Aedes larval bionomics and implications for dengue control in the paradigmatic Jafna peninsula, northern Sri Lanka

Abstract

Abstract Background: The larval bionomics of Aedes across the Jafna peninsula in northern Sri Lanka was investigated to obtain information needed for developing more efective larval source reduction measures to control endemic arbo viral diseases. Methods: The habitats of preimaginal stages of Aedes mosquitoes were surveyed, and ovitrap collections were car ried out in densely populated areas of the Jafna peninsula. Aedes larval productivities were analysed against habitat characteristics, rainfall and dengue incidence. Adults emerging from collected larvae were tested for dengue virus (DENV). Results: Only Aedes aegypti, Ae. albopictus and Ae. vittatus were identifed in the feld habitat collections and ovitraps. Aedes aegypti was the predominant species in both the feld habitat and ovitrap collections, followed by Ae. albopictus and small numbers of Ae. vittatus. Tires and open drains were the preferred feld habitats for Ae. aegypti, although larval productivity was higher in discarded plastic containers. The three Aedes species difered in feld habitat preferences. Concomitant presence of the three Aedes species was observed in the feld habitats and ovitraps. Larval productivities were inversely correlated with the salinity of the feld habitat. Rainfall in the preceding month signifcantly correlated with larval productivity in the feld habitats. DENV serotype 2 was detected in Ae. aegypti collected from ovitraps in the city of Jafna. High Breteau, House and Container indices of 5.1, 5.1 and 7.9%, respectively, were observed in the feld habitat surveys and ovitrap indices of up to 92% were found in Jafna city. Conclusions: Aedes larval indices in populated areas of the peninsula showed a high potential for dengue epidem ics. Unacceptable littering practices, failure to implement existing dengue control guidelines, vertical transmission of DENV in vector mosquitoes and preimaginal development in brackish water and open surface drains, as well as in domestic wells that provide potable water, are serious constraints to the current Aedes larval source reduction meth ods used to control dengue in the Jafna peninsula. Similar shortcomings in arboviral disease control are likely present in other resource-constrained tropical coastal zones worldwide.