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Resurgence of Schmallenberg virus in Belgium after 3 years of epidemiological silence
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Delooz Laurent1,2, Saegerman Claude2, Quinet Christian1, Petitjean Thierry1, De Regge Nick3,
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Cay Brigitte3
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(1) Association Régionale de Santé et d’Identification Animales - ASBL, Département Santé
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Animale, B-5590 Ciney, Belgium
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(2) Research Unit of Epidemiology and Risk Analysis applied to veterinary science (UREAR-
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ULg), Fundamental and Applied Research for Animals & Health (FARAH) Center, Faculty of
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Veterinary Medicine, University of Liège, Liège, Belgium
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(3) Veterinary and Agrochemical Research Centre (CODA-CERVA), Brussels, Belgium
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Keywords: Schmallenberg virus, SBV, Resurgence, Abortion, Cattle, Congenital,
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Malformations, Belgium.
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Abstract
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In spring 2016, three years after the last reported outbreak of Schmallenberg virus (SBV) in
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Belgium, an abortion was notified in a two year old Holstein heifer that previously had not
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been vaccinated against SBV. The autopsy of the eight-month-old malformed foetus revealed
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hydrocephalus, torticollis and arthrogryposis. Foetal brain tissue and blood were found to be
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SBV-positive by RT-PCR and ELISA test, respectively. Evidencing the circulation of SBV in
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Belgium in the autumn 2015 is important in order to anticipate future outbreaks and advise
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veterinarians about the risks associated with calving, as more bovine foetuses might have
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been infected.
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SIR, - Schmallenberg virus (SBV) was discovered in November 2011 by the Friedrich
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Loeffler Institute (FLI, Germany) following the metagenomic analysis of a pool of blood
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samples from bovines originating from a farm in the town of Schmallenberg, Nordrhein
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Westphalia, Germany (Hoffmann et al., 2012). These analyses were carried out following the
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report by breeders and veterinarians from this region of a drop in milk production associated
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with hyperthermia, diarrhoea and abortions in cattle since August 2011 (Hoffmann et al.,
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2012). In January 2012, the virus was detected by RT-PCR conducted at the Belgian National
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Reference Laboratory (NRL) in Brussels on a large number of malformed bovine aborted
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foetuses originating from different regions in Belgium (Martinelle et al., 2012). The
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emergence of this virus in Europe has caused a wave of abortions in cattle in 2012. It was
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estimated that 8.5% (95% CI: 7.7 to 9.4) of aborted foetuses presented lesions of the central
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nervous system and/or the musculoskeletal system (ARSIA, 2013) which were consistent with
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SBV infection (Herder et al., 2012). However, only a third of these suspected cases were
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found to be SBV-positive by RT-PCR. This could be explained by the fact that (i) these
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lesions are not specific to SBV infection, or (ii) the virus was no longer present in the foetus
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at the time of sampling due to the delay between infection and abortion (de Regge et al.,
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2013).
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The last case of SBV infection in Belgium was confirmed by PCR on aborted foetal
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tissues on the 26th March 2013.
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In 2014 and 2015, the rate of congenital abnormalities had remained low (1.7%; 95% CI: 1.4-
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1.9) and stable. While each reported abortion case was systematically screened for SBV
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infection by RT-PCR, no more cases of the disease were detected during this period. This may
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suggest that a large proportion of the Belgian cattle population had been previously exposed
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to SBV, and developed immunity against the virus (Méroc and collaborators in 2013).
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On the 4th April 2016, 1105 days after the last reported case, a two-year old Holstein
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cow aborted in Lavaux Saint-Anne, province of Namur, Belgium. The eight-month-old
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malformed foetus was autopsied at the Regional Association for Animal Registration and
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Health (ARSIA). The cow was not vaccinated against SBV. The foetus presented with
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hydrocephalus, torticollis and arthrogryposis. Brain and blood were sampled and analysed by
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SBV-specific RT-PCR and ELISA tests, respectively. The RT-PCR performed at the Belgian
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NRL revealed the presence of viral RNA of SBV in the brain sample. In addition, the ELISA
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antibody test performed at ARSIA on maternal and foetal sera showed that the cow and its
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foetus were seropositive for SBV. Based on the date of abortion and the age of the aborted
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foetus, we estimated that the conception occurred in August 2015. Gross lesions of the foetus
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suggested that the infection occurred between the 60th and 100th day of pregnancy (Martinelle
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et al., 2012). The cow had thus probably been infected in October or November 2015. The
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virus circulated during this period, which is known to be the period of activity of the vector.
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This was further confirmed by the detection of SBV-specific antibodies in another cow and its
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new-born calf on the 11th April 2016. These animals were sampled before colostrum intake,
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and had not been vaccinated against SBV. The farm from which they originated was used as a
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sentinel to monitor the circulation of various pathogens, and was located 50 kilometres away
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from the farm where the abortion case described in this paper took place. Evidencing the
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circulation of SBV during the autumn 2015 in Belgium is important in order to anticipate
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future outbreaks and advise veterinarians about the risks associated with calving, as more
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bovine foetuses may have been infected during this period. These results confirm the
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resurgence of the virus in Belgium (figure 1) as also observed in Germany in 2014 (Wernike
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et al. 2015).
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Insert Figure 1.
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Acknowledgements
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We thank Wayne Anderson and Guillaume Fournie for the reading of this note.
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Figure caption
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Figure 1: Geographical location of the two bovine herds found to be infected by SBV in 2016
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Legend: The area represents the southern part of the Belgium subdivided in five different
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provinces. The two infected herds are located in the province of Namur.
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References
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Fig. 1.