Acanthamoeba - Acanthamoeba Granulomatous Encephalitis

Acanthamoeba Granulomatous Encephalitis

This is an opportunistic protozoan pathogen that rarely causes disease in humans. Approximately 400 cases have been reported worldwide, with a survival rate of only two to three percent. Infection usually occurs in patients with an immunodeficiency, diabetes, malignancies, malnutrition, systemic lupus erythematosus, or alcoholism. The parasite's portal of entry is via lesions in the skin or the upper respiratory tract or via inhalation of airborne cysts. The parasite then spreads hematogenously into the central nervous system. Acanthamoeba crosses the blood–brain barrier by means that are not yet understood. Subsequent invasion of the connective tissue and induction of pro-inflammatory responses leads to neuronal damage that can be fatal within days. A post mortem biopsy reveals severe oedema and hemorrhagic necrosis. A patient who has contracted this illness usually displays subacute symptoms, including altered mental status, headaches, fever, neck stiffness, seizures, focal neurological signs (such as cranial nerve palsies and coma), all leading to death within one week to several months. Due to the rarity of this parasite and a lack of knowledge, there are currently no good diagnoses or treatments for Acanthamoeba infection.

Infection usually mimics that of bacterial leptomeningitis, tuberculous meningitis, or viral encephalitis. The misdiagnosis often leads to erroneous, ineffective treatment. In the case that Acanthamoeba is diagnosed correctly, the current treatments, such as amphotericin-B, rifampicin, trimethroprim-sulfamethoxazole, ketokonazole, fluconazole, sulfadiazine, or albendazole, are only tentatively successful. Correct and timely diagnosis, as well as improved treatment methods and an understanding of the parasite are important factors in improving the outcome of infection by Acanthamoeba.