Rachel A. Arendt, B.S., Veterinary Student, Class of 2004
The Ohio State University
Teresa Y. Morishita, D.V.M., Ph.D.
Extension Veterinarian, Poultry
Ohio State University Extension
There are many benefits of having a companion animal and these benefits often outweigh the risks of pet ownership. The infections that are shared by people and animals are termed zoonoses. These zoonoses can be serious in immunocompromised people. The risks of contracting an infection can be minimized by following some basic preventative measures. In many of these diseases, the most likely sources of infection are not pets. Therefore, education on disease transmission and prevention are important to minimize the risk of infection from all possible sources.
Immunocompromised people are more susceptible to acquiring infectious diseases and include individuals undergoing chemotherapy, such as for breast cancer, organ transplant recipients, and bone marrow recipients. This group also includes the elderly, especially those in nursing homes, hospices, and hospitals; infants; and children under five years of age.
Medical conditions that compromise the immune system include: diabetes; HIV/AIDS; chronic renal failure; asthma; and long term steroid medication usage.
| Type of Pet | Potential Diseases |
| Cats | Cat Scratch Fever, Toxoplasmosis, Cryptosporidiosis, Salmonellosis, Campylobacteriosis, Giardiasis, Ringworm, Roundworms, Hookworms, Q-Fever |
| Dogs | Cryptosporidiosis, Salmonellosis, Campylobacteriosis, Giardiasis, Ringworm, Roundworms, Hookworms |
| Reptiles (snakes, lizards, turtles) | Salmonellosis |
| Fish | Mycobacterium marinum |
| Birds | Chlamydiosis, Avian Tuberculosis, Salmonellosis |
The chart demonstrates that there are many diseases that can be acquired from household animals. We will discuss some of the more common infections that are encountered.
Toxoplasmosis: Household cats are only one of many sources of the protozoan parasite, Toxoplasma gondii. Many cases of human central nervous system toxoplasmosis are actually reactivations of previous infections from the ingestion or handling of contaminated meat products, such as pork. Contrary to popular belief, touching or caring for household cats is not the major transmission route. Once an infected cat has shed the Toxoplasma oocyst (egg), they are unlikely to shed again. They are most likely to shed infectious oocysts after ingesting infected tissues. Therefore, cats should not be allowed to hunt or eat raw meat. Oocysts need at least 24 hours to become infectious and so daily litter box cleaning should be done, preferably by an immunocompetent person or while wearing gloves. Improper meat preparation, contaminated soil in the environment, and stray cats are the most likely sources of infection. Stray cats have higher rates of infection than household cats. Stray cats can contaminate the environment and gloves should be worn when working outside, such as when gardening, and the handling of stray cats should be avoided. Proper kitchen hygiene will help decrease the risk from meat contamination. Don't reuse any utensils or cutting surfaces that were in contact with the raw meat and don't taste marinades that haven't been fully cooked.
Cat Scratch Disease: This disease is caused by the bacteria, Bartonella hensalea, and the disease has been associated with cat contact, especially if one is scratched or bitten, and with exposure to cat fleas. To help prevent infection, the immunocompromised should avoid kittens (they tend to scratch more than adults), avoid contact with stray cats, and use proper flea control. Immediately wash if any scratches or bites occur. Declawing may be an option for those cats that continue to scratch.
Salmonellosis and Campylobacteriosis: Dogs and cats are an infrequent source of infection of the Salmonella and Campylobacter bacteria. The most common sources for humans are contaminated water; and milk or food contaminated by domestic or farm animals. To prevent dogs and cats from being sources of infection, they should be fed a quality commercial diet and no raw or undercooked meat. They should not be allowed to hunt. The cat litterbox should be cleaned daily, preferably by an immunocompetent person, or if the immunocompromised person must clean it, they should wear gloves and wash immediately afterwards. The litter box should not be kept in kitchens, dining rooms, or anyplace where there is food.
Cryptosporidiosis: This infection is caused by the protozoan parasite, Cryptosporidium parvum, and is predominantly acquired from ingestion of fecal-contaminated food and water, such as pools, lakes, rivers, and municipal water supplies. Municipal water supplies have been found to be contaminated up to 90% if untreated and 30% if treated. Therefore, drinking bottled water and taking care to not accidentally ingest water at public pools and other bodies of water may help to greatly decrease the risk of infection. Any pets with diarrhea should be avoided and they should be examined by a veterinarian to determine the cause of the diarrhea.
Giardiasis: Giardiasis is a disease caused by the protozoan parasite, Giardia lamblia. Infection usually occurs from the environment, especially water sources. The frequency of transmission of Giardia between animals and people is not well established. Human outbreaks usually involve young children with exposure to day-care environments or originate from a water source, such as multiple-use pools.
The benefits of pet ownership outweigh the potential risk of disease in people. For many zoonoses, people are more likely to get the disease from sources other than their pets. The risks can be minimized for all people, including the immunocompromised, by practicing basic preventative measures. Contact your veterinarian and physician for more information.
Reviewed by:
John C. Gordon, DVM, MPH, Department of Veterinary Preventive Medicine, The Ohio State University.
Click here for a PDF version of this fact sheet.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868