Toxoplasmosis is a protozoal infection that can be acquired by ingesting undercooked or raw meats, through contact with soil, or by cleaning the litter box of cats that excrete Toxoplasma gondii . Symptoms may include focal neurologic signs, seizures, and/or altered mental status. CT or MRI scan shows multiple ring-enhancing brainstem lesions. Treatment is with a combination of sulfadiazine and pyrimethamine. If there is no radiologic improvement after 7 days, brain biopsy is recommended to rule out alternative diagnoses. A radiologic image of toxoplasmosis is provided in the Clinical Images in HIV tutorial: Neurocognitive Manifestations - Toxoplasmosis on CT Scan (Note: this link will open in a new window. Close the new window to return to this tutorial).

Primary toxoplasmosis prophylaxis is recommended in patients with a positive toxoplasma antibody test and CD4 count less than 100. TMP-SMX in the dose used for PCP prophylaxis is the drug of choice. Dapsone with weekly pyrimethamine and atovaquone are also effective.

Primary toxoplasmosis prophylaxis can be safely discontinued in HIV-infected patients if their CD4 count rises above 200 for three months on combination antiretroviral therapy. Secondary prophylaxis can be safely discontinued if they have completed their initial course of treatment and their CD4 count rises above 200 for at least six months.