Ovine Johne’s DiseaseGina 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 OJD75% 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 2000

• 2014• 93 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)

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 20140

10

20

30

40

50

60

70

80

90

100No of infected properties in WA

No of infected properties

Where is OJD?SW WA 2008-2012

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

• GudairR

• Single 1ml injection lasts for life

• Administered prior to exposure (lambs @ 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 2011• 27% 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