Christmas Pets and Disease Transmission
Zoonotic Illness May Be Carried by Live-Animal Gifts
Dec 9, 2008
Approximately 120 zoonoses have been identified to date. A zoonosis (zo-oh-NO-sis) is a disease that can be transmitted from animals to humans under natural conditions.
According to Dr. Lowell Breeden, Kansas State University Extension veterinarian, “The risk (of transmission) to humans may be great or small, depending on the disease and the situation.” (National Ag Safety Database Review April 2002)
A 1987 study estimated that 4 million pet-derived infections occur annually in the US. Since that time, the pet population has increased, with more than 50% of American households owning at least one pet. (Stehr-Green JK, Schantz PM. The impact of zoonotic diseases transmitted by pets on human health and the economy. Vet Clin North Am Small Anim Pract 1987;17:1-15)
The history of zoonotic infections is long and punctuated by dramatic actors like bubonic plague, tuberculosis, and bovine spongiform encephalopathy (“mad cow” disease). For most people, the likelihood of contracting a fatal or novel pet-borne illness is low; some basic knowledge and a few simple precautions will minimize the risk of zoonotic infection.
Common Zoonoses and Their Causes
Parasites
- Toxoplasmosis: Caused by a protozoan that is carried by cats and excreted in their feces (dogs have also been implicated as mechanical carriers, due to their habit of rolling in carcasses and feces). Cysts become infective 2-3 days after excretion.
- Toxocariasis: Roundworm infection is one of the most common zoonoses associated with dogs and cats. Many puppies are already infected when born. Most human infection is asymptomatic, but occasionally the parasite invades the liver, lungs, or eyes.
- Cutaneous larva migrans: A common condition caused by dog and cat hookworms invading human skin. Walking barefoot on contaminated beaches or in parks can lead to infection.
Bacteria
- Campylobacteriosis and Salmonellosis: Bacteria are found in the feces of multiple pet species, including cats, dogs, chicks, ducks, rodents, and reptiles. Serious outbreaks of these diarrheal illnesses have occurred in the US.
- Cat-scratch Disease: Carried by young cats or cats with fleas. Inoculation of humans occurs through scratch wounds; inflammation of nearby lymph nodes occurs several weeks later. Can cause serious disease in immunocompromised individuals.
- Leptospirosis: One of the most common zoonoses worldwide. In the US, most frequently found in dogs and acquired through contact with their urine. Human infection is usually mild, but can rarely lead to severe illness with hepatitis, renal failure, heart failure, and death.
- Lyme Disease: Carried by ticks that can be transferred to humans from outdoor pets. If untreated, may lead to a multi-system disease involving joints, nerves, brain, skin, and heart.
- Psittacosis: Caused by exposure to feces or nasal secretions of infected birds. Usually presents as a flu-like illness in humans.
- Mycobacterium marinum: Acquired from handling fish aquariums; usually causes a localized nodular swelling on an upper extremity.
Arthropods
- Scabies: Sarcoptic mites from dogs cannot reproduce in human skin, but they can cause intense itching and rash.
Viruses
- Rabies: While rare in the US, this fatal zoonosis is still found in certain wildlife reservoirs. Unvaccinated pets can become vectors.
- Monkeypox: A 2003 outbreak originated in infected prairie dogs being sold as pets. These animals had, in turn, acquired the virus from imported African rodents.
- Lymphocytic Choriomeningitis: This virus can be transmitted from hamsters, guinea pigs, and other rodents. Human infection is usually mild, but can cause viral meningitis; may cause fatal illness in organ transplant recipients.
When proper precautions are exercised in the selection of a pet and in its subsequent care, the benefits of pet ownership outweigh the potential risks of infectious disease. Veterinarians are excellent sources of information and education.
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