Ruminant Orthobunyavirus Takes Northern Europe By Surprise
January 14, 2012
A new virus has been found that causes fetal malformations and stillbirths in cattle, sheep and goats in northern Europe. Scientists don’t have a clue about the origin of the virus or why there is this sudden outbreak. Scientists want to share the virus and protocols to allow anyone interested to study the disease and develop tools and vaccines.
The virus has been named Schmallenberg after the German town where the first positive samples originated from and was detected in November in dairy cows which had shown signs of infection with fever and reduced milk production. The virus has now been detected in sheep and goats in dozens of neighboring farms in the Netherlands and Belgium. There have been 20 cases in farms in Germany, 52 in the Netherlands, and 14 in Belgium. There are many more suspected cases which are currently being investigated. It has become a serious threat to the health of animals in northern Europe.
The virus appears to be transmitted by midges (Culicoides spp.) and the infections had likely occurred in the summer and autumn of last year. Fetuses that were exposed to the virus are just only being born. Cases with congenital malformations such as hydranencephaly (parts of the brain have been replaced by sacs filled with fluid) and scoliosis (curved spine) appeared right before Christmas. Scientists are seeing 20% to 50% of lambs with such malformations in some herds. Most of these animals are stillbirths.
Scientists are expecting this to get worse, especially in cattle, as the fetuses will only come to term in February or March. Virologists have been able to isolate and culture the virus. Researchers at the Friedrich-Loeffler-Institute (FLI), the German federal animal health lab located on the island of Riems, have sequenced the genome of the pathogen. It’s been compared to a member of the group of orthobunyaviruses. These viruses are mainly transmitted by mosquitoes and midges and are best known in Asia. However some have been circulating in Europe for decades. The closest known virus to Schmallenberg is the Shamonda virus, which in turn belongs to the Simbu serogroup that has been known to infect ruminants.
The segmented genome of the orthobunyaviruses makes it easy for new combinations to emerge, just like with the influenza virus. It is yet unknown whether Schmallenberg can affect humans. There are at least 30 orthobunyaviruses that have been associated with human diseases. A risk assessment by the European Center for Disease Prevention and Control in Stockholm was issued just before Christmas stating that it is unlikely that this new orthobunyavirus will affect humans, but it cannot be excluded at this state.