Toxoplasmosis is a disease caused by a one-celled parasite called Toxoplasma gondii. In humans, it may affect many different organs of the body. The most common finding is a mild, flu-like illness that lasts a few days. Most people recover uneventfully. Even if the patient sees a physician, the illness may still be attributed to the flu unless special blood tests are run.

If a pregnant woman contracts toxoplasmosis, it is possible for the organism to affect the unborn baby. It is this form of the disease that has the most dire consequences because the baby may be affected for life.

The disease toxoplasmosis occurs in about 140 babies per million births in the United States. A like number of children will be infected with the organism at the time of birth and develop disease later in life. Therefore, the combined incidence of congenital and acquired toxoplasmosis in the United States is 0.028%. Although this is indeed a real disease with dire consequences, it should be noted that its incidence is very small, especially considering that about 1/3 of the people in the United States have Toxoplasma antibodies, showing that they have been exposed to the disease.

Transmission

Although several species may develop the disease toxoplasmosis, including humans and dogs, the organism can only complete its life cycle in the domestic cat. This means that the cat may be infected with the organism and transmit it to other cats or to other species, including humans. However, in order for this to occur the following must happen:

1. The cat must be infected with the organism. In order for this to occur, the cat must eat something infected with it. It is most commonly available to the cat by ingestion of infected mice or infected raw or undercooked meats, especially pork or mutton.
   
2. The cat must be shedding the organism in its feces. This occurs for only about a 10 day period. It usually only occurs once in the cat's lifetime. (In a few situations, the cat may shed the organism again; however, if that occurs, the number of organisms that are shed are so small that transmission is very unlikely.)
   
3. The organism must "incubate" in the cat's feces for 1-5 days before it is infective to humans. This "incubation" must occur after the feces leaves the cat's body and have access to oxygen (i.e. in the litter box or in soil).
   
4. The organism must be swallowed by the person being infected. It is not spread to humans through the air.

The organism may also be transmitted to humans by eating raw or undercooked meats, especially pork or mutton. Since many hamburgers from fast-food restaurants are made of beef diluted with pork, most authorities feel that human infection occurs much more frequently by this method than by association with cats. The incidence of Toxoplasma antibodies in veterinarians, a group of people who would be at much higher risk if transmission from cats was a large factor,  is no different than that of the rest of the population.

Testing your cat

If you are pregnant, or are planning on becoming pregnant, you might want to have your cat tested for toxoplasmosis. The test checks for antibodies to Toxoplasma parasites. If your cat tests negative, this means he has never been exposed to the Toxoplasma organism and cannot transmit the disease to you.

A positive antibody test means that there has been exposure to the organism in the past or that there is an active infection of toxoplasmosis in progress. In order to know which situation exists, a second test must be run 2-4 weeks later.  If the second antibody titer is significantly higher than the first, an active infection is in progress. If it is the same or lower, the exposure happened some time in the past.

In any event, a single positive test for Toxoplasma antibodies does not mean that you need to get rid of your cat if you are pregnant. In order for you to be infected, the cat must have an active infection (rare) and be in the once-in-a-lifetime, 10 day period of fecal shedding in order to infect you.

There are further tests that can be done to determine whether your cat is truly infective. It is easier, however, to take some basic precautions when handling the cat, and even more important precautions when handling meat and vegetables, which are far and away the most common means of infection.

Precautions

Do not allow your cat to eat mice or poorly-cooked meat. Feeding a commercial cat food and not allowing your cat outdoors virtually eliminates any possibility of the cat becoming infected.

1. Clean all feces from your cat's litter box daily. Even if the cat's feces is infected with toxo oocysts, they must incubate for 1-5 days before becoming infectious. To be extra safe, do not let a pregnant woman clean the litter box. (Women of the world, rejoice! Let the husband and kids take over this job, and don't take it back once the baby is born!)
2. When working in soil (flower beds) that cats might use for a cat litter box, wear gloves to keep from getting oocysts on your hands. Wash hands throroughly after gardening and before eating.
3. Avoid eating raw or poorly-cooked meats. Be especially careful of fast-food hamburgers. Since this is probably more of a threat to your baby than your cat, special attention should be paid here. Practice impeccable meat handling and sanitation, including frequent hand washing with an antibacterial soap.
4. Keep children's sandboxes covered. Outdoor cats will frequently use the sandbox for defecation. Even if the feces are scooped out, the sandbox may remain contaminated with parasites