Balamuthia mandrillaris

Balamuthia mandrillaris is a free-living amoeba that is known to cause the deadly neurological condition known as granulomatous amoebic encephalitis (GAE). B. mandrillaris is found in the soil and water and was first discovered in 1986 in the brain of a mandrill that died in the San Diego Wild Animal Park. B. mandrillaris can infect the body through skin wounds or by inhaling the dust containing Balamuthia. Balamuthia has been isolated in nature. It is believed to be distributed throughout the temperate regions of the world. This is supported somewhat by the presence of antibodies to Balamuthia present in healthy individuals. The genus name Balamuthia was given by Govinda Visvesvara (b. September 28, 1931), in honor of his late mentor, the renowned parasitologist William Balamuth (1914–1981) for his contributions to the studies of parasitic and free-living amoebae. It was in 1993 when Visvesvara isolated and studied the pathogen for the first time. B. mandrillaris is a free-living, heterotrophic amoeba, consisting of a standard complement of organelles surrounded by a three-layered cell wall (thought to be made of cellulose), and with an abnormally large cell nucleus. On average, a Balamuthia trophozoite is about 30 to 120 μm in diameter. The cysts fall around this range, as well. Balamuthia's lifecycle, like the Acanthamoeba, consists of a cystic stage and a non-flagellated trophozoite stage, both of which are infectious, and both of which can be identified as inclusions in the brain tissue on microscopic examination of brain biopsies performed on infected individuals. The trophozoite is pleomorphic and uninucleated, but binucleated forms are occasionally seen. Cysts are also uninucleated, possessing three walls: an outer thin irregular ectocyst, an inner thick endocyst, and a middle amorphous fibrillar mesocyst. B. mandrillaris is larger than human leukocytes, thus making phagocytosis impossible. Instead, the immune system attempts to contain them at the portal of entry by mounting a type IV hypersensitivity reaction. They may enter the body through the lower respiratory tract or through open wounds. Upon introduction, the amoeba may form a skin lesion, or may migrate to the brain, causing a condition known as granulomatous amoebic encephalitis, (GAE), which is usually fatal. This granulomatous feature is mostly seen in immunocompetent patients; immunocompromised individuals exhibit a 'perivascular cuffing'. Balamuthia-induced GAE can cause focal paralysis, seizures, and brainstem symptoms such as facial paralysis, difficulty swallowing, and double vision. Balamuthia may also cause a variety of non-neurological symptoms, including skin lesions, which can progress to GAE. Patients experiencing this particular syndrome may report a skin lesion (often similar to those caused by methicillin-resistant Staphylococcus aureus), which does not respond well to topical antibiotics. The lesion is usually localised and very slow to heal, or fails to heal altogether. In some presentations, the infection may be mistaken for certain forms of skin cancer or leishmaniasis. Balamuthia lesions on the face often cause swelling. Balamuthia is most easily identifiable in a brain biopsy performed on an individual suffering from GAE. The amoeba cannot be cultured on an agar plate coated with E. coli because unlike Naegleria or Acanthamoeba - Balamuthia mandrillaris does not feed on bacteria (at least in laboratory conditions). Instead, Balamuthia must be cultured on primate liver or human brain microvascular endothelial cells (the cells that constitute the blood–brain barrier). Vero cells have been suggested as a possible cheaper and faster alternative to culture the organism. Balamuthia infection has had successful treatments. Two individuals, a 5-year-old girl and a 64-year-old man, developed GAE. After diagnosis, they were treated with flucytosine, pentamidine, fluconazole, sulfadiazine, a macrolide antibiotic and trifluoperazine. Both patients recovered. In 2018, an unsuccessful attempt of treatment of a Balamuthia infection after nasal lavage with untreated tap water was reported.