EFSA assesses risks linked to transmission of bluetongue during animal transit

The European Commission asked EFSA’s Animal Health and Welfare Panel to look at the risk of transmission of the bluetongue virus (BTV) when animals are in transit from or through restricted zones identified by EU Member States[1]. EFSA was also asked to study the impact of different control measures in reducing the spread of BTV. 

By looking at such factors as the use of insecticides and repellents, as well as the period during which animals are moved (for instance, periods when the disease vector’s activity is limited[2]), the panel was able to estimate the relative risk of BTV transmission during animal transit. However, with the data currently available it was not possible to precisely estimate the absolute risk posed by moving a single animal.

The Panel assumed that BTV can be transmitted by infectious Culicoides midges on animals being transported through non-infected zones to susceptible animals in those zones. The Panel also confirmed that BTV infection could spread from infected animals being transported to Culicoides midges in non-restricted areas.

Due to a lack of data it was not possible to quantify the precise risk of these forms of BTV transmission, but the panel found that treating animals and vehicles with insecticides or repellents before loading may help to reduce the risk. The Panel therefore recommended further research to assess the impact of these treatments on BTV vectors.

The panel also stated that the risk of BTV transmission resulting from the transit of animals during a period when the general risk of BTV transmission is low (i.e. January-July) was significantly lower compared with other periods (i.e. August-December). However, data provided by the member states were not sufficient for the panel to be able to precisely assess the effect of the transit of animals during the “seasonally vector-free period” on BTV transmission.

Finally, with regard to the selection of animals to be transported, the available data indicates that vaccination may be more effective in reducing the risk of BTV transmission during transit than testing animals before transportation.

This opinion completes EFSA’s reply to a request from the European Commission covering several different aspects of the bluetongue disease. Earlier opinions on bluetongue – looking at issues including vaccination, the origins of BTV8 in Europe and the over-wintering of the virus – are available via the key topic section.

[1] BTV is a non-contagious infection transmitted by midges belonging to the Culicoides genus. It can be introduced into a non-restricted zone either through the release of infectious Culicoides midges travelling with animals which are in transit through that zone or by infectious animals which are in transit infecting Culicoides midges present in the zone.
[2] See EFSA’s previous opinion on bluetongue addressing the issue of vector-free periods .