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Dr. Lila Miller, DVM, ASPCA


Zoonosis is the term used to describe diseases that can be passed from animals to humans and vice versa. This is an issue of special importance today as more and more diseases are being recognized as zoonotic or are making headlines. Some of these diseases were rarely found in the US, such as Western Nile virus, which although it is transmitted by mosquitoes rather than by direct contact with an animal that has the disease, is considered to be zoonotic. The first case of plague found in New York City in a hundred years was recently diagnosed. The news had been filled with information about anthrax, which has been encountered by ranchers and veterinarians routinely for years in certain areas of the country, but took on new significance when it was used as a biological weapon. Zoonosis is big news. How concerned should we be?

People who work with animals are at the highest risk for contracting zoonotic diseases, yet they tend to be much more at ease dealing with this concern. This is because they avail themselves with up-to-date information about zoonotic diseases in their area and the real, versus perceived, risk. The risk may be even higher for animal shelter workers because of the unknown history of the animals, occasional poor sanitation and overcrowding that leads to stress and disease and the lack of sophisticated medical tests to diagnose illnesses. By way of contrast, veterinary and technical staff who work in animal hospitals, zoos and laboratories, for example, know much more about the medical history of their population. Yet my experience dealing with shelters for over twenty years has not caused undue concern about shelter workers having a high incidence of zoonotic illness. Fortunately, as shelters implement better training, health care programs and sanitation procedures, they are better prepared to deal with zoonotic diseases.

The ordinary public is at much less risk of contracting a zoonotic disease, even if they own a pet, but should be aware that there are some hazards. There are at least 200 known zoonotic diseases, and more are being continually added to the list. Fortunately for most shelter workers and pet owners dealing mainly with dogs and cats, the list of zoonotic diseases to be concerned about is much shorter than 200. The good news is also that most of these diseases can be avoided or their impact minimized by following a few straightforward rules. Finally, it should always be remembered that the vast majority of people who work with or own animals do not contract any of these diseases. The people most at risk are the elderly, young children, and people who are immune-compromised, such as HIV patients or people taking immunosuppressive drugs. The rewards obtained from the human animal bond far outweigh the risks of becoming ill from contact with animals.

The small animal diseases that are most readily encountered or likely to be contracted by the general pet owning public or shelter workers are listed below. Most of these diseases are not serious and respond readily to treatment.

  • Ringworm
  • Sarcoptic mange
  • Roundworms (Visceral larval migrans in humans)
  • Cat Scratch Fever (Bartonella)
  • Giardia
  • Pasteurella

Other diseases that are less frequently encountered but still of concern are listed below. Some of these diseases can be quite serious, or deadly, such as rabies.

  • Rabies
  • Toxoplasmosis
  • Leptospirosis
  • Brucellosis
  • Salmonella
  • Rocky Mountain Spotted Fever
  • Campylobacter
  • Capnocytophaga
  • Lyme Disease
  • Plague

To view Zoonosis, Part II, click here.

© 2002 ASPCA

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