Detection of preimaginal forms of dengue vectors from environmental samples in Jaffna city, northern Sri Lanka: an eDNA-based approach

Vector surveillance is crucial for implementation of appropriate vector control strategies to reduce the transmission of vector-borne diseases such as dengue, a major public health concern in Sri Lanka. Aedes aegypti and Ae. albopictus are the primary and secondary vectors of dengue virus, respectively. Dengue is endemic in the Jaffna District and the presence of dengue vectors from many water bodies, including brackish water habitats, is reported. The use of environmental DNA (eDNA) has emerged as a novel tool to detect and identify vector species present in any aquatic environment. This study, used environmental DNA to determine the presence of major dengue vectors in different aquatic habitats in the Municipal limits of the Jaffna District. Potential pre-imaginal developmental sites of dengue vectors were identified in randomly selected 10 blocks consisting of at least 40 houses within the study location. One hundred and twenty water samples without any visible preimaginal forms were collected from these sites to extract eDNA. PCR assays were performed using species-specific primers designed for Ae. aegypti and Ae. albopictus. The presence of Ae. aegypti and Ae. albopictus was identified in 12 (10.0%) and 30 samples (25.0%), respectively. The presence of both species was detected in nine samples (7.5%). The salinity of the water from which Aedes DNA was detected ranged from 0–7 gL-1. The results revealed that eDNA is an indirect but valid surveillance tool for monitoring preimaginal developmental forms of mosquitos in the aquatic environment.