Johne's Disease

Question 1

How long can Johne’s live in the environment?

Answer 1

12months in water
2 years in soil

Question 2

What causes Johne’s disease?

Answer 2

Mycobacterium avium subsp paratuberculosis

Question 3

What does johnes causes in cattle?

Answer 3

*Diffuse thickening of distal ileum + colon
*Lymph node involvement
*Thick corrugated intestine

Question 4

What are the clinical signs of johne’s disease?

Answer 4

*Weight loss
*Profuse diarrhoea
*Bright + Alert
*Bottle jaw

Question 5

How is Johne’s diagnosed?

Answer 5

-clinical signs
-loss of immune control
-infectious
-ELISA
-Faecal culture

Question 6

What are the infectious routes of johnes?

Answer 6

• Faecal-oral is major route.
• colostrum & milk
  – by 36% of heavy shedders.
  – by 9% of light shedders.
• Uterine infection.
  – in 20-40% of clinical cases.
  – in 9% cows with no clinical
  signs.

Question 7

What are the complications of Johne’s?

Answer 7

• give 4000kg less milk over lifetime
• milk production reduces in second lactation
• 5X more likely to be lame
• 2X more likely to develop mastitis/ SCC problems
• 1.8 times more likely to suffer digestive/ respiratory disease
  –LDA
  –pneumonia
  –etc. etc

Question 8

What are different tests for MAP?
Mycobacterium avium paratubercluosis

Answer 8

1. Faecal culture (blood and milk also possible)
2. Serology (ELISA)
3. PCR
4. Stained faecal smears
5. Tissue biopsy
6. Postmortem examination

Question 9

What are super shedders?

Answer 9

*Animals that shed >1million cfu/g of faeces
-equivalent to 50billioncfu per day
-Theoretically could infect 50,000 calves a day (as infective does = 100,000cfu)

Question 10

What are the infection routes in baby calves?

Answer 10

• in utero.
• dirty environment.
  – calving area
• dam faeces:
  – teat & skin
  – contamination of environment
• dam colostrum.
• pooled colostrum.
• waste milk.
• calf to calf

Question 11

What are minor risk factors?

Answer 11

• slurry & manure on land grazed by youngstock
• watercourses –esp stagnant ponds.
• contamination of feeds.
• other hosts:
  –sheep ?
  –wildlife –rabbits ?

Question 12

What is the problem with cross reactivity of Johnes with M. bovis?

Answer 12

*MAP may give false -ve to TB test
=reduces TB test sensitivity
*TB test will give false +ve to MAP ELISA test

Question 13

What is the human equivalent of Johne’s disease?

Answer 13

Crohne’s disease