Seasonal dynamics of biting midges (Diptera: Ceratopogonidae: Culicoides), the potential vectors of bluetongue virus, in Sweden

The outbreak of bluetongue (BT) in northern Europe 2006 initiated the monitoring of vectors, biting midges of the genus Culicoides in Sweden. In order to determine the diversity, distribution and seasonal dynamics of Culicoides, weekly collections were made during 2008 and during March-December 2009 using the Ondestepoort Veterinary Institute black light trap. Twenty sampling sites were selected in 12 provinces. In total of 30,704 Culicoides were collected in 2008 and 32,252 in 2009. The most abundant species were the potential vectors of BTV Culicoides obsoletus/C. scoticus that comprised of 77% of the total catches. Other biting midges collected were Culicoides impunctatus (9%), Culicoides grisescens (3%), Culicoides punctatus (2%), Culicoides chiopterus (2%) and Culicoides pulicaris (2%). Culicoides obsoletus/C. scoticus were most abundant during May-June and August-September. The majority of the species were active from March to November in 2008 and April to October in 2009. Species considered as potential vectors of bluetongue virus (BTV) occurred as far north as latitude 65°N (Kalix).