Johne’s Disease Flashcards
What type of disease is Johne’s Disease?
Incurable disease of cattle and ruminants
What is Johne’s Disease caused by?
•Mycobacterium avium subsp. paratuberculosis (MAP)
What is Johne’s disease characterised by?
- Wasting and diarrhoea
- Granulomatous enteritis
- Slow/long course
What is Johne’s Disease also known as?
paratuberculosis
What is the relationship between Johne’s disease and humans?
- 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
What is the course of disease for Johne’s Disease?
Infection - carriage - subclinical - clinical
What are the clinical signs?
- 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
- 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?
- Nutritional problem
- Liver fluke
- Left displaced abomasum
- PGE (gut worms)
- Trace element deficiency
- Toxic mastitis
- Salmonellosis
What differentials do you consider for a cow with chronic D+, weight loss, reduced yield? (8)
- Liver fluke
- Parasitic gastroenteritis
- Peritonitis
- Displaced abomasum
- Copper deficiency
- Abdominal neoplasia
- Chronic salmonellosis
What condition is usually a group problem and unusual in adults?
Parasitic Gastroenteritis
Why is peritonitis low on the differentials for a cow with chronic D+, weight loss ana reduced yield?
Would expect to find other signs e.g. abd pain, pain on rectal exam
TRP? – can be difficult to diagnose, norm no D+
Why is a displaced abomasum low on the differential list for chronic D+, weight loss and low yield?
Normally more acute, drop in yield more severe, low rumen turnover, “ping”
What type or problem and what else is seen (other than chronci D+, weight loss and low yield) for copper deficiency?
Usually a group problem
Would normally expect milder group level signs first (e.g. infertility)
+/- diarrhoea
Which 2 conditions are pretty rare?
- Liver fluke
- Parasitic gastroenteritis
- Peritonitis
- Displaced abomasum
- Copper deficiency
- Abdominal neoplasia
- Chronic salmonellosis
- Abdominal neoplasia
- Chronic salmonellosis
What is the course of disease for Johne’s disease? Draw a graph
What are the sources of infection or Johne’s disease? state where the clinical significane is uncertain (5) (2)
- Faeces from shedding cattle
- Faeces from shedding goats/sheep
- Colostrum/milk from infected cattle
- Environment/fomites *
- Wildlife reservoirs? *
What are the 2 basic idea to approaching a Johne’s disease diagnosis?
- Detect MAP in faeces
- Detect immune response to MAP
Name 3 advantages to detecting MAP for Johne’s disease diagnosis (4)
- Demonstrates shedding/danger of transmission
- Excellent specificity
- Sensitive methods of detection available
- Can use pooled samples
Name 2 disadvantages for detecting AP for Johne’s disease diagnosis (3)
- 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
- Often doesn’t occur until late in disease
- Insensitive techniques for detection are also available!
- Some tests have long turnaround times
How can we detect MAP? (3) What are the positives and negatives of this?
- 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
How can we go about immunodiagnosis? Discuss the positives ane negatives
- 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%
How do we approach treatment in an individual with Johne’s disease?
- No treatment
- Survival time from diagnosis very variable
- May get brief remission
- Usually cull as soon as possible
What are the 2 main objectives when there is Johne’s disease in the herd?
- 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!
What is the main ocus in a positive herd?
Prevent transmission
What is the main focus in a negative Johne’s disease?
Maintain herd biosecurity
What is the aim of preventing tranmision?
- Aim: Separate youngstock up to 1yr of age from potential sources of infection…
- Slurry
- Colostrum, milk
- Other species
- Fomite spread
- Contaminated pasture
- Vertical
How can we prevent new infection?
- 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!
How can we maintain biosecurity?
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?
What is the most common test and cull schemes?
- 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!
Name 4 problems of vaccinating (5)
- 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
What things do we need to discuss with a farmer if there is a confirmed case?
- Calves fed on her milk
- Where did she come from (home/bought)?
- Look out for other clinical cases
How can we prevent Johne’s on a UK level?
The National Johne’s Management Plan
How does Johne’s present in other species?
- 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
