Ecology of breeding habitats of mosquito population and screening for virus of Japanese encephalitis and West Nile in the coastal area of Kerala, India

Background & objectives: Japanese encephalitis (JE) and West Nile virus (WNV) are two mosquito-borne diseases of medical and veterinary importance. Climate impacts in certain ecosystems are better understood; however, coastal brackish water ecosystems and their role in vector borne viral diseases have not been well studied. Hence, the aim of this study is to evaluate the distribution, spatial pattern as well as the screening of these mosquitoes for JE and WN virus in coastal area of Alappuzha district, Kerala, India. Methods: Immature mosquitoes were collected using dipper methods along the coastal wetlands areas. Adult mosquitoes were collected in four sampling sites with light trap filled with dry ice, operating overnight. The collected mosquitoes were identified by species, using the taxonomic keys. Mosquitoes were pooled for virus detection. Water samples were collected using standard methods. Results: The total quantity of rainfall and salinity varied from zero to 365.2 mm and from 1.5 to 28 ppt respectively. A total of 10,695 adult mosquitoes and 38,083 immatures revealed the presence of five genus and 23 species. The most predominant species was Culex tritaeniorhynchus. Immature collections Cx. sitiens was the only one species collected during the summer season and in the monsoon season the pond was replaced by fresh water mosquitoes such as Cx. tritaeniorhynchus and Cx. gelidus. A total of 186 pools were screened for JEV and WNV. However, none of the pools were found as positive for the virus. Interpretation & conclusion: The major vector of JEV Cx. tritaeniorhynchus and Cx. gelidus have adapted to immature development in coastal brackish water habitats. The public health authorities need to recognize thepotential impact on human health of brackish water-adapted mosquito vectors that weretraditionally considered to be freshwater species, and take appropriate surveillance and control measures.