Weight loss in adult cows Flashcards
Johne’s disease
- also known as “paratuberculosis”
- inncurable disease of cattle and other ruminants
- caused by Mycobacterium avium subsp. paratuberculosis (MAP)
- controversial association with Crohn’s disease in humans
– some evidence both ways - can find MAP in pasteurized milk
- still (currently) no convincing evidence of causality
- potential major reputational risk to dairy/meat industries
- don’t find much of the organism in muscle and well destroyed by cooking - mostly just circulates in the gut
Johne’s disease presentation / CS
- characterised by wasting and d+
- granulomatous enteritis
- slow/long course
CS:
- d+ (intermittent becoming chronic)
- bubbly d+ thought to be associated with Johne’s, although normal for d+
- decreased production (i.e. milk yield)
- weight loss/emaciation
- +/- oedema (e.g. bottle jaw) (due to protein loss through the gut)
- dz normally develops at 2-6y/o
– rare to see clinical dz before 1st calving, and very old cows (>7) rarely get it
Johne’s - course of dz
- infection -> carriage -> subclinical -> clinical
- clinically affected animals = high likelihood of shedding
- carrier animals = low likelihood of shedding
- ~80% natural infections in 1st month of life, therefore control is about protecting replacement calves early on in life
- little increase in resistance after 1y/o
- for every wasting cow likely to have 4-5 cows in the production loss category
Subclinical impacts of Johne’s
- effects on fertility
- drop in milk production, etc
- intermittent shedding during this phase
Johne’s - sources of infection
- faeces from shedding cattle*
- colostrum milk from infected cattle
- faeces from shedding goats/sheep (esp goats, but d+ not as much of a CS, more just wasting)
- environment and fomite spread
- wildlife reservoirs (deer & rabbits, not a massive risk)
Ddx of weight loss and diarrhoea in cows
- liver fluke
- peritonitis
- displaced abomasum
- abdominal neoplasia
- chronic salmonellosis
- parasitic gastroenteritis
- copper deficiency
Liver fluke
- often group problem (but always has to have 1st case)
- can see peripheral oedema (as would in Johne’s)
- lab work very useful for differentiation
Peritonitis
- may find other signs (abdo pain, pyrexia), but not always
- TRP esp difficult to diagnose, but normally no d+
- tends to be very chronic in cattle - very slowly progressive so fits with weight and production loss
Displaced abomasum
- normally much more acute and with decreased yield more evident/severe
- fairly easy to rule out clinical exam (decreased rumen turnover, ‘ping’)
- but can be intermittent/chronic
Abdominal neoplasia
- rare in cattle
- can present very similarly to Johne’s
- would fit for 1 off sporadic case in an older cow
Chronic salmonellosis
- fairly rare
- farm history of salmonellosis may be useful
Parasitic gastroenteritis
- very rarely causes CS in adult cattle (they usually get effective immunity to it as they get older)
- almost always presents as a group problem
Copper deficiency
- usually group problem
- would normally expect milder group-level signs (e.g. infertility?) before
Diagnosing Johne’s
- detect MAP in faeces
- detect immune response to MAP
Detecting MAP in faeces
- directly demonstrates risk of transmission
- MAP only intermittently shed in faeces, so sensitivity quite poor, better in clinical cases
- usually PCR (culture slow/expensive, smear inaccurate)
- mostly used as a confirmatory test
- pooled samples occasionally used as herd-level diagnostic
- 20-65% sensitivity
- > 99% specificity
- £25 per test
- Pooled faecal samples rarely used in practice
Detecting immune response to MAP
- currently only detection of Ab (in milk or blood)
- generally higher Se than faecal testing
- Sp slightly lower (~99%)
- cheaper and quicker than faecal testing
- blood testing mostly for individual clinical cases and beef herd screening
- milk testing commonly used for dairy herd screening
– often uses lower threshold for positive - 20-90% sensitivity (sensitivity gets higher the closer you get to clinical dz)
- > 97-99%
- £2-5 per test
Managing Johne’s dz - clinical cases
- no tx, prognosis hopeless
- survival time variable, may get brief remission
- major risk to other animals (calves)
- high fibre diet can help the d+ but it will get worse again
Managing Johne’s dz - at herd level
- main goal is to minimise exposure of youngstock (<1y?) to potential sources of infection
– slurry (spreading slurry on pasture can spread infection)
– colostrum, milk
– fomites and pasture
– other species - MAP is pretty resilient - it can survive in the right environment for over a year
- direct vertical transmission has also been demonstrated
Every 3m testing of the entire herd - any animal with non-negative test get managed differently - calves never used as colostrum, colostrum not fed to other calves
Recommendations to minimise spread of Johne’s
- Test the colostrum quality with a brix refractometer (22%) or colostrometer.
- Make sure the calves that are being turned out are on fresh pasture – not following adult cows or had slurry spread on it.
- Ensure good biosecurity – more boot dips, hand washing, different clothes, wheel washes, etc.
- Clean PPE, gloves when managing the calves.
- Have a separate sick cow pen away from the dry cow.
- Smaller pens in the large straw yard to separate high risk from low risk – muck out the dry cow yard at least weekly.
- Move to a system where everything calves in an individual pen and in between cows muck it out and disinfect.
- Routine milk antibody testing for Johne’s.
- If you have a cow that has tested positive, then don’t put its colostrum into the pool for calves.
- Pasteurise the colostrum if sticking with pooling it.
- Move to completely individual colostrum feeding – then one cow can only infect a maximum of one calf.
- Reduce stocking density.
- Don’t put J3,4,5 in the group calving yard – give birth somewhere completely separate.
- Don’t breed replacements from the positive cows – breed for beef
Managing Johne’s dz - biosecurity
- avoid Johne’s entering a naive farm
- fomite spread
- wildlife
- slurry spreaders
- neighbours
Johne’s milk antibody testing: Categorisation
J0 - At least 2 repeat negative ELISA tests
J1 - Only one test but negative result
J2 - ELISA negative currently but has had a positive result in previous three tests
J3 - ELISA negative currently but has had a positive on previous test
J4 - ELISA positive but first positive test result
J5 - Repeat ELISA positive test results - at least 2 positives
