Japanese encephalitis: An update

[ Drs D Padung & M Lego ]
Twenty cases of Japanese encephalitis (JE) have been reported from a few districts of Arunachal Pradesh, and the situation has created panic among the people of the state.
Several instances are seen of people queuing up in front of pharmacies to get shots of JE vaccine, under the assumption that it will protect them instantly. This article is aimed at propagating proper information on JE and clearing doubts, misinformation and confusion among the people.
JE is a zoonotic disease that is transmitted by vector mosquitoes, mainly belonging to the Culex vishnui family, and often leads to infection of the brain. The virus normally infects birds and domestic animals, especially pigs, which serve as its reservoirs. Humans may contract the disease when a mosquito that has bitten an infected animal bites a human being. Outbreak or increased incidences of JE usually coincide with the monsoon and post-monsoon period, when the density of mosquitoes increases.
Acute encephalitis syndrome is characterized by an acute onset of fever, of not more than 5-7 days’ duration, and clinical neurological manifestation that includes mental confusion, irritability, somnolence, disorientation, delirium, or coma, with or without new onset of convulsion (excluding convulsion due to fever). In other words, with the above conditions, the case is a suspected JE infection.
It predominantly affects the population below 15 years of age, with no seasonal and geographical variation in the causative organism. The most vulnerable age groups are between 1 and 5 years, followed by 5 and 10 years, and 10 and 15 years. Infants are the least infected.
The preventive measures are directed at reducing the vector (mosquito) density. The risk of transmission increases when human dwellings and animal sheds, particularly piggeries, are situated very close to each other. It is required that piggeries are kept away (4-5 kms) from human dwellings to reduce the risk of transmission.
Personal protection against mosquito bites include using insecticide-treated mosquito nets, wearing sufficiently thick or loosely fitting clothing with long sleeves, and trousers with stockings to protect the arms and legs, which are the preferred sites for mosquito bites.
Household insecticidal products, namely, mosquito coils, pyrethrum space spray, and aerosols, have been used extensively for personal protection against mosquitoes. Electric vaporizer mats and liquid vaporizers are more recent additions that are marketed practically in all urban areas. Natural repellents like citronella oil, lemongrass oil, and neem oil are a common means of personal protection against mosquitoes and other biting insects.
Considering the risk of transmission, the actions for source reduction should not be limited to the actions by the health department but requires a multi-department and -stakeholder approach. The PHED could ensure the provision of safe drinking water and proper sanitation. The women & child development department can make special efforts to improve the nutritional status of the children in the affected areas. The local community needs to see to it that preventive measures are taken up at all levels on priority.

Role of JE vaccine under the routine immunization programme:
# Two doses of JE vaccine (at nine months and at 16-24 months of age) are provided under the routine immunization programme.
# If a child comes after the completion of the first year of life and before having completed two years of age without receiving any dose of JE vaccine, JE vaccine should be given at the first available opportunity and the second dose of the vaccine with a gap of three months after the first dose.
# If a child comes after two years of age without receiving any dose of JE vaccination, the child should be given only one dose of JE vaccine, and there is no recommendation of a second dose.
# If the child has missed the second dose at 16 to 24 months then he/she can receive JE vaccine through routine immunization till the age of 15 years at the earliest available opportunity.
# One dose of JE takes around three months for antibody formation, and therefore vaccination does not provide immediate protection from the virus. However, two doses of JE vaccine are recommended for lifelong protection.
Any person above 15 years of age can avail JE vaccine from various private pharmacies for protection.
To conclude, this is a disease that can be prevented through personal protection and timely JE vaccination as per the national immunization schedule.
Currently, JE vaccine is available free of cost at all the government health facilities in JE endemic districts of Changlang, Namsai, Lohit, and Papum Pare. (Dr Padung is State Immunization Officer, and Dr Lego is Director of Health Services.)