Johne’s Disease Flashcards
(33 cards)
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
