Abstract
Schmallenberg virus (SBV) is the member of Peribunyaviridae family, which comprises pathogens of importance for human and veterinary medicine. The virus is transmitted only between animals and mainly by biting midges of the genus Culicoides. This study was performed in order to determine SBV genetic diversity and elucidate the host–vector adaptation. All three viral segments were analysed for sequence variability and phylogenetic relations. The Polish SBV strains obtained from acute infections of cattle, congenital cases in sheep, and from Culicoides midges were sequenced using Sanger and next-generation sequencing (NGS) methods. The obtained sequences were genetically similar (99.2–100% identity) to the first-detected strain BH80/11—4 from German cattle. The sampling year and origin of Polish sequences had no effect on molecular diversity of SBV. Considering all analysed Polish as well as European sequences, ovine-derived sequences were the most variable, while the midge ones were more conserved and encompassed unique substitutions located mainly in nonstructural protein S. SBV sequences isolated from Culicoides are the first submitted to GenBank and reported.
Highlights
Schmallenberg virus emerged as an unknown orthobunyavirus, causing first unspecific signs of fever and diarrhoea in adult cattle in Germany and the Netherlands in 2011, which later unraveled into more serious outbreaks of foetal malformations, stillbirths and abortions
Seven fragments of Schmallenberg virus (SBV) detected in lamb brain tissue samples (Ct cut off 19.2–31.3) were obtained: three segment S, two segment M and one segment L as well as one fragment containing hypervariable region (HVR) corresponding to 410–687 aa of M polyprotein (Supplementary Table 1)
Still, comparing to better known orthobunyavirus of veterinary importance—Akabane virus, SBV presented 25 times higher mutation rate, as it is understood for the virus in its epidemic stage [22]
Summary
Schmallenberg virus emerged as an unknown orthobunyavirus, causing first unspecific signs of fever and diarrhoea in adult cattle in Germany and the Netherlands in 2011, which later unraveled into more serious outbreaks of foetal malformations, stillbirths and abortions. The viruses of Orthobunyavirus genus, Peribunyaviridae family, are transmitted by vectors such as mosquitos, biting midges and ticks. Some, such as Oropouche virus (OROV), cause human febrile illness in South America, while other, such as Akabane virus (AKAV), Aino virus (AINV) and Peaton virus (PEAV), infect animals causing abortions, stillbirths and malformations in domestic ruminants in Australia, Asia and Africa. The virus is transmitted by Culicoides Latreille (Diptera: Ceratopogonidae), which are known vectors of other emerging viruses such as Bluetongue (BTV) or African horse sickness (AHSV). Poland as most European countries is going through a secondary wave of SBV epidemics [1,2,3]
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