We have seen a lot of deformities in newborn calves this year in Co. Roscommon. In most cases these have been “dwarf” calves. Some herds have had one or two, whereas others have had many such calves. It seems that prolonged feeding of cows on silage of variable quality has led to the widespread occurrence of this problem. We have also seen a number of other deformities in cattle and sheep.
One farmer recently asked me if two deformed lambs which I delivered from a ewe were caused by “this new virus”. The virus he was referring to is Schmallenberg, and his lambs, like most other similar cases in the West and Northwest, have tested negative for the disease. In fact, unlike the south of the country, we are not aware of any confirmed cases of this new disease in our area this year.
Unfortunately, this means that almost all of the flocks and herds in the northern half of the country have no immunity to this disease. Even in herds where some cases have already occurred, many of the remaining animals may have no immunity to the disease due to the fact that it has had limited spread in Ireland last year during the midge biting season.
Schmallenberg Virus is a recently discovered disease which is spread by midges. It causes mild non-specific symptoms in non-pregnant cattle and sheep. However, the situation in pregnant animals can be very different, depending on when the animal is infected. Infection in the first third of pregnancy can cause deformities in the unborn calf or lamb. Many of these deformities can be quite severe, resulting in calving difficulties and subsequent euthanasia of the newborn calf or lamb. The disease can be diagnosed by detecting the presence of antibodies to the Schmallenberg virus, or by using PCR based tests to detect the virus itself.
The weather, yet again, will be a significant factor. If we are lucky enough to get a warm summer with high midge activity, next spring could be another challenging one for many livestock breeders.
Farmers should, therefore, consult with their vets on advice on how to test for the disease.