Page 847 - The Veterinary Care of the Horse

Topical treatment

• Topical pyrethroids e.g. Deosect applied at 2-week intervals
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VetBooks.ir • Fipronil spray (Frontline )
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• 1% selenium sulphide washes every fifth day for three treatments. The shampoo is left on

for 10 minutes before rinsing off thoroughly

• Lime sulphur dip weekly for 5 weeks.

With any topical treatment applied to inflamed skin it is sensible to perform a patch test first
(see page 566). Sufficient spray should be used to thoroughly wet the hair and skin surface.

Repeat treatments are needed to deal with newly hatched mites, as the life cycle is
approximately 3 weeks.

Systemic treatment

• injection of doramectin, which is a drug licensed for the control of parasites in cattle and
sheep. Two injections may be given 10–14 days apart

• oral ivermectin paste weekly for 4 weeks at 0.2–0.3 mg/kg (1−1 times the normal

worming dose) helps to reduce the numbers of mites where they have penetrated the skin
in chronic, long-standing cases.

• antibiotics are occasionally necessary to control secondary infection.

Control

The mites can live off the host for up to 10 weeks. When the horse is treated, the bedding
should be removed and the box sprayed with a suitable parasiticide recommended by your

vet. All in-contact horses should be treated, especially those sharing a grooming kit (which
should also be treated).

Prognosis

Many horses experience relief as soon as the treatment starts. However, it can be difficult to
completely eliminate the mites in heavily feathered animals. Some will need periodic

treatment. Other horses can tolerate the mite without showing any obvious symptoms.
However, they may experience a low level of discomfort causing them to kick out
unpredictably or occasionally stamp their feet.