With five cases of Amoebic meningoencephalitis being reported in adolescents in the State in the past three months and with three young lives lost, the Health department has come out with technical guidelines on the prevention, diagnosis and treatment of the infection, possibly the first set of guidelines in the country on this rare but fatal infection.
In all but one case, the causative organism was the amoebic parasite, Naegleria fowleri. In one case, the organism was Vermamoeba vermiformis, another free-living amoeba found in human environment was implicated.
These guidelines/standard operating procedure (SOP) are to be followed by all hospitals when dealing with cases of acute meningitis, it has been directed. Primary amoebic meningoencephalitis (PAM) is a rare but lethal central nervous system infection of rapid fatality caused by free-living amoebae found in freshwater, lakes, and rivers (never in seawater). It is usually caused by an infection with Naegleria fowleri, a microscopic amoeba commonly called a “brain-eating amoeba.” The amoeba enters through the nasal channels and destroys brain tissue, causing severe brain swelling and death in most cases.
This disease occurs more often during the warmer months of the year and in warmer climates. Patients with PAM typically have a history of swimming, diving, bathing, or playing in warm, generally stagnant, freshwater during the previous one to 9 days.
The diagnosis of PAM carries a high mortality rate of greater than 97%.
The clinical presentation of PAM is often indistinguishable from bacterial meningitis with headache, fever, nausea, and vomiting being the most common presenting signs and symptoms.
Very few individuals survive the infection, because of its rapid onset and delayed diagnosis. Only 11 survivors of confirmed N fowleri PAM have been reported in the literature.
Early diagnosis of PAM and timely initiation of an antimicrobial cocktail might be lifesaving and hence clinicians should have a high index of suspicion for PAM if the tests for other bacteria and common viruses turn out to be negative
Experts point out that a history of exposure increases the likelihood of PAM, but it is not always obtained. In the current Kerala context, any person with an epidemiological link should be immediately suspected of having PAM.
As far as treatment is concerned , the optimal approach to treatment of PAM due to N. fowleri is uncertain. In theory, the best drug regimen should include an amebicidal drug (or a combination of drugs) with good in vitro activity that is capable of crossing the blood-brain barrier. There should be good supportive care also.
Recommended SOP
A history of nasal exposure to fresh water in the 14 days before symptom onset should be asked of any patient who presents with symptoms of acute meningitis.
For patients with meningitis who have a history of recent nasal exposure to fresh water, the cerebro-spinal fluid (CSF) specimen should undergo rapid testing for N. fowleri/FLA . Microbiologist should be immediately alerted about the clinical suspicion before sending CSF sample.
In patients with clinical and CSF pictures suggestive of bacterial meningitis who are not responding to antibiotics or are rapidly deteriorating, consider PAM even in the absence of exposure to fresh water, experts have suggested.
All cases diagnosed as PAM through CSF microscopy should be immediately initiated on the recommended multi-drug regimen and supportive therapy aimed at lowering intracranial pressure.
All cases of PAM should be treated by a multidisciplinary team comprising physicians/paediatricians, intensivists, ID specialists, neurologists and microbiologists.
Avoiding exposure
Experts suggest that avoiding diving and jumping into stagnant water; use of nose plugs for unavoidable exposures; keeping head above water when swimming in freshwater, hot springs, and other untreated thermal bodies of water; avoiding digging, or stirring up the sediment when participating in water-related activities.
Using only filtered, or sterile water for nasal or sinus irrigation; daily emptying of wading pools; chlorination and proper maintenance of swimming pools/water theme parks, spas and ensuring that water is not forcefully drawn into the nose during showering or washing face are some of the possible measures to prevent PAM.
