Eco-climatic indicators for three Culicoides species of the Obsoletus complex in Italy

Bluetongue, Schmallenberg and African horse sickness viruses are transmitted by vectors belonging to the genus Culicoides (Diptera: Ceratopogonidae). Among this genus, species of the Obsoletus complex play a crucial role in Europe. In Italy the complex includes three species: Culicoides obsoletus sensu strictu, Culicoides scoticus and Culicoides montanus. These three sibling species were identified in 80 collection sites across Italy through a multiplex PCR test. Sixty‑four sites were classified with a predominant species through a Bayesian approach. Environmental, topographic and climatic factors together with landscape metrics were investigated in each species group using the non‑parametric Mann‑Whitney test. Culicoides obsoletus s.s. resulted the most widely distributed species across the peninsula (51 sites). This species was collected in many eco‑climatic conditions, at a wide range of temperature and altitudes, mainly in anthropogenic landscape. Conversely C. scoticus collection sites were dominated by natural vegetated areas or forest, at medium higher altitudes, preferably in a wilder and more pristine environment (predominant species in 8 sites). Culicoides montanus was a rarer species, statistically predominant in only 3 sites located in Southern Italy, characterized by temperatures higher than the other species. These results, together with other on‑going researches on the vector competence of the species belonging to the Obsoletus complex, and with investigation of larval and breeding habitats, could greatly improve epidemiological knowledge of possible spreading Culicoides‑borne viruses.