"Schmallenberg" virus: analysis of the epidemiological data

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Summary

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, including harmonised case definitions and reporting guidelines for a minimum dataset at herd/flock level and an extended dataset at animal level. Data from affected Member States from 1 August 2011 to 19 March 2012 (or date of transmission) were analysed. This report presents the analysis of the submitted data.

All Member States have reported the number of confirmed herds following viral detection by PCR or serological confirmation. In addition, France and Italy have also reported the number of suspect herds. The number of confirmed cases by PCR can constitute an underestimation of the number of infected herds, in particular for calves. The number of confirmed acute cases in adult cattle with viral detection by PCR is limited to eight cases in Germany, most likely corresponding to infection during the period of viral circulation in summer/autumn 2011.

Regarding temporal distribution of confirmed herds, an increase in the number of confirmed herds is observed up to the ninth week of the year 2012, followed by a steep decrease in the weeks 10 and 11. However, the latter should be interpreted with caution, given that the last reporting week might be incomplete. The observed pattern of case detection per species is in accordance with the hypothesis that infection may have occurred during a certain period of the gestation.

Maps representing the special distribution of cases are available.

For the purpose of this report, impact of the infection was defined as mortality and morbidity in the affected animal populations, estimated based on the proportion of cases in the populations. The total number of animals and herds of sheep, goats and cattle were compared with the numbers of animals in the confirmed herds and the number of confirmed herds. For all affected countries, the number of affected animals /herds is low in comparison with the total number of animals/herds. This figure should be interpreted cautiously since under-reporting or lack of diagnostic confirmation may affect the ratio. In order to estimate the disease impact, information was requested on the number of pregnant animals, arthrogryposis hydranencephaly syndrome (AHS) cases, abortions, live births, stillbirths, and cases of dystocia per herd during the reporting period. Unfortunately, most of the countries have not reported this data or provided information on more than one AHS case per herd yet.

Recommendations to improve data for further evaluation of the impact and magnitude of disease spread were provided.

Fonte: EFSA