Brain-eating amoeba Naegleria fowleri protozoans in trophozoite form, computer illustration. This organism is an opportunistic pathogen of humans, causing meningoencephalitis (inflammation of the brain and its surrounding membranes) when inhaled, often by children swimming in fresh water. Headaches, vomiting, sensory disturbance and a fatal coma may occur if the victim is not treated. Treatment is with antiprotozoal drugs. Infectious stage for humans are trophozoites and flagellate form.