First record of Anopheles stephensi in Sri Lanka: a potential challenge for prevention of malaria reintroduction

A G Gayan Dharmasiri,Kandasamy Aravindan,A Yashan Perera,Jeevanie Harishchandra,H T R Jayasooriya,Gaya R Ranawaka,Mihirini Hewavitharane,Hemantha Herath

doi:10.1186/s12936-017-1977-7

A G Gayan Dharmasiri, Kandasamy Aravindan + Show 6 more

Open Access

https://doi.org/10.1186/s12936-017-1977-7

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Abstract

BackgroundThe major malaria vector in Sri Lanka is reported to be Anopheles culicifacies with Anopheles subpictus, Anopheles annularis, and Anopheles varuna considered as potential vectors. The occurrence of Anopheles stephensi, which is the key vector of urban malaria in India and the Middle East, had never been reported from Sri Lanka.MethodsA series of entomological investigations were carried out by the Anti Malaria Campaign, Ministry of Health, Sri Lanka during December 2016 to April 2017 in two localities of the Mannar District in the Northern Province of the country. Adult mosquito collections were done through indoor and outdoor resting collections, animal and human biting collections and emergence traps. Potential mosquito breeding sites were investigated through larval surveys. The larvae and adults of An. stephensi were initially identified using morphological keys, and subsequently confirmed by sequencing the barcode region of the cytochrome c oxidase I (COI) gene.ResultsThis is the first report of the presence of An. stephensi in the island of Mannar in the Northern Province of Sri Lanka. Anopheles stephensi (36.65%) was the most abundant anopheline species in the larval habitats in Mannar. It was found breeding together with An. culicifacies (20.7%), An. subpictus (13.5%) and An. varuna (28.13%). Anopheles stephensi was found to be abundantly breeding in built wells used for domestic purposes. Adult females of An. stephensi were observed in emergence trap collections (93.9%), human landing catches all night (79.2%), pyrethrum spray sheet collections (38.6%), outdoor collections (8.3%), donkey-baited trap collections (14.3), and cattle-baited net trap collections (0.7%).ConclusionsSri Lanka was certified as malaria-free by the WHO in September 2016, however, this new finding may pose a serious challenge to the efforts of the Ministry of Health to prevent the re-introduction of malaria transmission in the country, considering the role that An. stephensi could play in urban and high vulnerability areas of Sri Lanka.

Highlights

The major malaria vector in Sri Lanka is reported to be Anopheles culicifacies with Anopheles subpictus, Anopheles annularis, and Anopheles varuna considered as potential vectors
Invasion from a neighbouring Indian state may be a possibility since An. stephensi has been incriminated as the main vector of urban malaria in India, and has shown a southwards spread on the mainland due to rapid urbanization and water storage practices
This paper describes the first confirmed report of An. stephensi in Sri Lanka

Summary

Introduction

The major malaria vector in Sri Lanka is reported to be Anopheles culicifacies with Anopheles subpictus, Anopheles annularis, and Anopheles varuna considered as potential vectors. In the past few decades, malaria was a major public health problem, being endemic in 22 districts of the intermediate and dry zones of the country [1]. In Sri Lanka, the major vector of malaria is reported to be Anopheles culicifacies, and Anopheles subpictus, Anopheles annularis and Anopheles varuna are considered as potential vectors [2, 3]. With the cessation of local malaria transmission in the country, disease surveillance along with entomological surveillance have been strengthened to prevent the re-introduction of malaria.

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