Sheep farmers have been urged to take steps to prevent nematodirus gut worms infecting lambs this spring.
The warning from Scotland’s Rural College – SRUC – comes after nematodirus battus gut worms were found in a lamb sent for a post-mortem examination to the St Boswells veterinary investigation centre.
SRUC said the worms are already killing lambs in some areas after a recent rise in spring temperatures had triggered a mass hatch of worm eggs. The eggs, which are eaten with grass, pose a serious threat to lambs aged between six and 12 weeks old.
SRUC said the lambs most at risk of infection are those born in February or March, and grazing permanent or heavily stocked pastures.
The rural college said outbreaks of the disease were most common on fields grazed by young lambs every year in the spring.
“The worms, which live in the intestines, cause a severe watery scour which can result in rapid death,” said SAC Consulting sheep vet Heather Stevenson.
“As these parasites are capable of killing lambs before eggs appear in the dung, any unexplained deaths should be investigated, for example by sending carcases to SAC Consulting disease surveillance centres for post-mortem examination.”
She urged farmers to take steps to prevent disease outbreaks and investigate any cases of severe diarrhoea in lambs with their vets.
Farmers are advised to treat high-risk lambs with an appropriate wormer from six weeks of age to prevent disease.
“It is important farmers take advice on which product to use and if resistance is suspected dung samples should be checked for eggs 10 days after treatment,” said SRUC.
The college said all five wormer groups were effective against nematodirus battus however some resistance has been found in Group 1 drenches, and use of Groups 4 and 5 is not advised for sole treatment of nematodirus battus to avoid overuse of these new wormer groups.
SRUC said any suggestion that treatment had been ineffective should be investigated by collecting 10 individual faecal samples for a pooled worm egg count.
“When an outbreak of clinical disease occurs and lambs remain on the same pasture, two doses of wormer seven to 10 days apart are recommended,” added SRUC.
“Where there is a severe problem, the best solution may be to move the ewes and lambs to lower-risk pasture if available.”