SRUC Vets Concerned at Rise in Incurable Viral Disease in Sheep

Published Wednesday, 28th January 2015 in SAC Consulting news

Sheep and lambs in field

Vets from Scotland’s Rural College believe many commercial sheep flocks could be threatened by a rise in the incurable viral disease Maedi Visna (MV).

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

“Farmers have started to heed our previous warnings about the disease,” says St Boswells based SRUC Veterinary investigation Officer Lynn Gibson “commercial flocks from throughout the UK have taken the opportunity to screen their animals using the MV diagnostic test package.”

In most cases screening was performed in flocks where there were suspicions of MV infection and in 23% (seven of the 31 of the flocks tested) these suspicions unfortunately proved to be correct. The owners of six of these flocks had reported seeing signs including 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 (Myday Vis na) derives from two Icelandic words describing the main clinical signs of pneumonia and wasting or ill-thrift. MV is a chronic disease caused by a retrovirus, introduced to the UK through imported animals. Contagious and difficult to diagnose it can lead to poor body condition; poorer fertility; increased mastitis; smaller, weaker lambs and increased deaths. There is no cure or vaccine.

According to Lynn Gibson MV 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,” says Lynn.

“We recommend any flock owners finding they have ewes which have lost condition since tupping (mating) time should check for MV. It is something to take seriously, not ignore. Disease in sheep flocks reduces productivity and income in a sector already operating on narrow margins.”

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. A similar approach should be taken to sheep showing ill-thrift or reacting badly to exercise.

For further information on Maedi Visna and testing, visit our pages on the Premium Sheep & Goat Health Scheme (PSGHS) and PSGHS Maedi Visna.

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