B. mandrillaris is most commonly isolated from soil, but has also been isolated from both fresh and salt water. Infections have primarily been associated with pursuits that include agriculture and gardening, plus sport and playing activities where lose soil is abundant. Specific information on the source of infection with this amoeba is meager. Inhalation of cysts in soil and breaks in skin may be the source of infection. Once the amoeba gains entry into the body it is likely spread via the blood to the brain. Both immunocompetent and immuncompromised individuals have been infected.