Tool 11.16 Common sheep diseases and their causes

Disease

Common signs

Predisposing factors

Management

Annual ryegrass toxicity

High stepping gait, staggering, collapse, trembling

Ingestion of annual ryegrass infested by toxic bacterium

No drug treatment is effective. Mildly affected sheep should be left undisturbed with access to water, feed and shade, and removal from the source of the toxin. Sheep in lateral recumbency should be euthanised.

Hypocalcaemia in ewes

Ewes cast after handling, neck turned back, muscle tremors, staggering gait, respond to calcium injection

Late pregnant, especially older ewes, heavily grain fed

Avoid handling within 4 weeks of lambing, add limestone 1.5% to grain, feed good quality lucerne hay if handling, treat cast sheep with calcium injection or calcium drench (10+ grams)

Perennial ryegrass staggers

Staggering, recumbent

Grazing high endophyte ryegrass

Remove sheep from toxic pastures and avoid stressful conditions, dilute toxic pasture with supplements, closely supervise cast sheep, replace high-risk pastures with safe pastures

Pink eye

Weeping cloudy eyes

Dust, summer grass seed infested pasture

Treat affected lambs with antibiotics, avoid high-risk grass seed pastures and dusty conditions

Vibrio (Campylobacter)

Late-term abortion storms with up to 30% of ewes aborting, but usually less than this

Occasionally occurs in flocks especially with grain feeding or intensive rotational grazing

Run maiden ewes with older ewes before mating to ensure maiden ewes are exposed before pregnancy or adopt a vaccination program for maiden ewes

Yersiniosis

Scouring in weaners

Stress in weaners in cold, wet weather

Treat with antibiotic (consult your veterinarian), avoid stressful conditions for weaners