Most amoebic meningoencephalitis cases in immunocompromised people or those who entered unchlorinated waterbodies: experts

Even as public concerns mount about the increase in the reported amoebic meningoencephalitis cases and the “unknown” mode of disease transmission in many cases in Kerala, experts have clarified that there is no change in the risk factors associated with this infection or the general dos and don’ts already issued to the public.

Experts at Government Medical College Hospitals in Kozhikode and Thiruvananthapuram point out that the infection is being reported from many districts and that it is just “diagnostic bias” that microbiologists seem to be picking up more cases in the northern districts.

“Much ado is being made about a few cases of amoebic meningoencephalitis in which the epidemiological link is unclear. That does not mean that the entire public is universally facing a huge public health risk. For the majority of cases we had identified, there were clear risks which pre-disposed people to the infection—many patients had underlying diseases which made them immunocompromised; some had the history of entering waterbodies which were clearly not chlorinated; some had previous skull injury (which could have compromised their cribriform plate) and in some cases, they had the seriously risky habit of nasal irrigation, either as part of their religious practices or as part of ‘clearing the sinuses’ and the water would not have been clean enough,” points out V.K. Shameer, Assistant Professor of General Medicine, Kozhikode Government Medical College.

In RCC patients

Health officials confirm that some of the amoebic meningoencephalitis cases reported this year were in immunocompromised cancer patients undergoing treatment at the Regional Cancer Centre.

“There is a lot that we still do not know and we are unearthing a lot of information that might be new to the rest of the world. But the biggest risk factor for a healthy person to contract amoebic meningoencephalitis continues to be diving into pools/waterbodies or putting tap water into the nostrils,” he says.

Medical literature says that Acanthamoeba is a ubiquitous organism that is everywhere in the environment, even in sea water and in the Antarctic and that it has been detected in the tap water distribution systems and even in treated water from drinking water treatment plants in the U.S., indicating that some treatment processes may not fully eliminate this amoeba.

“This is a free-living amoeba but is also an opportunistic pathogen. It does not typically affect healthy individuals but immunocompromised individuals are at risk of getting granulomatous amoebic encephalitis if they have skin wounds through which Acanthamoeba can enter and spread to the brain through the bloodstream,” points out R. Aravind, Head of Infectious Diseases, Government Medical College Hospital, Thiruvananthapuram.

High-antibody prevalence

Literature also says that environmental exposure to both Naegleria and Acanthamoeba is so common that high antibody prevalence has been detected even in healthy people without active disease, making serology not reliable for detecting individual infections.

“Colonisation of Acanthamoeba in the nasal cavity, without it invading the brain (cribriform plate prevents that) or causing active infection in healthy individuals has been clearly documented,” Dr. Aravind says.

Active amoebic infection is detected when an expert microbiologist spots the moving amoeba in cerebrospinal fluid samples, under direct microscopy. This is enough for clinicians to start empirical treatment (without waiting for confirmatory PCR) because early diagnosis is what saves lives.

“Since 2024, clinicians in the State are primed to pick up amoebic meningoencephalitis if patient history reveals a link to any waterbodies. In the case of acanthamoeba, the incubation period could range from weeks to months and hence patient history might not yield any info, a challenge that clinicians are facing daily,” says Dr. Aravind.

70 cases this year

Kerala had detected 39 cases of amoebic meningoencephalitis the past year and close to 70 cases have been reported this year.

Public health experts point out that the epidemiological data gathered by the Health department in all these cases remain out of bounds for researchers and public health experts, preventing all open scientific discussions on a disease about which there is much public concern. “This data hoarding does not bode well for the State’s public health. We need all epidemiologists and experts on board so that we can explore all aspects of this disease,” a public health expert says.