14 June 2002

Beware of risks following Maedi Visna outbreak

By Jonathan Long

CHECKING the health status of sheep before purchasing replacements is essential, following an outbreak of the potentially devastating condition Maedi Visna (MV) in pedigree flocks in Scotland, according to Barti Synge of SAC.

A number of Texel flocks, all MV accredited under the Sheep and Goat Health Scheme (SGHS), are believed to have been affected by the outbreak, although Mr Synge denies that the breed is more susceptible to the disease than other breeds.

"The majority of infection comes from contact with non-MV accredited sheep, although investigating the source of any outbreak is difficult. The current outbreak, however, is believed to have stemmed from one flock which sold stock to several more," says Mr Synge.

The condition is made up to two constituent parts, Maedi, which is a chronic pneumonia and Visna, which is a disease of the nervous system. The clinical symptoms include significant weight loss, inco-ordination, arthritis and sub-clinical mastitis. The condition can cause death of the affected animal and is generally seen in older animals, according to Mr Synge.

Losses to the disease can be large, and Mr Synge reports that some leading pedigree flocks have reported losses of more than £100,000.

"Infection is spread by direct contact, drinking contaminated colostrum or milk or on contaminated equipment.

"There have been major problems in America with MV and economic losses there have been immense," adds Colin Macaldowie of Moredun Research Institute.

While there is no logical reason for a sudden upsurge in the condition this year, Mr Macaldowie suggests that frequent movements between flocks could have enflamed the current outbreak.

"The nature of the outbreak suggests that it could be more down to management practices than any other factor.

"Commercial sheep producers, as well as pedigree breeders, need to think seriously about what they buy because they may be buying in trouble for future years. MV can be slow to show up in flocks, but many flocks are now experiencing serious losses," says Mr Synge. &#42

MAEDIVISNATHREAT

&#8226 Slow to show up.

&#8226 Mainly in older sheep.

&#8226 Potential financial losses.