Presence of Leishmania donovani DNA in wild-caught biting midges Culicoides sp. at a Leishmaniasis disease endemic area in Sri Lanka; An alternative vector for disease transmission

Biting midges, belonging to the Ceratopogonidae family, are a group of dipteran insects implicated as vectors for various parasites and viruses. In Sri Lanka, where leishmaniasis is endemic, biting midges are found in high densities, causing significant biting nuisance. This observation raises the possibility that these insects may serve as potential vectors for leishmaniasis in these areas. To investigate the presence of Leishmania donovani parasites within biting midge populations in a leishmaniasis-endemic area of Sri Lanka, a study was conducted in the Medawachchiya Medical Officer of Health area, Anuradhapura District. Biting midges were collected using cattle-baited net traps in December 2021. Morphological identification keys were used to classify the collected specimens, which were then surface sterilized and subjected to DNA extraction. Polymerase Chain Reaction (PCR) targeting the kinetoplast minicircle gene specific to L. donovani was employed to detect the presence of parasite DNA. The resulting PCR amplicons were visualized using gel electrophoresis. Out of the 42 biting midges collected, all were morphologically identified as Culicoides imicola. Interestingly, 4.76% (n=2) of the field-caught samples were positive for L. donovani DNA. These findings suggest that L. donovani circulates within biting midge populations. These insects may act as vectors for leishmaniasis transmission in the country. Therefore, it is strongly recommended to continue studying biting midges in Sri Lanka to enhance our understanding of their role in disease transmission.