Primary amoebic meningoencephalitis
Overview
Primary amoebic meningoencephalitis (PAM, or PAME) is a disease of the central nervous system caused by infection from an amoeba such as Naegleria fowleri or Balamuthia mandrillaris.
Causes
Naegleria fowleri is an amoeba that is ubiquitous in soils and warm waters. Infection typically occurs during the summer months and patients typically have a history of exposure to a natural body of water. The organism specifically prefers temperatures above 32°C, as might be found in a tropical climate[citation needed] or in water heated by geothermal activity. The organism is extremely sensitive to chlorine (<0.5ppm). Exposure to the organism is extremely common due to its wide distribution in nature, but thus far lacks the ability to infect the body through any method other than direct contact with the olfactory nerve; the contaminated water must actually be fully insufflated into the sinus cavities for transmission to occur. Michael Beach, a recreational waterborne illness specialist for the Centers for Disease Control and Prevention, stated in remarks to the Associated Press that the wearing of nose-clips to prevent insufflation of contaminated water would be an effective protection against contracting PAM, noting that "You'd have to have water going way up in your nose to begin with".
Treatment
The current standard treatment is prompt intravenous administration of heroic doses of Amphotericin B, a systemic antifungal which is one of the few effective treatments for systemic infections of Protozoan parasitic diseases (such as leishmaniasis and toxoplasmosis). The success rate in treating PAM is usually quite poor, since by the time of definitive diagnosis most patients have already manifested signs of terminal cerebral necrosis. Even if definitive diagnosis is effected early enough to allow for a course of medication, Amphotericin B also causes significant and permanent nephrotoxicity in the heroic doses necessary to quickly halt the progress of the amoebae through the brain. Rifampicin has also been used with amphoterecin B in successful treatment. However, there is some evidence that it does not effectively inhibit Naegleria growth.