Yale Physician Reviews Research to Dispel Myth About Pregnant Women and Cats

A pregnant woman is at higher risk of contracting toxoplasmosis, which can cause great harm to the fetus, from eating undercooked meat than from the family cat and its litter box, a Yale researcher says in a newly published research paper.

"It is more likely for a pregnant woman to acquire toxoplasmosis from eating undercooked meat or from contacting soil without gloves," said Jeffrey Kravetz, M.D., assistant professor of medicine at Yale School of Medicine and lead author of the review article published in the September issue of the Archives of Internal Medicine.

Toxoplasmosis is found throughout the world, predominantly in cultures that eat raw meat. There are about 3,000 cases of congenital toxoplasmosis in the United States each year. Transmission of toxoplasmosis from cats to humans rarely occurs, Kravetz said, because if the cats are infected it is only for two weeks of their lives, usually as kittens. Also, regular cleaning of a cat's litter should diminish contact with infective feces.

Kravetz, who owns two cats, said he decided to look into the matter when his wife became pregnant with their first child and friends began asking what he was doing to protect his wife from the cats.

"Everyone always asks how to behave with cats," he said. "The unofficial recommendation is to avoid cats when pregnant to lower the risk of toxoplasmosis."

Although cats can transmit many diseases, many pet owners are more likely to get infected when scratched by an outdoor cat or when they neglect routine veterinary care and basic personal hygiene.

"There are at least 57 million pet cats living in one third of all households in the United States," said Kravetz. "As common household pets, they serve as sources of joy and companionship for their owners. However, feline ownership also comes with its own inherent risks as cats can transmit an array of diseases to their owners, ranging from trivial to fatal ailments. By understanding the pathogenesis of cat-associated disease, owners and their pets can live together with little risk of disease transmission."

Overall, outdoor cats pose more of a risk of infection than indoor cats. Cats are more likely than dogs to infect humans when they bite them (more than 400,000 cat bites occur in the United States each year) because their teeth are long and sharp. Between 28 percent and 80 percent of cat bites are complicated by infection. Severe complications include meningitis, septic arthritis, osteomyelitis and endocarditis.

Another among several feline transmitted diseases - cat scratch disease (CSD) - is relatively common. There are about 22,000 cases each year leading to 2,000 hospitalizations. Complications from CSD can range from mild to extreme.

"Despite the statistics on cat scratches and infections, the risk of serious illness resulting from having a cat is still minimal," said Kravetz.

Simple preventive measures, such as washing hands before eating, using gloves when gardening and changing the litter daily can reduce the risk of acquiring diseases from a cat. Also, routine veterinary care, including appropriate vaccinations, deworming and care for sick animals, should reduce the risk of disease transmission.

Daniel Federman, M.D., associate professor internal medicine at Yale School of Medicine, was senior author of the article.