Following recent showers across some parts of the UK including South East and North West England, the Sustainable Control of Parasites in Sheep (SCOPS) are urging sheep farmers to be extra vigilant in monitoring parasite burdens and lamb performance.
Nerys Wright, Technical Adviser for SCOPS, warns that the combination of recent rainfall and earlier dry conditions could create a perfect storm for increased worm challenges on pasture.
“Rainfall creates ideal conditions for worm larvae to survive and migrate up the grass stem, increasing the risk of ingestion by grazing lambs,” says Nerys. “We’re encouraging farmers to carry out regular faecal egg counts (FECs) to monitor parasite burden and make informed treatment decisions.”
However, she stresses that FECs should be interpreted alongside lamb condition and performance. After a prolonged dry spell, large numbers of immature worms may be present and cause clinical disease before a high FEC is detected. This makes visual assessment and consideration of nutritional status equally important in decision-making.
The earlier dry weather also limited grass growth on many farms, adding nutritional stress to lambs. “A lamb’s immune system is closely linked to its nutritional status,” explains Nerys. “Lambs under nutritional stress are less able to withstand a parasite challenge.”
Rebecca Mearns, Parasitology Vet Lead at the Animal and Plant Health Agency (APHA), adds that while some areas are now seeing high FECs following the rain, others remain low—highlighting the importance of testing and monitoring rather than assuming worms are the cause of poor performance.
“It’s essential to consider other factors like grass quality and availability,” says Rebecca. “Not all poor performance is due to worms, and blanket treatments can do more harm than good in the long term.”
SCOPS is also reminding farmers in England to take advantage of the DEFRA-funded Worming Treatment Check (WTC) scheme, available through the Animal Health and Welfare Pathway Review. In Scotland, a similar scheme supports farmers in preparing for sustainable farming, while Wales currently does not have a comparable programme.
To benefit from funded testing, worm egg counts must be high enough to justify treatment. “The key message remains: check your FECs before undertaking the WTC to ensure the timing is right and the results are meaningful,” says Rebecca.
SCOPS continues to promote a targeted, evidence-based approach to worm control, including the use of FECs, regular monitoring of lamb weight gain, grazing management, and leaving a proportion of lambs untreated to maintain refugia and slow resistance development.
“By testing regularly and acting early, farmers can avoid performance losses and reduce the need for whole-flock treatments,” Nerys concludes. “It’s about being strategic and responsive to the conditions on your farm.”