Molecular Detection of Ehrlichia spp. in Stomoxys calcitrans and Their Vector Potentiality in Cattle Farms of Southern Karnataka, India

Stable flies (Stomoxys calcitrans) are significant haematophagous ectoparasites of cattle and potential mechanical vectors of several pathogens, including Ehrlichia spp. This study aimed to detect Ehrlichia spp. DNA in S. calcitrans collected from cattle farms across southern Karnataka, India. Ten cattle farms representing six districts of three zones viz., Central (Bengaluru Urban and Rural), Eastern (Tumakuru and Chikkaballapur), and Southern (Ramanagara and Mandya) zones were surveyed between June 2024 and May 2025. Adult S. calcitrans were trapped using customised aerial nets, morphologically identified, and pooled (three flies per pool) for genomic DNA extraction. The genomic DNA was subjected to PCR assay by targeting 16S rRNA gene using published primers. Out of ten fly pools analysed, seven pools yielded the expected 476 bp amplicon DNA fragment specific to Ehrlichia spp., indicating 70% detection rate. The detection of Ehrlichia DNA in S. calcitrans supports previous reports of stable flies retaining rickettsia pathogens post blood meal and suggests their potential involvement in the mechanical transmission of Ehrlichia spp. among cattle.