Parasitic infections of the nervous system and the eye in AIDS

Parasitic diseases have emerged as important opportunistic infections in persons with AIDS. The central nervous system and the eye have become key targets of parasitic infections in these patients. Among the important etiologies of CNS manifestations are those caused by reactivation of infection with Toxoplasma gondii. This parasite causes a necrotizing encephalitis in 15-20% of AIDS patients. Neuroimaging studies often reveal the lesions, and treatment with pydmethamine and sulfonamides has become routine, but other drug combinations have been explored. Ocular toxoplasmosis is another complication of infection with this parasite and may antedate or coexist with the CNS manifestations. AIDS patients in endemic areas of Latin America may experience reactivation of chronic Trypanosoma cruzi infection (Chagas' disease or American trypanosomiasis), causing CNS manifestations that are indistinguishable from those caused by T. gondii. There is no evidence that the course of infection with African trypanosomes (sleeping sickness) is altered in the setting of AIDS. However, relapse after anti- parasitic treatment may be more likely. Microsporidia have emerged as important pathogens in AIDS patients, causing diarrhea and occasionally encephalitis. Keratoconjunctivitis is an ocular manifestation of this infection. In recent years new staining techniques as well as the application of molecular biological techniques have led to increased awareness of this parasite. Albendazole and fumagillin have been used with success in some patients. The free-living amoebas such as those belonging to the genera Naeglaria, Acanthamoeba and Leptomyxa, cause disease in humans. Acanthamoeba causes granulomatous encephalitis in immunocompromised hosts including those with AIDS, and the CT scan may mimic toxoplasma encephalitis. The extrapulmonary manifestations of Pneumocystis carinii infection may include choroiditis.