A recent informal survey has suggested that there is an increasing problem with sheep scab in our local area alongside concern over the effectiveness of available treatments.

What is Sheep Scab?

Sheep scab is caused by a non-burrowing skin mite, Psoroptes ovis. This mite feeds on skin exudates, not blood. The presence of mite feces causes an intense allergic reaction in the skin leading to itchy, scabby lesions at the base of the wool.

Sheep are extremely itchy and therefore find it hard to do anything else other than rub and scratch. This constant level of intense discomfort means they do not eat or rest appropriately. They lose condition quickly, are less productive and become more prone to other diseases. Sheep scab is a major welfare issue and can lead to huge financial loss.

Infection can spread easily by sheep-to-sheep contact, at markets and in livestock lorries and can live for 17 days in the environment. It can survive on fence posts, branches, in sheds and fields. It is easily transmittable on shared moorland, shared trailers, equipment and even overalls. It can be brought onto your farm on purchased stock that appear healthy with up to 60% of the flock infected before you see any clinical signs.

Diagnosis is key

Diagnosis can be made easily with help from your vet by:

- Skin scrapes taken from the edge of the lesion and examined under a microscope

- Blood sample ELISA test which can be done from 2 weeks post exposure. This can also be used on incoming animals alongside your quarantine protocol.

Treatment - please get this right!

It is so important to treat correctly as there are now areas in the UK where Scab mites are showing resistance to all injectable treatments. Not being able to treat this debilitating disease is devastating for both farmers and the animals affected.

We have two options only, OP plunge dips or injectable macrocyclic lactones.

Plunge dips

Plunge dips contain highly toxic ingredients and must be used under supervision of someone holding an NPTC Certificate of competence in safe use of sheep dips.  They have very important and detailed instructions which must be followed for the safety of everyone involved in the procedure as well as the environment. For this treatment to be effective and remain effective for future use it must be done correctly with animals plunged for the appropriate amount of time and dip replenished frequently as instructed in the data sheet.

Injectable Macrocytic lactones (ML’s)

The MLs available for injection include: Ivermectin, Doramectin, Moxidectin 1% and Moxidectin 2%. There are very specific instructions for each product. You must dose for the heaviest animal in the group to avoid under dosing and treat all sheep that have been in contact with any infected animals.

Unfortunately, there is growing resistance to this group of injectable drugs. It is therefore very important to treat with the appropriate dose schedule and respect the rules to prevent reinfection. If we do not use these drugs correctly, we will be left with only plunge dips as a treatment option.

It is also vital to report any suspected treatment failures to your vet so they can be investigated.

For more information or to speak to one of the team at Derwent Vale please ring 01751 469343.

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