Public concern has risen with multiple cases of amoebic meningoencephalitis and resultant fatality being reported in recent times. Dr O Sasikumari, a specialist in clinical microbiology and associate professor at Government Medical College in Thiruvananthapuram, shares her insights about the infection, the misconceptions in circulation, and the precautions people need to take.
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There is still a sense of mystery around primary amoebic meningoencephalitis (PAM). What do we really know about it so far?
Brain-eating amoeba infection is a very acute disease caused by Naegleria fowleri. It can suddenly trigger headache, vomiting, and fever, and often leads to death within 10 days, sometimes before the cause is even identified.
Another type, Acanthamoeba, causes granulomatous amoebic encephalitis. Unlike Naegleria, it does not kill instantly, but can be fatal. Acanthamoeba is of particular concern today as it is scientifically proven to spread through the nasal route when contaminated water enters the body, reaching the brain via nerves.
Acanthamoeba exists in two forms: the trophozoite (active, motile form) and the cyst (dormant, resistant form). The trophozoite form is typically found in waterbodies. But cysts are widespread in nature, in water, soil, and air. They can enter the body through inhalation, skin cuts, or direct contact, eventually reaching the lungs, bloodstream, and brain. Many patients report no history of bathing in contaminated water, which shows that soil and air can also be sources. These cases highlight the need for more research, as multiple morphologies and species are involved, and our understanding is still limited.
What are the factors behind the recent spike in cases?
We cannot pinpoint a single reason without detailed studies, but several factors may be contributing. Global warming and climate change could play a role. Kerala has abundant rainfall and numerous waterbodies. Stagnant water is an environment favorable for amoebae. The organism survives well in warm climates. Our conditions support the growth of many microbes, including highly infectious ones.
Most documented infections in Kerala have a clear link to water exposure, with very few arising from unknown sources.
Is infection more common in individuals with weaker immune systems?
The brain’s immune response is poor compared to other parts of the body. In the past, granulomatous amoebic encephalitis was thought to affect mainly immunocompromised individuals such as those with HIV, cancer, diabetes, or at the extremes of age. However, our recent cases show that even people with normal immunity can be affected. Naegleria too can infect healthy individuals.
There are several misconceptions. Is it primarily a ‘rural issue’? And how effective is chlorination? We have seen cases across both rural and urban populations and in all age groups, without any clear distinction.
Chlorination is effective, but it has its limits. Household water, tap water, and even swimming pools can be chlorinated to kill amoebae. However, it is not possible to chlorinate large natural waterbodies like rivers and lakes, which remain potential sources of infection.
What are the treatments currently available?
There is no 100% cure for amoebic encephalitis like we have with antibiotics for bacterial infections. Unfortunately, most cases remain fatal. The Directorate of Health Services in Kerala has issued treatment guidelines that recommend using a combination of five drugs — Amphotericin B, Miltefosine, Fluconazole, Rifampicin, and Azithromycin. This regime has shown some benefit, but outcomes are inconsistent because the amoeba damages the brain rapidly.
On the preventive side, awareness is important. People should avoid bathing or swimming in unchlorinated waterbodies. That is all we can say at this point.