Schmallenberg threat creates vaccine demand

Vaccination for Schmallenburg needs to be carried out before breeding.
Vaccination for Schmallenburg needs to be carried out before breeding.

Farmers planning to serve cows in the coming months have expressed interest in a vaccine for Schmallenberg (SBV) due to the spread of the disease in GB and more recently an increase in the spread in the South of Ireland.

The disease can affect cattle and sheep and veterinary advice is where possible protection by vaccination plus an effective insecticide.

While protection with an insecticide effective against the Culicoides midge such as the deltamethrin in Fly & Lice Spot On™ is useful in the spring, summer and autumn months to control the vector, vaccination needs to be carried out before breeding.

Aurelie Moralis, Veterinary Consultant with Zoetis explains that Zulvac® SBV is the only vaccine licensed for Schmallenberg and beef or dairy farmers planning to breed cattle over the next few months could protect their animals from this virus which is so unpredictable.

She added: “The disease is difficult to detect in sheep but in cattle it can show as loss of appetite, fever and diarrhoea plus in dairy cattle a reduction in milk production. However the real problem occurs at calving or lambing when abortions, still births or poorly formed foetuses can result.”

In Northern Ireland antibodies to SBV virus were detected in the first quarter of last year in two calves with skeletal deformities from two different herds and a cow from a herd experiencing abortions and calf abnormalities. Whilst an antibody positive result does not confirm the involvement of the virus, it provides evidence that this virus is circulating in Northern Ireland.

Other cases in Northern Ireland last year included a three-day-old calf born into a dairy herd which was presented for post mortem at AFBI laboratories with a cleft palate and severe limb and spinal deformities; and a term stillborn lamb submitted from a lowland flock in mid-February. At necropsy, severe abnormalities of all four limbs of the lamb were noted. There was very little movement in the spinal column and the spinal cord was severely narrowed. SBV was considered likely in both cases.

Severe fetal abnormalities and abortion due to SBV were also diagnosed in individual animals in two herds during the 2nd Quarter of 2017.

The Royal Veterinary Laboratory in the South of Ireland has reported an increase in the number of suspected SBV cases in aborted calves and lambs in recent weeks and test results are awaited. These cases are coming from the more Northern counties in the Republic.

SBV is now considered to be an endemic disease in the UK. Discussion around protection against SBV should therefore form part of the flock/herd health planning which farmers do with their vets who are in an excellent position to know what the SBV situation is within your area as many of the deformed lambs and calves will need veterinary intervention at lambing or calving.

Many suspected cases of SBV however are not reported and confirmed, meaning we do not know the true extent of the problem.

DAERA advises farmers to inform their veterinary surgeon of any stillbirth, malformation or nervous disease in new born animals or foetuses born to ruminant dams. In addition, all farmers are asked to inform their PVPs about any serious malformation or nervous signs in new born animals in their herd or flocks.

DAERA also emphasises good biosecurity practices especially when dealing with imported animals. These practices include the single use of needles and good disinfection procedures when dealing with products of afterbirth.

The SBV virus is spread by the Culicoides midges, which are widely present across Europe and move easily between farms and regions allowing rapid and extensive spread of infection. The spread of infection therefore occurs predominantly when biting midges are most active between May and October, yet it is not until calving or lambing that the disease is discovered.

Following infection animals become immune, but how long that immunity lasts is unknown, and not all animals in the herd or flock may be infected, meaning some remain naïve. Therefore even where losses are experienced this year it does not necessarily mean that the herd or flock is not at risk of further losses next year.

Whilst vector control methods are an important part of a Schmallenberg Virus control strategy, and will certainly be useful at farm level, alone they are unlikely to be successful at controlling disease over a large area, because of the behaviour and movements of the midges.

Therefore vaccination alongside an effective insecticide is the most effective way to protect your flock/ herd against SBV.

Zulvac SBV is licensed for active immunisation of cattle and sheep from 3.5 months of age to reduce viraemia associated with infection of Schmallenberg Virus. Cattle require two doses given three weeks apart every 12 months, whereas female breeding sheep require one dose at least 14 days prior to every breeding.