Toxoplasmosis: Reducing the risk to humans and your cat
An extremely common source of concern, anxiety and confusion among cat caretakers, especially in families with expectant mothers, is a disease known as Toxoplasmosis. The following is an attempt to describe this disease and its transmission, and in so doing hopefully allay unnecessary fears and the needless euthanasia of household cats due to misinformation and paranoia.

Toxoplasma gondii is an organism whose only definitive hosts (i.e. the only species in which Toxoplasma can reproduce) are members of the cat family. Basically, the organism can produce oocysts in the cat, which are passed through the feces of infected cats for only a two-week period. If the environmental conditions are just right, these oocyts may survive and linger as a source of infection in soil or litter for about two years. If another animal or person ingests these oocysts while they are still infective, the transmission of Toxoplasmosis occurs.

The organism cannot reproduce within any other animal besides the cat. In other animals and in humans, the organisms migrate to various organs (heart, brain, muscle, lymph nodes) and remain there in an inactive state. The only way for transmission of the organism in this state to occur is through the ingestion of the infected animal. This is, in fact, the most common way for Toxoplasmosis to be transmitted. The frequency and risk of human infection are most likely associated with ingestion of infected meat, not exposure to cats. It must be emphasized that although the possibility of transmission from humans to cats exists, there has never been a documented case of prenatal Toxoplasmosis infection in a human caused by a cat.

Most people infected with Toxoplasmosis do not become ill or exhibit any symptoms. Veterinarians are often requested to run blood tests on cats from households where pregnant women have been found to have positive antibody titers to Toxoplasma. Many cats from households such as these have been euthanized if the blood test results show that the cat also has a positive titer to Toxoplasma. It is unjustifiable to euthanize cats on this basis for several reasons. In order for a mother infected with Toxoplasmosis to pass the disease to the fetus, she must have been exposed after conception. Otherwise, she is immune to the disease. In addition, most people contract this disease from eating raw or improperly cooked meat, mainly lamb or pork products.

There are several basic preventive measures which can eliminate the fear of Toxoplasma infection:
Always wash hands before eating and teach children to do the same.

Keep cats indoors. A roaming cat can kill and eat an infected animal, thereby ingesting the organism.

Never feed raw meat or unpasteurized dairy products to cats.

For extra precaution, pregnant women should have another family member change the litter box. If that is not possible, she should wear rubber gloves while handling soiled litter and wash her hands thoroughly with soap and water afterwards.

Changing the litter box daily will prevent disease transmission, as it takes 2 to 4 days before the oocysts shed in the cat's feces become infective.

Never eat raw or undercooked meat, especially lamb and pork products. Unpasteurized dairy products should also not be eaten.

Cover children's outdoor sandboxes to preclude contamination by stray or roaming cats.

References:
Brooks, Karen D., DVM, "Feline Toxoplasmosis and human health," Veterinary Technician, Vol. 13, No. 8, September 1992.

Client Information Bulletin: Toxoplasmosis; The Cornell Feline Health Center

Musselman, Kelly, "And Baby Makes Four," Cat Fancy, December 1995

O'Dea, Colleen, "The Facts About Toxoplasmosis and Pregnancy," Cats, March 1995.