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WORKING
TOGETHER
FOR A HEALTHIER FUTURE...
9
LIVESTOCK MATTERS
JOHNE’S DISEASE
Veterinary Surgeon
Kate Brodie
XLVets Practice
Drove Farm Vets
KATE BRODIE,
DROVE FARM VETS
Johne’s disease: find your
herd status and start a
control plan
Vet Kate Brodie of Drove Farm Vets would like all her dairy
farming clients to test their herds for the presence of Johne’s disease.
One starting point is a simple milk screening of 30 cows. It doesn’t
cost a lot of money and will enable a control strategy to be put in place
to prevent the spread of this performance-depressing disease.
‘Johne's is a disease that farmers often don't
want to discuss‘ says Kate. ‘But it’s a disease
that is not easy to eradicate and ignoring it is
not the way forward.
‘It is a very important disease to get under
control due to its immuno-suppressive effect:
Johne’s positive cows tend to have higher
SCC, are more likely to get clinical mastitis,
suffer from lameness and may have lower milk
yields too.
‘So if the disease is present, the sooner this is
known, the sooner control strategies can be put
in place.‘
Testing
Johne’s disease is an ‘iceberg’ disease – for
every one clinical case, there will be 10-20
animals that are Johne’s positive at sub-clinical
levels (ie not showing visible signs).
It is caused by
Mycobacterium avium
subspecies
paratuberculosis
, commonly referred
to as MAP. It progressively damages the
intestines, and causes diarrhoea and
weight loss.
MAP is shed in the dung, but not continuously.
Similarly, antibody presence in the blood is
variable. Plus, the clinical signs of infection
only become apparent as cows get older.
’This is why quarterly milk testing on an
ongoing basis, is needed,‘ says Kate. ‘This can
be done for the whole herd, or alternatively, to
start with, on a selection of 30 animals most
likely to be Johne’s positive – older cows, and
those with high cell counts, lameness or cases
of mastitis.
‘Animals can test Johne’s-negative, and then
become positive as the disease takes hold.
This is what makes the disease so tricky to
eradicate from a herd.
‘But once a cow has had a positive result,
then she should be kept on the farmer’s radar,
whatever the next result says!’