Autumn sheep movements pose major scab transmission threat

Autumn sheep movements are a major transmission route for sheep scab infestation, although symptoms may not show for several weeks or months, according to 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.

The three steps are:

(1) With new and returning sheep, yard them for 24 to 48 hours while they are treated.

(2) Treat all sheep with an injectable ML medication at the dosage rate for sheep scab and, at the same time, a levamisole (yellow) drench.

(3) 24 to 48 hours after treatment, turn out onto pasture that has already carried sheep this year. Keep the treated new arrivals 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 the sheep are still quarantined.

According to SAC sheep specialist Dr John Vipond, scab is undetectable in its early stages. "You cannot rely on your eyes to avoid bringing it onto the 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 with 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 foot bath as they leave the lorry," she says. "Then, keeping new arrivals separate for four weeks will allow most diseases that 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, Pfizer vet Dave Gilbert advises farmers to consult their veterinary practice or a suitably qualified person (SQP) at an animal medicines supplier.