The Schmallenberg virus epidemic in Europe—2011–2013
Introduction
The ongoing systematic collection and analysis of animal disease data is the core of an animal disease surveillance system. It should result in relevant intelligence at an appropriate spatial and temporal resolution to support risk managers in taking decisions to prevent and control animal diseases and possible public health implications. Important requirements for existing surveillance systems to ensure preparedness for emerging diseases at European level are: clear and specific case definitions, integration with laboratory services and use of appropriate and validated diagnostic reagents and methods, consistent and robust epidemiological indicators and generic data models to facilitate data transfer and analysis (Richardson et al., 2011). In recent years, the need to perform risk assessments at a European Union (EU) level for animal diseases required the development of ad-hoc data collections on emerging and re-emerging diseases like bluetongue serotype 8 (EFSA, 2007) and Q fever (EFSA, 2010). Such ad-hoc data collections were necessary to estimate disease prevalence, spread or impact.
In August 2011, farmers and veterinarians in North Rhine-Westphalia (Germany), the Netherlands and Belgium started to report cases of clinical disease in cattle (Hoffmann et al., 2012, Muskens et al., 2012, Cay et al., 2011). Clinical signs were unspecific and transitory: fever, drop of milk yield for several days and in some cases also diarrhoea. Several disease agents such as bluetongue virus, bovine viral diarrhoea virus, bovine herpes virus-1, malignant catarrhal fever virus foot-and-mouth disease virus and exotic viruses like epizootic hemorrhagic diseases virus, Rift Valley fever virus or bovine ephemeral fever virus were excluded by diagnostic analysis. In November 2011, the German national reference laboratory (FLI) detected genomic sequences of a new Orthobunyavirus; the virus was provisionally named “Schmallenberg virus” (SBV) (Hoffmann et al., 2012). Subsequently, the same virus was detected in samples from malformed lambs and calves in Germany, Belgium and the Netherlands (ProMEd-mail, 2011a, ProMEd-mail, 2011b, Van den Brom et al., 2012).
The disease situation was presented by these three countries at the Standing Committee on the Food Chain and Animal Health (SCoFCAH), the EU member states (MS) representation on matters related to Animal Health, in January 2012. The MS and the European Commission (EC) issued a statement on the disease, recognising the need to collect and share information (EC, 2012).
In the EU, the Animal Disease Notification System (ADNS) application is used to ensure rapid exchange of information between MS and the EC on outbreaks of notifiable diseases. The diseases which are classified by the EU as notifiable are listed in EU legislation (Annex I to Directive 82/894/EEC). Notification implies not just reporting but also the need for control or eradication measures to be put in place. However, the system does not include provisions for collection of information on emerging diseases and an ad hoc data collection was necessary. The European Food Safety Authority (EFSA) was requested by the EC to collect data on SBV occurrence from MS in order to provide an assessment on SBV spread and impact.
The EU and each of its MS are members of the World Organization for Animal Health (OIE) and therefore have the obligation to report animal diseases detected in their territory. The large majority of disease reports are on listed diseases. The inclusion of an animal disease to the OIE list follows a detailed procedure: a recommendation by the OIE relevant ad hoc group is submitted for endorsement by the relevant elected specialist commissions before it is presented for final adoption by the World assembly of delegates. The criteria for the inclusion of a disease in the OIE List are described in detail in the OIE code. In brief, they relate to feasibility of diagnosis, characteristics of the disease spread and its impact either on public health, animal health or the environment. Diseases can also be listed as emerging diseases when there is evidence of zoonotic potential, rapid spread or significant morbidity and mortality. An “emerging disease” is – as defined by the OIE – a new infection resulting from the evolution or change of an existing pathogenic agent, a known infection spreading to a new geographical area or population, or a previously unrecognized pathogenic agent or disease diagnosed for the first time and which has a significant impact on animal or public health (OIE, 2013).
Listing by the OIE as well as inclusion on the list of notifiable diseases by the EU legislation makes it necessary to establish surveillance measures that allow demonstration of disease freedom, early detection and control measures to avoid the spread or the introduction of the disease. The economic impact of such measures can be high and risk managers need to decide on their value. The OIE was notified of the first and of subsequent cases of SBV detected in various MS of the EU as an emerging disease. However, to make SBV infection a listed disease in accordance with the OIE, demonstrating the spread and impact of the infection is required.
The objectives of this study were to describe the European data collection effort regarding the SBV epidemic, present the results of the disease spatial and geographic distribution during 2011–2013 and discuss its possible impact. In addition, the level of under-ascertainment of the surveillance system was assessed in order to improve the accuracy of our estimates.
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Data collection: reporting officers network nomination and organization, data reporting guidelines
The notification of SBV in the EU was not compulsory. Neither mechanism nor guidelines were available for a harmonised data collection and reporting of a non-notifiable disease.
Harmonised case definitions were agreed between the MS. The information related to suspect and confirmed herds was collected at national level by National Veterinary Competent authorities and reported to EFSA by officially appointed reporting officers. The systems in place for dissemination of information on the case
Surveillance activities
Surveillance activities varied considerably within Europe. An overview of the surveillance activities in the reporting countries is presented in Table 2. The network of reporting organisations comprised a mix of veterinary organisations, agricultural ministries, research institutes, national animal health institutes, farmers’ organizations and food safety agencies depending on the existing structures within the countries. By May 2013, the network included twenty-six MS, two countries in the
Discussion
The objective of EFSA's coordinated SBV data collection at a European level was to investigate the spread of the disease and assess its impact in order to support EU risk managers to take decisions on the implementation of control measures and to provide information to trade partners.
At the start of the epidemic, surveillance activities were based on case reporting of clinical suspicions to the competent authorities. This type of surveillance is considered passive because the decision to report
Conclusions
The work developed by EFSA and experts of the member states of the European Union on the development of uniform case definitions and protocols for data submission demonstrated the possibilities of international collaboration in the investigation of an emerging disease. The collated data allowed for the assessment of the spread of SBV in Europe both temporally and spatially at an appropriate granularity to support decision makers.
Information on the results of the laboratory testing could be
Conflict of interest
None declared.
Acknowledgments
The authors would like to acknowledge all reporting officers that have submitted data on SBV occurrence in European countries, the EFSA Animal Health and Welfare Network on the Ad-hoc working group on Schmallenberg virus experts and EFSA scientific staff.
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