Recently after flood in Assam, Japanese Encephalitis has created havoc. In India, Japanese encephalitis outbreak is seen in sporadic epidemics in few parts of the country. The south east Asian countries like Japan, China, Indonesia, Thailand , India have high prevalence rate.
In India high prevalence states are Uttar pradesh, West bengal, Bihar, some north east states. In 2012, the acute encephalitis syndrome outbreak in Malkangiri, Odisha in 2012 killed many children. It was mostly due to vector, Culex visnoi.
Japanese encephalitis is caused by Flavivirus. It is transmitted by mosquitoes mainly of Culex species. The genus Culex Tritaenorhynchus is the vector in most cases. Pigs are the amplifier hosts. Human case occur by bite of mosquitoes mostly in night time. The surge in cases occur mainly in rainy season when breeding of mosquitoes are high. Cases can affect all age groups. Especially children below 15 years are affected.
Clinical Features– fever, headache, malaise, neck rigidity, altered sensorium, alteration of higher functions, motor deficit. Change of neurological signs (Chane from hyperreflexia to hyporeflexia and plantar signs) are the hallmark of Japanese encephalitis. In case of children some atypical findings like vomiting, pain abdomen, diarrhoea may be seen in acute encephalitic syndrome.
A suspected case is a case having clinical features suggestive of encephalitis with history of travel to endemic countries.
A confirmed case is a suspected case with above noted features with laboratory diagnosis.
Laboratory diagnosis– Mostly ELISA based on CSF samples are used for diagnosis. IgM specific for Japanese encephalitis virus by IgM capture ELISA is used for diagnosis. CSF sample is more specific than serum. CSF sampling done to avoid false positivity due to vaccination or previous infection.
Treatment– Treatment is mostly focussed on symptoms. Anti seizure measures should be taken after any episode of seizure.
Prevention and Control– The most effective way of prevention is vaccination. The different types of vaccines available are mouse brain derived vaccine, vero cell derived vaccine, live attenuated vaccine, cell culture vaccine.
The live attenuated SA 14-14-2 has been widely used in endemic countries. It was prequalified by WHO for use in 2013. In November 2013, GAVI announced to support JE vaccination campaign to eligible countries.
In India, a vero cell cultured vaccine is developed from Kolar strain with National Institute of Virology. It is a vaccine with high efficacy showing around 98% after a single shot.
JE vaccination is started in select endemic districts of India as a campaign. As per national immunization schedule, India two subcutaneous doses given in left upper arm, first at 9-12months and second at 16-24 months.
The travellers travelling endemic countries should take precautions to avoid mosquito bite. Personal protective measures like full clothing, repellents, vaporizers should be used.
Surveillance methods should be strengthened at district and peripheral level for JE control.
Source— who.int
Govt. Of India data
