Ovine Johne’s Disease Gina Micke BSc BVMS PhD

OJD 1.What is it 2.Where is it 3.Diagnosing the disease 4.Effect on your enterprise 5.Management options

What is OJD? Bacteria = Mycobacterium avium subsp. paratuberculosis Sheep strain (S) – goats, deer, (calves) Cattle strain (C) – goats, deer, alpacas, llamas, camels, (sheep) Found in rabbits & carnivores in Scotland, not in Australia Thickening of intestinal wall  ↓nutrient absorption Chronic wasting Ill-thrift Tail to mob May look like bad case of worms, lack of feed

What is OJD? Taken up by intestine within a few hours of ingestion (grazing; water; contaminated teats) ↓ 9-24 months from infection to shedding in manure ↓ 3-4 years before sheep show any signs of OJD 75% of infected animals show no signs ↓ Death within 3-4 months of clinical signs (“Passive shedding” – persists for 10 days after dosed but doesn’t become infected) Lives ~ 6 weeks outside animal Up to 55 weeks in moist, shady areas 99 – 99.9% lost per month in the sun Spread: stock, vehicles, run-off, foot-wear Trans-placental if ewe clinical Stock <2 years old are most susceptible Lambs Weaners

Where is OJD in WA? First case in WA in infected properties 13 new properties identified 2 cleared of suspect status 114,335 sheep from 292 PICs inspected No clinical disease in <400mm rainfall zone (have infection though)

Where is OJD? SW WA

Diagnosing OJD Index of suspicion Infected neighbours Run off/water courses from infected properties Trading Purchase from high prevalence area Mortality rates/weight loss in adult sheep

Diagnosing OJD Live sheep – faecal culture Pooled faecal sample from 350 adult sheep 14 weeks minimum to run 98% sure of detecting if 2+% infected Faecal PCR Results in 3 weeks Inaccurate at this stage Post-mortem inspection Abattoir inspection of adult sheep

Effect on Your Enterprise Previously loss of market access & stigma Dept. Ag notifiable disease: Category C3 management Established Feasible, or desirable, to manage to limit damage Control measures can prevent disease from increasing or moving to an area that currently is free of disease Southern NSW ~2003/4 MLA project 6.4% ↓in gross margin $7.70/DSE $66/ha (up to +$240/ha) Quoted death rates 2-15% per year NSW quote 20-30% loss by 3yrs of age in cell grazing system Wool and live weight loss ↓ Lambing %

Management Options Where are you at now? Where are your neighbours at – potential for infection or reinfection Your farm environment Wet areas Run-off Risk of introduction Fencing/stray sheep Trading sheep enterprise Origin of breeding & replacement stock MAP – Market Assurance Program Monitored negative (MN) 1, 2 & 3 Tested every 2+ years, 3 –ve tests = MN3 Source of replacement sheep with low risk of OJD Risk assessment for your farm

Management Options Destocking for 15 months, including 2 summers Risks of reinfection????? Long-term vaccination Biosecurity plan Eradication

Management Options Identify low risk paddocks Stubbles/hay Grazed by cattle/OJD vaccinates Grazed by young stock Destocked for 6-12 weeks over summer vs High risk paddocks Wet areas through summer Lots of shade Next to infected neighbours Water course/run-off areas Reduce level of exposure of young stock Narrow joining for early weaning Prepare lambing and weaning paddocks over summer Leave weaning paddock ungrazed or do so with cattle More important to have clean weaner paddocks than lambing paddocks Leave weaned lambs in low risk paddocks for as long as possible Very little shedding by young sheep so pastures remain low risk Rotationally graze with enough time between to allow bacteria to die off Lower stocking rates Graze high risk paddocks with terminal lambs Control – Live with it

Management Options Younger flock structure Decreases pasture contamination Younger animals = less shedding Avoids getting to a clinical stage Minimal weight/wool loss End stage disease ↑↑ shedding in faeces Cull clinically affected sheep or whole mob if high % affected Avoid having young sheep in holding paddocks, use portable yards Crutch ewes pre-lamb to remove faecal contamination from near udder Good ewe nutrition for milk production to limit the need for lamb grazing Minimise other disease/immunosuppression  shedding Avoid feeding on the ground Stray sheep policy Control – Live with it

Management Options Vaccination Reduces adult deaths by >90% Reduces shedding 7x compared to vaccinated animals, or by ~90% Delays onset of shedding by 12 months Doesn’t cure existing disease or prevent shedding in those already infected Doesn’t prevent disease on its own Lambs at between 4-16 weeks of age Control – Live with it

Management Options Delayed response to vaccination On 33/40 farms in NSW, shedding persisted for at least 6 years after a lamb vaccination program started When to start a vaccination program depends on the economic impact on your farm

Management Options Gudair R Single 1ml injection lasts for life Administered prior to exposure 4-16 weeks) Vaccinated sheep identified with V on year colour ear tag if part of SheepMAP Inject subcutaneously high on the neck just behind and below the base of the ear. Do not inject at any other site Oil based killed vaccine – safety syringe to administer Stored in fridge Hygiene & carcass damage important Control – Live with it

Management Options Victoria % of PICs infected 26,964 sheep inspected Victoria 2014 (July-Sept) 11% PICs infected 45,093 sheep inspected Does it all work???

Now What? Know where you’re at Understand the economics of OJD for your property Biosecurity plan for your property Buyer beware National Sheep Health Statement (SHS) SheepMAP

Thanks to… Anna Erickson – Dept. Ag. Narrogin – State OJD Co-ordinator Carey Hobson – LBS Regional Officer, WA Patrick Kluver – LBS, Victoria