Background Culicoides obsoletus is an abundant and widely distributed Holarctic biting midge species, involved in the transmission of bluetongue virus (BTV) and Schmallenberg virus (SBV) to wild and domestic ruminants. Females of this vector species are often reported jointly with two morphologically very close species, C. scoticus and C. montanus, forming the Obsoletus/Scoticus Complex. Recently, cryptic diversity within C. obsoletus was reported in geographically distant sites. Clear delineation of species and characterization of genetic variability is mandatory to revise their taxonomic status and assess the vector role of each taxonomic entity. Our objectives were to characterize and map the cryptic diversity within the Obsoletus/Scoticus Complex. Methods Portion of the cox1 mitochondrial gene of 3763 individuals belonging to the Obsoletus/Scoticus Complex was sequenced. Populations from 20 countries along a Palaearctic Mediterranean transect covering Scandinavia to Canary islands (North to South) and Canary islands to Turkey (West to East) were included. Genetic diversity based on cox1 barcoding was supported by 16S rDNA mitochondrial gene sequences and a gene coding for ribosomal 28S rDNA. Species delimitation using a multi-marker methodology was used to revise the current taxonomic scheme of the Obsoletus/Scoticus Complex. Results Our analysis showed the existence of three phylogenetic clades (C. obsoletus clade O2, C. obsoletus clade dark and one not yet named and identified) within C. obsoletus. These analyses also revealed two intra-specific clades within C. scoticus and raised questions about the taxonomic status of C. montanus. Conclusions To our knowledge, our study provides the first genetic characterization of the Obsoletus/Scoticus Complex on a large geographical scale and allows a revision of the current taxonomic classification for an important group of vector species of livestock viruses in the Palaearctic region.

BackgroundIn Europe, the life-cycle of Echinococcus multilocularis is predominantly sylvatic, involving red foxes (Vulpes vulpes) as the main definitive hosts and rodents such as muskrats and arvicolids as intermediate hosts. The parasite is the etiological agent of human alveolar echinococcosis, a malignant zoonotic disease caused by the accidental ingestion of eggs shed by definitive hosts in their faeces. The aims of this study were to investigate the prevalence of E. multilocularis in red foxes and raccoon dogs (Nyctereutes procyonoides) and to study the environmental factors favouring the perpetuation of the parasite in Latvia.MethodsA total of 538 red foxes and 407 raccoon dogs were collected across Latvia from 2010 to 2015. The sedimentation and counting technique was used for collecting E. multilocularis adult worms from fox and raccoon dog intestines. The morphological identification of the parasite was confirmed by molecular analysis.ResultsThe prevalence of E. multilocularis was significantly higher in foxes (17.1%; intensity of infection 1–7,050 worms) (P < 0.001) than in raccoon dogs (8.1%; intensity of infection 5–815 worms). In foxes, a significant positive correlation (r (10) = 0.7952, P = 0.001) was found between parasite prevalence and the intensity of infection. A positive relationship (R s = 0.900, n = 5, P = 0.037) between parasite prevalence and precipitation was also observed. In raccoon dogs, a significant negative relationship (F (1,8) = 9.412, P = 0.015) between animal density and parasite prevalence, and a significant positive relationship (F (1,8) = 7.869, P = 0.023) between parasite prevalence and agricultural land cover, were detected.ConclusionsThe results of this study confirm the red fox as the most important definitive host of E. multilocularis and, consequently, as the main target for control programmes in the Baltic countries. Raccoon dogs seem to play a secondary role in the life-cycle of E. multilocularis within the investigated European region.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1891-9) contains supplementary material, which is available to authorized users.

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