The infection with the Schmallenberg virus (SBV)continues its spread in Europe. From the description of the first cases of congenital malformations (mainly by the arthrogryposis-hydranencephaly syndrome) in December 2011, more than 3,200 farms have declared outbreaks of SBV infection in eight EU countries: Germany, The Netherlands, Belgium, UK, France, Luxembourg, Italy and Spain. However, according to official sources in each country, we know that there are almost 4,000 affected farms in just 6 months (Figure 1).

 

Fig. 1 (click to enlarge): Number of outbreaks of Schmallenberg in the eight EU countries affected to 11 May 2012. Data are shown notifications agencies of each country against the official statements of the OIE.

Of the total number of affected animals, sheep are the most affected (80.1%), followed by cattle (17.2%). Infection in goats seems to have been milder than in the other two species. As for the case of cattle, it is likely that outbreaks continue to appear until June 2012, transmission of the virus by the vectors occurred even until January of this year.

This situation is feasible given the uncommon weather conditions during the fall and winter of 2011, making possible the survival of the vectors until very late months. In turn, we must bear in mind that the drop of outbreaks in cattle may coincide with the start of the second wave of outbreaks, since there will be a sufficient number of vectors to start the transmission. Up to now  we do not know the consequences of this second epidemic wave, but everything indicates that this disease is much milder than other vector-borne diseases, such as bluetongue.

 

Víctor Rodríguez Prieto & José Manuel Sánchez-Vizcaíno
SUAT-UCM