Symptoms and Diagnosis

A severe headache that does not respond to pain relievers is often one of the first symptoms of toxoplasmic encephalitis. Toxoplasma infection can also cause weakness on one side of the body, fever, seizures, vision disturbances and difficulty with speaking and walking; later symptoms include confusion, decreased attentiveness and personality changes. Nausea, dizziness and vomiting also may result from brain involvement.

Toxoplasma infection is difficult to diagnose, particularly since not all patients show signs or symptoms of infection. Often, a positive response to therapy is used to confirm the diagnosis. Brain scans such as computerized tomography (CT) or magnetic resonance imaging (MRI), are sometimes used to identify brain abnormalities and see if the treatment is working.

Treatment

Acute. There are two drug regimens commonly used for the treatment of acute toxoplasmic encephalitis in people with AIDS. The standard therapy is a combination of pyrimethamine and sulfadiazine; a major drawback of this regimen is the frequency of side effects-Cmore than 40 percent in people with AIDS. An alternative regimen that recently has been found to be effective combines oral clindamycin and pyrimethamine. Folinic acid is administered with both therapies to help prevent some of the side effects.

Maintenance. After treatment is completed, patients must receive maintenance therapy for life to prevent a recurrence. Drugs used in treatment, such as pyrimethamine plus sulfadiazine, are used at a reduced dosage. Some research indicates that clindamycin in combination with pyrimethamine may be effective for maintenance therapy in those unable to tolerate sulfadiazine.

Prevention

Many physicians recommend treatment to prevent the onset of toxoplasmosis in people with a positive blood test for T. gondii and a CD4+ T-cell count under 100. Drugs that are being investigated for their effectiveness in preventing toxoplasmosis include trimethoprim/sulfamethoxazole, various combinations of pyrimethamine and dapsone.

People with HIV who do not show any evidence of having been exposed to T. gondii can take preventive measures to decrease their risk of infection:

• Wear gloves while gardening or working with soil or sand.
• Avoid eating raw or undercooked meat and wash hands after handling raw meat or vegetables.
• Wear gloves and a mask when cleaning cat litterboxes, or preferably, have someone else change the cat's litter. Litter- boxes should be cleaned frequently.

Research

Research studies are under way to evaluate the effectiveness of different drug regimens, both for treatment of acute infection and for prophylaxis of toxoplasmic encephalitis. Drugs under study include atovaquone with pyrimethamine or sufadiazine.

For information about clinical studies, call the AIDS Clinical Trials Information Service:

1-800-TRIALS-A
1-800-243-7012 (TDD/Deaf Access)

For federally approved treatment guidelines on HIV/AIDS, call the HIV/AIDS Treatment Information Service:

1-800-HIV-0440
1-800-243-7012 (TDD/Deaf Access)

Source:
Office of Communications
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892

Public Health Service
U.S. Department of Health and Human Services
November 1994