infections
Toxoplasmosis
Introduction
Toxoplasmosis is infection caused by the protozoan parasiteToxoplasma gondii. Infection occurs when people unknowingly ingest toxoplasma cysts from cat feces or eat contaminated meat. Usually, the infection does not cause symptoms, but some people have swollen lymph nodes, fever, a vague ill feeling, and sometimes a sore throat or blurred vision and eye pain. In people with a weakened immune system due to AIDS or another condition, toxoplasmosis can reactivate, usually affecting the brain. A reactivated infection can cause weakness, confusion, seizures, or coma or spread throughout the body. Pregnant women can pass the infection to a fetus(called congenital infection), and infected babies can have birth defects, loss of vision, seizures, intellectual disability, and other abnormalities. People acquire the infection by transferring the parasite's eggs from an object contaminated with infected cat feces to the mouth or by eating contaminated food. Most infections cause few or no symptoms. Women who become infected during pregnancy may transmit the parasite to the fetus, sometimes causing a miscarriage, stillbirth, or serious problems in the baby. Typically, only people with a Overview of Immunodeficiency Disorders have severe symptoms, usually resulting from brain inflammation (encephalitis), which may cause weakness on one side of the body, confusion, or coma. Less often, other organs are affected in people with a weakened immune system. Doctors usually diagnose the infection by doing blood tests that detect antibodies against the parasite. Most healthy people with toxoplasmosis do not require treatment, but adults with eye involvement, severe or persistent symptoms, or weakened immune systems, and pregnant women, and newborns with congenital infection are treated. People with AIDS or other conditions that weaken the immune system are treated until the disease is under control and are then placed on preventative therapy until their immune deficiency is reversed by anti-retroviral therapy (for those with AIDS) or other measures. Cooking meat thoroughly or freezing it and washing the hands thoroughly after handling raw meat, soil, or cat litter help prevent spread of the infection. (See also Overview of Parasitic Infections .) is a protozoa (single-cell infectious organisms) present worldwide wherever there are cats. The parasite infects a large number of animals as well as people. Many people in the United States have been infected, although few ever develop symptoms. Severe infection usually develops only in fetuses and people with a disorder that weakens the immune system (such as Human Immunodeficiency Virus (HIV) Infection or Pregnant women may become infected with the toxoplasmosis parasite by exposure to infected food or cat litter, and this can pass to a fetus and cause miscarriage, stillbirth, or serious problems in the baby. Although the parasite can grow in the tissues of many animals, it produces eggs (oocysts) only in cells lining the intestine of cats. Eggs are shed in a cat’s stool and, after 1 to 5 days, become able to cause infection. Eggs in the soil are able to cause infection for months. Wild birds, rodents, deer, and many domestic animals (particularly pigs and sheep) may ingest the eggs in food or soil contaminated by cat stool. The eggs release forms of the parasite called tachyzoites. Tachyzoites spread in the animal's tissues and eventually form cysts. 1a.Toxoplasmaeggs are passed in cat stool. Many eggs are passed but usually for only 1 to 2 weeks. After 1 to 5 days in the environment, eggs become able to cause infection. 1b. Cats can become reinfected by consuming food or other materials contaminated with the eggs. 2. Other animals (such as wild birds, rodents, deer, pigs, and sheep) may consume the eggs in contaminated soil, water, plant material, or cat litter and become infected. 3. Shortly after the eggs are consumed, the eggs release forms of the parasite that can move (called tachyzoites). 4. Tachyzoites spread throughout the animal's body and form cysts in nerve and muscle tissue. 5. Cats become infected after eating animals that contain these cysts. 6a. People can become infected by eating undercooked meat containing these cysts. 6b. People can also become infected if they eat food, water, or other materials (such as soil) contaminated with cat stool or when they touch a pet cat's litter and then touch their mouth. 7. Rarely, people are infected when they have a blood transfusion or organ transplant that contains the parasite. 8. Rarely, the infection is spread from mother to fetus. 9. In people, parasites form cysts in tissues, usually in muscle and the heart, brain, and eyes. The cysts may remain for the rest of the person's life without causing symptoms. They may become active and cause symptoms if the person's immune system is weakened by a disorder or medication. 