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Flashcards in Johnes Disease Deck (26)
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1
Q

What are the clinical signs of Johne’s disease?

A

Profuse diarrhoea
Weight loss
Remain bright and eating
Individual animals affected

2
Q

What are the production losses associated with Johne’s disease?

A
Clinical cases - loss through culling and production losses
Subclinical cases = over 50% of total losses
* reduced milk yield
* mastitis and high SCC
* lameness 
* infertility 
* LDAs 
* increased culling rate
3
Q

What are the routes of Johne’s disease transmission?

A

Oro- faecal = major route
Colostrum and milk
In uterus

4
Q

When is the most ‘at risk’ period of a cow acquiring Johne’s?

A

Newborn calf between 0-4 weeks

5
Q

For every clinical case, how many other animals can you expect to be infected and shedding into the environment?

A

10-25

6
Q

At what age to clinical signs begin to show and what is the peak age of clinical infection?

A

Over 3 years of age

Peak age - 5 years

7
Q

What factor may cause a Johne’s infected cow to switch from a th1 response to a th2 response?

A

Stress

8
Q

Describe the pathogenesis of Johne’s disease.

A
  1. Infection acquired in early life
  2. MAP enters macrophages
  3. Th1 immune response occurs which controls MAP infection
  4. Stressor occurs
  5. Th1 response switches to a humoral immune response
  6. Antibodies are produced against MAP = loss of immune control
  7. MAP proliferates and the animal is shedding
  8. Anergy - end stage disease, complete loss of control
9
Q

What categories of shredders are there?

A

Low shredders
High shedders
Super shedders

10
Q

What diagnostic tests are there for Johne’s and what do they tell you?

A

Faecal culture / PCR - detects shedders

ELISA - detects antibody levels = high probability they are shedding

11
Q

What is the gold standard test for Johne’s disease?

A

Faecal culture or PCR
Sensitivity - 50-60%

But takes time and cannot pick up the infected but non-infectious group

12
Q

What test must you use to pick up the infected but not infectious group of animals?

A

Gamma interferon test

13
Q

What is the ELISAs strengths and weaknesses?

A

Good for detecting infectious animals - good for control
Poor for detecting infected but non infectious animals
- but ELISA inky detects 40% of faecal culture positive animals

14
Q

How can you change calf management to reduce the risk of calves becoming infected?

A
Snatch calving 
Don't feed pooled colostrum 
Feed the dam's colostrum 
Clean calving pens
Individual calf hutches 
Keep young stock separate from adults 
No waste milk feeding
15
Q

How can you reduce the risk of calves getting Johne’s from colostrum and milk?

A

Collect colostrum from heifers / young cows / ELISA negative
Feed frozen colostrum
Do not feed pooled colostrum
Pasteurise waste milk and colostrum (25s not 15s for Johne’s)

16
Q

What are the two strategies of Johne’s control and what must you combine them with?

A

IMPROVEMENTS IN HYGIENE

  1. Test and cull
  2. Test and manage
17
Q

Describe a test and cull strategy for Johne’s management.

A

Preform an annual ELISA test on all animals under 2 years old

  • cull all positives
  • cull all recent daughters of positives

Poor ELISA sensitivity
If not combined with other measures, management is likely to fail

18
Q

Describe a test and manage strategy for controlling Johne’s disease.

A

Milk ELISAs are performed 3x a year and cows categorised

Low risk (green) - currently non infectious
Medium risk (yellow) - low level shedders 
High risk (red) - high level shedders 

These cows are managed separately at calving

MUST BE WITH IMPROVED HYGIENE

19
Q

What beef breeds have Johne’s problems?

A

Welsh black

Limousin

20
Q

What is different about beef cattle Johne’s management to dairy management?

A

Pedigree herds have Cattle Health Scheme

If Johne’s free it will be declared on the Cattle Health Certificate

21
Q

What should you advise a beef farmer when purchasing?

A

Only buy from low risk herds (CHECS 1)
No history of disease
Test negative on at least 3 occasions
ELISA test the whole herd for bull purchase

22
Q

How can a beef farmer improve his farm management to prevent to spread of Johne’s?

A

Outdoor calving
Cull daughters
Clip and clean teats before calving
Ensure bull is free from disease

23
Q

What should you advise a farmer to do to maintain good biosecurity to keep Johne’s out?

A

Only buy from clean herds - test negative on 3 occasions
ELISA test whole herd for bull purchase
*testing an individual can lead to false confidence

Vaccinate - reduces shedding, new infections and cases
- 1 to 28 days of age in the brisket

24
Q

What test might MAP affect?

A

To testing

Falsely increases the size of the M. avium top lump

25
Q

How long should you wait between TB testing and ELISA testing?

A

60 days

26
Q

How should you manage calves born to shedding cows?

A

Snatch and wash

Or Euthanise