Reassess pre-lambing worming treatments, farmers urged
The immune system of some ewes can weaken in late pregnancy.
The Sustainable Control of Parasites in Sheep (SCOPS) group has asked farmers to consider their anthelmintic use as lambing season approaches.
The group warns that unnecessary use of worming treatments could lead to resistance among flocks of sheep in the future.
Providing they are in good body condition and are well-fed, most adult ewes will have developed an immunity to roundworms by the time they are 12-18 months old. This immunity means they are often able to handle parasite burden without frequent treatment.
However, due to the strain of late pregnancy, the immune system of some ewes may weaken.
This ‘spring rise’ does not directly harm ewes, however the eggs do pass out in their dung. This poses a contamination risk to lambs, which will have no immunity to roundworms.
SCOPS recommends that worming treatments are specifically targeted to the ewes which are most at risk.
It suggests that the treatment is focused on ewes shedding the most eggs, rather than treating an entire herd. Ewes with lower body condition, particularly those which have lost condition during pre-lambing, are most likely to shed worm eggs in their faeces.
Farmers are advised to take regular faecal egg counts (FECs) in the weeks leading up to lambing season to detect whether the egg output has risen.
This information can then be used to decide whether to treat the animal and, if so, when and what to use. Farmers should speak to their veterinary surgeon, suitably qualified person or animal health advisor if they are unsure.
Nerys Wright, independent sheep consultant, said: “The most important reason for not using anthelmintics unnecessarily in ewes is to protect flocks from resistance in the long term, prolonging the efficacy of the products available, to ensure they are still available and effective in future years.
“Of course there is also a cost element to worming adult ewes and this is also a way of controlling costs without a detrimental impact on flock performance.”
Image © Shutterstock
BSAVA is to partner with BVA Live (11-12 June 2026) to champion clinical research.
