Amoebic encephalitis is a rare but lethal central nervous system infection caused by free-living amoebae found in freshwater, lakes, and rivers. Types of Amoebic encephalitis There are two types of amoebic encephalitis, namely primary amoebic meningoencephalitis (PAM) and granulomatous amoebic encephalitis (GAE). Primary amoebic meningoencephalitis (PAM) is a disease caused usually by infection with Naegleria fowleri, a microscopic amoeba commonly called a "brain-eating amoeba." This infection destroys brain tissue, causing severe brain swelling and death in most cases. PAM is rare and usually occurs in otherwise healthy children, teens and young adults. The initial symptoms of PAM are indistinguishable from bacterial meningitis, while the symptoms of GAE can mimic a brain abscess, encephalitis, or meningitis. These infections are almost uniformly fatal with only few reported survivors globally. The first case of PAM was described by Fowler and Carter in Australia in 1965 followed by the first case described in the United States in 1966. PAM is more common in warmer regions and in the warmer months of spring and summer. There is no seasonal variation with GAE. Incidence in India Kerala reported its first PAM case in 2016, and till 2023, the state had reported eight confirmed cases. 2024 reported 36 cases and nine deaths. During 2025, 69 cases and 19 deaths have already been reported. Causal agent Naegleria fowleri is the causal agent of primary amoebic meningoencephalitis (PAM). Naegleria species are ubiquitous in soil and fresh or brackish water (lakes, rivers, ponds). In general, they are sensitive to environmental conditions such as aridity and pH extremes and cannot survive in seawater. In humans, they are found in the throat and nasal cavity. N fowleri is heat-tolerant and can survive temperatures up to 45.8°C, pre-adapting the species to mammalian body temperature. As it grows best at elevated temperatures, N fowleri has been isolated from warm-water bodies, including man-made lakes and ponds, hot springs, and thermally polluted streams and rivers. It feeds on bacteria in the water bodies for survival. N fowleri is not found in saltwater sources such as seawater. Most N fowleri infections occur in the summer months Vulnerable population PAM commonly affects children and young adults who have previously been healthy (immunocompetent). This disease occurs more often during the warmer months of the year and in warmer climates. Granulomatous amebic encephalitis (GAE) affects individuals of all ages, although those at the extremes of age may be more susceptible. Persons with debility or immunocompromise may be more susceptible to GAE. There is no seasonal variation because the causative pathogens are ubiquitous. Symptoms Headache, fever, nausea, and vomiting are the most common presenting signs and symptoms. Studies show a median incubation period of 5 days and a median time from onset of symptoms to death of five days. Most patients present to medical care with signs or symptoms indicative of central nervous system involvement. The diagnosis of PAM carries a high mortality rate of greater than 97%. Preventive steps Measures to prevent primary amoebic meningoencephalitis include the following: Avoidance of diving and jumping into stagnant freshwater. Consider using nose plugs for unavoidable exposures or pinching your nose shut when diving or swimming in freshwater. Keep your head above water when swimming in freshwater, hot springs, and other untreated thermal bodies of water. When participating in water-related activities, avoid digging, or stirring up the sediment. Use boiled, filtered, or sterile water for nasal or sinus irrigation, not tap water. Wading pools should be emptied each day Swimming pools/water theme parks and spas should be kept clean, chlorinated and maintained correctly Keep sprinklers and hoses away from noses. Flush still water from hoses before letting children play with them If you are using unchlorinated water: Don’t let water go up your nose when showering or washing your face Watch children playing with hoses or sprinklers Teach children not to squirt water up their nose Source : Technical guidelines on preention, diagnosis and treatment of Amoebic encephalitis in Kerala