Ectoparasitic Diseases (excluding sheep scab)

Headfly

·         Can affect grazing patterns and cause sheep to isolate themselves in the shade. Often standing with head held lower, to one side or frequent head shaking/ear movements.

·         Kicking at the head can often cause damage to the skin around the neck and ears. The discomfort caused can reduce quality of fleece and reduce ovulation and litter size.

·         Ear tagging or notching should be done away from fly season.

·         Treatment includes using pour-on fly control (such as cis cypermethrin or deltamethrin) applied to the sheep (especially horned sheep) ready for the fly season.

Blowfly

·         (Cutaneous myiasis, maggots) can cause death if neglected. This kind of neglect could lead to prosecution.

·         Typical behaviour seen of affected lambs is attempting to nibble at flanks/tailhead. Sheep can be depressed and isolated. Maggots can be seen on the blackened skin and a putrid smell is associated.

·         Adult flies are attracted to area adjacent to the faecal staining surrounding the perineum and less commonly, flesh degraded by footrot, dermatophilosis lesions and urine scalding around the prepuce.

·         Treatment includes using a plunge dip and dip wash after layer of wool has been removed to show the infected area. Before preventative measures using chemicals,  grazing programmes can reduce the build-up of helminth larvae on pastures which may cause diarrhoea (and attract more flies). Also, in adult sheep, shearing during late May/June removes the attraction at peak blowfly season.

Lice (Pediculosis)

·         Most affected during late winter in sheep with poor body condition kept under unhygienic conditions. Most common infestation is by the chewing louse Bovicola ovis which may cause disrupted feeding patterns, damage to fleece and self-inflicted trauma.

·         Spread occurs by close contact. The louse reproduces slowly and therefore lice build up over several months.

·         Differential diagnosis include Psoroptic mange (sheep scab) which presents similar symptoms.

·         Treatment includes using a plunge dip of organophosphate preparation (which is used for other ailments such as sheep scab, cutaneous myiasis and headfly.)

·         Lice presence indicates very poor biosecurity measures  and overall flock plan.

Chorioptic Mange

·         Potentially important cause of poor breeding soundness in rams.

·         Characterised by superficial, exudative, fissured lesions on the lower third of the scrotum.

·         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.

·         Caused by sheep-adapted mange mite, Chorioptes bovis and the skin lesions are associated with hypersensitivity reaction.