Survey is launched to discover extent of MV in UK flock
By Shelley WrightScotland correspondent
A NEW survey, offering free laboratory testing for the first 500 farms to take part, has been launched by SAC in a bid to determine the extent of Maedi Visna in the UK sheep flock.
Brian Hosie, assistant head of SACs vet science division, estimates that at least 100,000 sheep in Britain are now infected with the virus.
Speaking at a Suffolk Sheep Society press conference held in Lanarkshire last week, Mr Hosie said that MV, introduced into the UK in the 1970s, causes symptoms ranging from wasting and chronic mastitis in ewes, to ill-thrift in lambs. And buying sheep which appear healthy is no guarantee because symptoms can take between two and four years to emerge. "By that time, 60% of the flock may already be infected."
The virus is highly contagious, easily transmitted through close contact, lambs suckling infected milk and even by using the same needle for more than one sheep when vaccines are administered," he pointed out.
The last national MV survey was in the mid-1990s and showed that about 1.5% of flocks had the virus present. "In the past year we have seen breakdowns in pedigree flocks and clinical cases in commercial flocks," said Mr Hosie.
A handful of lab tests have just been completed as part of the new survey, and already there is one positive result, confirming the disease is out there.
Adult mortality of up to 20% is common once clinical signs develop, but there are other factors making the disease economically disastrous for producers.
Lamb mortality and reduced growth rate due to lack of colostrum and milk, an increase in culling rate, arthritis, premature births and reduced conception rates are all associated with an outbreak of MV.
An outbreak at one lowland farm resulted in 68% of the flock becoming infected, a 1-4% adult mortality rate and 30% of the potential lamb crop being lost. Total cost was put at £32/ewe and, with infection spread throughout the flock and no cure, the entire flock was slaughtered, he explained.
Vet practices across Scotland and in sheep areas elsewhere in Britain have been sent details on the new survey.
Producers interested in testing their flocks should contact their own vet, who will arrange to visit to collect blood samples from 12 older and thinner animals. Lab charges of £2.05/sample will be free for the first 500 flocks.
Mr Hosie added that one way to keep MV out of flocks is to ensure that replacement stock and rams brought onto a farm are MV accredited. *
• Survey launched.
• Highly contagious.
• Buy accredited stock.needed.
Replacement rams should be MV accredited, says Brian Hosie.