Abstract
BackgroundWest Nile virus (WNV) is a zoonotic flavivirus maintained in mosquito-bird transmission cycle. Although humans are accidental hosts, fatal outcomes following WNV infection have been reported from India. Studies have identified WNV as an important etiological agent causing acute encephalitis syndrome in Assam, Northeast India. While circulation of WNV is evident, the role of vectors and avian hosts involved in the transmission remains unclear. In this study we identified local mosquito species for evidence of WNV infection along with seroconversion among sentinel chickens.MethodsMosquitoes were collected and pooled species wise from June 2014 through December 2015. Virus was screened using reverse transcriptase PCR followed by sequencing and phylogenetic analysis. Sentinel chicken blood was screened for WNV antibody to assess their role in WNV transmission.ResultsA total of 52,882 mosquitoes belonging to 16 species were collected. WNV was detected in 18 pools of Culex vishnui, Culex tritaeniorhynchus, Culex quinquefasciatus, Culex whitmorei, Culex pseudovishnui and Mansonia uniformis. Phylogenetic analysis revealed that all mosquito derived sequences belonged to Lineage 5 and were 99–100% similar to the Assam strain of WNV isolated from human CSF sample in 2007. All sentinel chickens had seroconverted by the month of July that happens to be the peak WNV transmission month among humans as well.ConclusionTo the best of our knowledge, this is the first report of WNV identification from field-collected Cx. pseudovishnui and Mansonia uniformis in India. Our study demonstrates potential vectors which may play a crucial role in WNV transmission and should be considered in the vector control strategies. Additionally, our study highlights the role of sentinel chickens for WNV surveillance.
Highlights
West Nile virus (WNV) is a zoonotic flavivirus maintained in mosquito-bird transmission cycle
Eighteen of the 1392 mosquito pools tested Reverse transcriptase polymerase chain reaction (RT-PCR) positive for WNV non-structural 1 (NS1) gene
Majority of the positive pools consisted of Ma. uniformis and Cx. vishnui followed by Cx. tritaeniorhynchus, Cx. quinquefasciatus, Cx. pseudovishnui and Cx. whitmorei (Table 2)
Summary
West Nile virus (WNV) is a zoonotic flavivirus maintained in mosquito-bird transmission cycle. Studies have identified WNV as an important etiological agent causing acute encephalitis syndrome in Assam, Northeast India. WNV is maintained naturally in an enzootic transmission cycle of mosquitoes (vectors) and birds (amplifying hosts) while humans, horses and other mammals serve. Recognition of WNV among acute encephalitis syndrome causing etiologies in Assam in 2006 was the first report of the flavivirus from eastern region of India [10]. WNV circulation in this region is evident, adequate knowledge of vectors and amplifying hosts involved in transmission of WNV are lacking. In this study we investigated local mosquito species as candidate WNV vectors along with the role of birds as amplifying hosts
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