Health dept. expands checking in amoebic encephalitis cases

Earlier, cerebrospinal fluid samples were sent for analysis only in cases where exposure to a waterbody was found. Now, all cases of meningoencephalitis are checked to see if it is caused by any free living amoeba, say Health officials

Amoebic meningoencephalitis cases have surfaced in the State again, and four persons are currently undergoing treatment at Government Medical College Hospital, Thiruvananthapuram.

All four are from different parts of the district and amoebic meningoencephalitis has been confirmed in all with the testing of cerebrospinal fluid (CSF) samples. Doctors said that they were all being treated as per the State protocol for amoebic meningoencephalitis.

While one of the four is a youngster from Navayikulam in the district and has a clear history of entering one of the many waterbodies in the locality, it is not sure if the epidemiology is the same in the case of other persons.

“The public might be concerned that too many cases of amoebic meningoencephalitis are being reported all at once but this is because we are doing an active case search. Earlier, we were sending CSF samples for analysis only in cases where we could find an epidemiological link (exposure to a waterbody). However, at a technical workshop on amoebic meningoencephalitis it was decided that we will test all cases of meningoencephalitis to see if it is caused by any free living amoeba (FLA),” a Health official told The Hindu.

“Globally, 60-70% of the cases of meningoencephalitis remain undiagnosed. This is the context in which we have decided to go in for an active case search. CSF wet mount microscopy will be done in all cases of meningitis to check for the presence of any FLA. The only technical hassle is that amoeba can be detected only in fresh CSF samples and hence we have to coordinate ahead with the Microbiology department before collecting the CSF sample,” he added.

It would seem that the situation involving amoebic meningoencephalitis in Kerala is in a state of flux and a lot of information has to be unravelled, before a more scientific explanation can be offered on what is happening.

Other cases

While most of the literature on amoebic encephalitis is about the Primary Amoebic Meningoencephalitis (PAM), caused by Naegleria fowleri, there is very little information on the central nervous system infections due to free-living amoebas (FLA) like Acanthamoeba spp., Balamuthia mandrillaris, Sappinia diploidea or Vermamoeba vermiforis, which are often underdiagnosed and underreported.

PAM caused by N. fowleri can be distinguished clinically because the disease progresses fast and the symptoms develop within 1 to 14 days. N. fowleri is found only in freshwater and never in sea water or chlorinated water. The history of exposure to a waterbody is thus useful in diagnosing PAM.

Long incubation period

However, the disease caused by Acanthamoeba spp., known as granulomatous amoebic encephalitis (GAE) is chronic, slow progressing and the mortality rate is between 50-70%. The incubation period could be several weeks or months before clinical signs establish and if not diagnosed and treated early, mortality can go up.

Acanthamoeba spp. are among the most prevalent protozoa found in the environment and these have been isolated from soil, air, sewage, seawater, chlorinated swimming pools, domestic tap water, bottled water, dental treatment units, hospitals, air-conditioning units, and contact lens cases. The amoeba can spread to the eyes through contact lens use, cuts, or skin wounds or by being inhaled into the lungs. Most people will be exposed to Acanthamoeba, but very few will become sick from this exposure, according to CDC.

The Health department now thinks that except in those cases wherein N.fowleri could be identified through PCR tests, many other meningoencephalitis cases being reported in the State in recent months may be caused by other FLA like Acanthamoeba and that it is the active case search which is now throwing up more cases.

Aggressive treatment

“More scientific research is needed into this but the proportion of meningoencephalitis cases caused by FLA might be much more than we have reckoned. This becomes more compelling when we consider the fact that even globally, 60-70% of meningoencephalitis goes undiagnosed. Some of the cases reported in the State and literature had only mild symptoms but once FLA is identified to be the causative organism, aggressive treatment is required,” a senior doctor said.

Published - September 29, 2024 09:29 pm IST