Susceptibility to common insecticides and detoxifying enzyme activities in Anopheles sundaicus (sensu lato) after cessation of indoor residual spraying of insecticides in the Jaffna Peninsula and its surroundings in northern Sri Lanka

Kokila Sivabalakrishnan,Ranjan Ramasamy,Amirtharasa Thileepan,Thilini C Weerarathne,S H P Parakrama Karunaratne,Sinnathamby N Surendran

doi:10.1186/s13071-018-3254-1

Kokila Sivabalakrishnan, Ranjan Ramasamy + Show 4 more

Open Access

https://doi.org/10.1186/s13071-018-3254-1

Copy DOI

Abstract

BackgroundSri Lanka has been malaria-free since 2013 but re-introduction of malaria transmission by infected overseas travelers is possible due to a prevalence of potent malaria vectors. Knowledge of the insecticide resistance status among Anopheles vectors is important if vector control has to be reintroduced in the island. The present study investigated the insecticide susceptibility levels and resistance mechanisms of Anopheles sundaicus (sensu lato) (previously classified as Anopheles subpictus species B) an important malaria vector in the Jaffna Peninsula and it surroundings in northern Sri Lanka after indoor residual spraying of insecticides was terminated in 2013.ResultsSpecies-specific PCR assays identified An. sundaicus (s.l.) in four locations in the Jaffna and adjacent Kilinochchi districts. Bioassays confirmed that An. sundaicus (s.l.) collected in Kilinochchi were completely susceptible to 0.05% deltamethrin and 5% malathion and resistant to 4% dichlorodiphenyltrichloroethane (DDT), whereas those from Jaffna were relatively susceptible to all three insecticides. Kilinochchi populations of An. sundaicus (s.l.) showed significantly higher glutathione S-transferase activity than population from Jaffna. However, Jaffna An. sundaicus (s.l.) had significantly higher Propoxur-resistant acetylcholinesterase activity. Activities of non-specific esterases and monooxygenases were not significantly elevated in An. sundaicus (s.l.) collected in both districts.ConclusionsThe susceptibility to malathion and deltamethrin in An. sundaicus (s.l.) suggests that they can be still used for controlling this potential malaria vector in the Jaffna Peninsula and adjacent areas. Continuing country-wide studies on other malaria vectors and their insecticide susceptibilities are important in this regard.

Highlights

Sri Lanka has been malaria-free since 2013 but re-introduction of malaria transmission by infected overseas travelers is possible due to a prevalence of potent malaria vectors
Malaria had been endemic in Sri Lanka for centuries until indigenous transmission was eliminated from the island in 2013 [1]
The collected An. subpictus (s.l.) from both districts collectively comprised 53, 25, 19 and 3% of mosquitoes collected by Larval collections (LC), cattle baited net (CBN), cattle baited hut (CBH) and IC, respectively

Summary

Introduction

Sri Lanka has been malaria-free since 2013 but re-introduction of malaria transmission by infected overseas travelers is possible due to a prevalence of potent malaria vectors. Many cases of malaria-infected travelers arriving from endemic countries are reported every year and the potential for resuming indigenous transmission remains high due to the prevalence of many anopheline vectors in the island [1]. This challenge is exacerbated by the recent spread from India of the efficient urban malaria vector Anopheles stephensi to Sri Lanka [2, 3]. In Sri Lanka too An. sundaicus (s.l.) is mainly found in coastal zones [9, 10], which include the 1130 km Jaffna Peninsula and areas in the Jaffna and Kilinochchi districts that surround the Jaffna Lagoon [14]

Methods

Results

Discussion

Conclusion