Genotype and biotype of invasive Anopheles stephensi in Mannar Island of Sri Lanka

Abstract

BackgroundAnopheles 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.MethodsMosquito larvae were collected in Pesalai village in Mannar and maintained in the insectary until adulthood. Adult An. stephensi were identified morphologically using published keys. Identified adult An. stephensi were molecularly characterized using two mitochondrial (cox1 and cytb) and one nuclear (ITS2) markers. Their 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.ResultsAll DNA sequences for the Mannar samples matched reported sequences for An. stephensi from the Middle East and India. However, a single nucleotide variation in the cox1 sequence suggested an amino acid change from valine to methionine in the cox1 protein in Sri Lankan An. stephensi. Morphological data was consistent with the presence of the Indian urban vector An. stephensi type-form in Sri Lanka.ConclusionsThe present study provides a more detailed molecular characterization of An. stephensi and suggests the presence of the type-form of the vector for the first time in Sri Lanka. The single mutation in the cox1 gene may be indicative of a founder effect causing the initial diversification of An. stephensi in Sri Lanka from the Indian form. The distribution of the potent urban vector An. stephensi type-form needs to be established by studies throughout the island as its spread adds to the challenge of maintaining the country’s malaria-free status.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2601-y) contains supplementary material, which is available to authorized users.

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“…Aedes aegypti is the main vector of Dengue and Dengue hemorrhagic fevers 12,13 . Anopheles stephensi larvae is a major malaria vector 14 . Hence researchers continuously study to control these larvae with herbal extracts and found Tridax procumbens L. 15 and Leucas aspera L. 16 with positive results.…”

Anopheles stephensias an emerging malaria vector in the Horn of Africa with high susceptibility to EthiopianPlasmodium vivaxandPlasmodium falciparumisolates

“…stephensi in the Horn of Africa poses considerable health risks of increased receptivity and local transmission of malaria in the increasing urban African settings requiring realignment of malaria control programs. Its frequent presence in human-made aquatic habitats [37] indicates that a simple bifurcation between urban and rural settings may be misleading and is context dependent. Additionally, urban populations are also at increased risk of Aedes -borne diseases, which are increasing in incidence in Africa [38–41].…”

Morphological and Molecular Characterization of ‘var. mysorensis’ form of Anopheles Stephensi

“…Kerala state and Lakshadweep islands [33]. Similarly, this species invaded Sri Lanka (from India via water carrying eggs in boats) through the narrow Palk Strait (southward) [33,34].…”