Last Updated: 27/04/2026
Genotype and biotype of invasive Anopheles stephensi in Mannar Island of Sri Lanka
Objectives
Anopheles stephensi, the major vector of urban malaria in India, was recently detected for the first time in Sri Lanka in Mannar Island on the northwestern coast. Since there are different biotypes of An. stephensi with different vector capacities in India, a study was undertaken to further characterise the genotype and biotype of An. stephensi in Mannar Island.
Malaria was eliminated from Sri Lanka in 2013 but has probably been endemic in the country since the thirteenth century. However, 36–95 cases of imported malaria per year have been detected in returning residents and visitors to the country after 2013. Due to high densities of many anopheline vectors being present on the island, continuing vigilance to prevent the re-initiation of indigenous malaria transmission from externally acquired infections is therefore necessary. Anopheles stephensi, never previously detected in Sri Lanka, was recently identified on the island of Mannar off the northwestern coast of Sri Lanka.
Mosquito larvae were collected in Pesalai village in Mannar and maintained in the insectary until adulthood. Adult An. stephensi were identified morphologically using published keys. They were then molecularly characterized using two mitochondrial [cytochrome oxidase subunit 1 (cox1) and cytochrome b (cyt b)] and one nuclear [internally transcribed spacer 2 (ITS2)] marker. Their polymerase chain reaction (PCR) – amplified target fragments were sequenced and checked against available sequences in GenBank for phylogenetic analysis. The average spiracular and thoracic lengths and the spiracular index were determined to identify biotypes based on corresponding indices for Indian An. stephensi.
Jan 2015
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