Schmallenberg virus has been associated with brief mild/moderate disease (milk drop, pyrexia, diarrhea) in adult cattle and deformities and neurological defects in unborn lambs and calves, has made a “grim return” in 2013, according to researchers at The University of Nottingham Veterinary School.
The university says data indicates that this year losses could be as high as 30% on some severely affected sheep operations. Identified in the U.K. in 2011, by the end of 2012 Schmallenberg has been found in most counties in England and Wales, and is widely distributed in northern and western Europe.
University of Nottingham veterinary surgeon Rachael Tarlinton says it will generally cause mild or no disease in adult animals but if the animal is pregnant the virus replicates in the nerve cells of the fetus and, depending at what stage they have reached in the pregnancy, this leads to abortion, abnormalities of the skeleton and neurological defects.
Nearly a year ago, a Bovine Veterinarian article said that Defra, the U.K. government department responsible for policy and regulations on the environment, food and rural affairs, indicated that evidence suggests that Schmallenberg virus was brought into the U.K. from infected biting midges blown across the Channel. The disease has not been shown to be transmissible to humans and has not been identified in the U.S.
Risk to cattle
Though the effects of Schmallenberg have mainly been seen in sheep and goats, cattle are susceptible to the virus.
A January report by DEFRA indicates that 752 cattle have tested positive for Schmallenberg virus, and 59 calves have presented with fetal malformations.
A report in ProMed, a program of the International Society for Infectious Diseases, says based on trail data using bull semen containing Schmallenberg virus (SBV) inoculated into calves, it has to be concluded that samples with a medium as well as with a low viral genome load (Cq values over 30) can be potentially infectious for bovines. The report said that these results confirm the requirement for a sensitive viral RNA-extraction as well as SBV-genome detection system for testing of semen from SBV-infected bulls.
Risk to U.S.
In an early 2012 statement, USDA Chief Veterinary Officer John Clifford, DVM, said: “USDA’s Animal and Plant Health Inspection Service is taking action to mitigate the entry of Schmallenberg virus, a pathogen that has been reported from a number of European Union countries since late 2011 but is not known to exist in the United States.”
Also in 2012 the USDA Animal Plant Health Inspection Services Veterinary Services placed additional restrictions on shipments of ruminant semen and embryos (germplasm) originating from the European Union (EU), and from countries that are not formally part of the EU but which follow EU legislation. These restrictions became effective February 21, 2012. Read more here.
For a USDA fact sheet on Schmallenberg virus, click here.