Orf vaccination for sheep a ‘no brainer’
While some units may not have been affected by orf last season, shepherds are being warned to remain vigilant, especially if their flocks have had problems with the disease before.
The virus can survive in lambing sheds and buildings for many years, and on the skin of carrier animals - acting as a source of future infection.
As a result, experts say even if only the odd case has been identified previously and vaccination did not take place last year, the vaccination of lambs this spring could easily make the difference between profit and loss in 2012.
According to Ian Jones from the Hafren Veterinary Group, based at Newtown, Wales, the orf virus is ubiquitous in the farm environment, but manifests itself in different ways.
“In some flocks, orf can be virtually undetectable because sheep can carry the virus without showing any disease signs, while in other cases the whole flock can be affected, with death rates exceeding 5 per cent. The virus can also infect humans.
“Flocks which have previously experienced the disease will generally see it time and time again, although a number of years may pass between outbreaks,” he says.
“Very often the disease starts with two or three cases in growing lambs one season, only to be followed in the subsequent year by an explosive outbreak. And with the vaccine shortages we experienced in 2011, some flocks with a history of the disease may be particularly vulnerable.
“But now the vaccine is available again, it makes sound economic sense to use it; the financial effects of flock infection can be very damaging indeed, simply because of the ‘knock-on’ effects of the disease.”
Vets in the Scottish Borders, another orf hotspot, are also urging flocks with a history of disease problems to vaccinate this year.
“Some of our hill farms had bad problems with orf last year and the shortage of vaccine reminded many how nasty and costly this disease can be in a flock,” says Andrew Robinson of the Hawick Veterinary Practice based in Roxburgshire.
“Anyone handling affected animals can catch the disease too, so it’s well worth controlling.”
Mr Jones says the bulk of the financial losses from orf come as a result of infected growing lambs failing to finish on time.
“Affected lambs are less keen to feed and slow to put on condition. In fact, growth rates can be severely reduced, which means lambs are much older and end up finishing at the wrong grade, potentially being devalued by at least 10 per cent.
“Older lambs, which hang around on the farm, also cause additional problems because they end up grazing the autumn grass needed for flushing ewes, potentially reducing the number of lambs born the following year.
“And a 10 per cent drop in lambing percentage could easily equate to a loss of £7.50 per ewe.”
Orf infections in young lambs can also quickly spread to the ewes, he warns: “Because the disease usually affects the mouth and nose, sucking lambs infected with the virus quickly transfer it to the ewe’s teats, causing soreness and mastitis.
“The ewe then doesn’t want the lamb sucking, so the lamb has to find another ewe to cross-suckle, thereby spreading the infection further.
“Mastitis in the ewe can be very serious, even fatal. A ewe which has mastitis is destined for the cull ewe market as she will not rear lambs successfully again.
“If the ewe is kept, the condition can become chronic, which means there can be no milk for lambs next season so they have to be cross-fostered.
“All this means if you have a history of orf in your flock, vaccination is a ‘no brainer’.
“In fact, at current market values, when you consider the cost of the loss of just one lamb from orf would cover the cost of vaccinating more than 125 lambs, the decision to vaccinate this season should be an easy one for all shepherds.”
Mr Robinson also urges farmers to use the vaccine correctly. “If your flock has had cases of orf in the past, the best disease management strategy this year is to vaccinate before the disease gets a hold in this season’s lambs.
This limits the disease’s impact on a flock and an annual flock vaccination should be carried out thereafter. But the vaccine must be used correctly for it to be effective,” he stressed.
“Ewes should be vaccinated at least seven weeks before lambing. Young lambs can be vaccinated at any time from birth. It is important to use the scratch applicator between the top of the foreleg and the chest wall - and not to apply the vaccine elsewhere. Make sure your applicator is working correctly - for many it may well be time to source a new one.
“After vaccination, it’s also important to check vaccinated animals for scabs at the vaccination site seven to 10 days afterwards. A row of scabs along the scratched area of skin indicates vaccination has been successful.
“If no scabs are observed, vaccination technique may have been incorrect, or possibly the vaccine improperly stored, or it may be the vaccinated animal is already immune. But if a ‘take’ has not been observed, re-vaccination should be considered.
“Scabivax Forte is a live vaccine, so do not scratch lambs under the rear leg because they will be able to rub the vaccination site with their faces and potentially infect themselves with the orf virus.
“The disease can be transmitted from scabs that develop at the vaccination site for up to seven weeks,” he says.