Field studies on breeding sites of Culicoides LATREILLE (Diptera: Ceratopogonidae) in agriculturally used and natural habitats.

Culicoides are vectors of pathogens mainly of veterinary importance. To establish targeted vector control measures, it is paramount to comprehend the ecological factors determining their distribution. Therefore, we used emergence traps to sample eight biotopes and assess their potential as breeding sites. Part one of the study investigates agricultural habitats, part two compares four biotopes of a forest-dominated area with less anthropogenic influence, including a physicochemical analysis of soil moisture, pH value and organic content. Thirteen culicoid species were collected, with a strong dominance of the Obsoletus Complex on meadows, and with Culicoides punctatus (MEIGEN), Culicoides pictipennis (STAEGER) and the Obsoletus Complex, to be the most abundant species in the natural habitats. Several co-existing species were found, some of them not having been described before. Our results suggest that ungrazed meadows seem unsuitable as breeding sites. Only the influence of livestock creates adequate conditions for certain midge species. The alder on fen site contained most culicoid species with the highest species diversity. Our study clearly indicates that knowledge of species-specific preferences for environmental habitat conditions (choice of breeding site) in connection to soil conditions is crucial to understand the biology and phenology of midges and their role as vectors of pathogens.

Activity of Culicoides spp. (Diptera: Ceratopogonidae) inside and outside of livestock stables in late winter and spring.

Culicoides Latreille, 1809 midge species are the putative vectors of Bluetongue virus (BTV) and Schmallenberg virus (SBV) in Europe. To gain a better understanding of the epidemiology of the diseases, basic knowledge about the overwintering of the vectors is needed. Therefore, we investigated culicoid activity in relation to air temperature at livestock stables during late winter and spring season. Ceratopogonids were captured weekly indoors and outdoors on three cattle farms, three horse farms and one sheep farm in the federal state of Brandenburg, Germany between January and May, 2015 by BG-Sentinel UV-light suction traps. First seasonal activity was measured inside a sheep barn and cattle stables in mid-March, suggesting the existence of a preceding vector-free period. The first species at all trapping sites were members of the Obsoletus Complex followed by Culicoides punctatus (Meigen), 1804 and Culicoides pulicaris (Linnaeus), 1758 simultaneously. In total, 160 collections were made, including 3465 Culicoides specimens with 2790 (80.6%) of them being members of the Obsoletus Complex. The remaining 675 individuals belonged to six other culicoid species. 59.8% of all Culicoides were collected indoors, and almost five times as many midges were sampled on cattle farms as on horse farms. Cattle farms harboured seven species while only two species were found on the horse and the sheep farms, respectively. Temperatures, husbandry practises and the presence/quality of potential breeding sites might be responsible for the difference in species and numbers of caught specimens between livestock holdings.

Schmallenberg virus in Germany 2011-2014: searching for the vectors.

Following the emergence of Schmallenberg virus (SBV) in 2011, 21,397 culicoid biting midges (Diptera: Ceratopogonidae) from targeted and non-targeted sampling activities carried out during the summer months of 2011 to 2013 and in late 2014 in various regions in Germany were analyzed for the virus by real-time RT-PCR. While no SBV was found in biting midges collected during 2011 and 2013, 2 out of 334 pools including 20 and 22 non-engorged females of the Obsoletus complex sampled in 2012 tested positive for the SBV S-segment with C(t) values of 42.46 and 35.45. In addition, 673 black flies (Diptera: Simuliidae) captured during the same studies were screened for the presence of SBV and proved negative. In late autumn 2014, biting midges were collected again in a limited study in eastern Germany after some cases of SBV infection had occurred in a quarantine station for cattle. Due to the unfavorable seasonal weather conditions, only few specimens were caught, and these were also negative for SBV. The German experience suggests that biting midge collections launched only after an outbreak and are not locally targeted may be ineffective as to virus detection. It rather might be advisable to collect biting midges at sentinel farms on a permanent basis so to have material available to be examined in the case of a disease outbreak.