Life cycle of Balamuthia mandrillaris parasitizing humans

Life cycle of Balamuthia mandrillaris parasitizing humans
Photographer: Centers for Disease Control/Division of Parasitic Diseases and MalariaRights holder: Centers for Disease Control/Division of Parasitic Diseases and Malaria

Balamuthia mandrillaris has only recently been isolated from the environment and has also been isolated from autopsy specimens of infected humans and animals.  The B. mandrillaris life cycle has only two stages, a dormant cyst stage (1) and an actively feeding and dividing trophozoite stage (2) (B. mandrillaris has no flagellated stage).  The trophozoites replicate by mitosis (the nuclear membrane does not remain intact) (3).  Although the trophozoites are the infective stage, both cysts and trophozoites gain entry into the body (4) through various means.  Entry can occur through the nasal passages to the lower respiratory tract (5) or through ulcerated or broken skin (6).  When B. mandrillaris enters the respiratory system or through the skin, it can invade the central nervous system by hematogenous dissemination causing granulomatous amebic encephalitis (GAE) (7) or disseminated disease (8), or skin lesions (9) in individuals who are immune competent as well as those with compromised immune systems.  Balamuthia mandrillaris cysts and trophozoites are found in tissue.

From Centers for Disease Control Parasites and Health website.