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Johne’s Disease:

Johne’s Disease:. An Emerging Issue for the Dairy Industry. Lecture 5 . Topics. Organism Involved Legal Status Prevalence Symptoms/Economic Consequences Diagnosis/Testing Transmission On Farm Control Processor Controls Potential (Unproven) link to Crohn’s Disease

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Johne’s Disease:

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  1. Johne’s Disease: An Emerging Issue for the Dairy Industry Lecture 5

  2. Topics • Organism Involved • Legal Status • Prevalence • Symptoms/Economic Consequences • Diagnosis/Testing • Transmission • On Farm Control • Processor Controls • Potential (Unproven) link to Crohn’s Disease • Implications for Dairy Sector

  3. Introduction “Johne’s disease is not at all widespread. It does occur, however, and as the years go by it will become more and more common and will places a great tax on the cattle industry” Beach and Hastings 1922

  4. Johne’s Disease -Chronic intestinal tract disease - Long incubation, 2 to 6 yrs Causal Bacterium MAP - mycobacterium (avium) paratuberculosis Related to some TB organisms

  5. MAP • Causes contagious infectious disease (Johnes) • Causes chronic inflammation of intestine • thickening of intestinal wall, impairs nutrient absorbtion • long incubation (2-6yrs) • affects cattle, sheep, goats, deer, (wildlife) • non treatable

  6. Legal Position • Compulsory notifiable since 1955 • Slaughter of an infected animal or suspected of being infected (e.g. recent progeny and compensation) • Post 1992 - Single Market - unrestricted importation from Europe (many dairy animals imported) • Voluntary import protocol

  7. Prevalence in Ireland • 1932 - 1982 = 92 animals (mainly imported) • 1995 = ~7 animals • 2001 = 54 animals in16 herds (26 from 1 herd) • 2002 = 100 animals/34 herds (+ 1 herd depop.)

  8. MAP an Imported Problem • DVO investigations frequently reveals import connection • Random sample (2000) • 3 counties, 143 herds • 30% herds animal positive (ELISA) • Research project (2001/02) • 1 county,100 herds • > 50% herds showing molecular signal

  9. International Prevalence • Denmark: almost half herds positive • Holland: 50 -80 percent herds infected? • New Zealand 16 - 50 • Imported stock are a high risk

  10. Clinical Symptoms • <5% of infected animals develop clinical symptoms • Not known what triggers clinical cases (stress) • Non clinical animals can: can be carriers/shedders • Symptoms vary - not easy to diagnose • Intermittent or persistent scouring • Progressive weight loss/ Drop in milk yield • Unhealthy appearance/rough coat • Appetite normal until well advanced?

  11. Economic Consequences -Animals • Ill thrift • Reduced milk production (6-16%) • Increased Mastitis? • Reproductive performance? • Premature culling/Increased Replacement Costs • Lower cull slaughter wt • Veterinary costs

  12. Diagnosis/Testing/ Vaccination • Veterinary diagnosis of clinical cases (difficult?) • Faecal culture: slow (16wks to culture MAP), expensive • PCR Test (Polymerase Chain Reaction) detect DNA • ELISA (Enzyme Linked Immunosorbent Assay) detect antibodies to screen milk or blood - false positives • Specificity (false positive), sensitivity (False negatives) • Vaccination interfere with TB testing

  13. Transmission - primary mode of infection Ingestion of contaminated faeces from infected animal shedding M.paratuberculosis: feed, water, bedding, dirty teats, dirty surfaces etc Calves most vulnerable to picking up infection

  14. Other Transmission Routes • Colostrum /Milk if dam has advanced clinical disease • In utero ( if cow has advanced clinical disease, 20 -50 of foetuses will be infected) • Using colostrum from other herds • Spreading manure from other herds • Semen? Contagious, spreads silently over a long time

  15. Severity of Shedding • Advanced Clinical Disease • Heavy shedder up to 500bn organisms/day • 36% of clinical cows will shed in milk/colostrum • Light shedders - • 9% of samples infected

  16. Survival of MAP Organism MAP can survive for a long time outside animal Cattle Faeces: 246 days Water: up to 17 months Soil: pH (acidity) seems to be a factor.

  17. Class ExerciseJohnes Risk Assessment Categorise Irish dairy herds on the basis of their risk of having Johnes. Categories: High Risk Moderate Risk Low Risk

  18. Risk Assessment Profile for Johnes Highest Risk: Herds with imported animals High Risk: Herds with offspring of imported animals Moderate Risk: Herds with bought in animals Low Risk: Closed Herds

  19. Class Exercise Objective at farm level is to block transmission from the MOST infectious to the MOST susceptible MOST of the time Develop a checklist of key control practices to block Johnes transmission in a dairy herd

  20. On Farm Controls • Replacement Heifer Rearing/Sourcing • Infected colostrum or milk • Ingestion of faecal material • Housing contaminated with adult faeces • Pasture used by adults and calves • Spreading manure on pastures grazed by calves • Infected water supplies

  21. Replacement Policy • “Keep infection outside” • Replace from within own herd • Don’t retain heifers from suspect cows • Purchase only from ‘clean’ herds

  22. Young Calves (Repl. Heifers) • Wash cows teats and udder before milking colostrum • Separate calf from cow as soon as possible after birth • Clean bedding to minimise faecal contact • Offer roughage (hay) to stop calves eating bedding • Avoid contact with faeces from adult herd

  23. Calf Feeding Policy • Do not bulk colostrum • - dam’s colostrum only • - colostrum from cows with at least 6 lactations • Do not feed bulk whole milk to replacement heifers • -feed milk replacer to female calves?

  24. Housing and Hygiene • House calves away from adult cows • Do not use equipment or utensils which have been in contact with adult cows to feed heifer calves • Do not allow replacements on to adult cow pasture

  25. Water Supply • Adult cattle may infect a pond or stream • - prevent access to such sources • Provide a clean water supply for all stock

  26. Prevention - Summarised • Hygiene at calf rearing • Contact between calves and adult herd • Not feed bulk whole milk to replacements • Manage manure

  27. Processor Controls • Pasteurisation temperature & duration critical • MAP is a heat resistant organism • Pasteurisation Regulations: 72 C -15 secs • Low levels of MAP found in pasteurised milk • FSAI recommend pasteurisation @72 C -25sec

  28. Is Johnes a Food Safety Issue Crohn’s Disease is a bowel disease in humans Overall incidence 5.6 cases per 100,000 Severe and very unpleasant condition Cause unknown, maybe infectious agent like MAP MAP (Johnes) organism foundin Crohn’s No firm link established, evidence inconclusive -but worrying

  29. Class Exercise Johnes Control: What are the responsibilities of: - Department of Agriculture - Processors - Vets/Farm Advisers - Farmers _

  30. Herd Bio-security • Bio security – protecting herd health • Protect against disease and parasites • Two levels: individual farm national biosecurity • Certain diseases/parasites can have major: economic, financial and food chain consequences.

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