Sheep farmers unaware of orf exposure

Sheep farmers who have never experienced an outbreak of orf are still likely to have a number of infected ewes and lambs in their flock, according to research.

The ongoing study, being carried out by the Moredun Institutein Edinburgh, found a high percentage of ewes from a large number of flocks tested positive for exposure to the virus.

The Institute’s Dr Colin McInnes says this came as a big surprise to flock owners who were adamant they’d never had an outbreak of orf – when clearly they had.

“We found it difficult to find ewes that hadn’t been exposed to orf in these flocks,” he says.

“Although it’s now too late for spring lambing flocks to be vaccinated against orf, these results prove farmers must remain aware of the risk of an outbreak. They need to be conscious of how easy it is for this highly contagious virus to spread among other sheep and the people working with them.”

Symptoms

The orf virus causes scabs and blisters to form on the lips and nostrils of infected sheep. It is most widely seen in lambs, where severe cases can lead to unthriftiness and even trigger other diseases. Affected lambs may starve if they are unable to suckle, and when ewes develop the scab virus on their teats it’s inevitable they will resist being suckled and become mastitic.

There is no specific treatment for orf, but some lambs may require antibiotic. Sheep and lambs that contract the virus don’t gain lifelong immunity, but future infections are usually less severe.

Orf can also infect humans by creating blister-like sores on any part of the body that comes into contact with the virus – usually the hands – and can cause general feelings of sickness and weakness, lasting several weeks.

Spread

Vets say it’s important for sheep farmers to fully appreciate the highly contagious nature of the virus to ensure its effective control and reduce the risk of further spread.

“Because it’s so contagious there are very clear rules that have to be followed meticulously when lambs or ewes are found to be infected. And because the treatment is a live orf vaccine, strict routines have to be followed for all treated sheep after vaccination,” says Dr McInnes.

Prevention

Despite the findings of the Moredun Institute research, vets advise sheep farmers not to vaccinate as a preventative measure when the virus has never been a problem. When one or two cases are still occurring in a flock it’s advisable to maintain a vaccination policy.

While the eight-week period needed for the vaccine to become effective now makes it too late for most farmers to protect their ewes against the disease, there are measures that can be undertaken to avoid an outbreak.

“When flock owners become concerned about orf they could undertake preventative vaccination of all their lambs within the first week of birth, using the traditional method of scratching the vaccine into the animal.

“But it’s essential that all lambs are vaccinated. Any that aren’t could catch the virus from those that have been treated,” says Dr McInnes.

The orf virus has also been found on sheep fleeces and in woodwork and can thrive in dry conditions. “One option for sheep farmers to reduce the chances of an orf outbreak – and where vaccination isn’t feasible – is to thoroughly steam clean the lambing shed and any inside areas where ewes and lambs may be housed,” says Dr McInnes.

Vet Matt Colston of Frame, Swift and Partners, says a bad outbreak of orf is “potentially devastating” when it erupts in the middle of a hectic lambing period.

“A strict routine must be followed when lambs are vaccinated. They must be kept away from any un-vaccinated lambs, and that regime must be continued for eight weeks when ewes and lambs are brought in or gathered in any way. They must not be mixed or the vaccinated lambs will spread the virus to un-vaccinated animals.

“We urge farmers not to be tempted to try and treat orf with anything other than approved vaccines and to seek guidance when the first signs appear.”

The current cost of orf vaccine is around 60p per dose. An applicator costs about £17.