Volume 22 • Issue 05 • 2018
on production.
4. However, the disease leads to increased
mortalities, and should not be regarded
unimportant.
We as veterinarians should NOT put our own
heads also under the sand about BLV infection in
our dairies. If the importing country requires BLV
free status, we cannot export from infected herds.
Period. Perhaps some others can chip in here, but
my opinion is that the only way you can certify
animals free of BLV infection from your herd
would be to put sero-negative animals under
strict quarantine far away from the positive herd,
and re-test them 4-monthly after that: once ALL
quarantined animals tested sero-negative for 2
years that quarantined herd is probably free from
the infection.
MJ - 3 May 2017
We have recently discovered EBL in a client’s
herd. The farmer is wanting to eradicate the
disease and has sold most of the positive cows,
with the remaining being marked and separated
from the rest of the herd. Are there any labs in SA
that test for Bovine Leucosis from milk samples?
What would be the best interval between testing
in order to eradicate the disease?
WG - 4 May 2017
Testing frequency is a trade-off between the cost
and the benefit of identifying and removing/
separating positive animals sooner. Three to
six monthly intervals were used in most of the
EU countries where the disease was eradicated.
It is important to remember that as you reduce
the prevalence in the herd the number of animals
that need to be tested increases (i.e. your costs
increase as you move towards achieving your
goal!).
The blood test is done by a number of labs in SA
and it is worth shopping around for the best price
if you are doing large numbers of samples at once.
There is currently no milk test commercially
available in the UK. Sello and I used one supplied
by Zoetis for our research and there are others on
the market internationally, so perhaps one of the
labs will introduce it if there is sufficient demand
from vets? In order to eradicate the disease
successfully it is important to have a robust
programme in place to minimise disease spread
alongside the test and cull/separate policy. You
will need to consider the following:
1. Preventing heifers from becoming infected
from their dam (calving management and
colostrum).
2. Preventing
spread
between
heifers
(dehorning and other procedures)
3. Reducing transmission in the milking herd
(needles, rectal gloves etc.)
ERADICATION AND CONTROL
RM - 26 Jun 2009
I have a herd with a high incidence of Clinical
cases. We bled the herd, and pooled samples(10/
tube), to save on tests. All groups of ten tested
positive. It appears that this is almost futile. With
such a high incidence, it is prob not worthwhile
eradicating. This is a dairy herd of 600 Holstein
cows in milk. We have already instituted seperate
gloves for rectals, new needle every Rx, etc.
GB - 1 Jun 2011
I am partly responsible for the health of the dairy
cows at the University of Pretoria proefplaas. At
some stage in the past, a cow or cows infected
with Bovine Leukosis was/were introduced into
the herd. I bled all animals, including very small
calves, and submitted samples for ELISA. Now, 11
animals (out of 112) are marginally BLV positive
on ELISA. They show titres of 35-39 (where
greater than 40 is considered positive and 30-40
is considered suspicious.)
The remainder of animals are negative on ELISA.
On occasion, clinical cases are presented to the
Production Animal Clinic here at Onderstepoort
with a raging lymphocytosis/lymphoblastosis
and spinal abscesses, discrete tumours etc. The
cardiac form has also been diagnosed. I intend to
retest the ELISA positives using AGID (primarily
for my own edification) as well as a control sample
of ELISA negatives to see what the correlation is.
Once I've done this, all positive animals will be
removed from the herd.
We are also implementing biosecurity measures
against transmission (fresh rectal glove per cow,
separation of positive and negative animals, new
needle per animal, etc) These animals are used in
various trials, so they need to be BLV negative to
remove potential confounding factors, so trying
to live with the disease is not an option. Do any
of you have any thoughts or personal experiences
with BLV that you would mind sharing with me?
TS – 1 Jun 2011
Your situation obviously differs from most
situations in the field where one has to live with
the disease. If memory serves, leucosis is also
transmitted to 20% of calves born from positive
mothers, so take this into consideration in your
attempt to eradicate the disease from the herd.
WG - 13 Sep 2013
There is not currently much known about the
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