Japanese Encephalitis vector abundance and infection frequency in Cuddalore District, Tamil Nadu, India: a five-year longitudinal study

An entomological monitoring of Japanese encephalitis vectors from the Cuddalore district, Tamil Nadu was undertaken at biweekly intervals for 1 hr after dusk for five years to find out the abundance and JE virus activity longitudinally in three villages. A total of 95,644 vectors belonging to 31 species constituted predominantly by Culex vishnui subgroup and Culex gelidus 98.5%. JE virus was identified from Cx. tritaeniorhynchus (18), Cx. vishnui (1) and Cx. gelidus (6) giving infection rate of 0.482, 0.608 and 0.221 respectively. Abundance of Cx. tritaeniorhynchus and Cx. gelidus differed significantly by area, season and year (P<0.05) whereas Cx. vishuni differed significantly by season and year (P<0.05). Transmission was not observed throughout all the seasons and the infection rate was recorded maximum during Hot-Wet season 0.46 (confidence interval: 0.17-1.02). Culex tritaeniorhynchus dominated the catch and the Culex gelidus steadily increased in its abundance during this period compared to the earlier studies conducted from these areas which acts as a secondary vector along with the major vector, Cx. tritaeniorhynchus.