Vector competence of Aedes vittatus (Bigot) mosquitoes from India for Japanese encephalitis, West Nile, Chandipura and Chittoor viruses.

BACKGROUND &

OBJECTIVES

Aedes vittatus (Bigot), an anthropophilic mosquito, plays an important role in the maintenance and transmission of yellow fever (YF), dengue (DEN), chikungunya (CHIKV) and Zika (ZIK) viruses in Africa. In India, though natural isolation of none of these viruses was reported from the mosquito, experimental studies have shown vector competence to DEN and CHIK viruses. Despite wide prevalence in India, their potential in transmitting viruses of public health importance viz., Japanese encephalitis (JEV), West Nile (WNV), Chandipura (CHPV), Chittoor (CHITV) etc., has never been investigated. The objective of the present study is to determine the vector potential of the mosquito to these viruses.

METHODS

Mosquitoes were infected by intra-thoracic inoculation as well as by oral feeding, and growth kinetics was determined. Virus dissemination to organs was investigated by determining virus in the harvested organs on specified days' post infection (PI). Vector competence was determined by detecting the virus in saliva.

RESULTS

Intra thoracic inoculation has shown vector competence of the mosquito to JEV, WNV, CHIV and CHPV. However, using the oral route of infection, replication was observed with only WNV, JEV and CHITV. High degree of WNV replication (6.7log TCID50/ml) with rapid dissemination to wings, legs and salivary glands was seen from 5th day PI onwards. WNV was detected in saliva with a titer of 0.7log10 TCID50/ml on 5th day PI. JEV and CHITV replicated in the mosquito yielding 3log and 4log10 TCID50/ml on 5th and 10th day PI respectively, but virus was not detected in saliva till 15th day PI.

INTERPRETATION &

CONCLUSION

From the results it is difficult to indict the mosquito as a vector of the viruses studied. However, presence of WNV in saliva of the mosquito shows its potential as a bridge vector and poses a concern especially when virulent WNV strains are circulating in the country.