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Maedi Visna (MV) – Is the Sheep Industry Listening?

04 July 2014

UK - Vets from Scotland’s Rural College are appealing to sheep farmers across the UK to be alert to an increasing threat from Maedi Visna (MV); an incurable viral disease of sheep.

They fear many in the industry have an out of sight out of mind attitude to the threat which can affect all sheep breeds.

Specialists working within Veterinary Services, part of the College’s SAC Consulting Division, say a high level of infection has been found in some flocks and there is evidence of infection increasing throughout the sheep population, including Wales and South West England. Amongst samples recently submitted for analysis, in one flock 11 out of 12 ewes tested positive and in another 41 out of 48 were positive.

“It is true to say that these flocks suspected an issue and were prepared to deal with it,” saidIan Pritchard, Health Schemes Manager.

“But how many flocks out there could have an issue but have not, or are afraid to look for MV? Producers cannot afford to be complacent and underestimate the risks of the disease. It could have a severe effect on the productivity and economics of their sheep system.”

The name Maedi Visna derives from two Icelandic words which describe the main clinical signs of pneumonia and wasting. It is a chronic disease of sheep caused by a retrovirus and was introduced into the UK through imported animals. Difficult to diagnose and contagious it has since spread, especially in commercial flocks. It can lead to poor body condition, poorer fertility, increased mastitis, smaller and weaker lambs and increased mortality. There is no cure for MV and no vaccine.

According to Mr Pritchard the warning signs are out there.

“Statistics from veterinary laboratories in England, Wales and Scotland show an increase in outbreaks. Several larger flocks have encountered MV to their cost. One example is a flock with 8% ewe mortality, a high cull rate due to mastitis and poor condition resulting in a high net replacement cost, and lambs often with poorer growth rates. Another large flock has estimated the cost, of a 20-40 per cent reduction in flock productivity predominantly due to MV, at between £30,000 and £50,000."

Sheep farmers are advised to take precautions seriously. At a basic level they should ensure boundary fences are secure to avoid contact with other flocks. Any new sheep brought on the farm should be quarantined and tested before they join the main flock. It is also important to investigate any cases of ill thrift in ewes.

“A group of 12 poorer, thin ewes can be blood tested for evidence of the disease”, says Mr Pritchard. “But, where possible, it is far better if flockmasters ensure they buy in any breeding replacements from MV accredited flocks.”

The MV accreditation scheme, run by Premium Sheep and Goat Health Scheme, has over 2,600 members who test their sheep on a regular basis following the rules and conditions of the scheme.
Ian Pritchard recommends that anyone selling breeding sheep should consider joining the accreditation scheme as customers may wish reassurance that they are not buying in MV.

"If you are already a member of the MV accreditation scheme then you are at a very low risk providing you follow the scheme’s stringent biosecurity regulations that are designed to protect your flock and the flocks of your customers,” says Mr Pritchard.

"The British sheep flock is renowned for the high quality of its product – let it be renowned for high standards of animal health. Do not let MV get a foothold."

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