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Background <p>Schmallenberg virus (SBV) was first detected in Germany in 2011 and today has an enzootic status in Central Europe. It is transmitted by biting midges of the genus <i>Culicoides</i>, which have a high abundance in livestock farms. In addition to SBV, <i>Culicoides</i> are considered vectors of other viruses relevant to livestock such as bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV). Monitoring of midges and transmitted viruses is of veterinary importance because the resulting diseases may cause animal suffering and entail economic losses due to control measures such as vaccination or trade restrictions.</p> Methods <p>To gain an overview of the prevalence of viruses in <i>Culicoides</i> vectors in Germany, a monitoring programme was established in 2018. From 2019 to 2023, biting midges were caught at 79 sites throughout the country, of which 511,788 were morphologically differentiated according to <i>Culicoides</i> species or subgenus and pooled accordingly. The nucleic acids extracted from 19,521 midge pools of up to 50 individuals were tested in real-time reverse transcription polymerase chain reactions (RT-PCRs) for the genomes of SBV, EHDV and BTV. The species in virus-positive pools were analysed with molecular biological methods to identify potential vector species.</p> Results <p>Whereas no EHDV and BTV were detected, SBV was found in every year of the five monitored years. The minimum infection rate (MIR) of SBV in the tested pools ranged from 3.75 in 2022 to 135.47 in 2023. Most SBV RNA-positive pools were represented by the subgenus <i>Avaritia</i> (<i>C. obsoletus</i>, <i>C. scoticus</i>, <i>C. dewulfi</i> and <i>C. chiopterus</i>). To a lesser extent, SBV RNA was detected in pools of the subgenus <i>Culicoides</i> (<i>C. punctatus</i>, <i>C. pulicaris</i>, <i>C. lupicaris</i> and <i>C. selandicus</i>). Only one pool of another subgenus, namely <i>C. griseidorsum</i>, was found positive for SBV genome.</p> Conclusions <p>The results from the monitoring programme confirm an enzootic circulation of SBV in the German <i>Culicoides</i> population during summer and autumn with varying infection rates between the years. The lack of detection of BTV in the midges may suggest a circulation of BTV at a low level. The absence of EHDV genome in biting midges is in line with the epidemiological situation in ruminants in Germany.</p> Graphical Abstract <p></p>

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Monitoring of Schmallenberg virus, bluetongue virus and epizootic haemorrhagic disease virus in biting midges in Germany 2019–2023

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  • 发表日期：

    2025年7月5日

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  • Sophie Zeiske,
  • Helge Kampen,
  • Franziska Sick,
  • Oliver Dähn,
  • Anja Voigt,
  • Elisa Heuser,
  • Martin Beer,
  • Doreen Werner,
  • Kerstin Wernike

摘要

Background

Schmallenberg virus (SBV) was first detected in Germany in 2011 and today has an enzootic status in Central Europe. It is transmitted by biting midges of the genus Culicoides, which have a high abundance in livestock farms. In addition to SBV, Culicoides are considered vectors of other viruses relevant to livestock such as bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV). Monitoring of midges and transmitted viruses is of veterinary importance because the resulting diseases may cause animal suffering and entail economic losses due to control measures such as vaccination or trade restrictions.

Methods

To gain an overview of the prevalence of viruses in Culicoides vectors in Germany, a monitoring programme was established in 2018. From 2019 to 2023, biting midges were caught at 79 sites throughout the country, of which 511,788 were morphologically differentiated according to Culicoides species or subgenus and pooled accordingly. The nucleic acids extracted from 19,521 midge pools of up to 50 individuals were tested in real-time reverse transcription polymerase chain reactions (RT-PCRs) for the genomes of SBV, EHDV and BTV. The species in virus-positive pools were analysed with molecular biological methods to identify potential vector species.

Results

Whereas no EHDV and BTV were detected, SBV was found in every year of the five monitored years. The minimum infection rate (MIR) of SBV in the tested pools ranged from 3.75 in 2022 to 135.47 in 2023. Most SBV RNA-positive pools were represented by the subgenus Avaritia (C. obsoletus, C. scoticus, C. dewulfi and C. chiopterus). To a lesser extent, SBV RNA was detected in pools of the subgenus Culicoides (C. punctatus, C. pulicaris, C. lupicaris and C. selandicus). Only one pool of another subgenus, namely C. griseidorsum, was found positive for SBV genome.

Conclusions

The results from the monitoring programme confirm an enzootic circulation of SBV in the German Culicoides population during summer and autumn with varying infection rates between the years. The lack of detection of BTV in the midges may suggest a circulation of BTV at a low level. The absence of EHDV genome in biting midges is in line with the epidemiological situation in ruminants in Germany.

Graphical Abstract