Johne’s Disease

Question 1

What type of disease is Johne’s Disease?

Answer 1

Incurable disease of cattle and ruminants

Question 2

What is Johne’s Disease caused by?

Answer 2

•Mycobacterium avium subsp. paratuberculosis (MAP)

Question 3

What is Johne’s disease characterised by?

Answer 3

• Wasting and diarrhoea
• Granulomatous enteritis
• Slow/long course

Question 4

What is Johne’s Disease also known as?

Answer 4

paratuberculosis

Question 5

What is the relationship between Johne’s disease and humans?

Answer 5

• Controversial association with Crohn’s disease in humans
• Some evidence both ways
• Can find MAP in pasteurized milk
• No convincing evidence of causality
• Potential major reputational risk to dairy/meat industries

Question 6

What is the course of disease for Johne’s Disease?

Answer 6

Infection - carriage - subclinical - clinical

Question 7

What are the clinical signs?

Answer 7

• Diarrhoea
  
  • Intermittent becoming chronic
• Decreased production
  
  • i.e. milk yield
• Weight loss/emaciation
• +/- oedema (e.g. “bottle jaw”)
• Disease normally develops at 2-6 years of age

Question 8

• Presented at routine farm visit
• “Pet” high SCC cow, milk used to feed calves for last lactation
• Calved 2 months ago
• Appears to be losing a lot of weight
• Diarrhoea evident
• “Bubbly” appearance
• Otherwise NAD on clinical exam….

What other diagnoses might we consider?

Answer 8

• Nutritional problem
• Liver fluke
• Left displaced abomasum
• PGE (gut worms)
• Trace element deficiency
• Toxic mastitis
• Salmonellosis

Question 9

What differentials do you consider for a cow with chronic D+, weight loss, reduced yield? (8)

Answer 9

• Liver fluke
• Parasitic gastroenteritis
• Peritonitis
• Displaced abomasum
• Copper deficiency
• Abdominal neoplasia
• Chronic salmonellosis

Question 10

What condition is usually a group problem and unusual in adults?

Answer 10

Parasitic Gastroenteritis

Question 11

Why is peritonitis low on the differentials for a cow with chronic D+, weight loss ana reduced yield?

Answer 11

Would expect to find other signs e.g. abd pain, pain on rectal exam

TRP? – can be difficult to diagnose, norm no D+

Question 12

Why is a displaced abomasum low on the differential list for chronic D+, weight loss and low yield?

Answer 12

Normally more acute, drop in yield more severe, low rumen turnover, “ping”

Question 13

What type or problem and what else is seen (other than chronci D+, weight loss and low yield) for copper deficiency?

Answer 13

Usually a group problem

Would normally expect milder group level signs first (e.g. infertility)

+/- diarrhoea

Question 14

Which 2 conditions are pretty rare?

• Liver fluke
• Parasitic gastroenteritis
• Peritonitis
• Displaced abomasum
• Copper deficiency
• Abdominal neoplasia
• Chronic salmonellosis

Answer 14

• Abdominal neoplasia
• Chronic salmonellosis

Question 15

What is the course of disease for Johne’s disease? Draw a graph

Answer 15

Question 16

What are the sources of infection or Johne’s disease? state where the clinical significane is uncertain (5) (2)

Answer 16

• Faeces from shedding cattle
• Faeces from shedding goats/sheep
• Colostrum/milk from infected cattle
• Environment/fomites *
• Wildlife reservoirs? *

Question 17

What are the 2 basic idea to approaching a Johne’s disease diagnosis?

Answer 17

• Detect MAP in faeces
• Detect immune response to MAP

Question 18

Name 3 advantages to detecting MAP for Johne’s disease diagnosis (4)

Answer 18

• Demonstrates shedding/danger of transmission
• Excellent specificity
• Sensitive methods of detection available
• Can use pooled samples

Question 19

Name 2 disadvantages for detecting AP for Johne’s disease diagnosis (3)

Answer 19

• Faecal shedding…
  
  • Often doesn’t occur until late in disease
    
    • Is unpredictable and can be intermittent
    • Will detect very few animals early in the course of infection
• Insensitive techniques for detection are also available!
• Some tests have long turnaround times

Question 20

How can we detect MAP? (3) What are the positives and negatives of this?

Answer 20

• ZN staining of faecal smear
  
  • Very low sensitivity
  • Dependant on skill of operator
• Faecal culture
  
  • Reasonable chance of detecting MAP if it is present
  • Long turnaround time
  • Expensive
• Polymerase chain reaction (PCR)
  • Good chance of detecting MAP if it is present
  • Cheaper and quicker cf culture

Question 21

How can we go about immunodiagnosis? Discuss the positives ane negatives

Answer 21

• Currently only Ab evaluation commercially available
  
  • Blood or milk
• More sensitive early in course of infection than faecal testing
• Still not great chance of detecting asymptomatic carrier animals
• Cheap, easy and quick
• Specificity ~99%

Question 22

How do we approach treatment in an individual with Johne’s disease?

Answer 22

• No treatment
• Survival time from diagnosis very variable
• May get brief remission
• Usually cull as soon as possible

Question 23

What are the 2 main objectives when there is Johne’s disease in the herd?

Answer 23

• Prevent transmission
  
  • Focus on replacement heifer calves
  • Several potential sources of infection (faeces>>colostrum>milk>other)
• Maintain herd biosecurity
  
  • Prevent buying in disease
  • Still important for positive herds!

Question 24

What is the main ocus in a positive herd?

Answer 24

Prevent transmission

Question 25

What is the main focus in a negative Johne's disease?

Answer 25

Maintain herd biosecurity

Question 26

What is the aim of preventing tranmision?

Answer 26

* Aim: Separate youngstock up to 1yr of age from potential sources of infection… * Slurry * Colostrum, milk * Other species * Fomite spread * Contaminated pasture * Vertical

Question 27

How can we prevent new infection?

Answer 27

* Can we try to “target” these measures? * Identify high risk cows? * Individual milk sample Ab testing * Reduces number of cows needing intensive calving management * Can we try to “target” these measures? * Quarterly individual cow milk Ab testing now common * Identifies animals at increased/high risk of shedding * BUT imperfect test!

Question 28

How can we maintain biosecurity?

Answer 28

Bear in mind potential sources and animals susceptible to infection Buying in stock! * Minimising the risk * Knowing about the source * Testing the individual? * Closed herd?

Question 29

What is the most common test and cull schemes?

Answer 29

* Various ways to do * Blood Ab test the commonest for this * May speed up rate of eradication in herd * but won’t eradicate disease by itself!

Question 30

Name 4 problems of vaccinating (5)

Answer 30

* Prevents disease not infection * Potential route to preventing new infection * Can import vaccine under license from Spain * Need to keep going for several generations * ??? Interference with TB test results ??? * ? False positives

Question 31

What things do we need to discuss with a farmer if there is a confirmed case?

Answer 31

* Calves fed on her milk * Where did she come from (home/bought)? * Look out for other clinical cases

Question 32

How can we prevent Johne's on a UK level?

Answer 32

The National Johne's Management Plan

Question 33

How does Johne's present in other species?

Answer 33

* Common in goats and sheep (probably under-diagnosed) * Disease looks similar * Often diarrhoea less noticeable, just wt loss * Routes of transmission and course of disease are similar * Control harder as more difficult to manage what happens around birth * Differential diagnoses will vary between species