Toxoplasmosis

Depending on their environment and eating habits, up to 70% of people in the United States are infected with Toxoplasma gondii - making toxoplasmosis one of the most common infectious diseases. Occurring worldwide, it's less common in cold or hot, arid climates and at high elevations.

The disease usually causes localized infection. However, it may produce significant generalized infection, especially in immunodeficient patients, such as neonates, acquired immunodeficiency syndrome (AIDS) patients, patients who recently had an organ transplant, those with lymphoma, and those receiving immunosuppressant therapy.

Causes

Toxoplasmosis is caused by the protozoan T. gondii, which exists in trophozoite forms in the acute stages of infection and in cystic forms in the latent stages. The infection is transmitted by ingestion of tissue cysts in raw or undercooked meat (heating, drying, or freezing destroys these cysts) or by fecal-oral contamination from infected cats. Toxoplasmosis also occurs in vegetarians who aren't exposed to cats, so some other means of transmission may exist.

Congenital toxoplasmosis follows transplacental transmission from a mother who acquires primary toxoplasmosis shortly before or during pregnancy. Congenital infection is more severe when acquired early in the pregnancy.

Signs and symptoms

Most people who are infected do not show any symptoms. A healthy person's immune system usually prevents the parasite from causing disease.

Those who do get sick with a mild form of the illness usually have flu-like symptoms including fever, sore throat, sore muscles and tiredness. Glands in the neck, armpits or groin can become swollen, but they are usually not sore. In some cases, the infection can also cause blurred vision or loss of vision temporarily.

Diagnostic tests 

Tests to determine infection or presence of cysts :

• serologic titers for toxoplasmosis
• MRI of head
• cranial CT scan
• brain biopsy
• slit lamp examination reveals characteristic retinal lesions

Treatment

Most effective during the acute stage, treatment consists of drug therapy with sulfonamides and pyrimethamine for 4 to 6 weeks. The patient also may receive folinic acid to control pyrimethamine's adverse effects.

These drugs act synergistically against the trophozoites but don't eliminate already developed tissue cysts. For this reason, and because they don't alleviate the underlying immune system defect in AIDS, an AIDS patient needs toxoplasmosis treatment for life.

An AIDS patient who can't tolerate sulfonamides may receive clindamycin instead. This drug also is the primary treatment in ocular toxoplasmosis.

Prevention

• Be careful not to breathe in dust when cleaning the cat litter box.
• Avoid cleaning cat litter boxes if you are pregnant or trying to become pregnant.
• Wash all fruits and vegetables. If possible, use a vegetable soap to wash fruits and vegetables, especially if you're eating them raw. Otherwise, scrub them carefully.
• Avoid unpasteurized goat's milk. Raw goat's milk and goat's milk products may contain toxoplasma parasites.