Culicoides Species Communities Associated with Wild Ruminant Ecosystems in Spain: Tracking the Way to Determine Potential Bridge Vectors for Arboviruses

Abstract

The genus Culicoides Latreille 1809 is a well-known vector for protozoa, filarial worms and, above all, numerous viruses. The Bluetongue virus (BTV) and the recently emerged Schmallenberg virus (SBV) are responsible for important infectious, non-contagious, insect-borne viral diseases found in domestic ruminants and transmitted by Culicoides spp. Both of these diseases have been detected in wild ruminants, but their role as reservoirs during the vector-free season still remains relatively unknown. In fact, we tend to ignore the possibility of wild ruminants acting as a source of disease (BTV, SBV) and permitting its reintroduction to domestic ruminants during the following vector season. In this context, a knowledge of the composition of the Culicoides species communities that inhabit areas where there are wild ruminants is of major importance as the presence of a vector species is a prerequisite for disease transmission. In this study, samplings were conducted in areas inhabited by different wild ruminant species; samples were taken in both 2009 and 2010, on a monthly basis, during the peak season for midge activity (in summer and autumn). A total of 102,693 specimens of 40 different species of the genus Culicoides were trapped; these included major BTV and SBV vector species. The most abundant vector species were C. imicola and species of the Obsoletus group, which represented 15% and 11% of total numbers of specimens, respectively. At the local scale, the presence of major BTV and SBV vector species in areas with wild ruminants coincided with that of the nearest sentinel farms included in the Spanish Bluetongue Entomological Surveillance Programme, although their relative abundance varied. The data suggest that such species do not exhibit strong host specificity towards either domestic or wild ruminants and that they could consequently play a prominent role as bridge vectors for different pathogens between both types of ruminants. This finding would support the hypothesis that wild ruminants could act as reservoirs for such pathogens, and subsequently be involved in the reintroduction of disease to livestock on neighbouring farms.

Schmallenberg virus detection in Culicoides biting midges in Spain: First laboratory evidence for highly efficient infection of Culicoides of the Obsoletus complex and Culicoides imicola

“…There, serology was negative for wild and domestic ruminants in 2011. The current putative SBV vectors of the Obsoletus complex were described to be in close contact with wild and domestic ruminants in the same mountainous region (Talavera et al., ). Our results are in agreement with those obtained in northern and central Europe where SBV was primarily detected in pools of the Obsoletus complex (reviewed in Balenghien et al., ).…”

Serological testing of Schmallenberg virus in Swedish wild cervids from 2012 to 2016

“…The virus spread rapidly north beyond the Arctic Circle, and occurred in high prevalence in tested animals [15]. However, it was not known if the virus did circulate (in 2012) or still is circulating in wildlife ruminant populations, and if they could act as reservoirs for the virus [16]. …”

Bluetongue: control, surveillance and safe movement of animals

“…In woodlands, higher abundance of Culicoides than expected considering the distance of the sampling sites to the farm, was observed, although this varied according to species (Rigot et al, 2013). Talavera et al (2015) showed that C. imicola and C. obsoletus/C. scoticus are found either in farms and in natural areas were wild ruminants species are the main hosts.…”

“…In the study by Talavera et al. (), samplings were conducted in Spain in areas inhabited by different wild ruminant species. The most abundant vector species were C. imicola and C. obsoletus/C.…”

“…Talavera et al. () showed that C. imicola and C. obsoletus/C. scoticus are found either in farms and in natural areas were wild ruminants species are the main hosts.…”