Entomological investigation of Japanese encephalitis outbreak in Malkangiri district of Odisha state, India

BACKGROUND A severe outbreak of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) with high case fatality was reported from Malkangiri district of Odisha state, India during September to November 2016 affecting 336 children with 103 deaths. OBJECTIVES The purpose of this study was to investigate the outbreak in the light of entomological determinants. METHODS Entomological investigation was carried out in 48 villages from four mostly affected Community Health Centres (CHCs) of Malkangiri district. Dusk collections of resting adults was done in villages from indoor and outdoor sites to record the density of mosquito species, including the known JE vectors, feeding behaviour, parity, dusk index and infection status with JE virus (JEV). FINDINGS The per man hour density and dusk index of JE vector species varied from 2.5 to 24.0 and 0.81 to 7.62, respectively in study villages. A total of 1136 mosquitoes belonging to six vector species were subjected to PCR and one pool of Culex vishnui was found to be positive for JEV. CONCLUSION The JE transmission in Malkangiri district was confirmed. Thorough screening of human blood samples of JE/AES suspected cases and JE vector mosquitoes for the presence of JEV during rainy season every year is recommended.

An outbreak of Japanese encephalitis after two decades in Odisha, India.

Sudden deaths in children due to acute encephalitis syndrome (AES) from a tribal dominated district of Malkangiri in Odisha, India, was reported during September-November, 2012. The investigation was carried out to search for the possible viral aetiology that caused this outbreak. Clinico-epidemiological survey and seromolecular investigation were carried out to confirm the viral aetiology. Two hundred seventy two suspected cases with 24 deaths were observed. The patients presented with low to moderate grade fever (87%), headache (43%), vomiting (27%), cold (18%), cough (17%), body ache (15%), joint pain (15%), rash (15%), abdomen pain (9%), lethargy (5%), altered sensorium (8%), convulsion (2%), diarrhoea (3%), and haematemesis (3%). Laboratory investigation showed Japanese encephalitis virus (JEV) IgM in 13.8 per cent (13/94) in blood samples and JEV RNA in one of two cerebrospinal fluid (CSF) samples. Paddy fields close to the houses, high pig to cattle ratio, high density (33 per man hour density) of Culex vishnui mosquitoes, low socio-economic status and low health awareness in the tribal population were observed. This report confirmed the outbreak of JEV infection in Odisha after two decades.