Can Your Pet Make You Sick? By Peter M. Rabinowitz, MD, MPH
Pets are wonderful sources of affection, companionship and enjoyment, and they may even lower your blood pressure, cholesterol levels and triglyceride levels. But did you know that Felix and Fido can also make you sick? Several million people in the US get infections each year from interactions with cats, dogs and other pets. These range from benign skin conditions to potentially serious illnesses such as salmonella, Monkeypox and MRSA (methicillin-resistant Staphylococcus aureus). However, with a little pet know-how and lots of plain old common sense, most pet-related illnesses can be avoided. For insight into the scope of pet-related illness, I spoke with Peter M. Rabinowitz, MD, MPH, director of clinical services in occupational and environmental medicine at Yale University School of Medicine. Dr. Rabinowitz is coauthor of an article published in a recent issue of American Family Physician that discussed 26 different pet-related infections.
MOST DISEASES STARTED WITH ANIMALS
Most human infectious diseases are zoonotic in origin, meaning they are passed from animals to humans. While examples of zoonotic diseases include Rabies, West Nile Virus, Lyme Disease and tapeworm infection, the Centers for Disease Control and Prevention (CDC) states clearly on its Web site, "Healthy Pets, Healthy People" (http://www.cdc.gov/healthypets/) that overall, you are less likely to get sick from germs from an animal than from these same germs in contaminated drinking water or food.
Still, with more than 60 million pet dogs and almost 70 million pet cats in the US, the number of pet-human encounters and therefore, the risk of pet-associated infections, is huge. Other trends, including growing interest in exotic pets, pets purchased through the Internet and suburban sprawl contribute to the problem. "Imported and exotic pets bring infections unfamiliar to the US into this country," said Dr. Rabinowitz. "Also, as suburban development encroaches on wildlife habitat, household dogs and cats have contact with wild animals outdoors. It is now commonplace to find deer, coyotes and foxes in one's backyard. If dogs and cats become infected with wildlife diseases, they can bring the infection into the house." Even "pocket pets" such as hamsters and mice are capable of transmitting infections such as salmonella to their owners.
TYPES OF PET-RELATED ILLNESSES
The most common pet-related illnesses fall into one of the following three categories:
Parasitic infections. If you are a cat owner, you probably already know about Toxoplasmosis gondii, a parasitic infection that people can get through direct contact with cat feces while cleaning the litter box or gardening in soil contaminated with cat feces. This is just one of several parasitic infections that can be transmitted this way.
Fungal infections. Both cat and dog owners (especially owners of puppies and kittens) can contract fungal infections of the skin such as ringworm, a skin and scalp disease characterized by a ring-shaped rash or bald, scaly patch of skin. Petting the animal or even touching contaminated bedding or other articles can directly spread the infection to a person's skin.
Bacterial infections. Dogs and cats can pass Campylobacter bacterial infections to people who come into contact with their feces, causing symptoms such as abdominal cramping, nausea, vomiting and diarrhea. Contact with lizards, snakes, turtles, baby chicks and ducklings can result in Salmonella bacterial infections, causing fever, diarrhea and abdominal pain.
NEW RISKS FROM PETS
Although incidence of those common infections has not necessarily increased in recent years, Dr. Rabinowitz voices concern about other, less common diseases newly linked to animals.
The Monkeypox virus belongs to a group of viruses not previously seen in the Western hemisphere that includes the smallpox virus (variola), the virus used in the smallpox vaccine and the cowpox virus. The symptoms of Monkeypox are similar to those of smallpox, but are usually milder. In 2003, US health officials traced several human Monkeypox cases to infected pet prairie dogs and rodents imported from Africa.
You've undoubtedly also already heard about MRSA (methicillin-resistant Staphylococcus aureus), a type of staph infection that is resistant to methicillin and other commonly used antibiotics in the same class, including penicillin, amoxicillin and oxacillin. Though the numbers of reported cases have thus far been small, it seems that people who are infected or are carriers of MRSA can also pass it to their pets, who can pass it back to people. In one case, a woman with diabetes had a MRSA skin infection. Her dog was found to be infected with the same strain, and the woman's recurrent infections only stopped when the dog was treated. "MRSA has recently been found in dogs, cats, horses and pigs. We are just starting to find out how big a problem this may be," says Dr. Rabinowitz.
PROTECTING YOURSELF FROM ILLNESS
The first line of defense is increased awareness of the problem among pet owners and the medical community, but primary care physicians are not always up-to-date on pet-related diseases and how to treat them. The implication? Your doctor may not ask questions about your pets and their illnesses, which could make it harder for your sickness to be properly diagnosed and treated. Many of these illnesses can also be contracted through other means (such as from other people) so Dr. Rabinowitz says, "it can take some detective work to figure out that the pet is playing a role in the infection."
To help address these problems, the American Medical Association (AMA) and the American Veterinary Medical Association (AVMA) have partnered together on a "One Health" task force. This expert panel is charged with making recommendations to encourage communication and collaboration between human health care providers and veterinary professionals to better recognize, prevent and treat diseases that involve both animals and people.
To reduce your and your family's risk of pet-related infections, be sure to tell your family physician about the presence of any pets in your household. This is particularly important if young children, elderly or immune-compromised family members live with you.
Additionally, to prevent pet-related illnesses:
Make sure your pet receives good preventive veterinary care that includes administering prescribed vaccinations and deworming treatments.
Maintain a dialog with your veterinarian, and remember to ask about new developments regarding diseases to look out for in your pet, and which ones can be transmitted to people.
Make sure that sick pets are promptly and adequately treated.
Wash hands before and after handling pets and avoid contact with pet feces.
If you own a cat, clean or change its litter daily. Pregnant women (and people with compromised immune systems) should keep cats indoors and avoid handling cat litter. To reduce risk of toxoplasmosis, never feed cats uncooked meat.
If you are thinking about getting a pet, consider these precautions:
Get one from a store or breeder who is licensed and regulated. Many Internet dealers are not licensed and some may be importing animals illegally without proper health and safety precautions.
Think twice before choosing an exotic pet. They may carry an increased risk of disease, including ones that your doctor may be unfamiliar with.
Don't adopt wild animals as pets.
Wash hands after handling raw meat, as this is another mode of transmission of certain zoonotic diseases.
Peter M. Rabinowitz, MD, MPH, an associate professor of medicine and director of clinical services in the occupational and environmental medicine program at Yale University School of Medicine, New Haven, Connecticut.
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