Toxoplasmosis a small risk in owning a cat

Domesticated cats

Dear Doctors: My fiance and I adopted a cat, and his mother is insisting that we must give it back. She says you can get toxoplasmosis from having a cat in the house, and if I get pregnant, I'll give it to the baby. Is that really true? What is toxoplasmosis?

Dear Reader: Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii. It's a single-celled organism found throughout the world. In healthy people, the immune system prevents the parasite from causing illness, or even many symptoms. When symptoms do occur, they include swollen glands, fever, skin rash and muscle aches.

Infection in people with weakened immune systems is more serious. It can lead to eye disease that can affect vision, lung infection that can interfere with breathing and inflammation of the brain. Known as encephalitis, it can cause mental lapses and confusion, muscle weakness, poor coordination and seizures.

Infection with Toxoplasma gondii can occur in a number of ways. The most common is by eating undercooked meat or shellfish that have been contaminated with the parasite. Pork, lamb, venison, mussels, oysters and clams are the more frequent vectors. Not washing your hands thoroughly after handling contaminated raw meat, using contaminated utensils in food preparation, and drinking or otherwise ingesting contaminated water or other liquids can also spread the parasite.

When it comes to cats, your future mother-in-law is only partially correct. First and foremost, the cat itself must be infected with the parasite. When a cat does become infected, it sheds the eggs of the parasite for about 10 days after initial exposure. This is the period of highest risk. After that, there is no further significant shedding.

The presence of a cat in the house doesn’t automatically mean you’ll contract toxoplasmosis. To become infected yourself, you must somehow ingest an infected cat's feces while it is actively shedding parasite eggs. This is possible if you don't wash your hands after cleaning a litter box, or accidentally ingest anything that met with infected cat feces. Toxoplasmosis is not transmitted through the skin.

Pregnant women who become infected have a small risk of passing the parasite along to their fetus. This can cause a range of physical problems for the baby, and in some cases can lead to premature birth. It is rare but possible for this type of infection to cause a miscarriage. If the mother becomes infected early in her pregnancy, it is less likely to spread to the baby. If infection does happen at that time, problems can be more severe.

A blood test can reveal whether a cat has antibodies to the parasite. Very high levels of antibodies indicate a current infection. When toxoplasmosis is suspected in a cat, it is usually treated with a course of antibiotics. Diagnosis in humans also focuses on the detection of antibodies. Treatment in humans is with an antiparasitic medication. If you are concerned about possible infection, you can arrange for tests for yourself, your fiance and your cat.

(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

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