Johne's Flashcards
What is the current estimated prevalence of Johne’s in UK dairy herds?
30-70%
How is Johne’s transmitted?
Intrauterine, infected colostrum, faecal-oral (major), carriers
Incubation period?
Often manifests around 3-5 years old
What clinical signs are associated with the disease?
Decreased milk yield, weight loss (maintain appetite), profuse diarrhoea, bottle jaw (submandibular oedema)
Name the bacteria which causes Johne’s.
Mycobacterium avium subsp. paratuberculosis
What pathological features characterise the disease?
MAP in macrophages, granuloma in distal ileum and LNs, diffuse gut thickening.
Describe the characteristics of MAP.
Slow growth (acid fast), resistant, environmental growth, sheep and cow strains.
What are the four stages of MAP associated disease?
- Non-infectious (silent)
- Infected (sub-clinical) but not shedding
- Infectious and shedding (failure of CMI)
- Resistence
How can MAP infection be diagnosed?
Faecal culture - time consuming
ELISA - 30-40% sensitivity
PCR
Clinical signs
Which specific culture medium can be used to detect MAP?
Herrolds egg
How much bacteria are MAP super-shedders capable of shedding?
> 1 million cfu/g faeces
Describe the route of infection in neonates of MAP.
In utero
Poor environmental cleanliness - dam/ cow faeces
Dam/ waste colostrum
Calf-calf
Test and cull
Annual ELISA test - cull positives and recent daughters.
Poor ELISA sensitivity
Test and manage
Repeat ELISA and categorise (persistent infected)
How can Johne’s spread at calving be reduced?
Avoid mixing age groups Cleanliness Snatch calving Don't use waste milk Ensure adequate colostrum intake Individual penning
