Exploring the uncharted: Novel potential filariasis vectors unveiled in Sri Lanka

Brugian filariasis (BF) has reemerged in Sri Lanka recently. Studies suggest the emergence of a variant brugian parasite. Knowledge on transmission dynamics is important in restraining the spread of infection. This study investigated the potential vector mosquitoes of this variant brugian parasite around six indexed human BF cases in five BF endemic districts in Sri Lanka. A total of 1711 mosquitoes from 20 species were analyzed. Potential infective mosquitoes were detected by the presence of L3 larval stage of brugian parasites within the head and thorax regions upon dissections and confirmed by amplification of the Brugia species-specific HhaI region. Twelve (12) mosquito species that could potentially serve as vectors for BF transmission in selected endemic areas in the country were identified due to the presence of L3 larvae in the head and thorax regions. This is the first report of Ma. indiana, Ar. subalbatus, Ae. albopictus, Cq. crassipes, Cx. tritaeniorhynchus, Cx. bitaeniorhynchus, Cx. quinquefasciatus, Cx. gelidus, Cx. lopoceraomyia and Cx. vishnui with the potential of serving as vectors for BF transmission in Sri Lanka and Cx. bitaeniorhynchus, Cx. gelidus, Cx. lopoceraomyia and Cx. vishnui in the world through a field study. Of these, Ma. indiana, Cx. tritaeniorhynchus, Cx. quinquefasciatus and Ar. subalbatus together with Ma. uniformis, Ma. annulifera had the highest prevalence and infection rate at certain study sites. The recovery of parasite-positive Ma. indiana, Cx. quinquefasciatus and Ar. subalbatus mosquitoes from window traps demonstrate the probable anthropophilic nature of these species, and their high prevalence in the respective areas deems further investigation on their vector potentiality essential. Author SummaryLymphatic filariasis (LF) is a debilitating disease affecting over 120 million people worldwide. Of the two types of LF, Brugian Filariasis (BF) has a wide range of definitive hosts, making it possible for the rapid spread of the disease. BF was considered eliminated from Sri Lanka in 1969 but is on the rise after four decades of quiescence. Effective vector control is an integral part of infection control. We carried out entomological investigations for potential vectors of re-emerged BF in five BF-endemic areas in Sri Lanka. Here we report Ma. indiana, Cx. tritaeniorhynchus, Cx. bitaeniorhynchus, Cx. quinquefasciatus, Cx. gelidus, Cx. lopoceraomyia, Cx. vishnui, Ar. subalbatus, Ae. albopictus and Cq. crassipes with the potential to serve as vectors for BF transmission in Sri Lanka due to the presence of L3 larvae in the head and thorax regions and Cx. bitaeniorhynchus, Cx. quinquefasciatus, Cx. gelidus, Cx. lopoceraomyia and Cx. vishnui in the world. The high prevalence and infection rate of Ma. indiana, Cx. quinquefasciatus and Ar. subalbatus mosquitoes and their anthropophagic nature in certain BF endemic areas are worrisome. This study emphasizes the importance of a comprehensive analysis of BF vectors for vector control strategies tailored to each region and season.