Last reviewed by Faculty of Harvard Medical School on February 3, 2011
By Henry H. Bernstein, D.O.
Boston Children's Hospital
Many families have pets at home, and they can make wonderful playmates for children. Besides providing hours of fun, research suggests that pets in the home can help children physically, emotionally and developmentally. For example, pets keep children physically active, help ease stress and depression, and teach children responsibility. Pets can be found in classrooms, as well, for these same reasons.
On the other hand, animals expose children to health risks, such as bites, scratches and allergies. Animals also carry germs that can cause infections in people, so-called zoonotic diseases. These infections are spread by direct contact with an infected animal or its feces, through insects that bite or that live on infected animals, or from organisms that live in the environment where an infected animal lives.
Certain people are more likely than others to get diseases from animals and therefore need to be extra careful. Those at high risk include infants and children less than 5 years old, pregnant women, elderly people and people with limited immune systems, for example, from cancer, HIV/AIDS, or organ transplants.
The germs that cause zoonotic diseases are found in different types of animals. Some of the more common are summarized here.
Salmonella, Campylobacter and E. coli are bacteria found in the stomach and intestines (gastrointestinal tract) of many animals. These germs spread to people when they touch an object or eat food that has been contaminated with stool from an infected animal. While animals often carry these bacteria without seeming sick, exposed people can get diarrhea, abdominal pain and fever, and, rarely, life-threatening blood infections.
Giardia and Cryptosporidium are another type of germ, protozoa, that can cause diarrhea in people. They are spread from animals to people, and from person to person through contact with infected stool.
Toxoplasma is another protozoa found in cat stool. In otherwise healthy people, this infection, called toxoplasmosis, is usually a mild flulike illness. Unfortunately, in people with limited immune systems or in young infants, this infection causes damage to the brain and eyes. In addition, a pregnant woman with toxoplasmosis early in the pregnancy can pass the infection to her unborn child, leading to severe mental and physical problems in the infant. The disease spreads to people when they touch their mouth after working with contaminated soil, cleaning a cat's litter box, or touching anything that has come into contact with cat stool.
Helminths are tiny worms that commonly infect the gastrointestinal tract of dogs, cats and other animals. When spread to people through contact with infected stool, they can cause a variety of illnesses, including fever, rash, allergic reactions, infections of the brain, and eye, liver and lung disease.
Chlamydia psittaci is another bacterium, found mostly in "psittacine" birds (such as parrots, parakeets, budgies, cockatiels and macaws, especially those smuggled into the United States), pigeons and turkeys. This bacterium causes a serious type of pneumonia called psittacosis. People get this disease by breathing in dust from infected bird droppings.
Rabies is the most serious disease that animals can transmit to people. If an exposed person is not treated promptly and properly, the rabies virus can cause an infection of the brain which is always fatal. Although it can infect any mammal, rabies is found most commonly in certain wild animals, including bats, raccoons, skunks, foxes, coyotes and groundhogs (woodchucks). It is spread to people and other animals mainly through contact with an infected animal's saliva, usually through a bite or scratch.
To prevent getting an illness from animals, the U.S. Centers for Disease Control and Prevention (CDC) recommends the following for all people, but especially for those at greatest risk of getting sick from pets (as listed above):
- Adopt pets from an animal shelter or purchase them from a reputable pet store or breeder. New pets, especially young puppies and kittens, should be taken to a veterinarian very soon after adoption or purchase.
- Take your pet to the veterinarian regularly for checkups, including scheduled shots and treatment for worms.
- Always wash your hands thoroughly with soap and running water after any contact with animals and after cleaning up their stool or touching dirt that may have been in contact with animal stool.
- Clean litter boxes every day. Wear gloves, put dirty litter in plastic bags, and wash your hands thoroughly afterwards.
- Keep sandboxes covered when not in use so that cats and other animals do not use them as litter boxes.
- Do not let children play in areas where dogs and cats "go to the bathroom."
- Avoid rough play with cats and dogs to prevent scratches and bites.
- Do not let your pet eat raw food or drink from the toilet.
- People at high risk of getting sick from animals should never have contact with puppies and kittens less than 6 months old, reptiles (turtles, lizards, and snakes), baby chicks and ducklings, or any pets with diarrhea.
Henry H. Bernstein, D.O. is a Senior Lecturer in Pediatrics at Harvard Medical School. In addition, he is chief of General Academic Pediatrics at Children's Hospital at Dartmouth and Professor of Pediatrics at Dartmouth Medical School. He is the former associate chief of General Pediatrics and director of Primary Care at Children's Hospital Boston.