Johnes Disease:

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Johnes Disease

An Emerging Issue for the Dairy Industry
Lecture 5
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Topics

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

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Introduction
Johnes 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
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Johnes Disease
- Chronic intestinal tract disease - Long
incubation, 2 to 6 yrs Causal Bacterium MAP -
mycobacterium (avium) paratuberculosis Related to
some TB organisms
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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

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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

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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.)

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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
• gt 50 herds showing molecular signal

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International Prevalence

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

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Clinical Symptoms

• lt5 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?

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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

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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

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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
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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
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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

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

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Replacement Policy

• Keep infection outside
• Replace from within own herd
• Dont retain heifers from suspect cows
• Purchase only from clean herds

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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

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Calf Feeding Policy

• Do not bulk colostrum
• - dams 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?

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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

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Water Supply

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

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Prevention - Summarised

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

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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 _at_72 C -25sec

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Is Johnes a Food Safety Issue
Crohns 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 Crohns
No firm link established, evidence inconclusive
-but worrying
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Class Exercise
Johnes Control What are the responsibilities
of - Department of Agriculture - Processors -
Vets/Farm Advisers - Farmers _
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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.