Downloaded from veterinaryrecord.bmj.com on October 12, 2014 - Published by group.bmj.com
News & Reports
Schmallenberg virus
EFSA assesses current knowledge of Schmallenberg virus SINCE Schmallenberg virus (SBV) emerged in Europe in 2011, the principal economic impact has been through international trade restrictions imposed by countries outside the EU, according to an overview published by the European Food Safety Authority (EFSA) last month. The scientific report, ‘Schmallenberg virus: state of the art’, reviews current knowledge of SBV and provides an overview of the research carried out on the virus in different member states. In the report, the EFSA notes that, since being identified in 2011, the virus has been found in domestic cattle, sheep and goats and 12 wild animal species, together with 19 zoo animal species. Seroprevalence studies in cattle, sheep and goats indicate that SBV ‘has probably spread over the whole of Europe’, it says. It reports that, according to seroprevalence studies conducted at a national level, prevalences at animal and herd levels were generally high, while studies at a regional level showed more variability. The EFSA concludes that, when compared with the level of infection 566 | Veterinary Record | June 7, 2014
indicated by seroprevalence studies, the number of herds suffering confirmed arthrogryposis hydranencephaly syndrome cases suggests that the frequency of clinical infection is low. ‘SBV induces malformed calves only in a very limited number of cases, as demonstrated by experimental infection studies on pregnant cows and ewes,’ it says. It also reports that, while several species of Culicoides midge have been shown to be potential vectors of SBV, no evidence has been found that mosquitoes are capable of transmitting the virus. There is also no current evidence that vertical transmission is a major route of transmission of SBV. The virus has successfully overwintered, despite a lengthy period of minimal vector activity, the EFSA says, adding that ‘The mechanism is unknown at present; however, vertical transmission in host or vector may play a role.’ Regarding immunity to the virus, it says that there are only limited data on duration of immunity in cattle and none for sheep. ‘The data for cattle suggest that immunity lasts for at least one year following natural
infection. Data on immunity over longer periods is not yet available.’ Turning to the impact of the virus, the EFSA says that the ability to estimate this was restricted by the limited availability of data. While studies reported a probable effect of SBV infection on abortion, shorter gestation, non-return to oestrus and the number of artificial inseminations per animal, ‘the principal economic impact has been felt via international trade restrictions, particularly in live animals and semen’. It says that, in the absence of data on a number of variables, it is not possible to estimate the future direct impact of SBV and the extent to which this will vary year on year. However, it warns: ‘In the event that Europe becomes SBV free, the population level of immunity will decline. Subsequent reintroduction of SBV in Europe could then result in an outbreak of similar magnitude to that seen in 2012.’ n The EFSA’s report can be downloaded from www.efsa.europa.eu/en/efsajournal/ pub/3681.htm doi: 10.1136/vr.g3572
Downloaded from veterinaryrecord.bmj.com on October 12, 2014 - Published by group.bmj.com
EFSA assesses current knowledge of Schmallenberg virus Veterinary Record 2014 174: 566
doi: 10.1136/vr.g3572
Updated information and services can be found at: http://veterinaryrecord.bmj.com/content/174/23/566.1.full.html
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News & Reports
Schmallenberg virus
EFSA assesses current knowledge of Schmallenberg virus SINCE Schmallenberg virus (SBV) emerged in Europe in 2011, the principal economic impact has been through international trade restrictions imposed by countries outside the EU, according to an overview published by the European Food Safety Authority (EFSA) last month. The scientific report, ‘Schmallenberg virus: state of the art’, reviews current knowledge of SBV and provides an overview of the research carried out on the virus in different member states. In the report, the EFSA notes that, since being identified in 2011, the virus has been found in domestic cattle, sheep and goats and 12 wild animal species, together with 19 zoo animal species. Seroprevalence studies in cattle, sheep and goats indicate that SBV ‘has probably spread over the whole of Europe’, it says. It reports that, according to seroprevalence studies conducted at a national level, prevalences at animal and herd levels were generally high, while studies at a regional level showed more variability. The EFSA concludes that, when compared with the level of infection 566 | Veterinary Record | June 7, 2014
indicated by seroprevalence studies, the number of herds suffering confirmed arthrogryposis hydranencephaly syndrome cases suggests that the frequency of clinical infection is low. ‘SBV induces malformed calves only in a very limited number of cases, as demonstrated by experimental infection studies on pregnant cows and ewes,’ it says. It also reports that, while several species of Culicoides midge have been shown to be potential vectors of SBV, no evidence has been found that mosquitoes are capable of transmitting the virus. There is also no current evidence that vertical transmission is a major route of transmission of SBV. The virus has successfully overwintered, despite a lengthy period of minimal vector activity, the EFSA says, adding that ‘The mechanism is unknown at present; however, vertical transmission in host or vector may play a role.’ Regarding immunity to the virus, it says that there are only limited data on duration of immunity in cattle and none for sheep. ‘The data for cattle suggest that immunity lasts for at least one year following natural
infection. Data on immunity over longer periods is not yet available.’ Turning to the impact of the virus, the EFSA says that the ability to estimate this was restricted by the limited availability of data. While studies reported a probable effect of SBV infection on abortion, shorter gestation, non-return to oestrus and the number of artificial inseminations per animal, ‘the principal economic impact has been felt via international trade restrictions, particularly in live animals and semen’. It says that, in the absence of data on a number of variables, it is not possible to estimate the future direct impact of SBV and the extent to which this will vary year on year. However, it warns: ‘In the event that Europe becomes SBV free, the population level of immunity will decline. Subsequent reintroduction of SBV in Europe could then result in an outbreak of similar magnitude to that seen in 2012.’ n The EFSA’s report can be downloaded from www.efsa.europa.eu/en/efsajournal/ pub/3681.htm doi: 10.1136/vr.g3572
Downloaded from veterinaryrecord.bmj.com on October 12, 2014 - Published by group.bmj.com
EFSA assesses current knowledge of Schmallenberg virus Veterinary Record 2014 174: 566
doi: 10.1136/vr.g3572
Updated information and services can be found at: http://veterinaryrecord.bmj.com/content/174/23/566.1.full.html
These include:
Email alerting service
Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions
To order reprints go to: http://journals.bmj.com/cgi/reprintform
To subscribe to BMJ go to: http://group.bmj.com/subscribe/
