Entomological factors in relation to the occurrence of Japanese encephalitis in Malkangiri district, Odisha State, India

Abstract

Japanese encephalitis is a mosquito-borne arbo-viral disease with seasonal occurrence. Since 2009, AES/JE cases have been reported from Malkangiri district of Odisha State, India at an interval of one year.In the current study, the entomological parameters of known JE vector mosquito species were assessed for one year in Malkangiri district. Mosquito collections were done fortnightly in the index villages from August 2015 to July 2016 to record the density, their breeding habitats, feeding behaviour, parity, dusk index (DI) and infection status with JE virus. A total of 2347 JE vector mosquitoes belonging to nine species were collected from dusk collections. Culex vishnui (38.3%) was the predominant species followed by Cx. whitmorei (17.3%), Cx. fuscocephalus (13.6%), Cx. tritaeniorhynchus (11.1%), Cx. bitaeniorhynchus (6.1%), Anopheles subpictus (4.8%), An. barbirostris (4.4%), Cx. quinquefasciatus (2.3%) and Cx. gelidus (2.2%). The average DI of Cx. vishnui was 0.37 which was highest among all JE vector species and varied between 0.02 (April) and 0.9 (November). The human blood indexof Cx. vishnui was 0.026. A total of 1835 JE vector mosquitoes were screened for the isolation of JE virus, but none was found positive. Presence of paddy fields and ponds, abundance of JE vectors and their human feeding habit indicate the risk of JE transmission in the study area. Detection of JE virus in Cx. vishnui during 2016 outbreak in Malkangiri district further confirms that there would be a threat of JE transmission during the favourable period.

High risk landscapes of Japanese encephalitis virus outbreaks in India converge on wetlands, rainfed agriculture, wild Ardeidae, and domestic pigs

“…fuscocephala , and Cx. pseudovishnui ) that also exhibit wide distribution across South and Northeast India(6,7). Given the wide range of suitable habitats for these mosquitoes, exposure to JEV vectors is extensive throughout the country.…”

Impact of cattle on joint dynamics and disease burden of Japanese encephalitis and leptospirosis

“…So, for our study we have a total of (111,518 888)=99,027,984 mosquitoes. Another study carried out in some villages of Malkangiri district showed that 69.1% of available mosquitoes are vectors for JEV [22]. Hence, the total number of JEV vectors we have is N m =99,027,984 × 69.1%=68,428,337.…”

“…We choose Malkangiri, the southern district of Odisha (Orissa) State in India. Malkangiri has a history of JE outbreaks since 2009 where the cases are documented as Acute Encephalitis Syndrome (AES) [22]. This AES can include infections other than JE.…”

“…We did not find any documented data for the size of cattle and pig populations (N c and N r respectively) in Malkangiri district. However, we found one documented data source which men- [22]. We use these numbers to estimate cattle and pigs per household, and then use our estimated number of households (111,518) to calculate numbers of total cattle and total pigs in the district in 2018, which gives N c = 80,583 29,667 × 111, 518 = 302, 911 and N r = 10,007 29,667 × 111, 518 = 37, 616.…”

“…We did not find any documented data for the size of cattle and pig populations ( N c and N r espectively) in Malkangiri district. However, we found one documented data source which mentioned that the numbers of humans, cattle and pigs in Korkunda block of Malkangiri district in 2014 were 143,867, 80,583 (75,772+4,811), and 10,007 respectively in 29,667 households [22]. We use these numbers to estimate cattle and pigs per household, and then use our estimated number of households (111,518) to calculate numbers of total cattle and total pigs in the district in 2018, which gives , 911 and .…”