Slowing down the rate of resistance

The ban on cypermethrin-based dips in recent weeks has underlined the increasing difficulties of ectoparasite control in sheep flocks.

With sheep scab rife in some areas and cases of lice infestation also on the increase, we need more, not fewer products in the battle to regain control.

Sustainable Control of Parasites (SCOPS) is particularly concerned because to slow development of anthelmintic resistance we need to protect the efficacy of the macrocyclic – lactones (MLs).

This means we need to use this group, which includes the endectocides carefully, for both endo- and ectoparasite control, if we are to minimise the rate at which resistance in the worm population develops.

Inititally, sheep farmers can minimise unnecessary use of MLs by getting a diagnosis before rushing in to treat for scab.

You cannot be certain a sheep has scab without vet diagnosis.

But, every year thousands of sheep are treated on the basis that people think they know.

When you get it wrong it will waste time and money, risk sheep health and increase risk of resistance in future.

Getting a diagnosis is easy.

When you suspect sheep scab, don’t guess.

Contact your vet and arrange for samples to be taken before taking action.

When it comes to dosing in general there are some key actions in the SCOPS recommendations for sheep farmers.

Always make sure you give the full dose.

Treat all incoming sheep with both levamisole (yellow) and macrocyclic-lactone (clear) groups of wormer to remove resistant worms.

It is also advisable to ask your vet to arrange a test for resistance on the farm.

Use anthelmintics only when necessary, as well as using Faecal Egg Count (FEC) monitoring to reduce frequency of treatments.

It’s vital producers choose the right product for the target parasite avoiding unnecessary use of combinations.

Reduce your dependence on anthelmentics, for example, by using grazing strategies and avoid drenching straight on to clean pastures.

Sit down and discuss your worming strategy with your vet and/or adviser – most people are amazed how long it is since they changed their programme.

For more information ask your vet or adviser or visit