In December 2011, HealthMap reported on a devastating new virus plaguing cattle and sheep farmers in Germany. Now, six months later, the European Food and Safety Authority (EFSA) released their assessment of the impact of Schmallenberg virus infection in the European Union.
After the virus was first detected in November 2011 in Germany, it rapidly spread throughout seven other EU member states: France, Netherlands, Belgium, Spain, Italy, Luxembourg, and the UK. By May 2012, 3,745 animal holdings reported confirmed cases of Schmallenberg virus (SBV).
Animals infected with SBV were predominantly sheep and cattle, followed by goats as well as one bison. Sheep holdings reported the greatest number of laboratory confirmed cases, more than twice as many as cattle. For example, the maximum proportion of reported sheep holdings was 4 percent per country, compared to 1.3 percent of cattle holdings.
There are two known modes of transmission: vectorborne (through biting midges), and transplacental (through the placenta from mother to offspring). Symptoms in adult animals are either entirely absent or non-specific, lasting for approximately one week. Some clinical signs include fever, loss of appetite, reduction in milk yield, and diarrhea. However, in some infected animals’ young, SBV causes stillbirths or mild to severe congenital malformations.
The EFSA’s current research examines the possibility of a second outbreak in 2013. If the virus is able to survive the upcoming winter, researchers suggest that an outbreak similar to the one observed in 2011 may occur. Past trends indicate the virus will re-emerge between mid-April and end of May and reach previously uninfected regions of Europe. A preliminary study showed that four animals re-infected with SBV remained unaffected, suggesting post-infection immunity. At this time, no vaccine for SBV has been developed.
New studies conducted by the EFSA verify the European Center for Disease Control and Prevention’s original statement that the virus poses no risk to humans. Nevertheless, various countries, such as Russia and Egypt, have suspended imports of live cattle and sheep from SBV-affected countries. The U.S., Mexico, and Uruguay followed suit by establishing a temporary ban on imports of livestock genetic material from the EU.
The impact on animal welfare and production was not yet evaluated due to limited data. Future assessments will also measure the impact of SBV infection on fertility, milk yield, and rates of dystocia (abnormal or difficult birth).