“Schmallenberg” virus: likely epidemiological scenarios and data needs

Abstract

Following a request from the European Commission, the European Food Safety Authority (EFSA) issued a technical report on likely epidemiological scenarios in Europe in relation to a recently detected virus provisionally named "Schmallenberg" (SBV) virus (Simbu serogroup, Bunyaviridae family, genus Orthobunyavirus), found in ruminants. Clinical signs in adults are mainly mild or nonexistent, but transient fever, loss of appetite, a reduction in milk yield and diarrhoea have been observed in association with the infection. The major clinical sign of SBV is congenital malformations in newborn animals similar to those observed in infections by Akabane virus. Germany, the Netherlands, Belgium, France and United Kingdom have reported confirmed cases. Due to limited information on the epidemiology of SBV, EFSA used a bluetongue virus (BTV8) model to assess whether SBV can spread into susceptible populations. BTV8 was chosen because: i) other Simbu serogroup viruses are primarily vector transmissible diseases as is BTV8, ii) BTV8 and SBV are circulating in the ruminant population iii) information is available regarding BTV8 in Europe whereas there has only been one case report for viruses of the Simbu serogroup in European Member States. The scenarios illustrate that whenever the number of vectors per host and the temperature are above a specific threshold, there is a possibility of disease epidemic in a susceptible population. In order to assess the situation in Europe and to refine the possible spread scenarios, knowledge of putative risk factors relevant for the disease transmission is necessary (including the immune status of the EU animal populations). EFSA proposes a coordinated data collection in all Member States in 2012 on the incidence and prevalence of the disease, number of malformed foetuses, as well as the presence of the virus in dams. Current knowledge suggests that it is unlikely that SBV can cause disease in humans; EFSA and ECDC are closely monitoring the situation in order to address public health concerns should these arise. EFSA will provide an overall assessment of the impact of SBV infection on animal health and welfare once further data become available from Member States.