National Wildlife Health Center

Trichinosis

Circular 1388

U.S. Department of the Interior

U.S. Geological Survey
Cover. Background image, “Sharing frozen, aged walrus meat” by Ansgar Walk. A, male walrus by Bill Hickey, U.S. Fish and Wildlife Service. 

B, large blacks by Amanda Slater, Wikimedia Commons . C, coiled larvae in muscle, William Foreyt. D, U.S. Fish and Wildlife Service. 

E, courtesy of Joel Reale©. F, common, black bear family, Anan Interpretive Staff, U.S. Forest Service.

A B

C

E D

F

cc c$
Trichinosis

By William J. Foreyt 

Edited by Rachel C. Abbott and Charles van Riper, III

Prepared by the USGS National Wildlife Health Center

Circular 1388

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Foreyt, William J., 2013, Trichinosis: Reston, Va., U.S. Geological Survey Circular 1388, 60 p., 2 appendixes, 

http://dx.doi.org/10.3133/cir1388.

Library of Congress Cataloging-in-Publication Data

Foreyt, Bill, author.

 Trichinosis / by William J. Foreyt ; edited by Rachel Abbott and Charles van Riper, III.

 pages cm. -- (Circular ; 1388)

 “Prepared by the USGS National Wildlife Health Center.”

 Includes bibliographical references.

 ISBN 978-1-4113-3638-4

 1. Trichinosis. 2. Trichinosis in animals. I. Abbott, Rachel, editor. II. Van Riper, Charles, editor. III. National Wildlife 

Health Center (U.S.) IV. Title.

 RC186.T815F67 2013

 616.9’654--dc23 2013024494

ISSN 1067–084X (print)

ISSN 2330–5703 (online)
iii

Foreword

C. van Riper, III, R. C. Abbott, M. Friend, and C. Bunck

Let both sides seek to invoke the wonders of science instead of its terrors. Together 

let us explore the stars, conquer the deserts, eradicate disease, tap the ocean depths, 

and encourage the arts and commerce.

John F. Kennedy

Increasingly, society is recognizing that parasitic zoonoses are an important component of 

emerging global infectious diseases (Daszak and Cunningham, 2002), not only for wildlife but 

for human populations. Because over 50 percent of the pathogens involved with human disease have had their origins in wild animal populations (Daszak and others, 2000; World Health 

Organization, 2004), there is more recognition than ever before of the need to better integrate 

the disciplines of human and animal health to address the phenomenon of infectious disease 

emergence and resurgence. Trichinosis (Trichinella spp.), one of the better known and more 

widespread zoonotic diseases, originated in wildlife species and is now well established as a 

human malady. 

Food- and waterborne zoonoses are receiving increasing attention as components of disease 

emergence and resurgence (Slifko and others, 2000; Tauxe, 2002; Cotrovo and others, 2004). 

Trichinosis is transmitted to humans via consumption of contaminated food, and the role of wildlife in this transmission process is becoming more clearly known and is outlined in this report. 

This zoonotic disease causes problems in wildlife species across the globe and is a major cause 

of concern for human health worldwide. Trichinosis is widely distributed, extending from the 

Arctic to the Tropics and even to oceanic islands (Dick and Pozio, 2001)

Disease emergence in wildlife since the late 1900s has been of unprecedented scope relative to geographic areas of occurrence, wildlife species affected, and the variety of pathogens 

involved (Friend, 2006; Daszak and others, 2000). The emergence of many new zoonotic diseases 

in humans in recent years is a result of our densely populated, highly mobilized, and environmentally disrupted world. As towns and cities expand, and wildlife populations increase in 

numbers, the wildland-urban interface broadens, and human associations with wildlife become 

increasingly frequent. With geographic distance and isolation no longer meaningful barriers, the 

opportunities for once isolated diseases to spread have never been greater. Future generations 

will continue to be jeopardized by trichinosis infections in addition to many of the other zoonotic 

diseases that have emerged during the past century. Dealing with emerging diseases requires 

the ability to recognize pathogens when they first appear and to act appropriately. Since outbreaks often are evident in the nonhuman components of the environment before humans are 

affected, understanding our environment and associated ‘sentinel’ wildlife is a prerequisite to 

protecting human health. Through monitoring trichinosis infection levels in wildlife populations, 

we will be better able to predict future human infection levels. This publication is the fifth in a 

series of U.S. Geological Survey Circulars on emerging zoonotic diseases.

In examining disease, we gain wisdom about anatomy and physiology and biology. 

In examining the person with disease, we gain wisdom about life.

Oliver Sacks
iv

Cotrovo, J.A., Bartram, J., Carr, R., Cliver, D.O., Cotruvo, J., Craun, G.F., Dufour, A., and Rees, G., 2004, 

Waterborne zoonoses: Identification, causes and control: Geneva, World Health Organization, 523 p.

Daszak, P., and Cunningham, A.A., 2002, Emerging infectious diseases: A key role for conservation 

medicine, in Aguirre, A.A., Ostfeld, R.S., House, C.A., Tabor, G.M., and Pearl, M.C., eds, Conservation 

medicine: Ecological health in practice: New York, Oxford University Press, p. 40–61.

Daszak, P., Cunningham, A.A., and Hyatt, A.D., 2000, Emerging infectious diseases of wildlife—Threats to 

biodiversity and human health: Science, v. 287, p. 443–449.

Dick, T.A., and Pozio, E., 2001, Trichinella spp. and trichinellosis, in Samuel, W.M., Pybus, M.J., and 

Kocan, A.A., eds., Parasitic diseases of wild mammals: Ames, Iowa State University Press, p. 380–396. 

Friend, M., 2006, Disease emergence and reemergence: The wildlife-human connection: Reston, Va., 

U.S. Geological Survey, Circular 1285, 388 p. 

Slifko, T.R., Smith, H.V., and Rose, J.B., 2000, Emerging parasite zoonoses associated with water and 

food: International Journal for Parasitology, v. 30, p. 1379–1393.

Tauxe, R., 2002, Emerging foodborne pathogens: International Journal of Food Microbiology, v. 78, 

p. 31–41.

World Health Organization, 2004, Expert consensus, in Contruvo, J.A., Dufour, A., Rees, G., Bartram, 

J., Carr, R., Cliver, D.O., Craun, G.F., Fayer, R., and Gannon, V.P.J., eds., Waterborne zoonoses: 

Identification, causes and control: London, IWA Publishing, p 3–16.
v

Contents

Foreword ........................................................................................................................................................iii

Overview..........................................................................................................................................................1

Background.....................................................................................................................................................2

Causative Agent.............................................................................................................................................2

Geographic Distribution................................................................................................................................4

Patterns and Trends ....................................................................................................................................12

Species Susceptibility.................................................................................................................................13

Human Infections................................................................................................................................13

Animal Infections................................................................................................................................13

Domestic Animals......................................................................................................................13

Pigs .....................................................................................................................................13

Horses ................................................................................................................................13

Ruminants .........................................................................................................................20

Wildlife ........................................................................................................................................20

Bears ..................................................................................................................................20

Arctic Mammals ...............................................................................................................20

Birds....................................................................................................................................20

Cold-Blooded Wildlife ......................................................................................................20

Invertebrates ....................................................................................................................20

Obtaining a Diagnosis .................................................................................................................................23

Disease Ecology...........................................................................................................................................24

Domestic Cycle....................................................................................................................................24

Sylvatic Cycle ......................................................................................................................................25

Points to Ponder...........................................................................................................................................33

Disease Prevention and Control................................................................................................................33

Treatment .............................................................................................................................................34

References Cited..........................................................................................................................................34

Glossary.........................................................................................................................................................41

Appendix 1. Locations and Hosts of the Different Species of Trichinella,

 and Common and Scientific Names of Hosts ...........................................................................49

Appendix 2. Common and Scientific Names for Species Cited ...........................................................53

Topic Highlight Boxes

Box 1. From Dinosaurs to the 20th Century—the Path of Discovery ....................................................4

Box 2. Life Cycle of Trichinella spp............................................................................................................6

Box 3. Anatomy of the Parasite..................................................................................................................9

Box 4. Trichinosis as an Emerging Disease ...........................................................................................14

Box 5. Trichinosis among Native Arctic Subsistence Hunters ...........................................................16

Box 6. Stages of Trichinosis in Humans..................................................................................................18

Box 7. Diet Matters.....................................................................................................................................28
vi

Illustrations

1–3. Maps showing:

1. Distribution of Trichinella spp. throughout the world ....................................................2

2. Distribution of Trichinella species found in the United States...................................10

3. Geographic distribution of A, T. spiralis; B, T. pseudospiralis, T. papuae, 

and T. zimbabwensis; C, T. murrelli, T. nelsoni, and T. nativa; D, T. britovi

and genotypes T6, T8, and T9 ..........................................................................................11

4. Graph showing number of human cases of trichinosis in the United States, 

1947–2007 .....................................................................................................................................12

5. Map showing prevalence of Trichinella spp. in black bears in North America...............21

6. Photograph showing coiled larva in compressed muscle...................................................23

7–8. Diagrams showing:

7. The domestic cycle of T. spiralis.....................................................................................25

8. General domestic pathways for infection with T. spiralis...........................................26

9. Map showing countries where T. spiralis is enzootic in pigs..............................................27

10–11. Diagrams showing:

10. Sylvatic cycle of Trichinella spp......................................................................................30

11. General pathways for infection of the arctic and subarctic cycles of 

T. nativa................................................................................................................................31

12–13. Graphs showing:

12. Examples of T. nativa larvae survival times in frozen tissue.......................................32

13. Increasing prevalence of Trichinella infection with age in polar bears...................32
vii

Tables

1. Minimum numbers of nonhuman species infected with Trichinella spp.............................1

2. Animals naturally infected with Trichinella spp. and probability of 

human infection ............................................................................................................................3

3. Taxonomy of Trichinella spp........................................................................................................3

4. Distribution, characteristics, and major hosts of eight currently 

recognized species of Trichinella ..............................................................................................8

5. Relation between larval forms and host susceptibility of Trichinella spp...........................8

6. Prevalence of Trichinella spp. in arctic mammals ................................................................22

7. Common techniques for evaluating exposure to Trichinella spp. 

in humans and other animals....................................................................................................24

8. Minimum internal cold temperatures and times necessary to kill 

T. spiralis larvae in pork .............................................................................................................33
viii

Conversion Factors and Abbreviations

Multiply By To obtain

Inch/Pound to SI

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

SI to Inch/Pound

millimeter (mm) 0.03937 inch (in.)

gram (g) 0.03527 ounce, avoirdupois (oz)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

ELISA Enzyme-linked immunosorbent assay

PCR Polymerase chain reaction

μm The micrometer, or micron, is a measurement unit of linear distance equal to one 

millionth (10–6) of a meter.

kGy The gray (Gy) is a measurement unit of the absorbed dose by matter of ionizing 

radiation. A kilogray (kGy) is expressed as 103 Gy.

Words in bold type in the text, the topic highlight boxes, and the tables are defined in the 

Glossary.
Trichinosis

By William. J. Foreyt1

1

Washington State University, Department of Veterinary Microbiology and 

Pathology.

“Trichinellosis: the zoonosis that won’t go quietly.” (Murrell and Pozio 2000)

Synonyms

Trichinellosis, trichinelliasis, trichiniasis, 

Trichina worm infection

Overview

Trichinosis, or trichinellosis, is one of the most widespread 

global parasitic diseases of humans and animals. This ancient 

disease is caused by the larval stage of parasitic roundworms (nematodes) in the genus Trichinella. Often called 

the “trichina worm,” this parasite is considered to be the 

king of the parasite community, because it has adapted to an 

extremely wide range of hosts including domestic animals, 

wildlife, and humans (table 1). Trichinella spiralis is the 

usual cause of the disease in humans, but humans and many 

other mammals, birds, and reptiles also can be infected with 

other species or strains of Trichinella. Regardless of climate 

and environments, a wide variety of hosts on most continents 

are infected.

Trichinella is transmitted through the ingestion of infected 

meat, primarily through predation or cannibalism of raw 

meat, and this ensures survival of the parasite in a wide variety of hosts. Humans become infected only by eating improperly cooked meat that contains infective larvae. While most 

people have only mild symptoms after infection, when high 

numbers of larvae are ingested trichinosis can cause serious 

disease, as well as death. Although trichinosis has been historically associated with pork, it is now emerging as a more 

widespread food-borne zoonosis as the consumption of wild 

game meat increases.

Table 1. Minimum numbers of nonhuman species infected with 

Trichinella spp.

[Adapted from Campbell, 1983b]

Order Minimum number of 

species infected

Carnivora 71

Rodentia 36

Primates 11

Insectivora 10

Artiodactyla 9

Lagomorpha 3

Cetacea 2

Marsupialia 2

Edentata 1

Chiroptera 1

Perissodactyla 1

Tylopoda 1
2 Trichinosis

Areas of Trichinella spp.

Figure 1. Distribution of Trichinella spp. throughout the world. (Modified from International Trichinella Reference Center)

Background

During the course of evolution, Trichinella spp. appear 

to have adjusted their life cycles in accord with the carnivorous feeding habits of their hosts, which allows ample 

opportunity for interspecies transmission. Trichinella likely 

was a parasite of northern regions and had its main center of 

distribution in the Arctic and Subarctic, where carnivorous 

animals are plentiful. Trichinella spp. is now found in almost 

every country of the world (fig. 1), but they are still more 

commonly associated with northern climates. In the course of 

development of civilization, pigs and humans became more 

intimately involved in the life cycle. Although most human 

infections in the world result from eating pork (Gottstein and 

others, 2009), infections can also result from eating meat 

of other domestic animals and wildlife species (table 2). 

Domestication of pigs over 10,000 years ago and adaptation 

of Trichinella spp. to a wide spectrum of wildlife species 

including mammals, birds, and reptiles apparently created a 

permanent reservoir of infection for humans.

Although trichinosis has been described as an ancient 

disease, it has only been during the last 150 years that the 

Trichinella parasite was first seen and determined to cause 

disease. With this knowledge, people could begin to implement control measures to mitigate the public health and 

economic impacts of trichinosis (Box 1). Worldwide, as many 

as 11 million people may be infected (Dupouy-Camet, 2000; 

Pozio, 2001). In the United States, the number of reported 

human cases has decreased dramatically since the 1940s, 

but repeated cluster outbreaks of disease in humans and a 

constant reservoir of infected wildlife indicate that this is 

a disease that will remain an important zoonotic disease in 

future years (Murrell, 2000).

In wildlife, predation, cannibalism, and scavenging are the 

main methods of transmission, but fecal-oral transmission

can occur when coprophagic animals eat feces from animals 

that have recently fed on infected meat or when animals eat 

meat-eating arthropods that have recently fed on infected 

meat. Detailed reviews on the history and the worldwide status of Trichinella spp. are available (Gould, 1970; Campbell, 

1983a; Dupouy-Camet, 2000; Dick and Pozio, 2001; Pozio 

and Zarlanga, 2005; Mitreva and Jasmer, 2006).

Causative Agent

The life cycle of Trichinella spp. is unique in that both 

adults and larvae develop within the same host, but two hosts 

are usually required to complete the life cycle (Box 2). The 

usual method of transmission of larvae from animal to animal 

is through predation, cannibalism, and scavenging, whereas 

transmission from domestic animals and wildlife to humans 

is through ingestion of improperly cooked meat containing 

infective larvae. Adult worms live in the intestine (Box 3). 

Larvae have a predilection for muscles with high oxygen 

concentration, such as the diaphragm, tongue, and masseter, 

but they can be found in many muscles, especially in heavy 

infections. Localization of larvae also differs among hosts. 
Causative Agent 3

For example, T. spiralis larvae concentrate in the tongue, diaphragm, and masseter muscles of horses, but larvae concentrate in the tongue and diaphragm of pigs.

The number of species or genotypes of Trichinella is 

a matter of considerable scientific controversy. For over 

100 years, T. spiralis was thought to be the only species of 

the genus, but differences in the ability to withstand freezing, DNA patterns, geographic distribution, reproductive 

abilities, survival times, host preference, and presence or 

absence of a nurse cell are characteristics that justify separating the genus into several species or subtypes. Eight species 

of Trichinella (table 3) have been determined by polymerase 

chain reaction (PCR) testing (Murrell and others, 2000; Pozio 

and others, 2002; Pozio, 2005). An additional three related—

but unclassified—genotypes, T6, T8, and T9, are of uncertain 

taxonomic status. Characteristics of the different species are 

listed in table 4. Of the eight Trichinella species, five have 

encapsulated larvae within muscle nurse cells and infect only 

mammals; T. pseudospiralis, T. papuae, and T. zimbabwensis 

have nonencapsulated larvae and can infect birds or reptiles 

as well as mammals (table 5).

In some cases, the encapsulation or nonencapsulation is 

a response of the host to the parasite (Worley and others, 

1986). Both types of larvae are able to penetrate muscle cells 

and induce dedifferentiation of the cells, but only those 

species with encapsulated larvae induce the nurse cell to 

stimulate collagen production. The significance of the nurse 

cell is that encapsulated larvae survive significantly longer 

than nonencapsulated larvae under adverse environmental 

conditions, such as in putrefied meat. The existence of both 

encapsulated larvae within a nurse cell and nonencapsulated 

larvae provides evidence of two evolutionary lines in the 

genus Trichinella, and this may eventually be one criterion 

for reclassifying nonencapsulated species to another genus 

(Pozio, Zarlenga, and LaRosa, 2001b).

Table 2. Animals naturally infected with Trichinella spp. and 

probability of human infection.

[Data from Ljungström and other, 1998; Murrell and Pozio, 2000; Centers for 

Disease Control, 2009]

Species Relative frequency 

of infection

Source for

human infection

Domestic animals

Pig Common Frequent

Horse Rare Infrequent

Sheep Rare Rare

Goat Rare Rare

Cattle Rare Rare

Dog Infrequent Occasional

Cat Infrequent Infrequent

Poultry Infrequent Infrequent

Wild animals

Boar Common Frequent

Bear Common Common

Felids Occasional Occasional

Canids Occasional Occasional

Marine mammals Common Common

Crocodile Infrequent Rare

Fish Rare Rare

Rodents Occasional Rare

Deer Rare Rare

Table 3. Taxonomy of Trichinella spp.

Classification Designation

Kingdom Animalia

Phylum Nematoda

Class Enoplea

Order Trichurida

Family Trichinellidae

Genus Trichinella

Species spiralis

nativa

britovi

pseudospiralis

murrelli

nelsoni

papuae

zimbabwensis
4 Trichinosis

Box 1 From Dinosaurs to the 20th Century—the Path of Discovery

Humans and animals have been infected by Trichinella

spp. for centuries. Larvae have been recovered from the 

body of an Egyptian mummified in approximately 1200 B.C. 

(Gould, 1970; Campbell, 1983a), and it has been suggested 

that Trichinella spp. could have been associated with 

carnivorous dinosaurs and ancient mammals (DupouyCamet, 2000). Trichinella larvae were first observed in 

a human cadaver in 1835 by James Paget, a first-year 

medical student at the London Hospital Medical School. 

After observing an autopsy on an Italian man who was 

thought to have died of tuberculosis, Paget became curious 

about what caused the “sandy diaphragm” in the man. He 

removed a piece of the diaphragm muscle, examined it with 

a microscope, and saw small worms coiled up inside each 

nodule. Richard Owen, the assistant conservator of the 

Museum of the Royal Society of Surgeons in London, also 

examined the muscle tissue. After seeing the coiled worms, 

he named them Trichina spiralis and presented his findings 

to the Royal Society (Owen, 1835). The worm was renamed 

Trichinella by Railliet in 1895 to avoid confusion with the 

genus of flies already known as Trichina (Gould, 1970).

In 1846, Joseph Leidy, an American zoologist, observed 

identical larval cysts in pieces of pork he was eating, but 

his observations were largely ignored at that time. In 1850, 

Ernst Herbst fed meat scraps to his pet badger and later 

observed Trichinella larvae in the muscles of the badger 

after it died, suggesting that transmission was by the 

ingestion of meat. He continued the chain of transmission 

by then feeding the badger meat to dogs, thereby infecting 

them. Rudolph Virchow, a German pathologist, continued 

this method of experimentation in 1859 by feeding infected 

human muscle tissue to a dog. When he autopsied the 

dog, he observed tiny adult worms, distinct from Trichuris

worms, in the gastrointestinal tract of the dog, thus 

demonstrating transmission of the parasite and contributing 

to the understanding of its life cycle. In addition, Virchow 

discovered that the cooking of infected meat inactivates the 

infectivity of the larvae. Virchow became a vocal advocate 

of the virtues of eating well-cooked pork products, much 

to the dismay of German veterinarians and smoke-cured 

ham enthusiasts. On at least two occasions, he challenged 

opponents to eat undercooked pork products, yet neither 

opponent dared to eat the meat, thus validating Virchow’s 

position on the risks of eating undercooked pork (Despommier and Chen, 2004). Additional work by German zoologist 

Rudolph Leuckart provided scientific support to Virchow’s 

campaign to create meat inspection laws in Germany. The 

American Joseph Leidy was also an early advocate of the 

thorough cooking of pork to kill the parasite and prevent 

infection, writing in 1853, “Cooking food is of advantage 

in destroying the germs of parasites, hence man, notwithstanding his liability to the latter, is less infested than most 

other mammalia.” (Despommier and Chen, 2004)

In 1860, Friedrich Albert von Zenker, a German pathologist 

and physician, provided the first evidence of transmission 

of Trichinella to humans from pig meat when he travelled to 

Geographic Distribution

Trichinella spp. are present throughout most of the world 

in over 150 different hosts (fig. 1; Kim, 1983; Dick and 

Pozio, 2001; Appendix 1). Because the parasite resides in 

so many different wildlife and domestic hosts, it is unlikely 

that it will ever be eliminated from the human food chain. 

Most human infections are associated with the ingestion of 

pork or meat from wildlife, but consumption of meat from 

horses and other animals can also be uncommon sources 

of human infection, depending on such factors as cultural 

practices, diet, changes in farm husbandry, and poverty. In 

China, for example, outbreaks of human trichinosis attributed 

to T. nativa have been caused by consumption of dog meat 

(Cui and Wang, 2001). Infection rates in dogs in different 

provinces in China ranged from 7 to 40 percent, indicating a 

very high environmental presence of Trichinella. In France 

and Italy, human infection has been linked to consumption of 

horsemeat (Dupouy-Camet, 2000).

In the United States, T. spiralis is the predominant species, 

but T. pseudospiralis and T. murrelli have also been identified 

(fig. 2). In addition, a freeze-resistant isolate of Trichinella

T6 that likely represents a different species or genotype was 
From Dinosaurs to the 20th Century—the Path of Discovery 5

a farm where several people were suffering from signs of 

trichinosis to determine the source of infection. He linked 

the infection to pork by finding numerous larvae in the ham 

and pork sausage the affected humans had eaten (Campbell, 1983a). He carefully documented a set of clinical signs 

(fatigue, fever, edema, muscle and joint pain) attributed 

to the infection found in the patients, particularly in one 

who died. This association of a defined pathogen with 

a defined disease was a milestone in the elucidation of 

Trichinella as a human pathogen and is considered by many 

to be the most significant helminthological contribution 

of the 19th century.

Von Zenker, Leuckart, and Virchow all contributed to an 

understanding of the epidemiology of Trichinella through 

their discoveries, which included recovery of the tiny adult 

parasites in the gut and larvae in the muscles of animals 

fed infected meat, early maturation of the adults in the gut, 

migration of larvae in the lymphatics, and finding larvae 

in the uterus of mature worms. It was now clear that infection was from ingestion of meat and that adult worms and 

larvae developed in the same host. 

Following the definition of trichinosis as a disease of 

humans with a known cause, numerous outbreaks in 

Europe and the United States were reported. In 1863, 158 

people in Germany were infected with Trichinella by eating 

infected pork, and 28 of those people died (Foster, 1965). 

In 1864, trichinosis was reported in the United States, and, 

in 1871, in England. By the 1870s, inspection of pig meat 

by trichinoscopy became mandatory in many parts of 

Germany thanks to the work of Virchow, Leuckart, and von 

Zenker. By the late 1800s, Trichinella infection in pigs was 

recognized as a major problem in the United States, and 

this caused many European countries to ban the import of 

American pork products. To protect this market, in 1894 the 

United States passed the Federal Meat Inspection Program 

for pork, which required trichinoscopy of export pork.

Additional legislation requiring the cooking of garbage to 

be fed to pigs was passed in the United States in 1953 

to combat another disease, vesicular exanthema, but 

the law had a considerable impact on reducing Trichinella

infections in pigs in the United States. At about the same 

time, recommendations for replacing garbage dumps with 

sanitary landfills were published, thus discouraging the 

practice of allowing pigs to scavenge through garbage 

dumps (American Public Works Association and U.S. Public 

Health Service Joint Committee, 1953). Improvements in 

biosecurity and hygiene on pig farms also contributed to 

decreasing trichinosis in pigs. These control measures 

have successfully decreased the prevalence of Trichinella

infection in pigs in the United States from 1.41 percent in 

1900 (Ransom, 1915) to 0.013 percent in 1995 (Gamble and 

Bush, 1999).

isolated from a cougar in Idaho that was eaten by several people as home-cured jerky, resulting in clinical illness (Dworkin 

and others, 1996). Freeze-resistant isolates, T. nativa, are 

found commonly in black bears, and these isolates are more 

likely causes of human infections than non-freeze resistant 

isolates (Worley and others, 1986). 

Trichinella species can be found in a wide range of 

ecological habitats from frigid circumpolar climates to hot 

equatorial climates (fig. 3). In the arctic and subarctic regions, 

T. nativa is commonly associated with carnivores (foxes, 

wolves, polar bears, seals, walrus, etc.), whereas in southern 

Africa T. nelsoni is in carnivores and wart hogs, and 

T. zimbabwensis is in crocodiles and monitor lizards 

(Appendix 1). It is a well-accepted concept that the 

natural distribution of the sylvatic species of Trichinella in wildlife is strongly influenced by climatic 

zones. However, T. spiralis is a cosmopolitan parasite and is found in most areas where pigs are present.
6 Trichinosis

Box 2 Life Cycle of Trichinella spp.

1.

Within hours after an animal ingests meat that contains the larvae of Trichinella spp., they are freed from their muscle 

cysts in the animal’s stomach during the digestive process. Larvae then migrate to the small intestine and penetrate the 

intestinal mucosa to reside within epithelial cells.

1 mm

2.

The larva undergoes four molts within the next 30 hours to become an immature adult worm, either male or female.

1.4−1.6 mm

3−4 mm

3.

Adult worms thread their way through epithelial cells in the small intestine and mate within the mucosa. 

Adult worms can live and reproduce for approximately 10 days to several weeks, depending on the host.

4.

Fertilized eggs develop within female worms, and larvae are deposited within the wall of the intestine 4 to 7 days after 

initial infection. A female worm may produce between hundreds to thousands of larvae for days to weeks before dying and 

passing out of the host.
Life Cycle of Trichinella spp. 7

5.

Larvae, 100 μm long and 6 μm diameter, migrate from the intestine, through the mucosal lymphatics and regional lymph

nodes to the thoracic duct, and then enter the venous circulation. They become distributed throughout the body by 

the peripheral circulation.

6.

Upon reaching skeletal muscle, most commonly the diaphragm, tongue, and masseter muscles, larvae penetrate the membranes covering the muscle fibers to enter the muscle cells, as early as 5 days after infection. They induce changes in the 

host cell to enhance their own survival.

7.

Within the muscle cell, the larvae coil up and, in most Trichinella species, the host muscle cell is transformed into a nurse 

cell to surround and encapsulate the larva by collagen and layers of connective tissue. Larval coiling and encystment

usually take 3 weeks or more.

8.

Encapsulated larvae absorb nutrients from the host muscle sarcoplasm and grow to become infective in about 4 to 

8 weeks. They remain inactive until they are eaten by another host. In some cases, the host may wall off the larvae, 

causing theirt death.
8 Trichinosis

Table 4. Distribution, characteristics, and major hosts of eight currently recognized species of Trichinella.

1

[Modified from Murrell and Pozio, 2000; Capó and Despommier, 1996. D, domestic; S, sylvatic]

Species Genotype Distribution Cycle Resistance 

to freezing

Pathogenicity 

to humans Major hosts

T. spiralis T1 Found on most continents as a 

cosmopolitan parasite

D, S No High Primarily associated with pigs, 

humans, and synanthropic

mammals. Wide host spectrum 

including pigs, rats, dogs, 

wild carnivores, omnivores, 

herbivores, and humans.

T. nativa T2 Arctic and subarctic regions of 

Europe and Asia

S High High Wild carnivores, dogs. Rare in pigs.

T. britovi T3 Primarily in temperate areas of 

South Africa, Namibia, Japan

S Yes High Carnivorous mammals (bears, 

canids, felids), horses, humans. 

Rare in domestic pigs and rats.

T. pseudospiralis T4 Australia, New Zealand, Thailand, 

nearctic and palearctic regions

S No High Broad host range, including 

marsupials and birds. Humans.

T. murrelli T5 Temperate areas of North America, including the United States

S Moderate Moderate Wild carnivores (fox, mustelids, 

felids, walrus, seals), horses, 

humans.

T. nelsoni T7 Southern one-half of Africa S No Low Carnivores in wildlife areas. 

Occasionally in pigs and 

humans.

T. papuae T10 Papua New Guinea D, S Moderate Moderate Pigs, carnivores, saltwater 

crocodiles.

T. zimbabwensis None Zimbabwe S No Unknown Farmed crocodiles and 

monitor lizards.

1

In addition to the identified species, the taxonomic status of genotype T6 (related to T. nativa) and genotypes T8 and T9 (related to T. britovi) 

remain uncertain.

Table 5. Relation between larval forms and host susceptibility of Trichinella spp.

[Adapted from Pozio, 2005. °C, temperature in degrees Celsius]

Host susceptibility and body temperature range

Trichinella species Larval form Mammals

(37.5–40°C)

Birds

(40.5–42.5°C)

Reptiles

(25–32°C)

T. spiralis Encapsulated Susceptible Not susceptible Not susceptible

T. nativa Encapsulated Susceptible Not susceptible Not susceptible

T. britovi Encapsulated Susceptible Not susceptible Not susceptible

T. murrelli Encapsulated Susceptible Not susceptible Not susceptible

T. nelsoni Encapsulated Susceptible Not susceptible Not susceptible

T. pseudospiralis Nonencapsulated Susceptible Susceptible Not susceptible

T. papuae Nonencapsulated Susceptible Not susceptible Susceptible

T. zimbabwensis Nonencapsulated Susceptible Not susceptible Susceptible
Anatomy of the Parasite 9

Box 3 Anatomy of the Parasite

Although Trichinella worms are the smallest nematode 

parasite of humans, they are the largest intracellular

parasite and have been described as “the worm that would 

be virus” (Despommier, 1990). Adult worms are intramulticellular parasites in the intestinal epithelium, where they 

reside in mucosal cells at the base of the villi, the deep 

pits between intestinal villi, and occasionally the tips of 

the villi. The morphology of the parasite’s esophagus is 

characteristic of the Trichinellidae family, and it occupies 

approximately one-third of the body length and is surrounded by large cells (Anderson, 1992). Adult males are 1.4 to 

1.6 mm in length and do not have spicules, but a pair of 

lateral flaps is found on each side of the cloacal opening

and two pairs of papillae are between them. Females are 

3 to 4 mm in length, and the vulva opens in the middle of 

the esophageal region. Females are viviparous (produce 

live young rather than eggs), and the viable larvae develop 

within the adult female 4 to 7 days after infection (Anderson, 1992). Adult worms usually live for less than 4 weeks, 

but longevity varies among hosts.

Adult female

Muscle cell

Internal fluids

Nerve ring

Stichocytes

Esophagus

Midgut

Hindgut

Intestinal gland cell

Testis

Seminal vesicles

Cloaca

Copulatory appenda

Muscle cell

Internal fluids

Nerve ring

Stichocytes

Esophagus

Hindgut

Uterus

Ovary

Embryos

Developing larvae

Newborn larvae

Rectum

Adult male

Morphology of adult male and female Trichinella worms. 

(Modified from Villela, 1970)
10 Trichinosis

spiralis

nativa

murrelli

T6

pseudospiralis

Trichinella species

EXPLANATION

Figure 2. Distribution of Trichinella species found in the United States. (Modified from International Trichinella Reference Center)
Geographic Distribution 11

T. pseudospiralis T. zimbabwensis

T. papuae

T. britovi

T6

T8

T9

T. murrelli

T. nelsoni

T. nativa

T. spiralis

A

C

B

D

 and genotypes T6, T. britovi , D. nativa; , and T T. nelsoni . murrelli, T, C; . zimbabwensis T , and T. papuae T. pseudospiralis, , BT. spiralis; 

richinella Reference Center)

, A Geographic distribution of Figure 3.

T8, and T9. (Modified from International T
12 Trichinosis

0

100

200

300

400

500

600

1947 1950 1953 1956 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007

YEAR

NUMBER OF CASES

Figure 4. Number of human cases of trichinosis in the United States, 1947–2007. (Data from Centers for Disease Control and 

Prevention, 2007; Centers for Disease Control and Prevention, 1994)

Patterns and Trends

Trichinosis has been a known public health threat for over 

150 years and continues to be an important human disease 

throughout the world. Worldwide, as many as 11 million 

humans may be infected (Dupouy-Camet, 2000). In many 

countries, such as the United States, the number of reported 

cases has decreased significantly during the last 50 years 

(fig. 4), largely because of improvements in surveillance, 

public education, animal husbandry systems, and hygiene. A 

survey of 12,000 human cadavers in the 1940s in the United 

States indicated that one in six was infected (Stoll, 1947). In 

the 1970s and 1980s, the number of cases in the United States 

was less than 300 per year, and between 1990 and 2006, the 

number of reported cases was less than 30 per year. However, 

trichinosis is an emerging and re-emerging disease in many 

countries, especially in Eastern Europe (Box 4). In the 1990s, 

an increased prevalence of up to 50 percent in swine herds in 

Byelorussia, Croatia, Latvia, Romania, Russia and Ukraine 

was reported (Pozio, 2001). In Argentina, Bolivia, Chile, and 

Mexico, trichinosis is still endemic and prevalent, primarily 

because of an increase in the number of small farms that often 

lack good management practices, lack of sanitary regulations, 

lack of regulations for home slaughter, and the misconception 

that trichinosis is no longer a disease concern (Gajadhar and 

Gamble, 2000). Major reasons for the dramatic increase in 

prevalence in many other countries include lack of veterinary 

control, poor diagnostics, war, political turmoil, changes in 

animal husbandry, changes in food marketing and distribution 

systems, manipulation of ecosystems, human practices, complacency, and an increase in wildlife reservoirs (Pozio, 2001). 

For more than 100 years after the discovery of T. spiralis, 

it was believed that transmission to humans occurred only 

through the consumption of pork, but in the last 50 years 

new transmission patterns have been discovered as a result 

of in-depth epidemiological investigations and advanced 

techniques in biotechnology (Pozio, 2000a; 2001). The new 

patterns in the epidemiology and transmission of trichinosis 

are related to several factors, including dramatic changes 

in the interaction between animals and humans and the 

discovery of three nonencapsulated species of Trichinella: 

T. pseudospiralis, which infects a wide variety of mammals 

and birds; T. papuae, which was discovered in New Guinea, 

a new geographical location (Pozio and LaRosa, 2000); and 

T. zimbabwensis, which infects cold-blooded vertebrates, the 

crocodile, and the monitor lizard (Pozio and others, 2002; 

Pozio, 2005). These new patterns were previously unknown 

because of the difficulty in detecting nonencapsulated larvae 

in muscles. Advanced techniques in biotechnology have 

been used to identify new parasites, to trace infections to 

their source, and to identify the location of transmission 

(Murrell and others, 2000). With this improved knowledge 
Species Susceptibility 13

and the development of new techniques for the isolation and 

identification of these parasites, it is likely that identification 

of new species and new patterns of transmission will follow. 

Species Susceptibility

Trichinosis is primarily a disease of pigs, humans, rats, 

and carnivorous wildlife. Pigs and wild carnivores are the two 

animal groups of hosts that are most frequently infected with 

one or more species of Trichinella. After humans and animals 

ingest meat infected with Trichinella larvae, most infections are subclinical and remain undetected. However, when 

infections are moderate to heavy, symptoms can be severe 

and death can result. All mammals are likely susceptible to 

Trichinella infections, and many of these animal species are 

susceptible to infection with more than one Trichinella species (Appendix 1).

Human Infections

In humans, trichinosis is an important food-borne disease 

that can cause acute and chronic illness. Humans are only 

infected with Trichinella larvae through the ingestion of meat 

that has not been properly cooked. All species of Trichinella, 

except for the nonencapsulated species (T. pseudospiralis, 

T. papuae, and T. zimbabwensis), can be highly pathogenic

in humans (Jongwutiwes and others, 1998; Kociecka, 2000). 

T. spiralis is apparently more pathogenic in humans than 

other species because more larvae are produced by the female 

worms (Pozio and others, 1992). In the Arctic, two distinct 

human disease syndromes associated with eating walrus meat

infected with T. nativa have been observed (Box 5) (MacLean 

and others, 1992). Recently, T. papuae has been implicated 

in outbreaks of human trichinosis (Khumjui and others, 

2008; Lo and others, 2009). Twenty-eight people in Thailand 

became sick after eating wild boar and suffered symptoms of 

trichinosis, and T. papuae was identified in a muscle biopsy

from one of the patients (Khumjui and others, 2008). T. papuae was also suspected as the cause of an outbreak of trichinosis in eight people who had eaten raw soft-shelled turtles in 

Taiwan (Lo and others, 2009).

Clinical manifestations are often complex, and they 

depend on the age of the human host, the state of resistance, 

and the numbers of larvae ingested. Most clinical symptoms 

are present between 1 and 6 weeks after infection (Capó and 

Despommier, 1996), and the psychological effects of affected 

humans further complicate the physical symptoms of the disease. Three stages of disease in humans have been described: 

the enteral or intestinal phase, the migratory or mucosal 

invasion phase, and the parenteral or convalescence phase 

(Box 6) (Gould, 1983). 

Animal Infections

Domestic animals and wildlife seem to tolerate high levels 

of infection with very few or no clinical signs of infection, 

even though many wild carnivores are highly susceptible. 

Domestic pigs and rats are resistant to infection with several 

of the sylvatic species of Trichinella. Malnourished, stressed, 

immunocompromised, or debilitated hosts appear to be more 

susceptible than healthy hosts to infections that normally 

cause lower infections in a particular host species. 

Domestic Animals

Pigs 

Pigs are the usual host for T. spiralis, but they rarely show 

signs of infection. Pigs are naturally resistant to most species 

of sylvatic Trichinella, except for T. pseudospiralis. Only 

experimental doses of 100,000 T. spiralis larvae in young pigs 

induced severe pathological changes and death (Dick and 

Pozio, 2001). Young pigs appear to be more susceptible than 

older pigs to infection. If pigs are infected by sylvatic species, 

few adult worms develop and few larvae survive (Kapel and 

others, 1998). 

Horses 

Trichinella spiralis, T. britovi, and T. murrelli have 

occasionally been found in horses (Boireau and others, 

2000), suggesting that horses may be infected in areas where 

many infected meat scraps are available in the environment. 

Horses likely become infected by inadvertently consuming 

meat scraps with vegetation. Horses are uncommon hosts for 

Trichinella spp. because they are not meat-eating animals, but 

over 3,000 human infections have been traced to ingestion 

of raw or improperly cooked horsemeat. Horses are important in the transmission of T. spiralis to humans in Italy and 

France, where horsemeat is eaten raw or undercooked. Since 

1975, more than 3,000 human cases of trichinosis in Italy and 

France have been linked to the consumption of horsemeat 

(Dupouy-Camet, 2000).

In Canada, Trichinella larvae were not detected in over 

200,000 horses that were examined between 1995 and 1999 

(Polley and others, 2000), indicating the limited role of horses 

in the maintenance of the parasite. Experimental infections 

of horses with 5,000 to 50,000 T. spiralis larvae resulted in 

no major clinical signs, but two horses infected with 50,000 

larvae had stiff hind legs, and one horse had an elevated rectal 

temperature (Soule and others, 1989). Naturally infected 

horses with heavy infections of 600 larvae per gram of 

muscle showed no apparent clinical signs.
14 Trichinosis

Box 4 Trichinosis as an Emerging Disease

Trichinosis has been regarded as a public health threat 

for more than 150 years. During this time, government 

agencies implemented regulatory measures in efforts to 

control and eradicate the disease in pigs and humans. 

Although the infection has not been eradicated, people in 

the United States and other areas of the world may tend 

to believe their risk of contracting trichinosis is very small. 

However, in the past 10–20 years, numerous outbreaks 

around the world and recent epidemiological findings have 

demonstrated that trichinosis is, indeed, a re-emerging 

disease in both developed and developing countries (Murrell and Pozio, 2000; Dupouy-Camet, 2000; Pozio, 2001). 

Many factors have contributed to the increasing prevalence 

of Trichinella spp. infections, from both domestic and 

sylvatic cycles.

Improved technology has resulted in detection of significantly more cases of trichinosis in both humans and 

animals than was expected (Murrell and Pozio, 2000) by 

enabling the detection of low numbers of larvae in animals 

and antibodies in infected people. Cases of trichinosis that 

would previously have been misdiagnosed as influenza are 

now being correctly classified and reported. In addition, advanced technologies have enabled researchers to identify 

the particular species of Trichinella involved in outbreaks 

and individual infections, demonstrating the increasing 

importance of sylvatic species in causing human infections.

Changes in animal husbandry can result in decreases or 

increases in trichinosis. Since World War II, no Trichinella

infections have been reported in pigs on industrialized pig 

farms in Western Europe because of control measures put 

in place to limit their contact with rodents and to prevent 

feeding pigs uncooked animal protein (Pozio, 2001). However, as the numbers of small backyard farming operations 

increase in many countries and as more pigs are raised in 

open pastures for humane reasons, pigs are being exposed 

to more sources of Trichinella, for example, in their feed 

and by contact with wild reservoirs of infection. Pigs raised 

on these “ecological” farms for personal or local consumption are not always required to be tested for Trichinella

infection, thus the meat from these animals poses a risk to 

the people who eat it.

Lack of veterinary surveillance controls in many countries 

where it is not required and of most backyard pigs raised 

by local inhabitants has also contributed to the increase 

in Trichinella infections. Outbreaks of trichinosis from 

ingestion of infected horsemeat in France and Italy have 

been attributed to inadequate or nonexistent testing of 

horsemeat. As a result, mandatory testing for Trichinella

in horsemeat was implemented in Europe in 1985 and has 

been periodically strengthened to decrease the risks of 

eating horsemeat.

Countries where trichinosis was emerging or declining, 

1965–99.

[Data from Dupouy-Camet, 2000]

Number of outbreaks1

Country 1965–1989 1990–1999

Countries where trichinosis was emerging

Russia 10 9

China 2 13

European Union 17 16

Yugoslavia 2 71

Countries where trichinosis was declining

United States 18 3

Canada 11 1

Slovakia 6 0

1

Number of outbreaks reported in journals indexed in 

MEDLINE.
Trichinosis as an Emerging Disease 15

Political turmoil and war may result in a decrease in biosecurity and government quality control of the meat processing industry, as well as a reduction in hygiene practices and 

the decreased availability of protein sources (Murrell and 

Pozio, 2000). Eastern Europe has been especially impacted 

by the increase in trichinellosis for these reasons. In Serbia, 

during the 1990s, Trichinella infection of pigs spread from 

four restricted areas to almost one-third of the country 

(Cuperlovic, 2001).

Changes in food marketing and distribution systems have 

resulted in worldwide distribution of potentially contaminated meats from enzootic countries. The horsemeat 

involved in outbreaks of trichinosis in France and Italy 

was imported from eastern Europe and Mexico, where the 

domestic cycle of Trichinella is enzootic (Pozio, 2000b). 

Increased international travel of more visitors to enzootic 

countries has resulted in increased exposure of those 

travelers to local foods that may be contaminated with 

Trichinella larvae. These infections may be spread when 

travelers bring back local delicacies to share with their 

families and friends.

Manipulation of ecosystems may provide for increased 

exposure to a variety of reservoir animals. An increase 

in forested area in Europe has led to an increase in the 

numbers of wild boars and bears, contributing to the 

maintenance of sylvatic trichinosis (Dupouy-Camet, 2000; 

Saunders, 2008). An increase in these wildlife reservoirs 

of trichinosis provides a continual source of infections for 

humans who eat wild game meat, as well as an increase in 

the risk of the infection spilling over into domestic animals 

that humans may eventually eat.

Human practices can increase the risk for infections in 

wildlife and domestic animals, as well as people. Allowing 

access of wildlife to viscera from slaughtered animals 

can dramatically increase the prevalence of Trichinella

in reservoir animals. The use of wild game as food and 

consumption of meats that have not been properly cooked 

can be responsible for localized outbreaks (Margolis and 

others, 1979; Dworkin and others, 1996; Moorhead and 

others, 1999; Forbes, 2000; Centers for Disease Control and 

Prevention, 1996, 2004, 2009; Ancelle and others, 2005; 

Wang and others, 2006). Horses, which are herbivores, may 

become infected with Trichinella by inadvertently eating 

feed contaminated with infected rodents or by being deliberately fed animal protein supplements for fattening prior 

to slaughter (Pozio, 2000a; Murrell and others, 2004).

Complacency is the result of many humans believing the 

food they eat in the form presented to them is completely 

safe. Appropriate testing and surveillance of meat products 

are key to the prevention of food-borne infections. As 

people become more interested in eating local food, they 

may increase their risk of becoming infected with Trichinella. Backyard butchering, which bypasses inspection for 

Trichinella, has led to numerous cases of the infection in 

several countries (Murrell and Pozio, 2000; Pozio, 2000; 

Gottstein and others, 2009). In the United States, while 

trichinosis from commercial pork has decreased, the proportion of cases associated with consumption of wild game 

has increased (Moorhead and others, 1999; Centers for 

Disease Control and Prevention, 1996, 2009). Vigilance concerning proper food preparation is always needed to ensure 

the safety of what is eaten. Just because food is “fresh” 

doesn’t mean it can safely be eaten raw or undercooked. 

Recent increases in the incidence of human cases of trichinosis in three countries.

Country Time period Increase 

in incidence Reference

Romania 1983–1997 17 times Olteanu, 1997

Argentina 1993–2000 7 times Bolpe and Bofi, 2001

Lithuania 1989–1994 9 times Rockiene and Rocka, 1997
16 Trichinosis

Box 5 Trichinosis among Native Arctic Subsistence Hunters

Approximately one-tenth of the roughly 4 million people living in the Arctic region, which contains the Arctic Ocean as 

well as parts of Canada, Greenland, Russia, Alaska, Iceland, 

Norway, Sweden, and Finland, are indigenous (Larsen, 

2004). These people, sometimes known as Eskimo (“eaters 

of raw meat”) or Inuit (“real people”), have adapted to 

life on the ice-covered ocean and treeless frozen ground 

and depend largely upon subsistence hunting for their 

food supply. Traditional food includes seal, whale, caribou, 

walrus, polar bear, Arctic hare, fish, and birds eaten fresh or 

frozen, raw, boiled, or fermented.

Trichinosis has been specifically named as “a direct threat 

to human health in communities that rely on wildlife as 

a source of food” (Parkinson, 2008) by the current 4th

International Polar Year (IPY, 2007–2008), which featured 

human health as a research theme with the ultimate goal 

of improving the health and well being of Arctic peoples. 

Surveys for Trichinella in human cadavers in the 1940s and 

1950s found a substantially higher prevalence in northern Canada (22–46 percent) compared with other areas 

(1.5–7.3 percent) (Appleyard and Gajadhar, 2000). The rate 

of human cases of trichinosis in the Northwest Territories 

and Quebec has been reported to be 200 times the national 

rate in Canada (Appleyard and Gajadhar, 2000), indicating 

a high risk of acquiring the infection from consuming Arctic 

wildlife. In the United States, Alaska has the highest rate of 

trichinosis (MacLean and others, 1989).

The prevalence of Trichinella infection in polar bears and 

walruses has been shown to range from 24 to 61 percent 

and 2 to 9 percent, respectively. In northern Quebec, up 

to 11 percent of the walruses are infected with T. nativa

larvae, resulting in periodic outbreaks of trichinosis in the 

Inuit who consume the meat either raw or insufficiently 

cooked. In general, Inuit of the Canadian Arctic prefer to eat 

polar bear meat well-cooked and walrus meat raw, making 

walrus meat a more common source of trichinosis. Although 

cases of trichinosis caused by eating polar bear meat 

have occurred in Inuit (Davies and Cameron, 1961), large 

outbreaks of the disease have resulted from consumption of 

infected walrus meat that has been widely distributed in a 

community according to the local tradition of sharing meat 

(Serhir and others, 2001).

Outbreaks of trichinosis in North American Native Arctic peoples from eating 

walrus meat.

Date Location Number of cases Reference

1975 Alaska 26 Margolis and others, 1979

1976 Alaska 4 Margolis and others, 1979

1982 Canada 10 Viallet and others, 1986

1983 Canada 40 MacLean and others, 1989

1984 Canada 9 MacLean and others, 1989

1984 Canada 15 MacLean and others, 1989

1987 Canada 42 MacLean and others, 1992

1999 Canada 62 Serhir and others, 2001

Photo courtesy of the U.S. Fish and Wildlife Service.
Trichinosis among Native Arctic Subsistence Hunters 17

In the Arctic, two distinct human disease syndromes associated with eating walrus meat infected with T. nativa

(MacLean and others, 1992) have been observed. The first 

syndrome is the classical muscular infection characterized by edema, fever, muscle pain, and rash. The second 

is thought to represent reinfection in previously infected 

humans, and it is characterized by persistent diarrhea that 

may last for several weeks.

A novel prevention program for human trichinosis has been 

instituted recently for Inuit peoples in northern Quebec 

(Proulx and others, 2002). When walrus are harvested, 

samples of tongue, digastricus, and intercostal and 

pectoral muscles are sent to a regional laboratory where 

the meat is tested with digestion methods and polymerase 

chain reaction (PCR) technology. When positive samples are 

identified, the meat from infected carcasses is destroyed 

rather than being eaten. This procedure has been accepted 

by the Inuit, and it has significantly reduced the number of 

human infections. Public education is the key factor to the 

success of this prevention program.

Urban area diet

Arctic region diet
18 Trichinosis

Box 6 Stages of Trichinosis in Humans

The clinical presentation of trichinosis in people varies and is influenced by the number of 

infective larvae ingested, the strain of Trichinella involved, and individual host factors such as 

age, sex, and immune status (Pawlowski, 1983; Ljungström and others, 1998).

Phase 1: Enteral Phase—penetration 

of larvae into intestinal mucosa and 

development to adults

Twelve hours to 2 days after the ingestion of infected meat, 

symptoms appear as worms are released from ingested 

muscle tissue and migrate through the intestinal epithelium. Symptoms may include diarrhea, nausea, abdominal 

pain, vomiting, and malaise. Most people who become 

infected suffer only mild transient diarrhea and nausea; 

people who have ingested low numbers of larvae may not 

experience any illness during this phase. Clinical signs 

mimic other intestinal disorders, such as food poisoning, 

and can cause the disease to be misdiagnosed if medical 

attention is sought after the onset of symptoms.

Signs and symptoms in mild to moderate trichinosis infection in 

humans.

[Capó and Despommier, 1996]

Sign/symptom1 Number of people affected, 

in percent

Diffuse muscle pain 30–100

Periorbital and/or facial edema 15–-90

Conjunctivitis 55

Fever 30–90

Headache 75

Skin rash 15–65

Paralysis-like state 10–35

Difficulties in swallowing 35

Bronchitis 5–40

Hoarseness 5–20

1

Infected people may also experience insomnia, anorexia, weight loss, 

peripheral nerve sensations, hot flashes, profuse nasal discharge, splinter

hemorrhages of the nail beds or the retina or both, visual disturbances, and 

paralysis of the ocular muscles.

Larvae released 

in small intestine

Larvae mature to 

adults

Adults produce larvae

Larvae get in 

circulation and 

are deposited in 

muscles
Stages of Trichinosis in Humans 19

Above: Clinical appearance of the conjunctivitis 

caused by trichinosis. 

Left: Splinter hemorrhages under the finger nails 

caused by trichinosis.

Both photos courtesy of the Centers for Disease Control 

and Prevention; photos by Dr. Thomas F. Sellers

Phase 2: Migratory Phase

Two to 6 weeks after infection, newborn larvae enter the 

venous circulation and migrate through tissues, causing 

mechanical damage to tissues as well as eliciting allergic 

responses from the host that lead to signs and symptoms 

that differ from those of the enteral phase. High numbers 

of white blood cells (eosinophils) appear about 2 weeks 

after infection. Damage to blood vessels may lead to localized edema in the face and hands. It is often during this 

phase that infected people first seek medical attention, especially if they have not experienced any symptoms during 

the initial phase of infection. During the migratory phase 

of infection, humans often have trouble walking, breathing, chewing, and swallowing because the muscles most 

heavily infected are masseters, muscles of the tongue, 

diaphragm, larynx and neck, the intercostals, and the 

muscular insertions of tendons and joint capsules.

In extremely heavy infections, signs and symptoms, such as 

high fever and severe muscle pain and swelling, are more 

prominent. Larvae may invade cardiac muscle or neural tissue, resulting in myocarditis, neuritis, and other central 

nervous system disorders. Common neurologic signs 

include headache, vertigo, tinnitus, loss of the ability to 

speak or write, and convulsions (Capó and Despommier, 

1996). Death in humans is usually associated with damage 

to the heart muscle and may occur between the third to 

fifth weeks after infection.

Phase 3: Parenteral Phase—penetration of 

muscle fibers by juveniles and nurse cell 

formation

In phase 3, patients may have few signs or symptoms 

because convalescence begins between 5 to 6 weeks after 

ingestion of infected meat. Some patients may continue 

to lose weight and feel tired. Patients who ingested large 

numbers of larvae may suffer the effects of the infection 

for up to 10 years after recovery (Harms and others, 1993). 

Infectious larvae can remain encysted in nurse cells months 

to years after recovery from clinical illness (Pawlowski, 

1983). Some patients may suffer protracted recoveries 

with depression and fatigue due to psychological effects of 

infection. Proper mental therapy is important to reassure 

patients that they can function normally in spite of the presence of encysted larvae in their muscles (Pawlowski, 1983).

Long-term effects in humans after severe trichinosis 

infection.

[Harms and others, 1993; Feldmeier and others, 1991]

Effect Number of people affected, 

in percent

Generalized myalgia 84–90

Ocular symptoms1 59–63

Abnormalities of the 

nervous system

35–52

1

Conjunctivitis, difficulty in focusing, burning sensation
20 Trichinosis

Ruminants 

Trichinella larvae are rare in ruminants, although sheep, 

goats, and cattle are susceptible to experimental infections 

(Murrell, 1994; Theodoropoulous and others, 2000). Human 

infections in China have been traced to eating domestic sheep 

(Wang and others, 1998; Takahashi and others, 2000). 

Wildlife 

A wide variety of wildlife hosts are the principal reservoirs 

for the sylvatic species of Trichinella, and some wildlife 

species also harbor T. spiralis (table 2 and Appendix 1). All 

species of wildlife, but especially carnivores, are more than 

likely susceptible to at least one of the species of Trichinella, and many wildlife species are hosts for more than one 

species. Numerous wildlife surveys have been conducted 

throughout much of the world and have been summarized 

(Kim 1983; Murrell and Pozio, 2000; Dick and Pozio, 2001). 

The data presently available clearly indicate that most mammals, some birds, and some reptiles (crocodiles and monitor 

lizards) are susceptible to infection.

Bears 

Trichinella larvae have been detected in many areas of 

North America where black bears have been evaluated (fig. 5) 

(Zimmerman, 1977; Kim, 1983; Schad and others, 1986; 

Stromberg and Prouty, 1987; Butler and Khan, 1992; Dick 

and Pozio, 2001; Pozio, Pence, and others, 2001). In North 

America, the black bear is one host that is a major potential 

source of human infection because bears are hunted and 

eaten. Bears are ubiquitous hosts for Trichinella, and, therefore, the meat should always be cooked well before it is eaten.

Arctic Mammals 

In the Arctic and Subarctic, marine mammals and carnivores are hosts of T. nativa, which has a circumpolar 

distribution (table 6). Polar bears and walrus are two mammals commonly infected with T. nativa, and they serve as 

the usual sources for human infection (Forbes, 2000). High 

prevalence of infection in polar bears throughout the Arctic region has been reported (Thorshaug and Rosted, 1956; 

Fay, 1960; Madsen, 1961; Larsen and Kjos-vHanssen, 1983; 

Born and Henriksen, 1990; Weyermann and others, 1993); 

infection is less prevalent in walrus populations (Forbes, 

2000). Other marine mammals that have occasionally been 

infected include Beluga whales, bearded seals, and ringed 

seals. Reports of Trichinella in Greenland seals, harbor seals, 

and narwhals are not well documented (Forbes, 2000). Arctic 

fox, sled dogs, and other carnivores, such as lynx, likely 

contribute to the life cycle of Trichinella in marine mammals 

by feeding on the infected carcasses of marine mammals 

(Kapel and others, 1996). In turn, carcasses of these landbased carnivores can also serve as sources of infection for 

marine mammals, either directly through carrion feeding or 

indirectly through ingestion of amphipods or fish that have 

fed recently on infected carcasses that have been deposited in 

the ocean (Forbes, 2000). 

Birds

Birds from several countries, including the United States 

(Wheeldon and others, 1983), are occasionally infected with 

T. pseudospiralis, but they are generally resistant to natural 

infections with other Trichinella species. Therefore, birds 

appear to be of limited importance in the maintenance and 

transmission of the parasite.

Cold-Blooded Wildlife

Reptiles and fish have limited importance in the maintenance or transmission of Trichinella infections, but 

T. zimbabwensis has recently been detected in crocodiles and 

monitor lizards in Africa (Mukaratirwa and Foggin, 1999; 

Pozio and others, 2002). T. papuae has been detected in saltwater crocodiles in Papua New Guinea (Pozio and others, 

2004). Among the fish that have been tested, carp retained 

infective larvae of T. britovi in the gut, body cavity, or muscle 

for up to 7 days after infection, indicating that carp are a 

potential source of transmission to other animals (Moretti and 

others, 1997).

Invertebrates 

Experimental infection of various arthropods and arthropod larvae indicated that some arthropods can maintain 

infections for up to several days, suggesting that the role of 

invertebrates in the transmission of Trichinella is limited 

(Pozio, 2000a).
Species Susceptibility 21

Not evaluated

Not detected

4 to 5 percent

6 to 10 percent

Greater than 10 percent

Percent of Trichinella

EXPLANATION

Figure 5. Prevalence of Trichinella spp. in black bears in North America. (Data from Zimmerman, 1977; Kim, 1983; Schad and 

others, 1986; Stromberg and Prouty, 1987; Butler and Khan, 1992; Nutter and others, 1998; Dick and Pozio, 2001; Pozio, Pence, and 

others, 2001)
22 Trichinosis

Table 6. Prevalence of Trichinella spp. in arctic mammals.

[<, less than]

Species Location

Number of animals 

tested positive 

per number tested

Animals tested 

positive,

in percent

Reference

 Carnivores

Polar bear Alaska 57/104 55 Fay, 1960.

56/92 60.9 Weyermann and others, 1993.

Greenland 56/231 24.2 Madsen, 1961.

12/38 32 Born and Henriksen, 1990.

Norway 118/376 31.4 Larsen and Kjos-Hanssen, 1983.

Barents and Norwegian Seas 163/278 59 Thorshaug and Rosted, 1956.

Arctic fox Greenland 16/266 6 Kapel and others, 1999.

Svalbard 8/53 15 Kapel and others, 1999.

Victoria Island Data not given 30 Dick and Pozio, 2001.

European lynx Finland 132/327 40 Oksanen and others, 1998.

Marine mammals

Walrus Russia 1/89 1 Forbes, 20001

.

Greenland 7/615 1 Forbes, 20001

.

Canada 21/600 3.5 Forbes, 20001

.

Barents and Greenland Seas 7/74 9 Forbes, 20001

.

Alaska 1/104 9.6 Forbes, 20001

.

Beluga whale Alaska, Canada, Greenland, 

Norway

1/482 <1 Brandly and Rausch, 1950.

Bearded seal Alaska, Canada, Greenland, 

Norway, Russia

3/876 <1 Forbes, 20001

.

Ringed seal Alaska, Canada, Greenland, 

Norway, Russia

3/2,743 <1 Forbes, 20001.

1

Individual studies cited in Forbes, 2000.
Obtaining a Diagnosis 23

Obtaining a Diagnosis

Methods for diagnosing trichinosis are similar for both 

humans and other animals. Over the last 100 years, the standard method for diagnosis of Trichinella larvae from muscles 

is trichinoscopy, which is the process of compressing small 

pieces of striated muscle, obtained by biopsy or after death, 

between two plates of glass and then viewing the pieces of 

muscle under a dissecting or compound microscope. Magnified larvae can be seen coiled in the compressed muscles 

(fig. 6). The preferred muscles for evaluation are the diaphragm, tongue, masseter, or intercostal. A second preferred 

method of diagnosis is the digestion method; muscle tissue 

is placed in a 1-percent hydrochloric acid-pepsin solution at 

37°C for several hours, and then the digest is filtered through 

a screen with a grid of 80 meshes per inch. Larvae can then be 

observed and counted under a dissecting microscope, and data 

can be quantified as number of larvae recovered per gram of 

tissue. Histopathologic evaluation of preferred muscles is a 

third useful technique, especially in heavy infections. Adults 

are not commonly found in intestine because they usually 

are very small and live for less than 2 weeks. However, after 

recent ingestion of infected meat, adult worms can be found in 

the mucosa and epithelium of the small intestine with the aid 

of a dissecting microscope. 

The diagnosis and identification of species and genotypes of Trichinella larvae have been dramatically improved 

through the development and application of biochemical 

techniques (LaRosa and others, 1992), molecular biology 

(Zarlenga and others, 1991), and PCR technology (Bandi and 

others, 1995; Zarlenga and others, 1999). Whereas these tests 

are valuable for identifying isolates of Trichinella and for 

surveys of animal populations, they are not recommended as 

a substitute for direct testing by trichinoscopy evaluation or 

digestion methods. Numerous immunological tests have been 

used to detect antibodies or circulating antigens (table 7) 

(Zarnke and others, 1997; Kociecka, 2000; Nockler and 

others, 2000). In humans, a history of eating infected meat, 

clinical symptoms, increased muscle enzyme levels, and the 

presence in blood of 5 to 80 percent or more eosinophils—a 

type of white blood cell—are also helpful in the diagnosis of 

infection (Capó and Despommier, 1996; Kociecka, 2000).

Figure 6. Coiled larva in compressed muscle. 

Photo courtesy of William Foreyt
24 Trichinosis

Table 7. Common techniques for evaluating exposure to Trichinella spp. in humans and other animals.

Technique Tissues evaluated Comments

Diagnosis of trichinosis

Trichinoscopy Diaphragm, tongue, 

masseter, intercostal 

muscles

Gold standard for diagnosis of Trichinella larvae 

in muscle tissue.

Digestion Same Another preferred assay for muscle tissue 

evaluations.

Histopathology Muscles and intestine Especially useful in heavy infections.

Polymerase chain reaction (PCR) Muscles and blood Not routinely used; expensive. May become 

more routinely used to detect circulating larvae or small numbers of larvae in 

muscle tissue.

Surveys and isolate identification

Enzyme-linked immunosorbent assay 

(ELISA)

Blood serum Detect antibodies to Trichinella spp. exposure; 

used to determine prevalence of infections and 

early detection of infection.

Indirect immunoflourescence test

Competitive inhibition assay

Immunoblotting

Counterimmunoelectrophoresis

Immunoradiometric assay

Blood Detection of antibodies or circulating antigens.

Polymerase chain reactionrestriction fragment length 

polymorphism (PCR-RFLP)

Larvae Distinguish among species of Trichinella larvae. 

May be useful in identifying subspecies or 

geographical strains. Applicable to identifying 

sources of infection.

Disease Ecology

The usual source of trichinosis in humans is from eating pork products or meat from horses, dogs, or a variety of 

wildlife species, including wild pig, bear, walrus, and seal. 

Trichinella spp. are transmitted by two specific cycles, the 

domestic cycle and the sylvatic cycle (Campbell, 1983b; 

Dick and Pozio, 2001).

Domestic Cycle

The domestic cycle of transmission primarily involves 

T. spiralis in a cycle of pig-to-pig transmission, and humans 

enter the cycle through eating pork (fig. 7). The infection can 

be highly pathogenic in humans. Synanthropic rats, mice, 

cats, dogs, and horses, as well as many wildlife species, also 

contribute to the cycle in many areas. Pigs maintain the cycle 

by eating pieces of infected meat scraps, eating infected 

rats or mice, biting the tails of infected pigs, cannibalizing 

dead pigs, ingesting feces from pigs that have recently eaten 

infected meat, or eating other species of infected mammals 

(fig. 8). The domestic cycle is prevalent on small farms where 

disease control is not a primary objective in food production. 

Areas where infection is endemic are found throughout the 

world (fig. 9) (Dupouy-Camet, 2000; Ortega-Pierres and others, 2000; Dick and Pozio, 2001). In areas where pig trichinosis is enzootic, T. spiralis often is transmitted to wildlife 

and, occasionally, to horses (Kapel, 2000). Pigs, synanthropic 

mice and rats, and humans are the usual hosts for T. spiralis, 

but sylvatic species of Trichinella can also infect these hosts. 

Conversely, T. spiralis is also present in wildlife. In the 

United States, T. spiralis has been reported from black bear 

and gray fox in Pennsylvania; coyote in Indiana; raccoon, 

coyote, and red fox in Illinois; wild boar in New Hampshire; 

grizzly bear and bobcat in Montana; black bear in Arizona; 

and raccoon, opossum, and skunk in New Jersey (Dame and 

others, 1987; Murrell and others, 1987; Snyder and others, 
Disease Ecology 25

1987; Worley and others, 1994; Dick and Pozio, 2001; Pozio, 

Pence, and others, 2001). In Europe and Asia, T. spiralis and 

T. britovi have been found in wild boars, but in the frigid 

arctic and subarctic regions, T. spiralis is restricted to animals living in close proximity to human settlements (Pozio, 

2000a). Based on all data, T. spiralis larvae in dead tissue are 

poorly adapted to environmental extremes, such as freezing, 

elevated temperatures, and degradation of host tissue. Thus, 

T. spiralis is found less frequently in wildlife when compared 

to the higher prevalence of the sylvatic species of Trichinella.

garbage/

meat scraps

Larvae released 

in small intestine

Larvae mature 

to adults

Adults produce larvae

Larvae get in 

circulation and 

are deposited in 

muscles Figure 7. Domestic cycle of T. spiralis. (Modified from Foreyt, 1990)

Sylvatic Cycle

The sylvatic cycle of transmission (fig. 10) predominantly 

involves predation, cannibalism, or scavenging behaviors of 

species of carnivorous wildlife. Trichinella spp. are transmitted when fresh, frozen, or decomposing carcasses or 

meat scraps are eaten. The parasite persists mostly through 

normal wildlife carnivorous and scavenging feeding habits, 

but humans can influence the prevalence and distribution 

of Trichinella in wildlife in several ways, such as by using 

infected carcasses or meat as bait for attracting animals to be 

harvested (Dick and others, 1986).

The species of Trichinella associated with the sylvatic cycle are T. nativa, T. britovi, T. murrelli, T. nelsoni, 

T. pseudospiralis, T. papuae, and T. zimbabwensis. T. spiralis

can also affect wildlife in temperate and tropical regions, but 

it does not survive in arctic and subarctic regions because 

larvae do not survive in a frozen carcass. Many surveys of 

wildlife throughout the world have indicated various wildlife 

species are often infected with different species of Trichinella 

(Appendix 1). Sylvatic cycles maintain the parasite without pig or human interaction, but humans or pigs enter into 

the life cycle through the ingestion of infected meat. Some 

outbreaks of sylvatic trichinosis in humans have resulted from 

eating meat from bears in Greenland, Canada, the United 

States, Japan, Eastern Europe, and China; walrus in Canada 
26 Trichinosis

Cannibalism

Eat infected meat scraps

Tail biting

Ingest feces from pigs 

that have recently eaten 

infected meat

Eat under cooked pork/horse meat

Eat infected mice/rats

Inadvertently eat infected meat scraps

Figure 8. General domestic pathways for infection with T. spiralis.

and Alaska (Margolis and others 1979; Proulx and others, 

2002); cougar in the United States (Dworkin and others, 

1996); fox in Italy (Dupouy-Camet, 2000); sheep in China 

(Wang and others, 1998); warthog in Africa (Kefenie and 

Bero, 1992); and dog in China and Slovakia (Dubinsky and 

others, 1999). Most of these cases resulted from eating raw or 

improperly prepared meat or meat products, primarily sausage 

(Box 7). The severity of disease is usually directly related to 

the number of larvae eaten and the immune status of the host.

Although pigs are most often infected with T. spiralis, 

T. britovi has been diagnosed in pigs from some European 

countries, T. nativa from a pig in China, T. pseudospiralis

from pigs in Russia, and T. papuae from pigs in southern 

New Guinea (Pozio and others, 1999; Dick and Pozio, 2001). 

Sylvatic species of Trichinella are of minor importance in pigs 

because they do not grow as well in pigs as in wildlife, the 

survival time of larvae in pigs is less than in wildlife, and the 

survival time of larvae in pork that has been exposed to cold 

or heat is limited. Therefore, the occurrence of sylvatic species of Trichinella in pigs is of limited importance compared 

with infections of T. spiralis.

Transmission cycles often vary with the species or isolate 

of Trichinella. In the Arctic and Subarctic, polar bear, brown 

bear, grizzly bear, Arctic fox, wolf, raccoon dog, seals, 

walrus, and other carnivores are commonly infected with 

T. nativa. The parasite is maintained through predation, cannibalism, and scavenging (fig. 11).

Characteristics of T. nativa are (1) a high resistance to 

freezing in muscles (Worley and others, 1990), (2) larvae surrounded by a thick capsule, and (3) low infectivity for domes-
Disease Ecology 27

EXPLANATION

Countries where Trichinella spiralis 

is enzootic in pigs

Figure 9. Countries where T. spiralis is enzootic in pigs. (Data from Dupouy-Camet, 2000; Ortega-Pierres and others, 2000; Dick and 

Pozio, 2001)

tic pigs and laboratory rats and mice. Larvae have survived 

in frozen meat for at least 3 years in naturally infected arctic 

wildlife (fig. 12) (Worley and others, 1986; Kapel and others, 

1999; Dick and Pozio, 2001) and 5 years in experimentally 

infected raccoons (Dick and Pozio, 2001). In mice, pig, 

and wild boar, the freeze tolerance is not present. Survival 

rates for other species and genotypes in meat from laboratory animals and free-ranging wildlife have been published 

(Dick and Pozio, 2001).

Polar bears and Arctic foxes are the primary reservoirs for 

T. nativa in the Arctic. In polar bears, prevalence has been 

shown to increase with age (fig. 13) (Henriksen and others, 

1994). The probable sources of infection in bears are ingestion of infected Arctic foxes and sled dogs. Prevalence of 

infection in Arctic foxes has been reported to range from 

6 to 30 percent (table 6). Infected Arctic foxes in Greenland 

had an average of 38 larvae per gram of muscle (range 0.1 to 

148) (Kapel and others, 1999). In Finland, European lynx are 

important hosts (table 6); the prevalence was correlated with 

the density of raccoon dogs that lynx utilize as food (Oksanen 

and others, 1998).

Trichinella nativa is a rare species in domestic swine 

because the adverse weather conditions and unfavorable habitat in which the parasite is most often found preclude most 

pig exposure to the parasite. Furthermore, larvae of T. nativa 

apparently do not persist in pigs (Kapel and others, 1998). In 

the more temperate regions of the world, T. nativa is present primarily in wild canids, the usual reservoir and source 

of infection.
28 Trichinosis

Box 7 Diet Matters

Although trichinosis is most often associated with consumption of pork products, the infection 

can potentially be transmitted by any of the more than 150 species of animals known to be 

susceptible to infection, if people choose to eat these animals without proper safeguards and 

methods of preparation. Consumers who process their own meat can avoid infection by having it tested for Trichinella larvae before they eat it.

Cougar 

In Idaho, a hunter killed a cougar and processed the meat 

for consumption (Centers for Disease Control and Prevention, 1996; Dworkin and others, 1996). After freezing the 

meat for 3 weeks, he made jerky by soaking it in a brine 

solution of table salt and then smoking it. He failed to use 

a commercial brine known to kill Trichinella larvae, and 

the smoker did not get hot enough to inactivate larvae. 

Eleven of 15 people who consumed the jerky were infected 

with Trichinella, strain T6. Although freezing normally 

kills T. spiralis larvae, T6 larvae are freeze-resistant and, 

thus, freezing was ineffective.

Bear

The consumption of bear meat has caused numerous 

outbreaks of trichinosis. In Canada, seven Chippewayan 

Indians were infected after eating boiled black bear meat 

(Emson and others, 1972). Four hunters in Alaska became 

infected after eating fried black bear meat cooked on a 

camp stove that did not reach high enough temperatures 

to kill the larvae (Alaska Division of Health and Social 

Services, 2000). Twenty-six people were infected with 

T. nativa in Canada after eating undercooked black bear 

meat even though the meat had been previously frozen; 

T. nativa larvae are freeze-resistant (McIntyre and others, 2007). Twelve people in Russia became infected after 

eating improperly cooked meat from an illegally killed bear 

that was not submitted for veterinary inspection (Despommier and Chen, 2004). Another outbreak in Russia involved 

71 people who consumed smoked bear meat (Despommier 

and Chen, 2004).

Wild Boar 

In Ethiopia, where there is a widespread tradition of eating 

raw meat, 20 soldiers who consumed uncooked wild boar 

meat became infected with Trichinella (Kefenie and Bero, 

1992). In Europe, outbreaks of infection with T. britovi as a 

result of eating wild boar have occurred. Twenty-one people 

were infected in Spain after eating sausage made from 

wild boar killed on a private hunt, despite the boar’s testing negative by trichinoscopy (Gallardo and others, 2007). 

Subsequent to the outbreak, the sausage tested positive by 

the artificial digestion method, which is more sensitive than 

trichinoscopy. In France, six people became infected after 

eating undercooked boar meat even though it had been 

previously frozen; T. britovi larvae are freeze-resistant (GariToussaint and others, 2005). One person who ate the boar 

meat well-done did not become infected. T. papuae caused 

an outbreak of trichinosis in 28 people who ate raw wild 

boar meat in Thailand (Khumjui and others, 2008).

Warthog

Three French people developed 

trichinosis after eating warthog ham in 

Senegal (Dupouy-Camet and others, 

2009). Three other people 

who also ate the ham were 

suspected of having trichinosis. The meat had been frozen 

before processing, suggesting 

infection by a freeze-resistant 

species, such as T. britovi.

Jackal 

One person living in France developed 

trichinosis after eating barbecued jackal 

meat while in Algeria (Despommier and Chen, 2004).
Diet Matters 29

Badger 

In Russia, 25 people became infected with Trichinella after 

eating shish kebabs made from badger meat that was not 

thoroughly cooked (Despommier and Chen, 2004). Patients 

claimed badger meat to be tasty, exotic, and cheap.

Walrus 

Numerous cases of trichinosis have occurred in native Arctic peoples as a result of eating raw or undercooked walrus 

meat (see Box 6). Freezing of this meat is ineffective in 

killing the T. nativa larvae causing the infections.

Polar Bear

Subsistence hunters consuming raw or undercooked polar 

bear meat may become infected with T. nativa. It has 

been suggested that three Swedish explorers searching 

for the North Pole by balloon in 1897 died as a result of 

trichinosis. After crashing onto the ice, the explorers were 

forced to hunt and eat polar bears, which they ate partially 

cooked or raw. Their remains and diaries detailing their 

ordeal were found 30 years later. A polar bear carcass with 

Trichinella larvae was also found in their camp. In 1987, 

three people in Alaska developed trichinosis after mistakenly eating dried polar bear meat intended for dogs (Alaska 

Division of Health and Social Services, 1987)

Horse

Since 1975, most cases of trichinosis in 

humans in western Europe have been 

caused by eating horsemeat. 

From 1975 to 1998, there have 

been more than 10 outbreaks 

infecting more than 2800 

people in France and Italy, 

where horsemeat is traditionally eaten fresh and raw 

(Ancelle and others, 1998). In 

1975, 89 people in Italy and 

125 people in France were 

infected in unrelated outbreaks 

with Trichinella as a result of eating 

horsemeat imported from Eastern 

Europe. Horses imported from North 

America have also caused outbreaks of 

trichinosis in France. As a result of the large numbers of 

people who have been infected, more stringent inspection 

methods have been implemented to protect consumers and 

the horsemeat industry in Europe.

Dog

Dog meat, infected with T. britovi and used in making 

smoked sausages, was associated with an outbreak 

among villagers at a folk festival in the Slovak Republic 

(Dubinsky and others, 1999). Five people in Russia developed trichinosis after eating dog meat (Despommier and 

Chen, 2004).

Sheep

In China in 1994, 10 people became infected after eating 

scalded mutton (Mao and others, 1995). The meat had not 

been inspected prior to consumption.

Pig

Consumption of pork products that are produced from 

home-slaughtered pigs not subject to veterinary inspection or from areas with high levels of infection put people 

at increased risk of becoming infected with Trichinella.

Outbreaks in China have resulted from the consumption of 

uninspected meat in poorly cooked dumplings and scalded 

pork dishes (Wang and others, 1998). In Serbia, salami 

made from pork led to the infection of 40–80 people (Bannister and others, 2000). Some of this salami was brought 

back to London as gifts where it infected 8 more people.

Similar outbreaks have occurred as a result of people 

bringing infective pork products from countries with high 

rates of Trichinella infection in pigs into other countries 

(Pozio and Marucci, 2003). Three people from Germany 

visited Romania, where they consumed mince meat, 

sausage, and bacon made from home-slaughtered pigs; 

the source of trichinosis was confirmed in these people 

by testing the pork products brought back with them from 

Romania (Nöckler and others, 2007). Four people in Italy 

were infected with Trichinella after consuming ham from 

an uninspected pig from Romania (Angheben and others, 

2008). Physicians treating patients in countries with low 

prevalence of swine trichinosis may be unfamiliar with diagnosing the infection in people; a history of consumption 

of imported pork products is an important clue in making 

the correct diagnosis of trichinosis.
30 Trichinosis

Walrus

Bears, cougars

Humans

Seals

Other 

carnivores

Figure 10. Sylvatic cycle of Trichinella spp.
Disease Ecology 31

x x

Walrus eat 

amphipods, seals

Arctic fox feed on 

infected carcass

Sled dogs feed on infected carcass

Polar bears eat infected walrus, seal, fox

Humans eat infected 

polar bear/walrus 

meat

Beluga whales/seals 

feed on fish/amphipods 

that have recently fed 

on infected animal 

Figure 11. General pathways for infection of the arctic and subarctic cycles of T. nativa.
32 Trichinosis

Arctic fox Greater than 4 years

Polar bear meat

Black bear

Grizzly bear

3 years

3 years

2 years 10 months

SURVIVAL TIME, IN YEARS

0 1 2 3 4 5

SPECIES

Figure 12. Examples of T. nativa larvae survival times in frozen tissue. (Data from Worley and others, 1986; Kapel 

and others, 1999; Dick and Pozio, 2001)

0

10

20

30

40

50

60

70

1 2–6 7–10 Greater than 10

AGE, IN YEARS

PREVALENCE , IN PERCENT

Figure 13. Increasing prevalence of Trichinella infection with age in polar bears. 

(Data from Henriksen and others, 1994)
Disease Prevention and Control 33

Points to Ponder

 Trichinosis is a food-borne zoonotic disease that is easily preventable in humans. Cooking all meat to an internal 

temperature of 71°C (160°F) will kill all larvae and prevent 

transmission. Freezing meat in areas where freeze-resistant 

Trichinella species are not present will also prevent transmission. International travelers who eat improperly cooked meat 

(McAuley and others, 1991) and people who have dietary 

preferences for raw or lightly cooked meats significantly 

increase their risk for infection. Improperly cooked wild 

game will continue to be a source of infection for hunters and 

others who eat wildlife, but with adequate cooking, human 

infection can be prevented.

However, the epidemiology of the disease has changed 

significantly during the last 10 years, and trichinosis is now 

an emerging disease in many countries, especially in Eastern Europe. As world tourism increases and food transport 

services are improved, the probability of contact between 

humans and infected meat increases dramatically. In countries 

where veterinary inspection, responsible farm management, 

and adequate quality-controlled diagnostic methods are practiced, Trichinella has almost been eliminated from pigs. In 

many less-developed countries, the prevalence of Trichinella

infections has increased because of an increase in the number of small farms. In several countries, the increase in the 

number of small farms with limited numbers of animals has 

resulted in increased farm animal contact with rodents and 

other reservoir hosts of Trichinella, increased feeding of food 

scraps to farm animals, and lack of post-mortem inspection 

of meat. 

Wildlife management is also becoming more important in 

the maintenance and transmission of Trichinella spp. When 

land use and management favor an increase in wild pig and 

wild carnivore populations, an increase in infection rate in 

those animals is likely to result. Although this would have no 

overt effect on population dynamics or the health of infected 

wildlife, the potential for disease transmission to humans is 

likely to increase accordingly. The use of wildlife carcasses 

by hunters and trappers as bait for harvesting other animals 

has also been shown to be important in transmission among 

wildlife species (Dick and others, 1986). For example, 

T. spiralis recently found in a black bear from Arizona, in the 

United States, likely resulted from hunters who attracted the 

bear with raw meat trimmings from supermarkets and restaurants (Pozio, Pence, and others, 2001).

Disease Prevention and Control

Prevention and control of trichinosis is a matter of education and hygiene in the environment and in the home. 

The transmission of trichinosis to garbage-fed pigs can be 

prevented by cooking the garbage to an internal temperature of 71°C (160°F) for 1 minute, thus inactivating Trichinella larvae and eliminating the possibility of transmission 

(Pozio, 2001). Cooking all meat to 71°C (160°F) (Gadjahar 

and Gamble, 2000) will kill larvae and prevent human infection; however it is more effective for producers, meat suppliers, and health agencies to ensure that infected meat does not 

reach the consumer. Good management practices to prevent 

or minimize infection in pigs include biosecurity, rodent 

control, and avoidance of feeding waste (van Knapen, 2000). 

A complete set of recommendations on methods for the 

control of Trichinella in domestic and wild animals intended 

for human use has been published as the official position of 

the International Commission on Trichinellosis (Gamble and 

others, 2000). The recommendations include: 

• Slaughter testing methods to prevent clinical infection 

in humans. For detection of larvae in pigs, pepsinhydrochloric acid digestion of at least 1 gram of 

muscle, or microscopic evaluation of at least 0.5 grams 

of muscle, is a minimum requirement for each carcass. 

For detection of larvae in horses and wildlife, a greater 

mass from preferred muscles is recommended by the 

International Commission on Trichinellosis for testing.

• Cooking the meat. If the meat has not been evaluated 

for larvae, then cooking to a proper temperature for 

a specific time will kill larvae. The time of cooking 

is dependent on the internal temperature of the meat 

(Gamble and others, 2000), but a standard recommendation is to cook to a minimum internal temperature 

of 71°C (160°F). Lower temperatures over time are 

generally also acceptable (table 8). A change in the 

Table 8. Minimum internal cold temperatures and 

times necessary to kill T. spiralis larvae in pork.

[From Gamble and others, 2000. °F, degrees Fahrenheit; 

°C, degrees Celsius]

Minimum internal 

temperature Minimum time

°F °C

0 -17.8 106 hours

-5 -20.6 82 hours

-10 -23.3 63 hours

-15 -26.1 48 hours

-20 -28.9 35 hours

-25 -31.7 22 hours

-30 -34.5 8 hours

-35 -37.2 30 minutes
34 Trichinosis

color of the meat from pink to grey throughout and a 

change in texture such that the muscle fibers are easily 

separated from each other are indicators that the meat 

is safe to eat. Microwave cooking is not recommended 

by the International Commission on Trichinellosis 

because of uneven heating. 

• Freezing the meat. For pork and horse meat with 

T. spiralis larvae, freezing at -15°C (5°F) or lower for a 

minimum of 4 weeks is recommended by the International Commission on Trichinellosis for consumer 

safety (Gamble and others, 2000). For wildlife meat, 

freezing is not recommended because wildlife often 

contains freeze-resistant Trichinella species, which 

survive freezing for long periods. Therefore, proper 

cooking of wildlife meat is recommended. 

• Irradiation. At levels that have been shown to inactivate larvae (0.3 kilogray), irradiation is an acceptable 

method for rendering meat safe for human consumption for sealed packaged food in countries were irradiation methodology is allowed.

• Curing, drying, and smoking. Curing, drying, and 

smoking processes are not recommended by the International Commission on Trichinellosis for control of 

Trichinella in meat because of the variability in the salt 

concentrations, temperatures used, and drying times. 

Only meat that has been found to be free of larvae 

should be used for curing, drying, and smoking.

Theoretically, the disease in humans can be prevented 

through education, by cooking or freezing all pork, by cooking all other meats, and by effective veterinary surveillance 

programs. With modern farm management practices and 

veterinary surveillance, the disease could be eliminated from 

domestic pigs.

Treatment

Most infections in animals and humans are undetected 

because of limited signs and symptoms, and mild infections 

are often misdiagnosed as influenza or other medical conditions. In humans, clinical trichinosis is often treated on a 

symptomatic basis with corticosteroids. Resolution of symptoms is generally the result of corticosteroid treatment rather 

than anthelminthic treatment, suggesting that the symptoms 

associated with trichinosis are primarily inflammatory and 

allergic reactions to the larvae. However, corticosteroid 

treatment may also increase the intensity of muscle invasion 

and may lead to an increased number of larvae in muscles. 

Anthelmintic drugs that have been used to treat infected 

humans are generally benzimidazole derivatives, such as 

albendazole, fenbendazole, flubendazole, and mebendazole (Kociecka, 2000). Pyrantel has also been used to treat 

infected humans. These drugs are often effective against adult 

worms and early migrating larval stages, but they are generally ineffective against larvae once they are encapsulated in 

muscle nurse cells. Therefore, the goal is to treat within the 

first 3 days after infection to kill the adult worms and prevent 

subsequent muscular invasion of larvae and development of 

clinical disease. Encapsulated larvae will live several years in 

muscles until the nurse cell induces the progressive calcification of the larvae. In severe human infections, complications 

of the respiratory, cardiovascular, and neurological systems can occur between 3 and 8 weeks after infection. Severe 

infections in humans can be life threatening, and intensive 

supportive therapy, including hospitalization and administration of fluids to compensate for water and electrolyte deficits, 

is mandated. 

References Cited

Alaska Division of Health and Social Services, 1987, Trichinosis from dried polar bear meat: State of Alaska Epidemiology Bulletin, v. 17, accessed July 16, 2008, at http://www.

epi.hss.state.ak.us/bulletins/docs/b1987_17.htm.

Alaska Division of Health and Social Services, 2000, Five 

cases of trichinosis—Why bear meat must be thoroughly 

cooked: State of Alaska Epidemiology Bulletin, v. 18, 

accessed July 16, 2008, at http://www.epi.hss.state.ak.us/

bulletins/docs/b2000_18.htm

American Public Works Association and U.S. Public Health 

Service Joint Committee, 1953, Refuse collection and 

disposal for the small community: Washington, D.C., 

U.S. Public Health Service, 39 p. 

Ancelle, T., 1998, History of trichinellosis outbreaks linked to 

horse meat consumption 1975–1998: Eurosurveillance, v. 3, 

no. 8, accessed July 14, 2008, http://www.eurosurveillance.

org/ViewArticle.aspx?ArticleId=120.

Ancelle, T., De Bruyne, A.E., Poisson, D., and Dupouy-Camet, 

J., 2005, Outbreak of trichinellosis due to consumption of 

bear meat from Canada, France, September 2005: Eurosurveillance, v. 10, accessed July 14, 2008, http://www.

eurosurveillance.org/ViewArticle.aspx?ArticleId=2809.

Anderson, R.C., 1992, Nematode parasites of vertebrates: 

Their development and transmission: Wallingford, United 

Kingdom, CAB International, p. 552–554.
References Cited 35

Angheben, A., Mascarello, M., Zavarise, G., Gobbi, F., Monteiro, G., Marocco, S., Anselmi, M., Azzini, A., Concia, E., 

Rossanese, A., and Bisoffi, Z., 2008, Outbreak of imported 

trichinellosis in Verona, Italy, January 2008: Eurosurveillance, v. 13, no. 22, accessed July 18, 2008, at http://www.

eurosurveillance.org/ViewArticle.aspx?ArticleId=18891.

Appleyard, G., and Gajadhar, A., 2000, A review of trichinellosis in people and wildlife in Canada: Canadian Journal of 

Public Health, v. 91, p. 293–297.

Bandi, C., La Rosa, G., Bardin, M.G., Damiani, G., Comincini, S., Tasciotti, L., and Pozio, E., 1995, Random amplified polymorphic DNA fingerprints of the eight taxa of 

Trichinella and their comparison with allozyme analysis: 

Parasitology, v. 110, p. 401–407.

Bannister, B., Bhagani, S., Burn, M., Milne, L., 2000, Outbreak of trichinellosis in south east England: Eurosurveillance, v. 4, no. 2, accessed July 18, 2008, at http://www.

eurosurveillance.org/ViewArticle.aspx?ArticleId=1676.

Boireau, P., Vallee, I., Roman, T., Perret, C., Mingyuan, 

L., Gamble, H.R., and Gajadhar, A., 2000, Trichinella in 

horses: A low frequency infection with high human risk: 

Veterinary Parasitology, v. 93, p. 309–320.

Bolpe, J., and Bofi, R., 2001, Causitry of human trichinellosis in Argentina registered from 1990–1999: Parasite, v. 8 

(supp.), p. S78–S80.

Born, E.W., and Henriksen, S.A., 1990, Prevalence of Trichinella sp. in polar bears (Ursus maritimus) from northeastern 

Greenland: Polar Research, v. 8, p. 313–316.

Brandly, P.J., and Rausch, R., 1950, A preliminary note on 

trichinosis investigations in Alaska: Arctic, v. 3, p. 105–107.

Butler, C.E., and Khan, R.A., 1992, Prevalence of Trichinella 

spiralis in black bears (Ursus americanus) from Newfoundland and Labrador, Canada: Journal of Wildlife Diseases, 

v. 28, p. 474–475.

Campbell, W.C., 1983a, Historical introduction, in Campbell, 

W.C., ed., Trichinella and trichinosis: New York, Plenum 

Press, p. 1–30.

Campbell, W.C., 1983b, Epidemiology I: Modes of transmission, in Campbell, W.C., ed., Trichinella and trichinosis: 

New York, Plenum Press, p. 425–444.

Capó, V., and Despommier, D.D., 1996, Clinical aspects of 

infection with Trichinella spp.: Clinical Microbiology 

Reviews, v. 9, p. 47–54.

Centers for Disease Control and Prevention, 1994, Summary 

of notifiable diseases, United States, 1994: Morbidity and 

Mortality Weekly Report, v. 42, p. 1–73.

Centers for Disease Control and Prevention, 1996, Outbreak 

of trichinellosis associated with eating cougar jerky—Idaho, 

1995: Morbidity and Mortality Weekly Report, v. 45, 

p. 205–206.

Centers for Disease Control and Prevention, 2004, Trichinellosis associated with bear meat—New York and 

Tennessee, 2003: Morbidity and Mortality Weekly 

Report, v. 53, p. 606–610.

Centers for Disease Control and Prevention, 2007, Summary 

of notifiable diseases, United States, 2007: Morbidity and 

Mortality Weekly Report, v. 56, p. 1-94.

Centers for Disease Control and Prevention, 2009, Trichinellosis surveillance, United States, 2002–2007: Morbidity and 

Mortality Weekly Report, v. 58, p. 1–9.

Cui, J., and Wang, Z.Q., 2001, Outbreaks of human trichinellosis caused by consumption of dog meat in China: Parasite, 

v. 8 (supp. S), p. S74–S77.

Cuperlovic, K., Djordjevic, M., Pavlovic, S., and SofronicMilosavljevic, L., 2001, Present status of trichinellosis in 

Yugoslavia-Serbia: Parasite, v. 8, p. S95–S97.

Dame, J.B., Murrell, K.D., Worley, D.E., and Schad, G.A., 

1987, Trichinella spiralis: Genetic evidence for synanthropic subspecies in sylvatic hosts: Experimental Parasitology, v. 64, p. 195–203.

Davies, L.E.C., and Cameron, T.W.N., 1961, Trichinosis in the 

Northwest territories: Medical Services Journal of Canada, 

v. 17, p. 99–104.

Despommier, D.D., 1990, Trichinella spiralis: The worm that 

would be virus: Parasitology Today, v. 6, p. 193–196.

Despommier, D., and Chen, S.X., 2004, The trichinella page: 

New York, Columbia University, Malman School of Public 

Health, accessed June 10, 2008, at http://www.trichinella.

org.

Dick, T.A., Kingscote, B., Strickland, M.A., and Douglas, 

C.E., 1986, Sylvatic trichinosis in Ontario, Canada: Journal 

of Wildlife Diseases, v. 22, p. 42–47.

Dick, T.A., and Pozio, E., 2001, Trichinella spp. and trichinellosis, in Samuel, W.M., Pybus, M.J., and Kocan, A.A., 

eds., Parasitic diseases of wild mammals: Ames, Iowa State 

University Press, p. 380–396.
36 Trichinosis

Dubinsky, P., Kinecekova, J., Tomasovicova, O., Reiterova, 

K., Ondriska, F., and Budajova, D., 1999, Trichinella 

britovi: Outbreak in the Slovak Republic: Helminthologia, 

v. 36, p. 45.

Dupouy-Camet, J., 2000, Trichinellosis: A worldwide zoonosis: Veterinary Parasitology, v. 93, p. 191–200.

Dupouy-Camet, J., Lecam, S., Talabani, H., and Ancelle, T., 

2009, Trichinellosis acquired in Senegal from warthog 

ham, March 2009: Eurosurveillance, v. 14, no. 21, accessed 

March 23, 2010, at http://www.eurosurveillance.org/

ViewArticle.aspx?ArticleId=19220. 

Dworkin, M.S., Gamble, H.R., Zarlenga, D.S., and Tennican, 

P.O., 1996, Outbreak of trichinellosis associated with eating 

cougar jerky: The Journal of Infectious Diseases, v. 174, 

p. 663–666.

Emson, H., Baltzan, M., and Wiens, H., 1972, Trichinosis 

in Saskatchewan: An outbreak due to infected bear meat: 

Canadian Medical Association Journal, v. 106, p. 897–898.

Fay, F.H., 1960, Carnivorous walrus and some arctic zoonoses: 

Arctic, v. 13, p. 111–122.

Feldmeier, H., Biensle, U., Jansen-Rosseck, R., Kremsner, 

P.G., Wieland, H., Dobos, G., Schroeder, S., Fengler-Dopp, 

D., and Peter, H.H., 1991, Sequelae after infection with 

Trichinella spiralis: A prospective cohort study: Wiener 

Klinische Wochenschrift, v. 103, p. 111–116.

Forbes, L.B., 2000, The occurrence and ecology of Trichinella in marine mammals: Veterinary Parasitology, v. 93, 

p. 321–334.

Foreyt, W.J., 1990, Veterinary parasitology reference manual: 

Pullman, Washington State University Press, p. 136.

Foreyt, W.J., High, W.A., and Green, R.L., 1999, Search for 

Prouterina wescotti in black bears in Oregon: Journal of 

Wildlife Diseases, v. 35, p. 622–623.

Foster, W. D., 1965, A history of parasitology: Edinburgh, 

United Kingdom, Livingstone, p.68–79.

Gajadhar, A.A., and Gamble, H.R., 2000, Historical perspectives and current global challenges of Trichinella and trichinellosis: Veterinary Parasitology, v. 93, p. 183–189.

Gallardo, M.T., Mateos, L., Artieda, J., Wesslen, L., Ruiz, C., 

Garcia, M.A., Galmés-Truyois, A., Martin, A., Hernández 

Pezzi, G., Andersson, Y., Gárate, T., and Christensson, D., 

2007, Outbreak of trichinellosis in Spain and Sweden due to 

consumption of wild boar meat contaminated with Trichinella britovi: Eurosurveillance, v. 12, no. 11, accessed July 

16, 2008, at http://www.eurosurveillance.org/ViewArticle.

aspx?ArticleId=3154.

Gamble, H.R, Bessonov, A.S., Cuperlovic, K., Gajadhar, A.A., 

van Knapen, F., Noeckler, K., Schenone, H., and Zhu, X., 

2000, International commission on trichinellosis: Recommendations on methods for the control of Trichinella in 

domestic and wild animals intended for human consumption: Veterinary Parasitology, v. 93, p. 393–408.

Gamble, H.R., and Bush, E., Seroprevalence of Trichinella

infection in domestic swine based on the National Animal 

Health Monitoring System’s 1990 and 1995 swine surveys: 

Veterinary Parasitology, v. 80, p. 303–310.

Gari-Toussaint, M., Tieulié, N., Baldin, J.L., Dupouy-Camet, 

J., Delaunay, P., Fuzibet, J.G., Le Fichoux, Y., Pozio, E., 

Marty, P., 2005, Human trichinellosis due to Trichinella 

britovi in southern France after consumption of frozen wild 

boar meat: Eurosurveillance, v. 10, no. 6, accessed July 

16, 2008, at http://www.eurosurveillance.org/ViewArticle.

aspx?ArticleId=550.

Gottstein, B., Pozio, E., and Nöckler, K., 2009, Epidemiology, 

diagnosis, treatment, and control of trichinellosis: Clinical 

Microbiology Reviews, v. 22, p. 127–145.

Gould, S.E., 1970, History, in Gould S.E., ed., Trichinosis 

in man and animals: Springfield, Ill., Charles C. Thomas, 

p. 3–46.

Gould, S.E., 1983, Symptomatology, in Campbell, W.C., 

ed., Trichinella and trichinosis: New York, Plenum Press, 

p. 269–306.

Harms, G., Binz, P., Feldmeier, H., Zwingenberger, K., Scheehauf, D., Dewes, W., Kress-Hermesdorf, I., Klindworth, C., 

and Bienzle, U., 1993, Trichinosis: A prospective controlled 

study of patients 10 years after acute infection: Clinical 

Infectious Diseases, v. 17, p. 637–643.

Henriksen, S.A., Born, E.W., and Eiersted, L., 1994, Infections 

with Trichinella in polar bears (Ursus maritimus) in Greenland: Prevalence according to age and sex, in Campbell, 

W.C., Pozio, E., and Bruschi, F., eds., Trichinellosis—Proceedings of the 8th International Conference on Trichinellosis: Rome, Innstito Superiore di Sanita Press, p. 565–568.
References Cited 37

International Trichinella Reference Center, Trichinella systematics and distribution, accessed February 12, 2010, at http://

www.iss.it/site/trichinella/scripts/sydi.asp?lang=2.

Jongwutiwes, S., Chantachum, N., Kraivichian, P., Siriyasatien, P., Putaporntip, C., Tamburrini, A., La Rosa, G., 

Sreesunpasirikul, C., Yingyourd, P., and Pozio, E., 1998, 

First outbreak of human trichinellosis caused by Trichinella pseudospiralis: Clinical Infectious Diseases, v. 26, 

p. 111–115.

Kapel, C.M.O., 2000, Host diversity and biological characteristics of the Trichinella genotypes and their effect on 

transmission: Veterinary Parasitology, v. 93, p. 263–278.

Kapel, C.M.O., Henriksen, S.A., Berg, T.B., and Nansen, P., 

1996, Epidemiologic and zoogeographic studies on Trichinella nativa in arctic fox, Alopex lagopus, in Greenland: 

Journal of the Helminthological Society of Washington, 

v. 63, p. 226–232.

Kapel, C.M.O., Pozio, E., Sacchi, L., and Prestrud, P., 1999, 

Freeze tolerance, morphology, +RAPD-PCR identification 

of Trichinella nativa-infected arctic foxes: The Journal of 

Parasitology, v. 85, p. 144–147.

Kapel, C.M.O., Webster, P., Lind, P., Pozio, E., Henriksen, 

S.A., Murrell, K.D., and Nansen, P., 1998, Trichinella 

spiralis, Trichinella britovi, and Trichinella nativa: Infectivity, muscle larvae distribution and antibody response after 

experimental infection of pigs: Parasitology Research, v. 84, 

p. 264–271.

Kefenie, H., and Bero, G., 1992, Trichinosis from wild 

boarmeat in Gojjam, Northwest Ethiopia: Tropical and Geographical Medicine, v. 44, p. 278–280.

Khumjui, C., Choomkasien, P., Dekumyoy, P., Kusolsuk, 

T., Kongkaew, W., Chalamaat, M., and Jones, J.L., 2008, 

Outbreak of trichinellosis caused by Trichinella papuae, 

Thailand, 2006: Emerging Infectious Diseases, v. 14, 

p. 1913–1915.

Kim, C.W., 1983, Geographic distribution and prevalence, in

Campbell, W.C., ed., Trichinella and trichinosis: New York, 

Plenum Press, p. 445–500.

Kociecka, W., 2000, Trichinellosis: Human disease, diagnosis 

and treatment: Veterinary Parasitology, v. 93, p. 365–383.

La Rosa, G., Pozio, E., Rossi, P., and Murrell, K.D., 1992, 

Allozyme analysis of Trichinella isolates from various host 

species and geographic regions: The Journal of Parasitology, v. 78, p. 641–646.

Larsen, J.N., ed., 2004, Arctic Human Development Report, 

2004: Akureyri, Iceland, Stefansson Arctic Institute, 

242 p., accessed June 6, 2008, at http://www.svs.is/AHDR/

AHDR%20chapters/English%20version/Chapters%20PDF.

htm.

Larsen, T., and Kjos-Hanssen, B., 1983, Trichinella sp. in 

polar bears from Svalbard, in relation to hide length and 

age: Polar Research, v. 1, p. 89–96.

Ljungström, I., Murrell, D., Pozio, E., and Wakelin, D., 1998, 

Trichinellosis, in Palmer, S.R., Soulsby, L., and Simpson, 

D.I.H., eds., Zoonoses: Biology, clinical practice, and 

public health control: New York, Oxford University Press, 

p. 789–802.

Lo, Y.-C., Hung, C.-C., Lai, C.-S., Wu, Z., Nagano, I., Maeda, 

T., Takahashi,Y., Chiu, C.-H., and Jiang, D.D.-S., 2009, 

Human trichinosis after consumption of soft-shelled turtles, 

Taiwan: Emerging Infectious Diseases, v. 15, p. 2056–2058.

MacLean, J.D., Poirier, L., Gyorkos, T.W., Proulx, J.F., 

Bourgeault, J., Corriveau, A., Illisituk, S., and Staudt, M., 

1992, Epidemiologic and serologic definition of primary 

and secondary trichinosis in the Arctic: The Journal of 

Infectious Diseases, v. 165, p. 908–912.

MacLean, J.D., Viallet, J., Law, C., and Staudt, M., 1989, 

Trichinosis in the Canadian Arctic: Report of five outbreaks 

and a new clinical syndrome: The Journal of Infectious 

Diseases, v. 160, p. 513–520.

Madsen, H., 1961, The distribution of Trichinella spiralis in 

sledge dogs and wild mammals in Greenland under a global 

aspect: Meddelelser on Grønland, v. 159, no. 7, p. 124.

Mao, F., Wang, Z., Cui, J., Wu, F., and Jin, X., 1995, Studies of an outbreak of trichinosis caused by the intake of 

scalded mutton: Journal of Henan Medical University, v. 30, 

p. 292–293.

Margolis, H.S., Middaugh, J.P., and Burgess, R.D., 1979, Arctic trichinellosis: Two Alaska outbreaks from walrus meat: 

Journal of Infectious Diseases, v. 139, p. 102–105.

McAuley, J.B., Michelson, M.K., and Schantz, P.M., 1991, 

Trichinella infection in travelers: Journal of Infectious Diseases, v. 164, p. 1013–1016.

McIntyre, L., Pollock, S., Fyfe, M., Gajadhar, A., IsaacRenton, J., Fung, J., Morshed, M., 2007, Trichinellosis 

from consumption of wild game meat: Canadian Medical 

Association Journal, v. 176, p. 449–451.
38 Trichinosis

Mitreva, M., and Jasmer, D.P., 2006, Biology and genome of 

Trichinella spiralis: WormBook, Nov. 23, 2006, p. 1–21, 

accessed July 21, 2008, at http://www.wormbook.org/

chapters/www_genomesTrichinella/genomesTrichinella.

html.

Moorhead, A., Grunenwald, P.E., Dietz, V.J., Schantz, P.M., 

1999, Trichinellosis in the United States, 1991–1996: 

Declining but not gone: American Journal of Tropical Medicine and Hygiene, v. 60, p. 66–69.

Moretti, A., Piergili Fioretti, D., Pasquali, P., Mechelli, L., 

Rossidivita, M.E., and Polidoro, G.A., 1997, Experimental 

infection of fish with Trichinella britovi: Biological evaluations, in Ortega Pierres, G., Gamble, R., van Knapen, R., 

and Wakelin, D., eds., Trichinellosis: Mexico, Centro de 

Investigacion y Estudios Avanzados del Instituto Politecinco 

Nacional, p. 135–142.

Mukaratirwa, S., and Foggin, C.M., 1999, Infectivity of 

Trichinella sp. isolated from Crocodylus niloticus to the 

indigenous Zimbabwean pig: International Journal for Parasitology, v. 29, p. 1129–1131.

Murrell, K.D., 1994, Beef as a source of trichinellosis: Parasitology Today, v. 10, p. 434.

Murrell, K.D., 2000, Trichinellosis: Now and forevermore: 

Parasite, v. 8, p. S11–S13.

Murrell, K.D., Djordjevic, M., Cuperlovic, K., Sofronic, 

Lj., Savic, M., Djordjevic, M., and Damjanovic, S., 2004, 

Epidemiology of Trichinella infection in the horse: The risk 

from animal product feeding practices: Veterinary Parasitology, v. 123, p. 223–233.

Murrell, K.D., Lichtenfels, R.J., Zarlenga, D.S., and Pozio, E., 

2000, The systematics of the genus Trichinella with a key to 

species: Veterinary Parasitology, v. 93, p. 293–307.

Murrell, K.D., and Pozio, E., 2000, Trichinellosis: The zoonosis that won’t go quietly: International Journal for Parasitology, v. 30, p. 1339–1349.

Murrell, K.D., Stringfellow, F., Dame, J.B., Leiby, D.A., 

Duffy, C., and Schad, G.A., 1987, Trichinella spiralis in an 

agricultural ecosystem. II. Evidence for natural transmission 

of Trichinella spiralis from domestic swine to wildlife: The 

Journal of Parasitology, v. 73, p. 103–109.

Nöckler, K., Pozio, E., Voigt, W.P., and Heidrich, J., 2000, 

Detection of Trichinella infection in food animals: Veterinary Parasitology, v. 93, p. 335–350.

Nöckler, K., Wichmann-Schauer, H., Hiller, P., Müller, 

A., and Bogner, K., 2007, Trichinellosis outbreak in 

Bavaria caused by cured sausage from Romania, January 2007: Eurosurveillance, v. 12, no. 34, accessed July 

16, 2008, at http://www.eurosurveillance.org/ViewArticle.

aspz?ArticleId=3254.

Nutter, F.B., Levine, J.F., Stoskopf, M.K., Gamble, H.R., and 

Dubey, J.P., 1998, Seroprevalence of Toxoplasma gondii and 

Trichinella spiralis in North Carolina black bears (Ursus 

americanus): Journal of Parasitology, v. 84, p. 1048–1050.

Oksanen, A., Lindgren, E., and Tunkkari, P., 1998, Epidemiology of trichinellosis in lynx in Finland: Journal of Helminthology, v. 72, p. 47–53. 

Olteanu, G.H., 1997, New studies on epidemiology and 

control of trichinellosis in Romania, in Ortega-Pierres, 

M.G., Gamble, H.R., Van Knapen, F., and Wakelin, D., eds., 

Trichinellosis: Mexico, Centro de Investigacion y Estudios 

Avanzados del Instituto Politecnico Nacional, p. 517–531.

Ortega-Pierres, M.G., Arriaga, C., and Yepez-Mulia, L., 2000, 

Epidemiology of trichinellosis in Mexico, Central and South 

America: Veterinary Parasitology, v. 93, p. 201–225.

Owen, R., 1835, Description of a microscopic entozoon infesting the muscles of the human body: Transactions of the 

Zoological Society of London, v. 1, p. 315–323.

Parkinson, A.J., 2008, The international polar year, 2007–

2008, an opportunity to focus on infectious diseases in 

Arctic regions: Emerging Infectious Diseases, v. 14, p. 1–3.

Pawlowski, Z.S., 1983, Clinical aspects in man, in Campbell, 

W.C., ed., Trichinella and trichinosis, New York, Plenum 

Press, p. 367–402.

Polley, L., Gaschler, C., and Gajadhar, A., 2000, National 

occurrence reporting of Trichinella and trichinellosis using 

a computerized database: Veterinary Parasitology, v. 93, 

p. 351–363.

Pozio, E., 2000a, Factors affecting the flow among domestic 

synanthropic and sylvatic cycles of Trichinella: Veterinary 

Parasitology, v. 93, p. 241–262. 

Pozio, E., 2000b, Is horsemeat trichinellosis an emerging disease in the EU?: Parasitology Today, v. 16, p. 266.

Pozio, E., 2001, New patterns of Trichinella infection: Veterninary Parasitology, v. 98, p. 133–148.

Pozio, E., 2005, The broad spectrum of Trichinella hosts: 

From cold- to warm blooded animals: Veterinary Parasitology, v. 132, p. 3–11.
References Cited 39

Pozio, E., Foggin, C.M., Marucci, G., La Rosa, G., Sacchi, L., 

Corona, S., Rossi, P., and Mukaratirwa, S., 2002, Trichinella 

zimbabwensis n.sp. (Nematoda), a new non-encapsulated 

species from crocodiles (Crocodylus niloticus) in Zimbabwe 

also infecting mammals: International Journal for Parasitology, v. 32, p. 1787–1799.

Pozio, E., and La Rosa, G., 2000, Trichinella murrelli n. sp.: 

Etiological agent of sylvatic trichinellosis in temperate 

areas of North America: The Journal of Parasitology, v. 86, 

p. 134–139.

Pozio, E., La Rosa, G., Rossi, P., and Murrell, D., 1992, Biological characterization of Trichinella isolates from various host species and geographical regions: The Journal of 

Parasitology, v. 78, p. 647–653.

Pozio, E., and Marucci, G., 2003, Trichinella-infected pork 

products: A dangerous gift: Trends in Parasitology, v. 19, 

p. 338.

Pozio, E., Owen, I.L., La Rosa, G., Sacchi, L., Rossi, P., and 

Corona, S., 1999, Trichinella papuae n.sp. (Nematoda), a 

new nonencapsulated species from domestic and sylvatic 

swine of Papua New Guinea: International Journal for Parasitology, v. 29, p. 1825–1839.

Pozio, E., Owen, I.L., Marucci, G., and La Rosa, G., 2004, 

Trichinella papuae in saltwater crocodiles (Crocodylus 

porosus) of Papua New Guinea: Emerging Infectious Diseases, v. 10, p. 1507–1509.

Pozio, E., Pence, D.B., La Rosa, G., Casulli, A., and Henke, 

S.E., 2001, Trichinella infection in wildlife of the southwestern United States: The Journal of Parasitology, v. 87, 

p. 1208–1210.

Pozio, E., and Zarlanga, D.S., 2005, Recent advances on the 

taxonomy, systematics and epidemiology of Trichinella: 

International Journal for Parasitology, v. 35, p. 1191–1204.

Pozio, E., Zarlenga, D.S., and La Rosa, G., 2001, The detection of encapsulated and non-encapsulated species of 

Trichinella suggests the existence of two evolutive lines in 

the genus: Parasite, v. 8, p. 27–29.

Proulx, J.-F., MacLean, J.D., Gyorkos, T.W., Leclair, D., Richter, A.-K., Serhir, B., Forbes, L., and Gajadhar, A., 2002, 

Novel prevention program for trichinellosis in Inuit communities: Clinical Infectious Diseases, v. 34, p. 1508–1514.

Ransom, B.H., 1915, Trichinosis: Report on US Livestock 

Sanitary Association, Chicago, 16–18 February 1915, 

p. 147–165.

Rockiene, A., and Rocka, V.S., 1997, Seroprevalence studies on human trichinellosis in Lithuania, in Ortega Pierres, 

M.G., Gamble, H.R., Van Knapen, F., and Wakelin, D., eds., 

Trichinellosis: Mexico, Centro de Investigacion y Estudios 

Avanzados del Instituto Politecnico Nacional, p. 503–506.

Saunders, D., 2008, Romanians in a showdown with bears: 

The Globe and Mail, accessed July 14, 2008, at http://www.

theglobeandmail.com/servlet/story/RTGAM.20080312.

wbears12/BNStory/International.

Schad, G.A., Leiby, D.A., Duffy, C.H., Murrell, K.D., Alt, 

G.L., 1986, Trichinella spiralis in the black bear (Ursus 

americanus) of Pennsylvania: Distribution, prevalence, and 

intensity of infection: Journal of Wildlife Diseases, v. 22, 

p. 36–41.

Serhir, B., MacLean, J.D., Healey, S., Segal, B., and Forbes, 

L., 2001, Outbreak of Trichinellosis associated with arctic 

walruses in northern Canada, 1999: Canada Communicable Diseases Report, v. 26–04, accessed July 16, 2008, 

at http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/01vol27/

dr270S4eb.html.

Snyder, D.E., 1987, Prevalence and intensity of Trichinella 

spiralis infection in Illinois wildlife: The Journal of Parasitology, v. 73, p. 874–875.

Soule, C., Dupouy-Camet, J., Georges, P., Ancelle, T., Gillet, 

J.P., Vassaire, J., Delvigne, A., and Plateau, E., 1989, Experimental trichinellosis in horses; biological and parasitological evaluation: Veterinary Parasitology, v. 32, p. 19–36.

Stoll, N.R., 1947, This wormy world: The Journal of Parasitology, v. 33, p. 1–18.

Stromberg, B.E., and Prouty, S.M., 1987, Prevalence of 

trichinellosis in the north-central United States: Proceedings of the Helminthological Society of Washington, v. 54, 

p. 231–232.

Takahashi, Y., Mingyuan L., and Waikagul J., 2000, Epidemiology of trichinellosis in Asia and the Pacific Rim: Veterinary Parasitology, v. 93, p. 227–239.

Theodoropoulos, G., Kapel, C.M.O., Webster, P., Saravanos, 

L., Zaki, J., and Koutsotolis, K., 2000, Infectivity, predilection sites, and freeze tolerance of Trichinella spp. in 

experimentally infected sheep: Parasitology Research, v. 86, 

p. 401–405.

Thorshaug, K.N., and Rosted A.F., 1956, Researches into the 

prevalence of trichinosis in animals in arctic and Antarctic 

waters: Nordisk Veterinaermedicin, v. 8, p. 115–129.
40 Trichinosis

van Knapen, F., 2000, Control of trichinellosis by inspection 

and farm management practices: Veterinary Parasitology, 

v. 93, p. 385–392.

Viallet, J., MacLean, J.D., Goresky, C.A., Staudt, M., Routhier, G., Law, C., 1986, Arctic trichinosis presenting as 

prolonged diarrhea: Gastroenterology, v. 91, p. 938–946.

Villella, J.B., 1970, Life cycle and morphology, in Gould, 

S.E., ed., Trichinosis in man and animals, Springfield, Ill., 

Charles C. Thomas, p. 19–60.

Wang, Z., Li, H., Wu, L., and Mao, F., 1998, Some observations on trichinellosis in China: Helminthologia, v. 35, 

p. 27–29.

Wang, Z.Q., Cui, J., and Xu, B.L., 2006, The epidemiology 

of human trichinellosis in China during 2000–2003: Acta 

Tropica, v. 97, p. 247–251.

Weyermann, D., Worley, D.E., and Seesee, F.M., 1993, Survey 

of Trichinella nativa in Alaskan polar bears, Ursus maritimus: Helminthologia (Bratislava), v. 30, p. 143–145.

Wheeldon, E.B., Dick, T.A., and Schulz, T.A., 1983, First 

report of Trichinella spiralis var. pseudospiralis in North 

America: The Journal of Parasitology, v. 69, p. 781–782.

Worley, D.E., Seesee, F.M., Espinosa, R.H. and Sterner, M.C., 

1986, Survival of sylvatic Trichinella spiralis isolates in 

frozen tissue and processed meats: Journal of the American 

Veterinary Medical Association, v. 189, p. 1047–1049.

Worley, D.E., Zarlenga, D.S., and Seesee, F.M., 1990, Freezing resistance of a Trichinella spiralis nativa isolate from 

a gray wolf, Canis lupus, in Montana (USA) with observations on genetic and biological characteristics of the biotype: Journal of the Helminthological Society of Washington, v. 57, p. 57–60.

Worley, D.E., Seesee, F.M., Zarlenga, D., and Murrell, K.D., 

1994, Attempts to eradicate trichinellosis from a wild boar 

population in a private game park (USA), in Campbell, 

W.C., Pozio, E., and Bruschi, F., eds., Trichinellosis: Rome, 

Instituto Superiore di Sanita Press, p. 611–616.

Zarlenga, D.S., Al-Yaman, F., Minchella, D.J., and La Rosa, 

G., 1991, A repetitive DNA probe specific for a North 

American sylvatic genotype of Trichinella: Molecular and 

Biochemical Parasitology, v. 48, p. 131–138.

Zarlenga, D.S., Chute, M.B., Martin, A., and Kapel, M.O., 

1999, A single multiplex PCR for unequivocal differentation of sex distinct geographical genotypes of Trichinella 

pseudospiralis: International Journal for Parasitology, v. 29, 

p. 215–221.

Zarnke, R.L., Gamble, R., Heckert, R.A., and Verhoef, J., 

1997, Serologic survey for Trichinella spp. in grizzly bears 

(Ursus arctos) from Alaska, 1973 to 1987: Journal of Wildlife Diseases, v. 33, p. 474–479.

Zimmermann, W.J., 1977, Trichinosis in bears of western and 

north central United States: American Journal of Epidemiology, v. 106, p. 167–171.
Glossary 41

Glossary

A

acute Sharp or severe, such as an illness 

with a sudden onset and a relatively short 

course.

allergic reaction Development of a hypersensitivity reaction by the host in response 

to foreign substances in the body, primarily 

antigens and other proteins.

amphipod A small, shrimp-like crustacean 

living mainly in aquatic habitats.

anorexia Lack of appetite.

anthelmintic A chemical substance used to 

treat infestations of parasitic worms.

antibody A protein formed in the body of a 

vertebrate that is used by the immune system 

to identify and neutralize the effects of foreign 

invading proteins, called antigens, such as 

bacteria and viruses.

antigen Any foreign substance (generally 

proteins) to which the body reacts by producing antibodies. Antigens may be soluble 

substances such as toxins, particulate matter 

such as pollen, or microorganisms such as 

bacteria or viruses.

arctic Referring to regions near the North 

Pole or describing very cold or frigid conditions.

arthropod A member of the phylum 

Arthropoda, invertebrate animals that have 

exoskeletons, segmented bodies, and jointed 

legs, including insects, crabs, spiders, etc.

autopsy Examination of a dead human body 

to determine the cause of death.

B

biopsy A test involving the removal of cells 

or tissues from a living subject for examination, usually by microscope, to determine the 

presence or extent of a disease.

birds Warm-blooded vertebrates, belonging 

to the Class Aves, with wings and feathers 

(although the wings are poorly developed for 

some flightless species like ostriches). (See

warm-blooded.)

bronchitis Inflammation of the bronchi, the 

airways connecting the nose and the lungs, 

characterized by coughing and difficulty 

breathing.

C

cadaver A dead body, most often a human 

body, preserved for anatomical study.

calcification The hardening of a tissue by 

deposition of calcium salts.

canid Mammal within the Family 

Canidae,for example, wolves, coyotes, jackals, foxes, and other dog-like animals.

cannibalism The act of eating the flesh of 

one’s own species.

cardiovascular system The system that circulates blood throughout the body, consisting 

of the heart and blood vessels.

carnivore Mammals with teeth and other 

body adaptations for feeding on flesh; primarily species belonging to the Order Carnivora 

(for example, wolves, bears, raccoons, weasels, civets, hyenas, and tigers).

carnivorous Eating flesh.

carrion Dead and decaying animal flesh.

central nervous system (CNS) The brain and 

spinal cord.

chronic Persisting for a relatively long time.

circumpolar Surrounding or near the North 

or South pole.
42 Trichinosis

clinical signs Readily observable indications of a disease or injury. (See also symptoms.)

cloacal opening The opening of the common passage for the fecal, urinary, and reproductive discharges of most lower vertebrates 

(birds, reptiles, and amphibians).

cluster outbreak The occurrence of a 

higher-than-expected level of disease among 

individuals in proximity to each other and 

within a particular time period.

cold-blooded Species such as fishes and 

reptiles, which have blood that varies in 

temperature to approximately that of the surrounding environment.

collagen The protein component of connective tissue found in skin, tendon, bone, 

and cartilage.

competitive inhibition assay A laboratory 

test used to measure the concentration of 

antigen in a sample by simultaneously adding 

sample and labeled-antigen to antibody bound 

to a surface; the result is a color change that is 

inversely proportional to the concentration of 

unlabeled antigen in the sample.

compound microscope An instrument 

used to magnify small objects and structures not distinguishable by the naked eye, 

using two lens systems to increase the power 

of magnification.

conjunctivitis Inflammation of the mucous 

membrane that lines the inner surface of the 

eyelid and the exposed surface of the eyeball.

convalescence Gradual healing after sickness or injury.

convulsion A seizure or violent involuntary 

contraction or series of contractions of the 

voluntary muscles.

coprophagic Ingesting dung or feces.

corticosteroid Class of steroid hormones 

that are produced in the adrenal cortex or synthetically and are used as anti-inflammatory 

agents and to suppress the immune response.

cosmopolitan Having a worldwide distribution wherever the habitat is suitable.

counterimmunoelectrophoresis A laboratory technique used to evaluate the binding of 

an antibody to its antigen in which an electrical field is applied across a substance, such 

as a polyacrylamide gel, to induce migration 

of antibodies and antigen toward one another 

until they bind forming a line of precipitation.

cyst A stage in the life cycle of certain parasites, during which they are enclosed within a 

protective wall.

D

dedifferentiation A loss of differentiation of 

cells and of their orientation to one another.

digastricus The muscle that acts to lower 

the jaw.

dissecting microscope A type of microscope using separate optical paths to provide 

slightly different viewing angles for each eye 

to create a three-dimensional visualization of 

the sample.

DNA (deoxyribonucleic acid) The carrier of 

genetic information for all organisms except 

the RNA viruses and found in all living cells.

domestic Pertaining to an environment 

managed by humans.

domestication The adaptation of an animal 

or population of animals to life under human 

management through captive breeding for the 

purposes of human benefit; examples are dogs 

for companionship and service, livestock for 

food and labor.
Glossary 43

E

edema The accumulation of excessive fluid 

in the intercellular tissue spaces of the body; 

may be peripheral (in the limbs) or within 

organs.

electrolyte A charged molecule, such as 

sodium, potassium, calcium, and chloride, 

needed by cells to control the flow of water 

molecules through cell walls.

ELISA (enzyme-linked immunosorbent 

assay) A molecular-based test used to detect 

the presence of either antigen or antibody in 

a sample.

emerging Referring to infectious diseases 

that have newly appeared and/or increased in 

frequency of occurrence within the past three 

decades, or threaten to increase in the near 

future relative to populations affected, geographic distribution, or magnitude of effects.

encapsulated Enclosed within a protective 

cover.

encystment The process of becoming 

enclosed by a protective covering. (See cyst.)

endemic A disease that is commonly present 

within a human population or a geographical 

area or having the quality of being constantly present in a human population in a 

specific location.

enteral Within or via the small intestine.

enzootic An animal disease that is commonly present within a population or geographical area or having the quality of being 

constantly present in a specific location within 

an animal population.

enzyme A substance, usually a protein, produced by the body to facilitate a 

chemical reaction.

eosinophils The white blood cells involved 

in combating parasitic infections and controlling allergic reactions.

epidemic An outbreak of disease affecting 

a disproportionately large number of humans 

within a population, community, or region 

during a period of time.

epidemiological Pertaining to epidemiology. (See epidemiology.)

epidemiology The study of the causes, 

occurrence, and control of disease in 

populations.

epithelial Pertaining to the cells that cover 

the external and internal surfaces of the body.

epithelium The cellular covering of the 

internal and external surfaces of the body 

and organs.

eradicate To completely eliminate.

F

fecal-oral route/transmission Passing 

a disease from one individual to another 

via direct or indirect ingestion of feces 

containing pathogens.

felids Mammals within the Family Felidae 

(for example, domestic cats, lion, tiger, leopard, lynx, cheetah, and many other wild cats).

fish Refers to finfish (for example, coldblooded strictly aquatic vertebrates with a 

well differentiated skull and a bony skeleton), 

in contrast to shellfish (invertebrates) and jawless fishes.

G

gastrointestinal tract The tubular organs 

that form a digestive pathway from the mouth 

to the anus, including the esophagus, stomach, 

and intestines.

genotype The genetic makeup of a cell, 

an organism, or an individual usually with 

reference to a specific character under 

consideration.
44 Trichinosis

H

helminthological Pertaining to the scientific 

study of parasitic worms.

herbivores Mammals that feed almost 

exclusively on plants (for example, cattle, 

sheep, manatee).

histopathologic Pertaining to histopathology. (See histopathology.)

histopathology The study of the microscopic changes in tissues caused by disease.

host An organism that harbors or nourishes 

microbes, viruses, and parasites.

I

immune status Refers to the host’s ability to 

fight infections.

immunoblotting A laboratory test in which 

proteins are separated by their lengths using 

gel electrophoresis. The proteins are then 

transferred to cellulose sheets and identified by staining with specific antibodies. The 

test can also be used to identify the presence 

of antibodies to specific antigens in serum 

samples. Also known as Western blotting.

immunocompromised Incapable of developing a normal immune response, usually as a 

result of disease, malnutrition, or immunosuppressive therapy. (See immunosuppressive 

agents.)

immunological Relating to immunology, 

the study of the structure and function of the 

immune system.

immunoradiometric assay A laboratory 

test using radiolabeled antibodies to measure 

specific proteins in the blood.

immunosuppressive agents Drugs that 

are used to inhibit or prevent activity of the 

immune system in patients undergoing organ 

transplantation and treatment of autoimmune 

diseases.

incidence The probability of a new case of 

a specific disease developing in a population 

at risk during a specified time period.

indigenous Native to a particular place 

or country.

infective Capable of producing infection.

inflammatory Pertaining to or characterized by inflammation, the reaction of tissue 

to injury or infection that is characterized by 

redness, pain, swelling, and heat.

intercostals The muscles between adjacent 

ribs.

intracellular Within a cell or cells.

intramulticellular Within more than one 

cell.

Inuit A member of a group of native people 

of northern North America, inhabiting areas 

from Greenland and eastern Canada to Alaska.

invertebrates Animals lacking a spinal column (for example, insects, crustaceans).

irradiation The use of gamma rays, X-rays, 

or electron beams to sterilize food.

isolate A bacterial or fungal strain that has 

been separated as a pure strain from a mixed 

bacterial or fungal culture.

J

K

L

larva/larval The immature, early form of 

an organism that at birth or hatching is not 

like its parent and has to undergo a series of 

form and size changes before assuming adult 

features.

larynx Part of the respiratory tract between 

the pharynx and trachea that contains the 

vocal cords. Also known as the “voice box.”
Glossary 45

lymph nodes Rounded, encapsulated 

aggregations of lymphoid tissue distributed 

throughout the body along the lymphatic 

system. These nodes filter the flow of lymph 

circulating within the body.

lymphatics The lymphatic system, a vast 

network of tubes transporting lymph, a clear, 

watery, sometimes faintly yellowish fluid 

derived from body tissues that contains white 

blood cells and acts to remove bacteria and 

certain proteins from the tissues, transport fat 

from the small intestine, and supply mature 

lymphocytes to the blood. (See lymphocyte.)

lymphocyte A type of white blood cell 

important for producing antibodies (B-lymphcytes) and cellular immunity (T-lymphocytes).

M

maintenance The act of continuing or keeping in existence, for example, a maintenance 

host is an organism that keeps a disease agent 

in existence in nature and is a source of infection for susceptible hosts.

malaise A vague feeling of bodily discomfort, as at the beginning of an illness.

mammal Warm-blooded vertebrate animal 

that possesses hair during some part of its life 

and suckles its young. (See warm-blooded.)

marsupials Mammalian species having 

an external abdominal pouch (marsupium) 

enclosing the mammary glands for carrying their young until their development is 

complete; young of these species are born in a 

very underdeveloped state and must be carried 

and nourished for a prolonged period of time 

(for example, opossums, kangaroos, koala, 

and wombats).

masseter The muscle used to close the jaw 

during chewing.

molt The normal shedding of hair, horns, 

feathers, and external skin before replacement 

by new growth, usually on an annual basis.

morphology The study of the form and 

structure of an organism or its parts.

mucosa The thin layer of tissue that lines 

body cavities and passages; mucous membrane.

mucosal Pertaining to the mucosa. 

(See mucosa).

muscular insertion The point of attachment 

of a skeletal muscle to the bone that it moves.

mustelid Mammal within the Family Mustelidae, for example, weasels, otters, mink, 

ferrets, and badgers.

myocarditis Inflammation of the heart 

muscle.

N

nearctic The biogeography subregion that 

includes Greenland, arctic America, and 

the parts of North America north of tropical 

Mexico.

nematode Unsegmented, cylindrical parasitic worm of the class Nematoda; roundworm.

neuritis Inflammation of a nerve or group 

of nerves that is characterized by pain, loss of 

reflexes, and atrophy of the affected muscles.

neurological system The group of structures (brain, spinal cord, nerves) that regulate 

the body’s reactions to external and internal 

stimuli. Also known as the nervous system.

nodule A small solid lump.

nurse cell A skeletal muscle cell infected by 

the trichinosis parasite that stimulates blood 

vessel development so the cell can provide 

nutrients to the parasite.

O

ocular Pertaining to the eye.

omnivore An animal with a diet of both 

plants and animals.
46 Trichinosis

outbreak The occurrence of a specific disease within a small, localized group of people 

or organisms.

P

palearctic The biogeographic subregion that 

includes Europe, Asia north of the Himalayas, 

Arabia, and Africa north of the Sahara.

papillae Plural of papilla, a small nippleshaped projection.

paralysis The loss of muscle function 

resulting in the inability to move affected 

body parts.

parasite An organism that lives in or on 

another organism of a different species from 

which it derives nutrients and shelter.

parasitic Pertaining to parasites. 

(See parasite).

parenteral Located outside the digestive 

tract.

pathogen Typically, microorganisms capable of inducing disease, but broadly includes 

all disease-inducing agents.

pathogenic Able to produce disease.

pathogenicity The ability of an agent to 

produce disease in another organism.

pathological Pertaining to pathology. 

(See pathology).

pathologist A person who studies pathology 

(See pathology.)

pathology The study of the structural and 

functional effects of disease.

PCR (polymerase chain reaction) A laboratory technique used to amplify exponentially a 

single or few copies of a selected sequence of 

DNA using enzymatic replication of the DNA 

in order to generate millions or more copies of 

a particular DNA sequence. (See DNA.)

PCR-RFLP (polymerase chain reactionrestriction fragment length polymorphism) A laboratory technique in which a 

DNA sample is amplified by PCR and then 

fragmented by restriction enzymes. The DNA 

fragments are separated by length using gel 

electrophoresis. The differences in lengths of 

similar DNA molecules are analyzed to identify specific genotypes. (See DNA, PCR.)

pectoral Pertaining to the thorax or chest.

periorbital Located around the eye socket.

peripheral circulation The system of 

blood vessels outside of the heart, the central 

circulation.

pneumonitis Inflammation of the lung.

predation The characteristic of preying on 

other animals as a source of food.

prevalence The total number of cases of a 

disease divided by the number of hosts examined in a population at a given time.

prevalent Widely or commonly occurring.

public health The science and practice of 

protecting and improving the health of a community, through disease prevention, education, control, surveillance, and sanitation.

putrefied Decayed or rotten with a 

foul odor.

Q

R

reptile Vertebrates of the Class Reptilia that 

breathe by means of lungs and have external 

coverings of scales or bony plates; includes 

snakes, lizards, crocodiles, turtles, and 

dinosaurs.

reservoir The host population that maintains 

the disease agent in nature and provides a 

source of infection to susceptible hosts.
Glossary 47

resistance The ability of an organism to 

remain either uninfected or disease-free 

despite becoming infected by a diseasecausing organism; the ability of an organism, 

a tissue, or a cell to tolerate the effects of a 

harmful physical or environmental condition.

respiratory system The group of structures 

(airways, lungs, and muscles) that act to bring 

air into the body to supply oxygen to the 

blood and to expel carbon dioxide and other 

gaseous wastes.

retina The thin layer of neural cells lining 

the back of the eye.

rodent Member of the Order Rodentia, a 

diverse group of mammals characterized by 

incisor teeth that grow throughout life and 

must be worn away by cutting and gnawing 

hard materials; includes squirrels, mice, rats, 

voles, chipmunks, gophers, lemmings, beaver, 

porcupines, and many others.

roundworm See nematode.

ruminant Even-toed, hoofed mammals that 

have complex four-chambered stomachs and 

chew the cud; includes cattle, sheep, goats, 

and deer.

S

sarcoplasm The cytoplasm of a striated 

muscle fiber.

scavenging Feeding on dead or decaying 

matter.

schizophrenia A psychiatric disorder 

marked by severely impaired thinking, emotions, and behavior.

sera/serum The pale fluid that remains after 

blood has clotted.

spicules Parts of the male genital apparatus in nematodes that are used to engage the 

female genital orifice during copulation.

splinter hemorrhage Linear bleeding 

under a toenail or fingernail that resembles a 

splinter.

strain A genetically or biochemically distinguishable subtype of a microorganism.

striated muscle A muscle with fibers 

arranged in parallel bands, for example, skeletal muscle.

subarctic Pertaining to the area immediately 

south of the Arctic Circle covering much of 

Canada and Siberia where temperatures range 

from below -30°C (-22°F) in the winter to 

30°C (86°F) in the summer.

subclinical Pertaining to an inapparent, 

asymptomatic infection.

subsistence hunting The practice of 

pursuing and killing wild animals for food 

and other essentials necessary for living, as 

opposed to recreational purposes.

surveillance The systematic collection, 

analysis, and interpretation of data pertaining 

to the occurrence of specific diseases for the 

purpose of monitoring trends in disease and 

death. 

susceptibility/susceptible Pertaining to 

the ability of an animal to become infected 

by a disease-causing organism or to develop 

disease after becoming infected.

swine Pigs, hogs, and boars.

sylvatic Existing normally in the wild, not 

in the human environment.

symptoms A subjective indication of a disorder or disease perceived by the patient, such 

as pain, nausea, fatigue, or weakness.

synanthropic Living in or around human 

dwellings.

syndrome A group of signs and symptoms 

characterizing a specific disease or condition.
48 Trichinosis

T

taxonomic Pertaining to taxonomy. 

(See taxonomy.)

taxonomy The systematic principles and 

procedures of grouping and arranging organisms into a hierarchical order.

temperate Marked by moderate temperatures, weather, or climate.

thoracic duct The largest lymph vessel in 

the body, that collects lymph from the portions of the body posterior to the diaphragm 

and from the left side of the body anterior to 

the diaphragm.

tinnitus A ringing, buzzing, or whistling 

sound in one or both ears, not caused by any 

external stimulus.

trichinoscopy A method for identifying 

Trichinella spiralis larvae in muscles by 

compressing small pieces of striated muscle 

between two plates of glass until they become 

translucent and then viewing the pieces of 

muscle under a dissecting or compound 

microscope to look for coiled larvae.

Trichuris A genus of parasitic roundworms 

that infect the intestines of mammals; also 

called whipworms.

U

V

venous circulation The network of blood 

vessels, i.e., veins, used to transport deoxygenated blood from the capillaries to the heart 

and lungs.

vertigo Dizziness characterized by a feeling 

of movement of oneself or one’s surroundings.

vesicular exanthema A highly infectious 

viral disease of pigs with vesicles on the 

snout, feet, and inside the mouth.

villi Tiny, finger-like projections on the 

mucous membrane of the small intestine 

that increase the surface area to enable rapid 

absorption of nutrients from food.

viscera The internal organs, particularly of 

the thoracic and abdominal cavities, such as 

heart, lungs, liver, kidneys, and intestines.

viviparous Bearing living offspring rather 

than laying eggs.

W

warm-blooded Species, such as birds and 

mammals, that have a constant body temperature, independent of the surrounding environment.

X

Y

Z

zoologist A person who studies animals.

zoonosis Infectious disease transmissible 

between animals and humans, and vice versa.

zoonotic Transmissible between animals 

and humans, and vice versa.
Appendix 1. Locations and Hosts of the Different Species of Trichinella, and Common and Scientific Names of Hosts 49

Appendix 1. Locations and Hosts of the Different Species of Trichinella, 

and Common and Scientific Names of Hosts

North America (Nearctic)

T. spiralis

Black bear, Ursus americanus

Bobcat, Lynx rufus

Brown bear, Ursus arctos

Brown rat, Rattus norvegicus

Coyote, Canis latrans

Domestic cat, Felis catus

Domestic pig, Sus scrofa

Horse, Equus caballus

Humans, Homo sapiens

Pig, Sus scrofa

Red fox, Vulpes vulpes

T. nativa

Blue fox, Alopex lagopus

Domestic dog, Canis lupus familiaris

Marten, Martes americana

Polar bear, Ursus maritimus

Red fox, Vulpes vulpes

Wolf, Canis lupus

T. pseudospiralis

Black vulture, Coragypus atratus

Trichinella spp. (T5, T6, T8, or uncertain)

Badger, Taxidea taxus

Bearded seal, Erignathus barbatus

Beaver, Castor canadensis

Black bear, Ursus americanus

Bobcat, Lynx rufus

Brown lemming, Lemmus sibiricus

Common shrew, Sorex minutus

Coopers hawk, Accipiter cooperi

Cougar, Felis concolor

Coyote, Canis latrans

Ermine, Mustela erminia

Fisher, Martes pennanti

Fox squirrel, Sciurus niger

Gray fox, Urocyon cinereoargenteus

Gray wolf, Canis lupus

Great horned owl, Bubo virginianus

Grizzly bear, Ursus arctos

Ground squirrel, Citellus undulatus

Lesser shrew, Sorex minutus

Marten, Martes americana

Mink, Mustela vison

Mountain lion, Felis concolor

Muskrat, Ondatra zibethicus

Opossum, Didelphis marsupialis

Pomarine jaeger, Stercorarius pomarinus

Raccoon, Procyon lotor

Red-backed vole, Clethrionomys rutilus

Red fox, Vulpes vulpes

Red squirrel, Tamiasciurus hudsonicus

Ringed seal, Phoca hispida

Spotted skunk, Spilogale interrupta

Striped skunk, Mephitis mephitis

Varying hare, Lepus americanus

Vole, Microtus gregalis

Walrus, Odobenus rosmarus

Weasel, Mustela frenata

Weasel, Mustela nivalis

Weasel, Mustela rixosa

White-footed deer mouse, Peromyscus maniculatus

White-footed mouse, Peromyscus leucopus
50 Trichinosis

North America (Nearctic)—Continued

Trichinella spp. (T5, T6, T8, or uncertain)—Continued

White whales, Dilphinapterus leucas

Wolverine, Gulo gulo

South America (Neotropical)

T. spiralis

Cougar, Felis concolor

Pig, Sus scrofa

Eurasia (Palearctic, Mediterranean, Oriental)

T. spiralis

T. nativa

T. britovi

Blue fox, Alopex lagopus

Brown rat, Rattus norvegicus

Domestic cat, Felis catus

Domestic dog, Canis lupus familiaris

Pig, Sus scrofa

Red fox, Vulpes vulpes

Wildcat, Felis silvestris

Wolf, Canis lupus

Blue fox, Alopex lagopus

Brown bear, Ursus arctos

Brown rat, Rattus norvegicus

Corsac fox, Vulpes corsax

Domestic cat, Felis catus

Domestic dog, Canis lupus familiaris

Far eastern forest cat, Felis euptilura

Jackal, Canis aureus

Lynx, Lynx lynx

Polar bear, Ursus maritimus

Raccoon dog, Nyctereutes procyonoides

Red fox, Vulpes vulpes

Tiger, Panthera tigris

Wild boar, Sus scrofa

Wolf, Canis lupus

Badger, Meles meles

Beech marten, Martes foina

Black bear, Ursus americanus

Black rat, Rattus rattus

Brown bear, Ursus arctos

Brown rat, Rattus norvegicus

Domestic cat, Felis catus

Domestic dog, Canis lupus familiaris

Horse, Equus caballus

Human, Homo sapiens

Jackal, Canis aureus

Lynx, Lynx lynx

Raccoon dog, Nyctereutes procyonoides

Red fox, Vulpes vulpes

Wildcat, Felis silvestris

Wolf, Canis lupus

T. pseudospiralis

Eagle, Aquila rapax

Human, Homo sapiens

Little owl, Athene aoctua

Pig, Sus scrofa

Raccoon dog, Nyctereutes procyonoides

Tawny owl, Strix aluco

Trichinella spp. (T5, T6, T8, or uncertain)

Afghan hedgehog, Hemiechinus megalotis

Black bear, Ursus americanus

Buzzard, Buteo buteo

Common mole, Talpa europea

Common shrew, Sorex araneus

Corsac fox, Vulpes corsac

Domestic pig, Sus scrofa

Fared seal, Eumetopias jubatus

Greenland seal, Phoca groenlandica

Harvest mouse, Micromys minutus

Hedgehog, Erinaceus europeus

Human, Homo sapiens

Indian mole rat, Bandicota bengalensis

Jackal, Canis aureus

Laxmann’s shrew, Sorex caecutiens
Appendix 1. Locations and Hosts of the Different Species of Trichinella, and Common and Scientific Names of Hosts 51

Eurasia (Palearctic, Mediterranean, Oriental)—Continued

Trichinella spp. (T5, T6, T8, or uncertain)—Continued

Lesser shrew, Sorex minutus

Marten, Martes martes

Muskrat, Ondatra zibethicus

Polecat, Mustela putorius

Reindeer, Rangifer tarandus

Rook, Corvus frigileus

Sable, Martes zibellina

Siberian ferret, Mustela sibiricus

Squirrel, Sciurus vulgaris

Striped field mouse, Apodemus agrarius

Water shrew, Neomys fodiens

Wildcat, Felis silvestris

Yellow-necked mouse, Apodemus flavicollis

Africa (Ethiopian)

T. spiralis

Black-backed jackal, Canis mesomelas

Bush pig, Potamochoerus porcus

Domestic cat, Felis catus

Domestic dog, Canis lupus familiaris

Human, Homo sapiens

Pig, Sus scrofa

Serval, Felis serval

Soft-furred rat, Praomys natalensis

Striped jackal, Canis adustus

Wildcat, Felis silvestris

Wild dog, Lycaon pictus

T. nelsoni

Bat-eared fox, Otocyon megalotis

Cheetah, Acinonyx jubatus

Leopard, Panthera pardus

Lion, Panthera leo

Spotted hyena, Crocuta crocuta

Striped hyena, Hyaena hyaena

Wart hog, Phacochoerus aethiopicus

T. zimbabwensis

Crocodile, Crocodylus niloticus

Monitor lizard, Varanus exanthematicus

Trichinella spp. (T5, T6, T8, or uncertain)

Bat-eared fox, Otocyon megalotis

Cheetah, Acinonyx jubatus

Lion, Panthera leo

Striped hyena, Hyaena hyaena

Spotted hyena, Crocuta crocuta

Australia, New Zealand, New Guinea, Tasmania, Hawaii (Oceanic)

T. spiralis

Brown rat, Rattus norvegicus

T. papuae

Pig, Sus scrofa

Saltwater crocodile, Crocodylus porosus

T. pseudospiralis

Spotted-tailed quolls, Dasyurus maculatus

Wild boar, Sus scrofa

Trichinella spp. (T5, T6, T8, or uncertain)

Black rat, Rattus rattus

Little rat, Rattus exulans

Mongoose, Herpestes javanicus

Wild hog (scientific name unknown)

Appendix 2. Common and Scientific Names for Species Cited 53

Appendix 2. Common and Scientific Names for 

Species Cited

Common name Scientific name

Mammals

Arctic fox Vulpes lagopus

Arctic hare Lepus arcticus

Badger (European) Meles meles

Bandicoot (Eastern barred) Perameles gunnii

Bear Ursus spp.

Bearded seal Erignathus barbatus

Beluga whale Delphinapterus leucas

Bennett’s wallaby (red-necked wallaby) Macropus rufogriseus

Bison Bison bison

Black bear Ursus americanus

Black-faced kangaroo (western grey) Macropus fuliginosus

Black-flanked rock wallaby Petrogale lateralis

Bobcat Lynx rufus

Bottlenose dolphin Tursiops truncatus

Brown bear Ursus arctos arctos

Brown hare Lepus europaeus

California sea lion Zalophus californianus

Camel Camelus spp.

Canadian cougar (North American) Puma concolor cougar

Caribou Rangifer tarandus

Cat (domestic) Felis catus

Cattle (domestic) Bos taurus

Cheetah Acinonyx jubatus

Chicken Gallus gallus

Chinchilla Chinchilla spp.

Common dolphin Delphinus delphis

Cougar Puma concolor

Coyote Canis latrans

Cuvier’s gazelle Gazella cuvieri

Dama gazelle Gazella dama
54 Trichinosis

Common name Scientific name

Mammals—Continued

Dasyurid (kowari and mulgara) Dasyuroides byrnei and Dasycercus cristicauda

Dik-dik Madoqua guentheri

Dog (domestic) Canis lupus familiaris

Duck (mallard) Anas platyrhynchos

Eastern barred bandicoot Perameles gunnii

European lynx (Eurasian lynx) Lynx lynx

Ferret (European polecat) Mustela putorius furo

Fox Vulpes spp.

Gerenuk Litocranius walleri

Goat (domestic) Capra hircus

Gray fox Urocyon cinereoargenteus

Greenland seal (harp seal) Pagophilus groenlandicus

Gray seal Halichoerus grypus

Grizzly bear Ursus arctos horribilis

Gundi Ctenodactylus gundi

Harbor seal Phoca vitulina

Harp seal Pagophilus groenlandicus

Hawaiian monk seal Monachus schauinslandi

Hooded seal Cystophora cristata

Horse (domestic) Equus caballus

Human Homo sapiens

Indo-Pacific bottlenose dolphin Tursiops aduncus

Iriomote cat Prionailurus iriomotensis

Jackal (golden) Canis aureus

Jaguar Panthera onca

Koala Phascolarctos cinereus

Lion Panthera leo

Lynx (Canadian) Lynx canadensis

Mink (American) Neovison vison

Moose Alces alces

Mountain gazelle Gazella gazella

Mule deer Odocoileus hemionus

Narwhal Monodon monoceros

Northern fur seal Callorhinus ursinus

Ocelot Felis pardalis
Appendix 2. Appendix 2. Common and Scientific Names for Species Cited Common and Scientific Names for Species Cited 55

Common name Scientific name

Mammals—Continued

Opossum (Virginia) Didelphis virginiana

Pacific walrus Odobenus rosamarus

Pallas cat Felis manul

Pig (domestic) Sus scrofa

Polar bear Ursus maritimus

Pronghorn Antilocapra americana

Rabbit family Leporidae

Raccoon dog Nyctereutes procyonoides

Raccoon Procyon lotor

Rat Rattus spp.

Red deer (elk, wapiti) Cervus elaphus

Red fox Vulpes vulpes

Red kangaroo Macropus rufus

Reindeer Rangifer tarandus

Rhim gazelle Gazella leptoceros

Ribbon seal Histriophoca fasciata

Ringed seal Pusa hispida

Risso’s dolphin Grampus griseus

Roe deer (western) Capreolus capreolus

Saiga antelope Saiga tatarica

Sand cat Felis margarita

Sea lion (California) Zalophus californianus

Sheep (domestic) Ovis aries

Skunk Spilogale putorius, Mephitis mephitis

Southern sea otter Enhydra lutris nereis

Spinner dolphin Stenella longirostris

Spotted seal Phoca largha

Squirrel Sciurus carolensis, Sciurus griseus, Spermophilus 

tridecemlineatus, Tamiasciurus hudsonicus

Striped dolphin Stenella coeruleoalba

Tammar wallaby Macropus eugenii

Tasmanian pademelon Thylogale billardierii

Turkey Meleagris spp.
56 Trichinosis

Common name Scientific name

Mammals—Continued

Walrus Odobenus rosmarus

Wapiti (elk) Cervus elaphus

Warthog Phacochoerus aethiopicus, Phacochoerus africanus

Water buffalo Bubalus bubalis

White-tailed deer Odocoileus virginianus

Wild boar Sus scrofa

Wolf Canis lupus

Wombat (common) Vombatus ursinus

Yellow-footed rock wallaby Petrogale xanthopus

Birds

American coot Fulica americana

American crow Corvus brachyrhynchos

Blue-gray tanager Thraupis episcopus

Brewer’s blackbird Euphagus cyanocephalus

Canary Serinus canaria

Cattle egret Bubulcus ibis

Clay-colored robin Turdus grayi

Common barn owl Tyto alba

Common grackle Quiscalus quiscula

Crimson-backed tanager Ramphocelus dimidiatus

Finch Carduelis spp.

Great-tailed grackle Quiscalus mexicanus

Hawaiian crow Corvus hawaiiensis

House sparrow Passer domesticus

Laughing gull Larus atricilla

Little penguin (fairy penguin) Eudyptula minor

Mockingbird (northern) Mimus polyglottos

Ostrich Struthio camelus

Palm tanager Thraupis palmarum

Plain wren Thryothorus modestus

Red-winged blackbird Agelaius phoeniceus

Ring-billed gull Larus delawarensis

Robin (American) Turdus migratorius
Appendix 2. Appendix 2. Common and Scientific Names for Species Cited Common and Scientific Names for Species Cited 57

Common name Scientific name

Bird—Continued

Rock dove Columba livia

Ruddy ground dove Columbina talpacoti

Spotted dove Streptopelia chinensis

Starling (common) Sturnus vulgaris

Tree sparrow (Eurasian) Passer montanus

Turkey vulture Cathartes aura

Turkey (wild) Meleagris gallopavo

Vulture (white-backed) Gyps africanus

Wood duck Aix sponsa

Cold-blooded animals

Carp (common) Cyprinus carpio

Crocodile (Nile) Crocodylus niloticus

Horned toad (horned lizard) Phrynosoma spp.

Monitor lizard Varanus exanthematicus

Northern anchovy Engraulis mordax

Saltwater crocodile Crocodylus porosus
58 Trichinosis

Publishing support was provided by the USGS Columbus Publishing Service Center.

Layout by Elizabeth Ciganovich.

Illustrations by Rosemary Stenback.
For more information concerning this report, contact:

Director

U.S. Geological Survey

National Wildlife Health Center

6006 Schroeder Road

Madison, WI 53711-6223

jsleeman@usgs.gov

or visit our Web site at:

http://www.nwhc.usgs.gov/
Foreyt—Trichinosis—Circular 1388

ISSN 1067–084X (print) 

ISSN 2330–5703 (online)

http://dx.doi.org/10.3133/cir1388