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Classification and external resources
A dog with rabies.
DiseasesDB 28555
MeSH D015047

Zoonosis (; also spelled zoönosis; plural zoonoses) is any process whereby an infectious disease is transmitted between different species of animals. Often the term is used specifically to refer to diseases that originate in other species of animal, but that get transmitted to humans. Zoonoses in which humans are infected may originate in either domestic animals or wildlife, such as insects, mammals, reptiles, or birds. In some zoonoses, humans infect other animals; this is sometimes called reverse zoonosis or anthroponosis ("anthropo-" being Greek for "human").

In direct zoonosis the agent needs only one host for completion of its life cycle, without a significant change during transmission. Many strains of influenza are common examples.[1] "Direct zoonosis" also may refer to transmission between hosts when one animal directly passes the disease to another. In contrast, in those terms indirect zoonosis is transmission via an intermediate host species that may carry the disease without showing ill effects itself. An animal that transmits a disease in such a way is are known as a vector.

Many serious epidemic diseases are zoonoses that originated in animals. These include rabies, Ebola virus disease and influenza. In a systematic review of 1,415 pathogens known to infect humans, 61% were zoonotic.[2] The emergence of a pathogen into a new host species is called disease invasion or disease emergence.

The emerging interdisciplinary field of conservation medicine integrates human and veterinary medicine, and environmental sciences; conservation medicine is largely concerned with zoonoses.


Zoonosis is derived from the Greek words ζῷον zoon "animal" and νόσος nosos "ailment".

Historical development of zoonotic diseases

During most of human prehistory groups of hunter-gatherers usually numbered fewer than 150 individuals. Such groups seldom made contact with other bands. Such isolation commonly caused epidemic diseases to burn out after their first run through a population, because epidemics depend on constant contact with humans who have not developed an immune response. To persist in such a population, a pathogen either had to be a chronic infection, staying alive and infectious in the host for long periods, or it had to have a non-human reservoir in which it could survive until new hosts made contact. In fact, for many 'human' diseases, the human is actually an accidental or incidental victim and a dead-end host. Examples include rabies, anthrax, tularemia and West Nile virus. Thus, much of human exposure to infectious disease has been zoonotic.

Many modern diseases, even epidemic diseases, started out as zoonotic diseases. It is hard to be certain which diseases jumped from other animals to humans, but there is increasing evidence from DNA and RNA sequencing, that measles, smallpox, influenza, HIV, and diphtheria came to us this way. Various forms of the so-called "common cold" and tuberculosis also are adaptations of strains originating in other species.

Zoonoses are of interest because they are often previously unrecognized diseases or have increased virulence in populations lacking immunity. The West Nile virus appeared in the United States in 1999 in the New York City area, and moved through the country in the summer of 2002, causing much distress. Bubonic plague is a zoonotic disease,[3] as are salmonella, Rocky Mountain spotted fever, and Lyme disease.

A major factor contributing to the appearance of new zoonotic pathogens in human populations is increased contact between humans and wildlife.[4] This can be caused either by encroachment of human activity into wilderness areas or by movement of wild animals into areas of human activity. An example of this is the outbreak of Nipah virus in peninsular Malaysia in 1999, when intensive pig farming began on the habitat of infected fruit bats. Unidentified infection of the pigs amplified the force of infection, eventually transmitting the virus to farmers and causing 105 human deaths.[5]

Similarly, in recent times avian influenza and West Nile virus have spilled over into human populations probably due to interactions between the carrier host and domestic animals. Highly mobile animals such as bats and birds may present a greater risk of zoonotic transmission than other animals due to the ease with which they can move into areas of human habitation.

Because they depend on the human host for part of their life-cycle, diseases such as African schistosomiasis, river blindness, and elephantiasis are not defined as zoonotic, even though they may depend on transmission by insects or other vectors.

Contribution of zoonotic pathogens to foodborne illness

The most significant zoonotic pathogens causing foodborne diseases are Escherichia coli O157:H7, Campylobacter, Caliciviridae, and Salmonella.[6][7][8]

In 2006, a conference held in Berlin was focusing on the issue of zoonotic pathogen effects on food safety, urging governments to intervene, and the public to be vigilant towards the risks of catching food-borne diseases from farm-to-dining table.[9]

Many food outbreaks can be linked to zoonotic pathogens. Many different types of food can be contaminated that have an animal origin. Some common foods linked to zoonotic contaminations include eggs, seafood,meat, dairy, and even some vegetables.[10] Food outbreaks should be handled in preparedness plans to prevent widespread outbreaks and to efficiently and effectively contain outbreaks.

Zoonosis research centers

A zoonosis research center is being developed in Kazakhstan as of February 2014, according to BioPrepWatch. The U.S. Department of Defense helped plan and construct the Central Reference Laboratory in Kazakhstan. Scientists at the lab will study diseases like the plague and cholera, and try to use their research to find cures and treatments for the diseases. The lab will be run by the Kazakh Scientific Center of Quarantine and Zoonotic Diseases.[11]

Lists of zoonotic diseases and incidents

List of vectors of zoonotic diseases

List of infectious agents

Zoonoses can be classified by infectious agent type:

Partial list of zoonoses

a transmissible spongiform encephalopathy (TSE)
from bovine spongiform encephalopathy (BSE) or "mad cow disease"

Other possible zoonoses might be:

Partial list of outbreaks of zoonosis associated with fairs and petting zoos

Outbreaks of zoonoses have been traced to human interaction with and exposure to animals at fairs, petting zoos, and other settings. In 2005, the Centers for Disease Control and Prevention (CDC) issued an updated list of recommendations for preventing zoonosis transmission in public settings.[13] The recommendations, developed in conjunction with the National Association of State Public Health Veterinarians, include educational responsibilities of venue operators, limiting public and animal contact, and animal care and management.

In 1988, a person became ill with swine influenza virus (swine flu) and died after visiting the display area of the pig barn at a Wisconsin county fair. Three healthcare personnel treating the case patient also developed flu-like illness with laboratory evidence of swine influenza virus infection.[14] Investigators from the CDC indicated in their final report that the swine flu had been transmitted directly from pig to human host.[15]

In 1994, seven cases of E. coli O157:H7 infection were traced to a farm in Leicestershire, United Kingdom. An epidemiological investigation into the outbreak revealed that the strain of E. coli O157:H7 isolated from nine animals on the farm was indistinguishable from the strain isolated from human samples. Investigators concluded that the most likely cause of this outbreak was direct human contact with animals.[16]

In 1995, 43 children who had visited a rural farm in Wales became ill with Cryptosporidiosis. Cryptosporidium was isolated from seven of the ill children. An epidemiological investigation indicated that the source of the children's illness was contact with calves at the farm.[17]

Also in 1995, at least 13 children became ill with Cryptosporidiosis after visiting a farm in Dublin, Ireland. In a case-control study, researchers compared the activities of the 13 ill children, or cases, to the activities of 52 out of 55 people who had visited the farm – the controls. The study revealed that illness was significantly associated with playing in the sand in a picnic area beside a stream where animals had access.[18]

In 1997, an E. coli O157:H7 outbreak was identified among one child who lived on an open farm and two children who visited the farm during school parties. Two of the three children developed hemolytic-uremic syndrome (HUS). Isolates collected from the three children and from samples taken at the farm were indistinguishable, demonstrating evidence of the link between the farm and the children's illness.[19]

In 1999, what is believed to be the largest outbreak of waterborne E. coli O157:H7 illness in United States history occurred at the Washington County, New York fair. The New York State Department of Health identified 781 individuals who were suspected of being infected with either E. coli O157:H7 or Campylobacter jejuni. An investigation into the outbreak revealed that consumption of beverages purchased from vendors supplied with water drawn from an unchlorinated fairgrounds well was associated with illness. In all, 127 outbreak victims were confirmed ill with E. coli O157:H7 infections; 71 were hospitalized, 14 developed HUS, and two died.[20]

In 2000, 51 people became ill with confirmed or suspected E. coli O157:H7 infections after visiting a dairy farm in Pennsylvania. Eight children developed HUS. A case-control study among visitors to the dairy was conducted jointly by the CDC, Pennsylvania Department of Health, and the Montgomery County Health Department. The study's authors concluded that E. coli was transmitted to visitors as a result of contamination on animal hides and in the environment.[21]

Also in 2000, 43 visitors to the Medina County fair in Ohio were confirmed ill with E. coli O157:H7 infections. An investigation into the outbreak suggested that the water system from which food vendors were supplied was the source of the E. coli outbreak. Several months later, five children became ill with E. coli infections after attending a "Carnival of Horrors" event held at the Medina County fairgrounds. PFGE analysis of the strains of E. coli isolated from members of both outbreaks revealed an indistinguishable pattern, and investigators from the Medina County Health Department and the CDC determined that the Medina County Fairgrounds water distribution system was the source of both E. coli outbreaks.[22]

In 2001, an E. coli O157:H7 outbreak was traced to exposure in the Cow Palace at the Lorain County Fair in Ohio. CDC investigators identified 23 cases of E. coli infection associated with attendance at the Lorain County Fair, with additional secondary cases likely. Two people developed HUS. An investigation revealed E. coli contamination on doorways, rails, bleachers, and sawdust. Investigators concluded that the Lorain County Fair was the source of the outbreak.[23]

Wyandot County, Ohio, also reported an E. coli O157:H7 outbreak in 2001. Ninety-two E. coli infections were reported to the Wyandot County Health Department and the CDC, with 27 cases confirmed using laboratory analysis. Two cases developed HUS. Contact with infected cattle was believed to be the source of the outbreak; however, a specific cause was never identified.[23]

In 2002, seven people became ill with E. coli O157:H7 infections after visiting a large agricultural fair in Ontario, Canada. Outbreak investigators conducted a case-control study, which indicated that goats and sheep from a petting zoo were the source of the E. coli among fair visitors. Other indications were that the fencing and environment surrounding the petting zoo could have been a source of transmission.[24]

What is believed to be the largest E. coli O157:H7 outbreak in Oregon history occurred among attendees at the Lane County fair in 2002.[25] An Oregon Department of Human Services – Health Services investigation led to the belief that the E. coli outbreak originated from exposure in the sheep and goat barn. In all, 79 people were confirmed ill with E. coli infections as part of the outbreak; 22 were hospitalized, and 12 suffered HUS.[26]

In 2003, fair visitors and animal exhibitors at the Fort Bend County Fair in Texas became ill with E. coli O157:H7 infections. An outbreak investigation led to the determination that 25 people had become ill with E. coli infections after attending the Fort Bend County Fair; seven people were laboratory-confirmed with E. coli, and 5 developed HUS or TTP (Thrombotic thrombocytopenic purpura). Investigators isolated a strain of E. coli indistinguishable from the outbreak strain from four animal husbandry sites, and found high levels of E. coli contamination in both rodeo and animal exhibit areas.[27]

In 2004, a large E. coli O157:H7 outbreak occurred among visitors at the 2004 North Carolina State Fair. During its investigation into the outbreak, the North Carolina Department of Health and Human Services (NCDHHS) received over 180 reports of illness, and documented 33 culture-confirmed cases of E. coli O157:H7 associated with attendance at the fair, with 15 children developing HUS. In its final investigation report, NCDHHS concluded that the North Carolina State Fair E. coli outbreak had originated at a petting zoo exhibit. The conclusion was supported by a case-control study, environmental sampling, and laboratory analysis of samples collected from the fair and members of the outbreak.[28]

In 2005, a petting zoo that exhibited at two Florida fairs and a festival was traced as the source of an E. coli O157:H7 outbreak. Sixty-three people who had visited either the Florida State Fair, the Central Florida Fair, or the Florida Strawberry Festival reported illness to investigators for the Florida Department of Health, including 20 who were culture-confirmed and 7 with HUS. A case-control study revealed that illness was associated with exposure to a petting zoo exhibit present at all three events.[29]

See also


  1. ^ "Zoonosis". Medical Dictionary. Retrieved 30 January 2013. 
  2. ^ Taylor, L. H.; Latham, S. M.; Woolhouse, M. E. J. (2001). "Risk factors for human disease emergence". Philosophical Transactions of the Royal Society B: Biological Sciences 356 (1411): 983–989.  
  3. ^ Meerburg BG, Singleton GR, Kijlstra A (2009). "Rodent-borne diseases and their risks for public health". Crit Rev Microbiol 35 (3): 221–70.  
  4. ^ Daszak, P.; Cunningham, A. A.; Hyatt, A. D. (2001). "Anthropogenic environmental change and the emergence of infectious diseases in wildlife". Acta tropica 78 (2): 103–116.  
  5. ^ Field, H.; Young, P.; Yob, J. M.; Mills, J.; Hall, L.; MacKenzie, J. (2001). "The natural history of Hendra and Nipah viruses". Microbes and infection / Institut Pasteur 3 (4): 307–314.  
  6. ^ Humphrey, Tom et al.; O'Brien, S; Madsen, M (2007). "Campylobacters as zoonotic pathogens: A food production perspective". International Journal of Food Microbiology 117 (3): 237–257.  
  7. ^ Cloeckaert, Axel (2006). "Introduction: emerging antimicrobial resistance mechanisms in the zoonotic foodborne pathogens Salmonella and Campylobacter". Microbes and Infection 8 (7): 1889–1890.  
  8. ^ Frederick, A. Murphy. "The Threat Posed by the Global Emergence of Livestock, Food-borne, and Zoonotic Pathogens".  
  9. ^ Med-Vet-Net. "Priority Setting for Foodborne and Zoonotic Pathogens" (PDF). Retrieved 5 April 2008. 
  10. ^ "Investigating Foodborne Outbreaks" (PDF). Centers for Disease Control and Prevention. 15 September 2011. Retrieved 5 June 2013. 
  11. ^ Clark, Marjorie. "Pentagon not developing biological weapons in Kazakhstan". BioPrepWatch. 1/27/14. Retrieved 2/5/14.
  12. ^ Bell, D., Roberton, S. and Hunter, P. R. (2004). Animal origins of SARS coronavirus: possible links with the international trade in small carnivores. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 359(1447): 1107−1114.
  13. ^ Centers for Disease Control and Prevention (2005). "Compendium of Measures To Prevent Disease Associated with Animals in Public Settings, 2005: National Association of State Public Health Veterinarians, Inc. (NASPHV)" (PDF). MMWR 54 (RR–4): inclusive page numbers. Retrieved 28 December 2008. 
  14. ^ Wells, et al.; Hopfensperger, DJ; Arden, NH; Harmon, MW; Davis, JP; Tipple, MA; Schonberger, LB (1991). "Swine influenza virus infections. Transmission from ill pigs to humans at a Wisconsin agricultural fair and subsequent probable person-to-person transmission". JAMA 265 (4): 478–81.  
  15. ^ Centers for Disease Control and Prevention (1988). "Human infection with swine influenza virus – Wisconsin". MMWR 37 (43): 661–3.  
  16. ^ Shukla, et al.; Slack, R; George, A; Cheasty, T; Rowe, B; Scutter, J (1995). "Escherichia coli O157 infection associated with a farm visitor center". Communicable Disease Report 5 (6): R86–R90.  
  17. ^ Evans, M. R. and D. Gardner (1996). ""Cryptosporidiosis" Outbreak Associated with an Educational Farm Holiday". Commun Dis Rep CDR Rev. 29 6 (4): R67. 
  18. ^ Sayers, et al. (1996). "Cryptosporidiosis in children who visited an open farm". Commun Dis Rep CDR Rev. 13 6 (10): R140–4.  
  19. ^ Milne; Plom, A; Strudley, I; Pritchard, GC; Crooks, R; Hall, M; Duckworth, G; Seng, C et al. (1999). ""Escherichia coli" O157 incident associated with a farm open to members of the public". Communicable Disease and Public Health 2 (1): 22–26.  
  20. ^ New York State Department of Health and A.C. Novello (2000). "The Washington County Fair outbreak report". 
  21. ^ Centers for Disease Control and Prevention (2001). O157:H7 infections among children associated with farm visits—Pennsylvania and Washington 2000"Escherichia coli"Outbreaks of . MMWR 50 (15): 293–297.  
  22. ^ Rickelman-Apisa, J.M. (28 September 2001). "Summary of E. coli O157:H7 Outbreak Associated with the Medina County Fairgrounds 2000 Fair and 2000 Carnival of Horrors". Medina County Health Department. 
  23. ^ a b Varma, J.K. (15 February 2002). "Trip report epi-aid # 2001-84: Outbreaks of E. coli O157:H7 infections associated with Lorain and Wyandot County fairs, Ohio, September–October 2002 From Jay K. Varma, EIS officer, Food borne and Diarrheal Diseases branch to Forrest Smith, State Epidemiologist, Ohio department of Health". Public Health Service. Department of Health and Human Services. 
  24. ^ Warshawsky; Gutmanis, I; Henry, B; Dow, J; Reffle, J; Pollett, G; Ahmed, R; Aldom, J et al. (2002). "Outbreak of Escherichia coli 0157:H7 related to animal contact at a petting zoo". Canadian Journal of Infectious Diseases 13 (3): 175–181.  
  25. ^ Oregon Department of Human Services (13 September 2002). "Hemorrhagic Escherichiosis from a County Fair" (PDF). CD Summary 51 (19). 
  26. ^ Oregon Department of Human Services, Health Services (2005). "2005 Ways and Means Presentation – Phase 1" (PDF). Oregon Department of Human Services. Retrieved 22 May 2007. 
  27. ^ Durso, L.M., et al. (2005). "Shiga-Toxigenic Escherichia coli (STEC) O157:H7 Infections Among Livestock Exhibitors and Visitors at a Texas County Fair". Vector-Borne and Zoonotic Diseases 5 (2): 193–201.  
  28. ^ Goode, B.; O'Reilly, C. (29 June 2005). "Outbreak of Shiga toxin producing E. coli (STEC) infections associated with a petting zoo at the North Carolina State Fair – Raleigh, North Carolina, November 2004 Final Report". North Carolina Department of Health and Human Services. 
  29. ^ Centers for Disease Control and Prevention (2005). "Outbreaks of Escherichia coli O157:H7 Associated with Petting Zoos — North Carolina, Florida, and Arizona, 2004 and 2005". MMWR 54 (= 50): 1279. 


  • H. Krauss, A. Weber, M. Appel, B. Enders, A. v. Graevenitz, H. D. Isenberg, H. G. Schiefer, W. Slenczka, H. Zahner: Zoonoses. Infectious Diseases Transmissible from Animals to Humans. 3rd Edition, 456 pages. ASM Press. American Society for Microbiology, Washington DC., U.S. 2003. ISBN 1-55581-236-8
  • Jorge Guerra González (2010) (in German), Infection Risk and Limitation of Fundamental Rights by Animal-To-Human Transplantations. EU, Spanish and German Law with Special Consideration of English Law, Hamburg: Verlag Dr. Kovac, ISBN 

External links

  • AVMA Collections: Zoonosis Updates
  • WHO tropical diseases and zoonoses
  • Detection and Forensic Analysis of Wildlife and Zoonotic Disease
  • Publications in Zoonotics and Wildlife Disease
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