First record of Culicoides deltus as a putative vector of Onchocerca flexuosa in Slovak red deer (Cervus elaphus)

Abstract

In the research conducted in years 2016–2022, 63,950 biting midges were trapped during 74 collections conducted in the area of Volovsky Mountains in Slovakia for the purpose of identifying the species composition, the host preference and the transmission or potential parasites in wild nature. The collected biting midges were of 29 species, while the most frequently detected were the Culicoides biting midges (C. obsoletus/C. scoticus/C. montanus), representing 47.9% of all biting midges. The species identification of biting midges was carried out based on their morphology and by applying molecular methods. The host preference of biting midges was molecularly identified by sequencing a 350-bp sequence of the mitochondrial cytochrome b gene (cyt b). The presence of Onchocerca flexuosa DNA in Culicoides deltus was confirmed by the sequencing of fragments of mitochondrial genes cox1. The sequences matched the previously published sequences for O. flexuosa. Data on high prevalence of infections caused by Onchocerca worms in red deer in Slovakia has already been published and indicates that there are favourable conditions for vectors and a suitable environment for parasite circulation in Slovakia. According to the authors’ knowledge, this was the first-ever detection of O. flexuosa in C. deltus in wild nature.