Vets from Scotland’s Rural College (SRUC) are urging farmers to test their commercial sheep flocks for maedi-visna (MV) – a viral disease for which there is no cure or vaccine.

They warn SRUC’s testing has identified a worrying number of infected flocks, suggesting infection is spreading throughout the sector.

SRUC veterinary investigations officer Lynn Gibson said farmers had started to take notice of previous warnings about the disease.

“Commercial flocks from throughout the UK have taken the opportunity to screen their animals using the MV diagnostic test package,” she said.

In most cases screening was performed in flocks where there were suspicions of MV infection, of which 23% (seven of the 31 of the flocks tested) proved to be correct.

The owners of six of the flocks had reported seeing signs of breathlessness in adult sheep, lameness and swollen joints.

As signs of MV are not usually seen until around half the sheep in a flock are infected, SRUC vets believe it is likely these flocks have a high level of infection.

The name maedi-visna derives from two Icelandic words describing the main clinical signs of pneumonia and wasting or ill-thrift.

Contagious and difficult to diagnose, MV can lead to poor body condition; poor fertility; increased mastitis; smaller, weaker lambs and increased deaths. There is no cure or vaccine.

According to Ms Gibson MV also has a long incubation period. “This means the clinical signs can take years to develop, by which time one single animal can have spread infection through the flock.

“The first indications of a problem can include an increase in barren ewes or the numbers of thinner sheep, meaning more are being culled from the flock as unproductive.

“Sheep never develop immunity to MV and with no effective treatment or cure the only option with heavily infected flocks is to depopulate and restock from reliable sources.

“We recommend any flock owners finding they have ewes that have lost condition since tupping (mating) time should check for MV. It is something to take seriously, not ignore.”

SRUC recommends concerned flock masters should target test 12 older, thinner animals using the MV diagnostic test to indicate if losses are due to the disease.
Visit the SRUC website to download an MV testing and diagnostic form.
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