Qualitative risk assessment: introduction of bluetongue disease, serotypes 4 and 8
Bluetongue disease (BT) virus serotype 4 (BTV-4) currently circulating in South-Eastern Europe is still spread-ing toward the north, but slower than last year. Since September 2014, Hungary also reports BT outbreaks. The causative agent is the same BTV-4 strain which currently circulates in the Balkan countries. In November BT has been detected in Austria for the first time since seven years. The virus also belongs to serotype 4. Also Slovenia reported a BT outbreak in the immediate vicinity of the Austrian Border. Currently (30.11.2015), the 150 km BT-restriction zone reaches out 80 km to the German border (one year ago, the distance was about 400 km). Especially Italy notifies infections with BTV-4, but this virus is not identical with the BTV-4 found in the Balkan countries. Furthermore, in September 2015, the first case of BTV-8 since 2010 (and in the EU since 2011) was confirmed in France. The infection has since spread widely, and a total of 90 affected farms have been identified. Currently (30.11.2015), the BTV-8 restriction zones reach out about 100 km to the German border.
The entry risk for the introduction of both BTV-4 and BTV-8 comprises
- aerial spread of live vectors infected with BTV
- introduction of infected vectors by trade or traffic and
- trade with susceptible animals, bull semen, ova and embryos.
Due to the rapid spread of the virus in southeastern Europe, the entry risk concerning living vectors (midges) in the following vector-active season is assessed as probable to high. Concerning the introduc-tion via trade, the entry risk is estimated as low to probable due to the trade of animals from affected regions during the high risk period.
In the exposure assessment, the risk is estimated high with regard to the spread by live vectors, and as low for all remaining potential routes of entry. In the consequence assessment, the risk is estimated as high, as susceptible animals are not protected in Germany, neither against BTV-4 nor BTV-8. Therefore, probably many animals would get diseased resulting in animal suffering and high production losses.
To mitigate the risk, it is possible to carry out the control measures required by EU legislation and to im-plement a vaccination program. However, vaccination only prevents the spread of the disease if a high coverage is achieved. By vaccinating the animals, clinical signs are reduced, and thereby animal welfare increased, although it might cause considerable costs.