Information for Public Health & Medical Professionals

Balamuthia mandrillaris is a free-living ameba (a single-celled living organism) naturally found in the environment. Balamuthia can cause a rare and serious infection of the brain called granulomatous amebic encephalitis (GAE). Balamuthia can present with a local skin lesion, isolated neurologic disease, or disseminated disease affecting the skin, brain, and other organs.

The environmental niche of Balamuthia mandrillaris is not well defined. It has been isolated from soil and dust. It is possible that Balamuthia may also live in water. Exposure to Balamuthia might be common although disease caused by Balamuthia is rare. Infection is thought to occur by inhalation of airborne cysts or through direct skin inoculation; GAE is thought to occur when organisms then travel from the lower respiratory tract, sinuses, or skin to the meninges and brain by the hematogenous route, although invasion of the olfactory neuroepithelium via the nasal route has also been postulated.

Since it was first described in 1989, over 200 cases of Balamuthia disease have been reported worldwide. There have been 109 Balamuthia cases reported to CDC during 1974–2016 in the United States Although cases reported in Latin America, Europe, Asia, and Australia occurred mostly in immunocompetent patients, some of the U.S. cases were immunocompromised individuals For example, during 2009–2012, CDC identified three clusters of Balamuthia GAE transmitted by organ transplantation. Additionally, there seems to be a disproportionate involvement of patients of Hispanic ethnicity among the U.S. cases: 55% of the U.S. case patients were Hispanic.