Ectoparasitesâexternal parasites affecting the skin, wool, and fleeceâare a significant source of suffering in sheep. Blowfly strike, sheep scab, and lice infestation cause persistent pain, irritation, and distress, and can rapidly become life-threatening when severe. Effective prevention and prompt treatment are welfare priorities.
Blowfly strike occurs when blowflies (principally Lucilia sericata) lay eggs in moist, soiled wool, and hatching maggots feed on skin tissue. The condition causes excruciating pain, tissue destruction, toxaemia, and death within days if untreated. Behavioral signsâtail wagging, biting at flanks, withdrawalâshould prompt immediate inspection. Risk is highest in summer, particularly in wet conditions, in sheep with dag (faecal contamination around the tail), or those with skin wounds. Prevention includes: dagging (removing soiled fleece), preventive insecticide application (organophosphate dips, pour-ons), and targeted breeding for shorter wool around the breach.
Sheep scab, caused by the mite Psoroptes ovis, is a notifiable disease in some countries. Mites cause intense pruritus (itching), with affected sheep rubbing against fences, biting at their fleece, and losing wool. If untreated, skin lesions expand, secondary bacterial infection develops, and animals lose condition rapidly. Treatment with macrocyclic lactones (injected) or organophosphate dip is effective but requires correct timing and dosing. A single untreated affected sheep can spread scab to an entire flock.
Biting and sucking lice cause significant irritation and fleece damage. Affected sheep rub and bite themselves, causing wool loss and skin damage. Treatment with appropriate insecticides is effective; biosecurity prevents re-introduction from purchased animals.
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