Early-season sheep sales are a timely reminder for farmers to be aware of the risk that bought-in sheep pose for scab infestation.

Autumn sheep movements are a serious transmission route for sheep scab infestation, although symptoms may not show for several weeks or months, says Pfizer vet Dave Gilbert. By following the Sustainable Control of Parasites in Sheep (SCOPS) three-step plan for all bought-in sheep and those returning from tack, he says farmers can minimise the risk to their own flocks from both sheep scab and anthelmintic-resistant worms.

First, all new and returning sheep should be yarded for 24 to 48 hours while they are treated. Second, all sheep should be treated with an injectable macrocyclic lactone medication at the dosage rate for sheep scab and, at the same time, a levamisole (yellow) drench.

Then 24 to 48 hours after treatment, sheep should be turned out on to pasture that has already carried sheep this year. New arrivals should be kept separate from all other sheep on the farm for at least three weeks.

Farmers who prefer to use an OP dip against sheep scab should treat with both an ML and levamisole drench at step two, then dip 14 days later while sheep are still quarantined.

SAC sheep specialist John Vipond says scab is undetectable in its early stages. “You cannot rely on your eyes to avoid bringing it on to farm,” he says. “Sheep using transport that has not been cleaned thoroughly between loads can pick up scab mites. So, even if you know uninfected sheep were loaded, they may arrive infected. Quarantine and an effective treatment for scab for all newly arriving sheep is essential to ensure the farm stays clear of the disease.”

ADAS principal consultant and sheep specialist Kate Phillips says farmers should always assume the worst that bought in sheep are carrying sheep scab, resistant worms and foot rot, unless they have a cast-iron guarantee from the breeder that they are free from these diseases.

“Treat with the most appropriate endo- and ecto-parasiticides and walk all sheep through a footbath as they leave the lorry,” she says. “Then, keeping new arrivals separate for four weeks will allow most diseases they may be carrying to emerge and be treated appropriately before mixing with the home flock. Quarantine pays dividends by saving money on unnecessary whole-flock treatments.”

For advice about treatment choices, farmers should consult their vet practice or a suitably qualified person at an animal medicines supplier.