Johne's disease

Question 1

What is seen with johnes disease?

Answer 1

• Older animals >3yr old
• Often after calving (stress)
• Profuse diarrhoea (often w bubbles)
• Weight loss
• Animal remains bright and eating

Question 2

Whats the most important transmission route for johnes?

Answer 2

• New born calves (0-4wks)

Question 3

What are the infection routes in young calves?

Answer 3

• In utero.
• Dirty environment.
• Dam faeces =
  – Teats (wipe before calf suckles?)
  – Contamination of environment
• Dam colostrum.
• Pooled colostrum.
• Waste milk.
• Calf to calf

Question 4

What are ‘super-shedders’?

Answer 4

• > 1million cfu/g faeces
• 50kg faeces per day
• 50 billion cfu per day
• Theoretically can infect 50,000 calves a day

Question 5

How can johnes be diagnosed?

Answer 5

• Faecal culture +/or PCR - time + cost
• ELISA - detects antibody (high probability of being a shedder)
• Actiphage
• Gamma interferon - detect cell mediated immunity

Question 6

What cows would you select to test for johnes?

Answer 6

• The cows most likely to be +ve =
• thin
• mastitis
• lame
• poor yield
• older

Question 7

What are the different Johnes classification?

Answer 7

• J0 = repeat ELISA -ve - minimum 2 tests
• J1 = ELISA -ve - one test only
• J2 = ELISA -ve but positive within previous 3 tests
• J3 = ELISA -ve but positive on previous test
• J4 = ELISA +ve - 1st positive test
• J5 = Repeat ELISA +ve

Question 8

What is the risk of cross-reaction of TB + Johnes

Answer 8

• With TB test (mammalian) = false +ve in TB test
• With TB test (avian) = false -ve in TB test
• Should not Johnes ELISA test soon after TB test

Question 9

How can you control johnes disease?

Answer 9

• Reduce transmission to youngstock by =
• reducing risk factors
• cull animals likely to be shedding the infection
• possible faecal PCR testing of youngstock

Question 10

How can you reduce risk factors of johnes?

Answer 10

• Avoid faeces.
• Calving area – snatch calving at birth.
• Clean calving pens.
• Calf pens / hutches – individual (?) clean.
• Keep young stock separate from adults.
• Colostrum – only feed dam’s colostrum.
• No pooled colostrum feeding.
• No waste milk feeding – throw it

Question 11

What are other risk factors?

Answer 11

• Slurry & manure being spread on grazing.
  (where else are you going to put it?)
• Water courses – esp. stagnant ponds.
• Contamination of feeds.
• Other hosts =
  – Sheep ?
  – Wildlife – rabbits, deer