Toxoplasmosis

Toxoplasmosis (toxo) is an infection caused by a single-celled parasite toxoplasma gondii. A parasite lives off of another living organism (the host). One out of every two people has this parasite. In healthy people, the immune system keeps the parasite from causing any disease. In people with weakened immune systems, the parasite can cause a brain infection (encephalitis), coma or death.

Symptoms

The first signs of toxo include fever, confusion, headache, disorientation, personality changes, tremor and seizures. After a person is infected, the parasites can spread to every organ of the body, including the heart, eyes and lungs. One of the most common diseases from toxoplasmosis is encephalitis, a brain infection.

Causes

The toxoplasma gondii parasites live in cat feces, raw vegetables and dirt. It is also common in raw meat, especially pork, lamb or deer meat. It does not seem to spread from person to person. Pregnant women who are exposed to toxo may pass it to their newborn child. People usually get toxoplasmosis by touching their mouths with their hands after changing cat litter or by eating raw or undercooked meat.

Prevention

The risk of getting toxo can be reduced by eating well-cooked meat or fish. Gloves and a facemask should be worn when cleaning a cat box. Afterward, the hands should be washed thoroughly. Taking antiretroviral drugs will build up the immune system and help prevent the parasites from getting out of control. People who have a CD4 cell count of less than 100 should take drugs to prevent toxo infection. People who have CD4 cell counts of less than 200 are usually given Bactrim or Septra to prevent pneumocystis pneumonia. These drugs also protect against toxo infection.

Diagnosis

Toxo is usually diagnosed by testing for antibodies to Toxoplasma gondii. If the test comes back positive for the antibody, it doesnÕt mean that the person has toxo encephalitis. If the test comes back negative, it means that the person has not been infected with toxo.

A computerized tomography (CT) scan or a magnetic resonance imaging scan of the brain may help diagnose toxoplasmosis. The MRI scan is more sensitive. It makes it easier to see toxo without confusing it with other types of infections.

Treatment

Two drugs -- pyrimethamine (Daraprim) and sulfadiazine Ð are used to treat toxoplasmosis. Both drugs cross the blood-brain barrier. The parasite needs Vitamin B to live. Pyrimethamine stops it from getting vitamin B; sulfadiazine stops it from using the vitamin. About eight out of 10 people given these drugs starts to get better in two to three weeks.

There are side effects to these drugs. Because they interfere with vitamin B, they can cause anemia. Someone taking these drugs is usually given leucovorin. This is a form of folic acid (a B vitamin), which helps prevent anemia. Pyrimethamine and sulfadiazine can cause a drop in white blood cells and kidney problems.

Sulfadiazine is a sulfa drug. Almost half the people who take are allergic to it. They get a skin rash and sometimes a fever. Clindamycin (Cleocin) can be used in place of sulfadiazine in the combination for people who cant take sulfa drugs.

Once toxoplasmosis has been treated, it usually comes back. People who get the infection should keep taking the drugs at a lower dose.