"Schmallenberg" virus: analysis of the epidemiological data (April 2012)

Question Number
30 aprile 2012
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Following a request from the European Commission, the European Food Safety Authority (EFSA) issued a technical report in February 2012 on likely epidemiological scenarios in Europe in relation to a recently detected virus provisionally named "Schmallenberg" virus (SBV) (Simbu serogroup, Bunyaviridae family, genus Orthobunyavirus), found in ruminants. The report also included guidance on data to be collected in Member States, with harmonised case definitions and reporting guidelines for a minimum dataset at herd/flock level and an extended dataset at animal level. This second epidemiological report presents the analysis of the submitted data (1 August 2011 – 16 April 2012), updating the previously published report on the epidemiological situation of SBV.

At present, eight Member States (Belgium, France, Germany, Italy, Luxembourg, the Netherlands, Spain and United Kingdom) have confirmed cases of SBV. All affected Member States have reported the number of confirmed herds following viral detection by PCR, virus neutralisation test or serological confirmation and France, Italy, Luxembourg, the Netherlands, Spain and United Kingdom, have also reported the number of suspect herds. Switzerland reported herds where malformed offspring were tested by RT-PCR and the dams by serological testing, all results were negative. Ireland reported surveillance testing of herds and all herds were negative. Estonia reported that there have been no suspect or confirmed herds in the country. Moreover Demark and Norway reported suspect herds, in all herds foetuses/neonates were tested by RT-PCR and the results were negative. The total number of SBV confirmed herds in Europe as of the 16 April 2012 is 3444. No confirmed acute cases have been reported in adult animals in the year of 2012.

The data shows a decrease in the number of reports of SBV confirmed herds following a peak in week 9 (February, 27 – march, 4) of 2012. The decrease after week nine is clearly observed in sheep in both numbers of confirmed and suspect herds. However in cattle there is no clear decrease and any drop in confirmed and suspect herds could be due to incomplete reporting for the month of April. The decrease in number of confirmed herds is most probably linked to the end of the lambing season in affected countries, the fact that lambs and goat kids born in April would have been in a stage of gestation potentially vulnerable to SBV when vector levels were low and other factors including reporting priorities in Member States.

The data available only allows an impact assessment based upon the comparison between the number of SBV confirmed herds and the total number of herds in each affected country by species. For all affected countries, the number of herds with at least one SBV confirmed animal is low in comparison with the total number of herds. This analysis should be interpreted cautiously since under-reporting or lack of diagnostic confirmation may affect the ratio.

The data provided allows an understanding of the temporal and geographical distribution of the SBV outbreak. In order to fully characterise the outbreak and the epidemiology of SBV in Europe, efforts to obtain comparable data on the number of herds tested, the number of newborns and foetuses within a herd with arthrogryposis hydranencephaly syndrome (AHS) type clinical signs and the number of animals within the herd tested by either direct or indirect laboratory methods are required. This could be achieved by following up selected herds or by performing a survey to properly evaluate the impact and magnitude of the spread of SBV infection. As more data becomes available the impact assessment for SBV (in particular within herd and local impact) could be subject to change.

4 maggio 2012