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 Implications for Dairy Sector

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

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

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

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

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

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

International Prevalence Denmark: almost half herds positive Holland: percent herds infected? New Zealand Imported stock are a high risk

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?

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

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

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

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

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

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.

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

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

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

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

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

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

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?

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

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

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

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 C -25sec

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

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

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.