Cause

Toxoplasmosis is an infection caused by a tiny parasite that infects birds and mammals, including humans. Cats are the only live carriers of toxoplasmosis. When a cat is infected, its feces contain toxoplasma eggs for about 2 weeks. These eggs can survive in moist soil for up to 18 months. Eggs in soil or sand can also contaminate food and water.

Cats that never go outside and do not catch mice indoors cannot be infected with toxoplasmosis.

Infection by mouth

You can get toxoplasmosis from cat feces or in contaminated food or water. People most often get toxoplasmosis by:

• Eating the eggs. You can become infected by mouth after touching anything that has come into contact with infected cat feces, such as when cleaning a cat's litter box or gardening where a cat has left feces. Eating contaminated food, such as unwashed vegetables, or eating with contaminated hands are examples of how you can get infected with toxoplasma eggs.
• Eating the meat of an infected animal. You can get toxoplasmosis from meat that is not fully cooked or has not been frozen. For more information on meat preparation, see the Prevention section of this topic.

Fetal infection

If you are first infected while you are pregnant or up to 8 weeks before becoming pregnant, you can pass the parasite on to your unborn baby (fetus). If you have already developed immunity to toxoplasmosis before pregnancy, you cannot get reinfected or pass the infection on to your fetus.