The researchers from Liège have published an article in the Antiviral Research journal (3) that includes the clinical, pathological, virological and epidemiological facts made public during the first six months of the emergence of the Schmallenberg virus.

A new wave of infection expected in spring-summer 2012

It is difficult to give an exact figure for the number of farms affected by this new epidemic in Europe since it is continuing to evolve, but we are talking about more than 3 500 cattle farms affected, including sheep, goats and cattle. “The vector needs humid and relatively warm places, such as barns, to survive. But the colder periods this winter prevented the circulation of the culicoides during the last months”, Mutien-Marie Garigliany points out. So while the epidemic may have gone through a quiet period over the winter, a new wave of infection is expected, but probably to a lesser extent, with the arrival of fine weather and new calves. 

As regards the evolution of the epidemic in the coming months, it would appear that the worst of the storm has passed. “It’s likely that some adult animals will still have clinical signs and that some young ruminants will be born with malformations during the next season, but that should then stop for several years at least”, the researcher continues. “The majority of animals will have been infected and once the mothers have a high level of antibodies in their blood, which is the case in 70 to 90% of cattle in Europe, this will have a neutralising effect and prevent the virus from passing through the placental barrier”, Mutien-Marie Garigliany adds. Hence, the Schmallenberg virus should soon no longer be able to cause too much damage.

In the longer term, European cattle may however become gradually naive – i.e. seronegative for the Schmallenberg virus – or quite simply, the whole herd may be renewed in the next five to six years and then there may be a new epidemic.

No health risks for humans

While the idea of developing a vaccine for ruminants against the Schmallenberg virus was mentioned at the beginning of the epidemic, this was quite quickly abandoned because by the time the vaccine reaches the market, 100% of ruminants will have been infected by the virus and will be immunised. 

As for the risks on human health, there don’t appear to be any. “The virus doesn’t cause any clinical signs in man. Better still, humans don’t seroconvert, i.e. they don't produce antibodies, even after close contact with sick animals. This shows that the Schmallenberg virus is incapable of infecting man”, explains Mutien-Marie Garigliany. “We have also done tests on mice and we obtained an identical result. Clearly, there is a species barrier”. 

The Pathology Laboratory team is currently continuing its research on the biology of the Schmallenberg virus and is attempting, among other things, to find out more about what prevents this virus from crossing the species barrier. “We are examining whether this could change because the consequences of this virus infecting humans could be dramatic", the scientist concludes.

(3) Garigliany, M-M., Bayrou, C., Kleijnen, D., Cassart, D., Jolly, S., Linden, A., Desmecht, D., Schmallenberg virus: a new Shamonda/Sathuperi-like virus on the rise in Europe, Antiviral Research (2012), doi: http://dx.doi.org/10.1016/j.antiviral.2012.05.014