The lead researchers, Massimo Palmarini and Alain Kohl at the MRC Centre for Virus Research at the University of Glasgow, claim to have ‘laid bare’ the ways by which the virus causes disease in livestock.
The researchers designed and assembled the viral ‘genome’ completely in a test tube in a form that can be easily introduced and replicated in cultured cells. From these cells the researchers recovered the virus with identical infection properties to the ‘natural’ SBV.
This approach, known as ‘reverse genetics’, allowed the scientists to control the viral genome and identify a gene, called NSs, which is involved in protecting the virus against the immune response of infected animals.
The researchers then made viruses missing the NSs gene. They discovered that, without it, the virus adversely affected mice in the laboratory less than the virus containing the NSs gene.
The researchers said their work pregnancy has ‘paved the way for future development of new vaccines’.
The work has also shed light on how the virus causes horrific defects in newborn lambs and calves when their mothers are affected in the early stages of pregnancy.
They researchers discovered that SBV rapidly grows in the brain and spinal cord of aborted lambs and calves and that the virus prefers to infect neuron cells, which explains why it infects and damages the brain.
This also results in muscular defects such as abnormally flexed legs often seen in stillborn animals when virus is transmitted from an SBV infected mother to the calves or lambs in the uterus during
The full report about the study publishes on January 10 in the Open Access journal, PLOS Pathogens.
Professor Palmarini, director of the Centre for Virus Research at the University of Glasgow, said: “Insect-borne viruses, known as ‘arboviruses’, are increasingly becoming a problem throughout the world, whereas years ago they were limited mainly to the tropical areas of the globe.
“The spread of arboviruses is probably the result of several factors including increase in travelling and commercial exchanges, climate and ecological changes, and increased livestock production. This study will help us to understand how Schmallenberg virus works, but it can also serve as an example for other related viruses that may emerge in the future.”
SBV, which causes stillbirths, abortions and fetal defects in pregnant cows and ewes, has spread rapidly throughout Europe since its discovery in Germany in October 2011. It is currently being discovered in newborn lambs and calves across Britain and is causing real concern within the livestock community.
SBV can be transmitted to livestock when they are bitten by insects such as midges which carry the virus.
These insects control the viral infection by mounting a complex immune response meaning they themselves are not adversely affected by the virus.
Recent work led by Alain Kohl and Esther Schnettler, published in the Journal of Virology, has provided an insight into how midges themselves respond to viruses such as SBV, potentially, they claim, helping the development of new control strategies that target the insect rather than the animal.