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

Background Sri Lanka is experiencing a re-emergence of brugian filariasis post-Lymphatic Filariasis elimination. A comprehensive understanding of the mosquito species that can facilitate the development of the brugian parasite is essential for implementing targeted surveillance and control measures. This study evaluated the vector potentiality of field-caught mosquitoes for brugian parasites across endemic districts within the filarial transmission belt in Sri Lanka. Methods Mosquito surveillance was conducted at six sites across five districts with the highest reported brugian cases during 2021–2022. Mosquitoes were collected within a 500m buffer zone surrounding identified human cases using dog-baited, window and gravid traps to maximize species diversity in the sample. Mosquitoes were identified morphologically, and randomly selected mosquitoes were molecularly confirmed via a PCR targeting the CO1 region. Vector potentiality was evaluated through observation of nematode parasites upon dissection, molecular confirmation via PCR amplification and sequencing of the Brugia sp. specific Hha 1 region. Mosquitoes harboring brugian parasites were tested for the presence of human blood to investigate their involvement in human brugian filariasis transmission. Statistical analyses were performed using generalized linear mixed models to account for site-specific factors. Results Of 794 mosquitoes from 15 species examined, 10.05% (77 out of 766 mosquitoes dissected) carried potentially infective L3 larvae molecularly confirmed as Brugia spp. in their head and thorax. Nine species across four genera demonstrated competence for parasite development: Mansonia annulifera, Ma. indiana, Ma. uniformis , Culex. lopoceraomyia, Cx. tritaeniorhynchus , Cx. quinquefasciatus , Cx. vishnui , Armigeres subalbatus , and Coquillettidia crassipes. Notably, Ma. indiana which has previously not been identified as a potential vector for brugian filariasis in Sri Lanka showed the highest weighted infectivity at S ₁ site. Site-based risk assessment identified the S ₁ site as having the highest risk of brugian filariasis followed by S ₆ . Conclusions Many mosquito genera demonstrate competence for Brugia spp. development, expanding beyond the previously known Mansonia vectors. The diversity of potentially infective species indicates complex transmission dynamics requiring integrated surveillance approaches. Experimental vector competence studies are needed to confirm natural transmission capability and inform evidence-based control strategies.