First occurrence of Culicoides obsoletus-transmitted Bluetongue virus epidemic in Central Europe

Abstract

In August 2006, Bluetongue virus disease (BTD) was detected for the first time in the Netherlands, Belgium, Germany and Northern France. Serological tests as well as reverse transcriptase polymerase chain reaction (RT-PCR) proved the occurrence of Bluetongue virus (BTV) in diseased sheep and cattle, and the virus was identified as serotype 8. Therefore, the search for possible vectors was immediately initiated in the outbreak region in Germany. Traps with automatically regulated ultraviolet light lamps were placed at two different farms with sero-positive cattle, and insect monitoring was done from August 2006 until January 2007. The caught arthropods were weekly determined, and it could be observed that midges of the dipteran family Ceratopogonidae occurred in large numbers, sometimes representing up to 40% of all individuals. The microscopical analysis of the wing morphology showed that the species (complex) Culicoides obsoletus was most abundant covering about 97% of the analysed midges. On the second place ranged C. pulicaris, while C. nubeculosus and C. festivipennis were found only as single individuals. Fed and unfed females were separated, sent to the National Reference Laboratory for Bluetongue disease (Friedrich-Loeffler-Institut, Isle of Riems, Germany) and investigated with a BTV-8-specific real-time RT-PCR. It could be demonstrated that at both farms both fed and unfed C. obsoletus were tested positive for BTV-8 genomes, while none of the other species scored positive. This finding strongly supports that the BTD-epidemic, which reached in the meantime wide regions of North Rhine-Westphalia in Germany and of the neighbouring countries with several hundreds of affected farms, is initiated by virus transmission during the blood meal of midges of the C. obsoletus complex. Since they were captured still at the 21st of December close to cattle with clinical signs, it must be feared that BTV-8 is now established in Central Europe, where it had been absent until now.

A survey of biting midges of the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) in NE Bulgaria, with respect to transmission of avian haemosporidians

“…are vectors of BTV (Reoviridae: Orbivirus), a virus that can replicate in any ruminant, first detected in Central Europe in 2006 (Mehlhorn et al 2008). C. obsoletus, C. pulicaris and C. scoticus are considered the main vectors of BTV in Europe and their bloodmeals derived only from livestock (Mehlhorn et al 2007, Bartsch et al 2009). Santiago-Alarcon et al (2012) found C. obsoletus, which has previously been found in Germany, and together with C. scoticus and C. pulicaris, has been feeding mainly on humans.…”

Orientation behaviour of Culicoides obsoletus (Diptera: Ceratopogonidae), a relevant virus vector in northern Europe, toward host-associated odorant cues

“…Behavioural studies using olfactometers or wind or flight tunnels in which a specific number of biting insects are released are very rare (Bhasin et al, 2000b) due to the difficulty of obtaining a sufficient number of insects, given the complexity of maintaining many Culicoides species of interest under controlled conditions. Only a few speciesof limited interest in northern Europe -are commonly bred (Jones, 1964;Fahrner and Barthelmess, 1988;Kremer and Lienhart, 1998), and these do not include species of the subgenus Avaritia (particularly Culicoides obsoletus Meigen 1818), considered to be vectors of BTV and SBV (Mehlhorn et al, 2007;Carpenter et al, 2008;Hoffmann et al, 2009;De Regge et al, 2012;Elbers et al, 2013).…”

Genetic Characterization of Toggenburg Orbivirus, a New Bluetongue Virus, from Goats, Switzerland

“…From 1998 through 2006, a total of 5 serotypes (1, 2, 4, 9, and 16) became established in southern Europe (5), but they were kept confi ned to this area, most likely because their main insect vector, C. imicola, has never been detected north of the Alps in Europe (6). A BTV-monitoring program in cattle herds has been in effect in Switzerland since 2003 in Ticino Canton, south of the Alps (7)(8)(9). However, no BTV has been detected until now in this region of the country.…”

“…In 2006, BTV serotype 8 (BTV-8) of likely African origin was introduced into Belgium by an as yet unknown mechanism (8). This virus spread throughout many northern European countries.…”

“…The complete coding sequence for the 7 RNA segments (2,5,6,7,8,9, and 10) was determined. Segment 2 was chosen because it encodes the viral structural protein VP2 that contains the serotype-specifi c determinants, whereas the genome segments 5 through 10 are short enough to enable sequencing of the cloned cDNA without the need for internal sequencing primers.…”