NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare.

Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.

Chorioptic mange

Chorioptic mange is a potentially important cause of poor breeding soundness in rams, characterised by superficial, exudative, fissured lesions on the lower third of the scrotum. Handling of the scrotum often initiates a nibble response. Irritable areas of hair loss, skin thickening, exudation and scab formation are also sometimes seen on the lower limbs and poll of both ewes and rams. The disease is caused by the sheep-adapted mange mite, Chorioptes bovis and the skin lesions are associated with a hypersensitivity reaction.

MANGE LESIONS ON THE SCROTUM OF A SUFFOLK RAM

SEVERE EXUDATATION OF THE LOWER LIMB OF A SUFFOLK RAM

MANGE LESION ON THE POLL OF A SHETLAND RAM

The diagnosis of chorioptic mange is usually based on the clinical signs, but can be confirmed by the identification of mites in superficial skin scrapings. Mites are only present in small numbers, so scrapings from several animals and from several sites are required.

The re-emergence of chorioptic mange in British sheep is probably associated with the withdrawal of compulsory plunge dipping for the control of sheep scab. Systemic endectocides appear to be ineffective for the control of scrotal mange, probably due to the feeding behaviour of the mite. Overseas, prevention and treatment is usually achieved by the topical application of an organophosphate dip. Your vet can provide advice about the significance and management of chorioptic mange in your flock.

Neil Sargison BA VetMB DSHP FRCVS