Balamuthia mandrillaris is a free-living amoeba that causes the rare but deadly neurological condition granulomatous amoebic encephalitis (GAE).

[1] B. mandrillaris is a soil-dwelling amoeba and was first discovered in 1986 in the brain of a mandrill that died in the San Diego Wild Animal Park.

The generic name Balamuthia was given by Govinda Visvesvara, after his mentor, parasitologist William Balamuth, for his contributions to the study of amoebae.

Cysts are also uninucleated, possessing three walls: an outer thin irregular ectocyst, an inner thick endocyst, and a middle amorphous fibrillar mesocyst.

Instead, the immune system attempts to contain them at the portal of entry (usually an open wound) by mounting a type IV hypersensitivity reaction.

[11] Upon introduction, the amoeba may form a skin lesion, or in some cases, may migrate to the brain, causing a condition known as granulomatous amoebic encephalitis (GAE),[12] which is usually fatal.

Patients experiencing this particular syndrome may report a skin lesion (often similar to those caused by MRSA), which does not respond well to antibiotics.

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.

[14] Axenic culture methods that are of importance to antiprotozoal drug development have also been reported within the last decade [17][18] Infection seems to be survivable if treated early.

[19] In 2018, an unsuccessful attempt at treatment of a Balamuthia infection after nasal lavage with untreated tap water was reported.