Zoonotic diseases are naturally transmitted to people from other animals. People can be infected with these diseases by direct contact with cats (e.g., feces, respiratory secretions, infected lesions, bites, scratches) or through contact with shared vectors (e.g., fleas, ticks). Many zoonotic diseases can infect anyone, but disease is often more common or more severe in immunocompromised individuals (e.g., very young, very old, those being treated with chemotherapy or immunosuppressive medications).

Zoonoses are estimated to make up approximately 75% of today’s emerging infectious diseases. These infectious agents can be transmitted by many different animals, including wildlife, exotic pets, and even traditional pets, such as dogs and cats. For example, studies have shown that cats, both healthy and those with diarrhea, can shed zoonotic organisms in feces. In two studies in the United States, between 13% and 40% of the cats examined were shedding at least one zoonotic enteric pathogen.1,2 Although the prevalence of shedding was variable for specific pathogens, numerous organisms including Toxocara cati, Giardia spp., Cryptosporidium spp., Salmonella spp., and Campylobacter spp. were identified. This chapter will highlight zoonotic diseases that are commonly associated with domestic cats and what steps can be taken to reduce exposure and transmission (Box 42.1). Additional zoonotic infections that are rarely associated with cats are in Tables 42.1 and 42.2. More information can be found in the resources in Box 42.2, including the 2019 American Association of Feline Practitioners (AAFP) Feline Zoonoses Guidelines.³ Additional information on diagnosis and treatment for most of the pathogens discussed here is found in other relevant chapters in this book.

Although dog bites account for approximately 80% of reported animal bites in people, cats are the second most common animal reported to cause bites.4 Because cats typically cause puncture wounds when biting, introduction of bacteria deep into the tissues of the wound is common. Up to 80% of cat bites become infected with a variety of aerobic and anerobic bacteria. Pasteurella spp. are the most common bacteria isolated from cat bite wounds and can cause sepsis, meningitis, and septic arthritis, among other complications.⁵ Cat bites to the hands often require extensive treatment and are more likely than dog bites to result in complications such as cellulitis, osteomyelitis, and tenosynovitis.⁴ Immunodeficient people more commonly develop systemic illness after exposure to Pasteurella spp. and Capnocytophaga spp.^6,7

Prevention of cat bites in veterinary practices can often be achieved by understanding feline behavior, using sedation in defensive cats when appropriate, and other cat-friendly handling techniques. Despite these efforts, cat bites will still occur and should be treated as soon as possible. Delaying treatment is a risk factor for infection and other complications. Pain, swelling, erythema, and swelling of local lymph nodes can occur within 1 to 2 hours of a cat bite. Wound care is essential although the use of prophylactic antibiotics is still controversial. However, one study that examined a small number of people who had been bitten by cats found that 67% of those not treated with antibiotics developed infection, while none of those treated with antibiotics developed infection.⁸ Additionally, postexposure prophylaxis for rabies virus may be indicated, depending on the vaccination history of the cat, the circumstances of the bite, and whether the disease is present in the area. The victim’s history of tetanus prophylaxis should also be reviewed by the physician, especially if the bite wound is contaminated with soil. Treatment for cat bites will vary from case to case, but all should include aggressive and careful wound care (e.g., cleaning, irrigation, and débridement when necessary) and measures to prevent infection with bacteria such as Pasteurella spp., or rabies virus.