Almost a quarter of ewes tested for maedi visna (MV) by SAC Consulting Veterinary Services are carrying the disease, which could mean large numbers of livestock are at threat of illthrift this winter.
The tests were carried out on flocks throughout England, although vets are warning the disease is also present in Scotland and Wales.
Most flocks tested were crossbreeds 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 that 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 fatal.
As flock owners and shepherds are preparing their flocks for mating in the weeks ahead, SAC Consulting is urging them to investigate any cases of illthrift in ewes with their veterinary surgeon.
“Ewes should be in good condition at tupping this year, given the good weather we have seen this autumn,” said Brian Hosie, head of SAC Consulting. “This makes it all the more important farmers and crofters quickly work out why some ewes may not be performing.”
Farmers worried about their flock should condition score their ewes and manage them accordingly; this will allow them to identify ewes which are not improving.
Many diseases other than MV can cause illthrift in sheep flocks, including liver fluke, worms, trace element deficiency, Johne’s disease and ovine pulmonary adenocarcinoma/Jaagsiekte.
Veterinary surgeons can find out what is causing illthrift through collecting samples of faeces or blood for analysis, or through arranging for some animals to be examined postmortem. Often, more than one condition is responsible; however, the results will allow flock owners and shepherds to set up a suitable treatment and control programme for the flock.