surface of

the tongue, are caused by a virus

different from the rabbit (Shope)

papilloma virus. Several spontaneous outbreaks of this disease have

occurred, but all have been in the

State of New York. The growths

on the tongue usually regress without specific treatment.

FUNGAL DISEASES

Two main groups of fungi, Trichophyton and Microsporum, are

found on the rabbit and produce

disease of the skin and fur under

certain conditions. Not only may

rabbits serve as reservoirs for human infection, but man may transmit his fungus infection to rabbits.

Because they produce a similar disease known as ringworm, the two

organisms will be discussed together in this section.

Fungus infections cause patchy

areas of hair loss with thickened

skin covered with yellow, dry

crusts (fig. 10). The hairs may be

broken close to the skin surface and

become matted. The name "ringworm" is suggested by the circular

lesion that often develops from the

outward growth of the fungi. Lesions are usually found on the nose,

ears, eyelids, and feet. Their size

varies, and in severe cases whole

areas of the body may be involved.

The infection is usually most severe

in the nursing young; single small

lesions are more likely found in the

adult. Diagnosis of fungus infection depends on finding fungi in

skin and hair scrapings and by culture. Examination under Wood's

(ultraviolet) light may indicate

Microsporum, but not Trichophyton.

Infection of the young probably

occurs in the nestbox. The nestbox

material becomes contaminated

with fungus from the adult, and

minor skin abrasions allow the

fungus to become established on the

young. During nursing, the young
lg AGRICULTURE HANDBOOK 490, U.S. DEPT. OP AGRICULTURE

PN-4333

FIGURE 10.—Ringworm infection showing loss of fur and scaling of the sltin on the

ears (arrow).

are in direct contact with skin and

fur around the teats, and the fungus is easily transferred to the

mouth and nose regions of the infants. These same fungal organisms

are found on dogs, cats, domestic

livestock, and wild rodents around

farm buildings.

When small numbers of animals

are involved, a topical medication

may be tiseful. A synthetic compound, hexetidine, has been valuable in treating isolated cases of

ringworm. It is applied directly to

the affected areas. In larger outbreaks, an oral or systemic medication is preferred. Griseofulvin, an

antifungal drug, is the medication
DOMESTIC RABBITS: DISEASES AND PARASITES 19

of choice. Each animal should receive 12 milligrams per pound body

weight per day for at least 15 days.

Griseofulvin can be added to the

pelleted ration, 0.37 grams per

pound of feed, and fed to all animals for 14 days. During treatment,

a fungicidal dust (sulfur) should

be added to the nestbox material.

PARASITIC DISEASES

Rabbits are susceptible to a number of parasites, but only a few are

of economic importance. The problems caused by all these parasites

are greatly influenced by methods

of feeding, handling, or housing. If

these are satisfactory and recently

acquired animals are quarantined

for a few days and checked for disease, most economic parasitisms can

be avoided.

Prevention and Control

The best preventive measures are

sanitation, good housing, adequate

food ration, and an understanding

of potential parasite problems.

Where good husbandry is the rule,

rabbits are rarely infested with

parasites in significant numbers.

Modern pens are so constructed

that they can be kept clean and

free from the infective forms of

parasites. The proper cleaning of

cages and use of good disinfectants

together with a good diet are the

keys to parasite control. Prevention of parasite infection is far

cheaper and preferable to treatment.

External Parasites

EAR AND SKIN MANGE

Psoroptes cuniculi, the common

ear mite of rabbits, causes ear

mange or canker. This condition is

probably the second most common

parasitic disease in commercial rabbitries. It is surpassed in importance only by coccidiosis. Both occur in well-managed colonies that

are housed on wire floors.

The mites live in the ear canal

and cause damage to the skin lining this area. An exúdate of

brown, waxy material soon covers

the inner ear (fig. 11). This dark

encrustation consists of cellular debris, keratin, dried blood, and mites

in varying stages of development.

In severe cases, the entire inner surface of the external ear may be involved.

An effective medicine for ear

mange is made of 1 part iodoform,

10 parts ether (to dissolve the iodoform), and 25 parts mineral oil.

Lindane (benzene-hexachloride) is

also effective when used as a 0.25-

percent suspension in oil. Mineral

oil by itself may be used. The following procedure is recommended
20 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

PN^334

FiGUBE 11.—Treating ear mites witli cotton swab soaked in medicated oil.
DOMESTIC RABBITS : DISEASES AND PARASITES 21

for treatment. First, treat all animals. Start with those rabbits

showing few signs of disease, and

finish with those having severe

lesions. This will minimize spreading of the parasite. Second, swab

the entire inner ear with medicine

on a cotton applicator stick. Allow

a small amount to run down into

the ear passage. Third, if scales or

crusts are sparce, be sure to work

the oil well into the ear. If heavy

crusts are present, saturate them

with oil until they become soft, and

then remove them with tweezers.

Then medicate the ear again. Burn

all cotton swabs and material removed from the ear.

Ear mange can be treated and

eliminated from colonies by rigidly

following the above treatment program. However, all animals must

be treated, and all new introductions to the colony must be free

of mites to keep the condition from

recurring.

Psoroptes cuniculi^ Notoedres

cati^ and Cheyletiella parasitovorax may also cause mange on the

skin of the head and body in rabbits. These parasites may cause the

skin to become dry, scaly, irritated,

and itching with hair loss in affected areas. Treatment is by dusting with talc containing 0.25 percent lindanc.

CUTEREBRID FLIES

Larvae of Cuterebra flies are

common subcutaneous parasites of

wild rabbits but infrequent parasites of domestic rabbits. The adult

fly appears wherever populations

of wild rabbits exist. Eabbits are

infected when the fly deposits eggs

on the fur. Grub worms hatch from

these eggs and burrow into the skin

to form warbles. The larvae grow

under the skin and may get as long

as three-quarters of an inch (fig.

12). When full grown, the grubs

leave the skin, drop to the ground,

and develop into adult flies. The

warbles cause little trouble when

they are found in small numbers.

The larvae can be removed by enlarging the opening in the skin and

drawing them out with tweezers.

The wound then should be painted

with an antiseptic.

FLEAS AND TICKS

Kabbits are not commonly infested with fleas, but the rabbit flea,

SpUopsyllus cuniculi^ and the dog

and cat fleas, Ctenocephalides cams

and O, felis^ occasionally have

been reported on rabbits. There are

four stages in the life cycle of these

fleas—^gg^ larva, pupa, and adult.

FIGURE 12.—Cuterebra larva. An eraser

on a pencil is shown for size comparison.
22 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

The eggs are deposited on bedding

and in cracks of the nestboxes and

develop into larvae in a short time.

These larvae then form pupae from

which the adult fleas emerge. Control is aimed at killing the adults

on the host and the immature forms

in the nestbox. To destroy adult

fleas, dust the animals with a commercial preparation of pyrethrum

or rotenone. Dusting should be repeated several times during a 2-

week period. Immature forms can

be controlled by burning old nestbox litter and scrubbing nestboxes

with hot water and household

bleach.

The rabbit tick, Haemaphysalis

leporispalustris^ is a common parasite of wild rabbits, but is rarely

found on domestic rabbits because

their housing is not compiatible

with the life cycle of the tick ; however, this tick is one of the reservoirs of tularemia. This is a serious

human disease, and care should be

taken to insure that wild rabbits

are not allowed access to areas in

which domestic rabbits are being

raised.

Internal Parasites

COCCIDIA

Coccidiosis is the most prevalent

parasitic disease of domestic rabbits. It is caused by a microscopic

parasite that invades the lining of

the intestine or liver. In these locations, the parasite multiplies extensively, and then leaves the body

in the feces. At least four species

or types of coccidia live in the intestine, and one species grows in

the liver.

Not all species of coccidia are

equally harmful, and rabbits tolerate moderate numbers of some

without displaying illness. The

most dangerous of the intestinal

forms are Eimeria magna and E,

irresidua. These produce diarrhea,

poor appetite, weight loss, and

sometimes death. E, irresidua

evokes the most severe tissue damage. In some cases, patches of epithelium die and slough away from

the intestinal wall. The diagnosis

of coccidiosis depends on the finding of the oocysts (parasite) in the

feces or intestinal contents. However, experience is needed to judge

if sufficient numbers of parasit.^^s

are present to account for the

disease signs, since other disorders

may produce similar signs.

Control of intestinal coccidiosis

depends largely on management

practices that minimize the danger

of fecal contamination of feed,

water, and hutch floors. Wire bottom floors greatly reduce the hazard presented by solid floors or

slots. Feeders should be designed

so that fecal contamination is held

to a minimum. An automatic water

system is recommended. Oocysts

passed out in the feces require moisture and warmth to sporulate and

become infective (fig. 13). Dry,

wire floors and automatic water

systems hinder sporulation of tJie

parasite.

Treatment has only a temporary

effect on intestinal coccidiosis, but

may be useful in controlling out-
DOMESTIC RABBITS: DISEASES AND PARASITES 23

ADULT PASSES

NONINFECTIVE

OOCYSTS

—^^ RE-INFECTl

ADULTS

LIFE CYCLE

OF COCCI DIA

CONTAMINATE

FOOD AND WATER

AND

INFECT YOUNG

RABBITS

OOCYSTS

DEVELOP

INTO INFECTIVE

FORMS

FIGURE 13.—Life cycle of coccidia.

breaks. When indicated, a ration

containing 0.025 percent sulfaquinoxaline may be fed for 2 or 3

weeks to reduce the numbers of the

parasites to a level where control

can be accomplished by proper

management. Intestinal coccidia

develop a tolerance to the drug if

used continuously, so treatment is

not suggested unless clinical disease

appears.

Eimeria stiedae^ the one species

of coccidia that multiplies in the

liver, is considered to be the most

pathogenic coccidia of rabbits. Like

the other forms, it enters the intestinal wall, but migrates to the

bile ducts where it reproduces. Infections lasting more than 16 days

can be recognized by the white, circular nodules on the liver (fig. 14).

The parasite multiplies in the epithelial cells of the bile ducts, which

become thickened and tortuous and
24 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

FIGURE 14.—Livers of rabbits affected witli liepatic coccidiosis.

PN-4335

contain a vast number of oocysts.

In the early stages of infection,

there are no unusual symptoms,

then the appetite decreases, a potbelly develops, and sometimes

death follows. In moderate infections, there is no mortality, but

disfigurement of the liver makes

it unmarketable; hence, this type

of coccidiosis is always of economic significance.

Liver coccidiosis is acquired in

the same manner as intestinal coccidiosis. The control measures are

also similar; however, liver coccidiosis can be controlled moi-e easily

by proper management. When the

disease does occur, feed containing

0.025 percent sulfaquinoxaline is MU

effective treatment. It can be fed

at this level for a long time; it

should be used only until manag;ement control measures can be introduced.

NOSEMA

Nosema cunicuU is the cause of a

mild but longstanding disease in

rabbits. The condition was first

described as a chronic encephalitis

and later as a spontaneous paralytic disease. A chronic nephritis

caused by the parasite was overlooked for many years, but current

studies indicate that many apparently healthy animals have kidney

lesions related to this infection.

These lesions vary from cortical

scarring with small, multiple, indented gray areas on the surface

to a granulomatous nephritis (fig.

15). The scars extend from the cortical surface to the medulla.

Nosematosis is a contagious,

colony infection. The organisms are

passed in the urine and transmitted

when there is urinary contamination of feed or water. Transmission may also occur to unborn rabbits in the uterus when the doe has

the disease. The disease can be

controlled by providing good sanitation and preventing contamination of food and water by urine. No

treatment is available.
DOMESTIC RABBITS : DISEASES AND PARASITES 25

PN^336

FIGURE 15.—Halves of kidneys from two

rabbits showing pitting of their surface caused by Nosema nuniculi.

ROUNDWORMS

Obeliscoides cmiiculi and 7'richostrongylus calcaratus are slender, cylindrical roundworms found

in the digestive tract. Fortunately,

infections are rarely encountered in

commercial operations.

Obeliscoides, the stomach worm,

is a very slender, reddish worm

about one-half inch long. Trichostrongylus is about the same size but

is found in the small intestine.

Both have similar life cycles. Eggs

are passed in the feces, and after

a short period small infective larvae develop. Moisture and warmth

favor larval development; larvae

are ingested and pass to the stomach or small intestine where they

grow into adults.

Signs of infection depend on the

degree of the infestation. Light infestations produce little effect;

heavy infestation may cause diarrhea and emaciation. The stomach

worm produces ulcération of the

stomach wall. Rabbits kept on the

ground are more apt to be parasitized than those on wire. Control

can be accomplished by proper

sanitation.

The pinworm, Passalurus am,-

iiguus, is a common parasite of

rabbits. These worms are glistening, white worms, one-half inch

long. They are often seen on the

surface of freshly passed feces or

through the wall of the cecum

when animals are slaughtered. Ordinarily, pinworms do little harm.

As the mature worms become inactive, thej' are passed out of the cecum as fecal pellets are formed.

These parasites are spread from

animal to animal by ingesting feed

and water contaminated by the

droppings of infected animals.

Management methods used to control coccidiosis are effective against

pinworms. When treatment is necessary, piperazine citrate is effective when administered at 100 mg/

100 ml drinking water for 1 day.

TAPEWORMS

Tapeworms occur in rabbits as

adults in the intestine and as larval

forms in the liver and abdominal

cavity. The adult forms are very

rare in hutch-raised rabbits, but

larval forms are occasionally observed.

The rabbit tapeworm, Cittotaenia ctenoides, is flat, ribbon shaped,

and made up of numerous segments. It has a head with four

suckers with which the worm attaches to the lining of the intestine. Rabbits harboring a few tapeworms show no signs of disease.

When many tapewomis are present,

diarrhea and emaciation occur.
26 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

Control is readily accomplished by

good sanitation.

The larval forms of tapewomi

most often found are those of

Taenia pisiformis. They are found

in the abdominal cavity and in the

liver. Rabbits acquire these tapeworms infections by ingesting contaminated feed and water containing tapeworm segments and eggs

from the feces of dogs. The young

larvae are then released from the

eggs, penetrate the digestive tract,

and migrate to the liver. They migrate within the liver, leaving white

streaks behind, then leave the liver

and enter the abdominal ciivity.

They form small fluid-filled cysts

(cysticerci), which may be attached

to the membranes holding the intestinal tract or may exist free in

the abdominal cavity (fig. 16).

Each cyst contains an embryonic

tapeworm, which, when consumed

by a dog, will develop into a mature tapeworm.

By excluding dogs from the rabbitry, transmission of tapeworm

eggs can be prevented (fig. 17).

Dogs kept on premises where rabbits are raised should not be allowed to eat any part of a raw

rabbit carcass. Treatment for larval stages in the rabbit is not practical so control must be accomplished by management.

PN^337

FIGURE 16.—Rabbit liver witli several

cysticerci attached (arrow).

NUTRITIONAL DISEASES

Pregnancy Toxemia

Also known as ketosis, this disease is a toxemia of pregnancy

that is most commonly noted in

first-litter females. Signs of ketosis are dullness of the eyes, sluggishness, respiratory distress, prostration and death after 1 to 4

days. The disease occurs in the last

week of pregnancy and is more

prevalent in obese animals. The

probable cause is starvation. For

some reason, there is a loss of appetite and failure to eat. This may

be the result of minor digestive

upset, an abrupt reduction in exercise, or a ration containing too

little digestible carbohydrate.

When carbohydrate enei'gy declines, body fat is mobilized for

energy, and ketone bodies are produced which enter the bloodstream.

The liver becomes fatty and appears yellow and soft.

Birth of the litter or abortion is
DOMESTIC RABBITS: DISEASES AND PARASITES 27

ADULT TAPE WORM IN DOG'S INTESTINE

FIGURE 17.—Life cycle of the dog tapeworm.

apt to be curative if either occurs

shortly after the onsest of signs. Injections of fluids containing glucose

may reverse the breakdown of body

fats and halt production of ketones.

Junior does should not be too fat

when bred for the first litter.

Vitamin A Deficiency

Low-grade vitamin A deficiency

adversely affects the reproductive

performance of the female, often

before other signs are noted. Premature degeneration of the ovum

and reduced numbers of fertilized

ova result. Resorption of the fetus

or abortion during late gestation is

also noted.

Rabbits born to females fed a

diet deficient in vitamin A may be

hydrocéphalie at birth. Hydrocephalus, also called water on the

brain, is characterized by distention of the portion of the skull that

covers the brain. Cases may not be

apparent because the young die

soon after birth or are born dead.

Animals that live show signs of

nervous system involvement. Wryneck, loss of equilibrium, and incoordination persist for several
28 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

days or weeks. Impaired coordination may prevent animals from

eating, and eventually they die of

starvation. Enlargement of the

head is caused by increased pressure on the brain. On cut section,

the ventricles (cavities) of the

brain are greatly enlarged and

filled with a clear, colorless fluid.

Hydrocephalus is caused by low

maternal blood levels of vitamin A

throughout the gestation period.

When maternal blood levels fall

below 20 fxg/100 ml serum, hydrocephalus appears in a large percentage of the young. Commercial

diets, in general, supply adequate

levels of vitamin A; however, the

vitamin does deteriorate after prolonged storage of alfalfa hay.

Vitamin E Deficiency

Infant mortality, characterized

by death of entire litters at 3 to

10 days of age without clinical

signs prior to death, has been associated with vitamin E deficiency.

Affected infants do not reveal any

gross lesions of diagnostic significance. Producing females become

less fertile as the deficiency progresses. The problem can be treated

since adequate supplementation of

vitamin E will stop infant mortality and correct infertility. Alfalfa hay is a suitable source of

vitamin E in commercial rations,

and 8 to 9 mg/100 g feed is adequate.

HEREDITARY DISEASES

Glaucoma

Glaucoma occurs in both laboratory and commercial rabbit colonies. This condition is of interest

to ophthalmologists because of its

similarity to congenital glaucoma

in humans, and the rabbit may

serve as a useful animal model.

Glaucoma appears first as a lightbluish cloudiness on the cornea.

One or both eyes may be affected.

Progressive opacity follows, and

protrusion of the eyeball becomes

noticeable. Corneal opacity may

lead to blindness. Complications associated with glaucoma are difficulty in breeding affected animals, poor appetite, and a general

loss of good health.

Glaucoma is probably the result

of an abnormal drainage mechanism and the inability to maintain

normal fluid relationships in the

eye. It is a semilethal defect that

is transmitted as a recessive trait.

Malocclusion

Malocclusion or wolf teeth has

long been recognized as a common minor problems in rabbit colonies. The dental formula of the rabbit is: Incisors 2/1, canines 0/0,

premolars 3/2, and molars 3/3.

Constant chewing and gnawing
DOMESTIC RABBITS : DISEASES AND PARASITES 29

keep the teeth ground down to

proper length and size. When the

lower jaw is shorter or longer than

the upper jaw, malocclusion of the

incisors results in overgrowth (fig.

18). The cheek teeth (premolars

PX-433S

FIGURE 18.—Maloccliision.

and molars) meet and grind evenly

in normal animals. These teeth continue to grow and depend on constant grinding against opposing

teeth to maintain their shape. If

there is a malposition of the jaw,

broken teeth, or malformation,

overgrowth will occur in the cheek

teeth similar to that which occurs

in the incisors.

Signs of malocclusion are gradual loss of appetite and weight.

Both sides of the mouth may become stained with saliva. Animals

become progressively listless, dehydrated, and unable to chew properly. Complications are abscessed

teeth, growth of teeth into the Tipper jaw, and death from starvation.

Malocclusion of the incisors can

be corrected temporarily by cutting back the teeth so the animals

can eat and attain good condition

prior to slaughter. Since malocclusion is inherited, it can be eliminated by selective breeding.

Splay Leg and Ataxia

Splay leg in rabbits is due to a

simple recessive genetic factor. The

condition is similar to the hip dysplasia found in certain breeds of

dogs.

The disease is characterized by

an inability to put weight on one

or both hindlegs, and may even

involve all four limbs. The limbs

are twisted so that the animal exhibits a double-jointed posture. The

animals are not paralyzed. They

eat normally, appear to be well,

and move by wriggling along on

their belly and chest. The pathologic effects are limited to the hip

and shoulder.

Ataxia (muscle incoordination)

resembles splay leg in some respects. It is, however, a lethal recessive genetic factor. The disease

usually appears when the animal is

2 to 3 months of age and runs its

course in 30 days. In ataxia, the

nervous system is involved, and at

first the animal may not be able to

use its hindlegs effectively. Later

the animal cannot move, and its

body temperature drops below normal until death ensues.
30 AGRICÜLTUEE HANDBOOK 490, U.S. DBPT. OF AGRICULTURE

MISCELLANEOUS

Mucoid Enteritis

Mortality statistics show that enteritis accounts for almost 50 percent of the deaths from nestbox

to weaning in commercial rabbitries. Enteritis incidence is very

low until the fourth week, peaks at

7 weeks, declines sharply after 8

weeks, and is unimportant after 16

weeks.

Generally, sick rabbits lose their

appetite, have a hunched appearance with dull, squinted eyes, and

have diarrhea of varying intensity (fig. 19). The fur loses its

sheen, and the coat becomes rough.

Rectal temperature may be normal

(102.5° F) or subnormal. As diarrhea and dehydration progress, the

animal may lose 20 to 25 percent of

its body weight in 24 to 48 hours.

The course of the disease may terminate in death after 24 to 72

PN-4339

FIGURE 19.—This rabbit has mucoid enteritis. Note feces on hindfeet. rough

fur coat, hunched posture, and

squlnty eyes.

hours following acute signs ; whereas in the chronic phase, the animals

may live for 4 to 10 days. In general, 95 percent of the mortality

has occurred by the sixth day. Not

all cases terminate in death; however, less than 50 percent recover,

and these generally prove unprofitable because of weight loss and

poor feed conversion.

Pathologic changes are confined

to the gastrointestinal tract. The

small intestine may show only increased mucus production. In

chronic or subacute cases, the cecum and large intestine may be

packed with a clear, thick gelatinous substance. Acute cases show

excess fluid in the intestine. Varying degrees of gastritis are noted

when the .stomach is distended with

fluid. Other viscera are not affected

except through secondary infection.

Pneumonia is a frequent complication.

The cau.se of mucoid enteritis is

obscure and probably complex. Diet

has been implicated; however, extensive research using different

combinations of cereal grains, plant

protein supplements, vitamins,

minerals, legumes, and carbonaceous hays have led to the conclusion that the kinds of foods used

were not primary factors in preventing, causing, or curing the disease. Diet may be implicated in the

multiple causation theory of the

disease.

Several bacterial species have

been isolated from affected rabbits,

but their importance is difficult to
DOMESTIC RABBITS : DISEASES AND PARASITES 31

assess. Coliform bacilli and anaerobic bacteria have been isolated,

but these are normally present in

the intestine, and their pathogenicity has not been proved.

Limited attempts to isolate a

virus or to transmit one have failed.

Coccidiosis is often found in animals with enteritis, but their presence is probably not related to the

disease.

Unfortunately, there is no specific treatment for mucoid enteritis.

Chlortetracyclines and oxytetracyclines added to food or water have

been reported effective in reducing

loss. These antibiotics may be fed

to does during the entire suckling

period.

Cannibalism

Most cases of cannibalism are the

result of the diet being inadequate

in either quality or quantity or because the doe was disturbed following kindling. Proper feeding and

seclusion at kindling will usually

prevent the tendency. A valuable

doe that destroys her first litter

should be given another chance. If

she continues, she should be culled

from the breeding population. •

Heat Prostration

Heat prostration results from

prolonged exposure to excessive

heat. Losses may be high in females

due to kindle or in infant rabbits

if the nestboxes are poorly ventilated. Just before dying, the animals breathe rapidly and become

comatose.

Adult animals suffering from the

heat may be relieved by spraying

them with water or placing a wet

burlap feed sack on the cage floor

for the animals to rest on. Bedding

and fur should be removed from

the nestbox to allow free circulation of air in the boxes for the

infants.

In locations subject to high temperatures, overhead water sprinklers help to reduce the air's temperature by evaporation. Aluminum-roofed sheds help to reflect the

heat, and burlap sacks soaked in

water can be hung from the edges

of the roofs to shade and cool the

air.

Broken Back

This condition is characterized

by sudden paralysis with no apparent cause. Paralysis extends

from the middle of the back with

complete paralysis from this point

back. The animal moves with its

front legs and drags the hindquarters. The urinary bladder may

become greatly distended. Paralyzed animals have a misplaced or

slipped vertebra. Malposition of

the vertebra compresses and damages the spinal cord with resulting

paralysis. Injury to the vertebra

may be caused by improper handling, using a tatoo box too short for

the size of the animal, or by injuries occurring in the cage. Many

injuries occur at night when predator animals invade the rabbitry. In

an effort to evade the predator

and protect the young, the adult
32 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

"stamps" firmly with its hindfeet.

As a result the vertebi'a becomes

misplaced and the spinal cord becomes damaged. There is no treatment, and the affected rabbit should

be killed.

Sore Hocks

Sore hocks are inflamed bare

spots, devoid of fur, found on the

bottom surface of the hindlegs (fig.

20). In more severely affected cases,

secondary infections with staphylococcus and abscesses occur. Both

front and hind feet may become

involved. As the hocks of the hind

feet become painful, the animal

throws more weight to the front

feet, adding stress to the front feet

and causing them to become affected. Wet, dirty hutch floors and

the ii'ritating action of urine ammonia are predisposing factors.

The breed of the rabbit is also a

factor in the development of sore

hocks as the disease is seen more

r

PN-1340

FIGURE 20.—Sore hocks.
DOMESTIC RABBITS: DISEASES AND PARASITES 33

often in large breeds as compared eriocarpa^ are toxic to the rabbit.

with smaller breeds. The leaves are greenish yellow and

broad, and the underside is coverMilkweed Poisoning ^^^ ^^ ^ ,,.ooiiy growth (fig. 21).

The leaves and stems of the Leaves may be found in wheat or

woollypod milkweed, Asclepias oat straw, but never in rice straw.

PN^341

FIGURE 21.—Woollypod milkweed.
34 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

The milkweed plant grows only in

the Pacific Southwest.

When rabbits eat the leaves or

stems of the plant, they develop a

paralysis of the neck and shoulders.

The head is tucked down between

the front legs, and the nose rests

on the floor. The back is arched

higher than normal. As neck muscles become paralyzed, the animal

is unable to lift its head or to control its legs. The front legs extend

to the sides while the hindlegs extend outward and forward. In

more advanced stages, the head lies

flat on the floor, the ears droop to

the sides, and any movement is

jerky and unsteady. Eventually, the

animal becomes completely paralyzed and succumbs to starvation.

In the early stages, the animal can

be saved if it can be force fed and

given water.

Tumors

Spontaneous tumors in the rabbit are rarely reported because the

animals are slaughtered before they

reach the age at which tumors are

most apt to occur. With the increasing use of the rabbit as a laboratory animal, interest in these

growths can be expected. Tumors

have been observed in the uterus,

kidneys, blood, lymph nodes, bones,

testicles, skin, and other organs.

Adenocarcinomas of the uteri are

not uncommon in does over 2 years

old. Usually they are multiple and

occur in both uteri. Most cases of

lymphosarcoma (tumors of cells

from lymph nodes) have been in

mature females. Neoplastic cells are

found in numerous body organs,

but the most outstanding lesions

are in the kidneys. Tumors originating from embryonic cells from

the kidneys (embryonal nephroma)

are observed with some frequency

in domestic rabbits.

Fur Eating and Hairballs

Several rabbits in a hutch may

eat body fur, eyelashes, and

whiskers. Single rabbits eat fur on

their sides, back and rump. The

cause is most likely improper diet;

however, sometimes it appears to

be a vice. Fiber deficiency or inadequate protein may be factors. A

15-percent fiber level is probably

the minimum that should be fed to

either growing or producing rabbits.

Eabbits may also eat small

amounts of hair by licking or

grooming themselves. The hair

may accumulate in the stomach and

form hairballs These usually cause

no disease, but they may obstruct

the stomach. When obstruction occurs, the rabbit quits eating, loses

weight, and may die. Mineral oil

given by stomach tube is recommended for treatment.

Coprophag-y

The process of taking soft fecal

pellets from the vent and swallowing them intact is a natural physiological procedure for the rabbit

that should not be misinterpreted

as a nutritional condition or de-
DOMESTIC RABBITS : DISEASES AND PARASITES 35

praved appetite. Coprophagy is

practiced at night by tame rabbits

and during the day by wild rabbits

in their burrows. Fermentation of

the feces in the large intestine supplies an abundance of certain B vitamins to the fecal pellets, probably improves the quality of the

protein in the soft pellets, and improves fiber breakdown by bacterial

action. By permitting a second passage of food through the digestive

tract, the rabbit gains additional

nutritive value from the food.

Yellow Fat

Yellow fat is not an abnormal

condition nor the result of an infectious process. It is included here

only to prevent misunderstanding

or association with a disease condition. Yellow fat is a genetic trait

determined by a recessive gene. Alfalfa and other green feeds contain

xanthophyll, a fat soluble compound that is yellow in color. Animals with the yellow fat g&jie^ lack

an enzyme that reduces (changes)

the xanthophyll pigment to a colorless product. Therefore, the xanthophyll is deposited in the body

fat making it yellow. White fat in

meat rabbits is preferred to yellow

fat.

HOW TO PACK AND SHIP SPECIMENS

FOR LABORATORY DIAGNOSIS

The best way for a rancher to

obtain an accurate diagnosis is to

take the dead animals, or two or

three sick animals showing typical

signs, to the nearest laboratory.

Then he can supply any additional

information the pathologist may

need. If this is not convenient, the

dead animals may be shipped.

Shipping Dead Animals

As it is against postal regulations to send frozen carcasses of

diseased animals through the mail,

shipment must be made by bus

or air express. Label the outside of the box, "Biological Specimen," "Rush," and "Keep in a

Cool Place."

If the carcass is to be shipped a

short distance, chill it thoroughly

and place it in the center of a box

containing sawdust or shavings.

For long-distance shipments, place

dry ice around the carcass, then

pack it as indicated above. Never

put dry ice in an airtight jar or

can. When the ice melts, gas is

formed if the gas cannot escape, it

may cause an explosion. Properly

used, dry ice will prevent spoilage

for 2 or 3 days.

If dry ice is not available, place

the animal in a can with a tight

lid, freeze solid, and pack in crushed ice surrounded by sawdust to

take up the water. A wooden box

can be used for shipment, but if a

bucket can be substituted for a

wooden box, no sawdust is necessary.
36 AGRICULTURE HANDBOOK 490, U.S. DEPT. OF AGRICULTURE

Many specimens decompose after

arriving at the laboratory because

no one is available to take care of

them promptly. With this in mind,

do not send fresh specimens that

will arrive on a weekend ; most laboratories do not operate on Saturday and Sunday. Address the

package to the laboratory itself, not

to an individual employee. This

will insure more immediate attention. Do not send carcasses that

have started to decompose. It is

better to kill an animal or two that

show typical signs, or to ship them

alive if there is a chance that they

may reach their destination before

death.

Accompanying Information

Letters that do not contain sufficient information are a problem

to the pathologist. In some diseases, a complete history is more

useful than the carcass. The accompanying letter should contain

the following information:

(1) Number of rabbits on the

ranch.

(2) Number of sick or dead

animals.

(3) Age and sex of affected

animals.

(4) Description of the disease

as you observed it. For

example, rabbits develop

watery diarrhea, quit eating and drinking, and die

in 1 or 2 days.

(5) Dates of first losses and

subsequent losses.

(6) Incidence of infection

(whether it is in just one

house or pen, or scattered

throughout the rabbitry).

(7) What treatment, if any,

has been given.

(8) Type and brand of feed

used for past 6 months.

(9) Type of housing (whether

the rabbits are kept on

wire or solid floors).

(10) Any other information

that might help explain

the outbreak.

It is best to telephone the laboratory so they can be alerted to the

arrival of the specimen. Should

further information be necessary,

it can also be obtained at that time.

-ÙVS. GOVERNMENT PRINTING OFFICE: 1976 O 590-948