Vets are advising sheep farmers to investigate any ill-thift in ewes at tupping, after test results from SAC Consulting Services revealed a quarter of sheep were carrying the deadly maedi visna (MV) virus.

The tests were carried out on flocks throughout England, although vets are warning the disease is also present in Scotland and Wales.

Maedi visna facts

  • Caused by a highly contagious virus
  • No cure or vaccine and is fatal
  • Symptoms in lambs include increased mortality, decreased growth rates from reduced colostrum intake, reduced fertility and increase in culling rates
  • Sheep do not normally show signs until they are adults, as the virus has a long incubation period. The main signs are paralysis, wasting, arthritis and chronic mastitis
  • Transmitted by shedding of the virus in milk, colostrum, faeces and respiratory secretions, contaminated water or feed when uninfected sheep are housed or at pasture with infected sheep.

See also: Maedi visna sheep losses double

Most flocks tested were cross-breeds and Mules and the owners reported ewes being thin, breathless and sometimes lame.

The ewe mortality rates were increased and lambing percentages and growth rates reduced. 

MV is a chronic viral disease which was introduced into the UK through imported sheep.

It has since spread, especially in commercial flocks.

The condition is highly contagious, difficult to diagnose and is fatal.

Brian Hosie, head of SAC Consulting Veterinary Services, says in the run up to tupping it is important farmers and crofters quickly work out why some ewes may not be performing.

He suggests producers condition score their ewes and manage them accordingly.

“This will allow farmers to identify ewes which are not improving,” he says.  

Other diseases asides from MV can cause ill-thrift in sheep flocks.

These include liver fluke, worms, trace element deficiency, Johne’s disease and ovine pulmonary adenocarcinoma – also known as Jaagsiekte. 

He says farmers should get their vets to test underperforming stock by taking samples of faeces or blood for analysis or through arranging for some animals to be examined postmortem.