Oorsig/Review
only bet, but this is discussed in the above article.
Also sounds like EBL can cause some economic
impacts on dairy farms so maybe eradication
attempts are worth it either way, but I guess that
there are field vets that will have an opinion on
this.
TC – 10 Nov 2014
I possibly speak on behalf of many KZN dairy
vets - and maybe some of you guys will add your
pound of flesh. EBL is a disease we live with. The
vast majority of our herds are infected and the
number of clinical cases is minimal. Having said
that we cannot quantify the indirect effect of
immunosuppression and reduced productivity,
though many of our herds which live with the
disease are at the top of our league tables w.r.t.
production and reproductive parameters. In a
perfect world yes, test (which perfect tests??)
and eradicate to achieve negative herd status.
It not being a perfect world we concentrate our
ruthless culling and management strategies
on conditions that are far more serious (in our
experience) to dairy economics, and – coward
that I am – we CAN get a handle on! Frankly
I think the Zim authorities are living in cloud
cuckoo land, but I suppose if one is tasked with
the job of setting up import protocols, one will
dot every i and cross every T. (And thereby miss
out on importing some excellent genetics?!)
As has been discussed in many forums, the
single negative EBL serological result will not
necessarily be conclusive, so those beaurocrats
are simply “going through the motions.” Like
paying your TV licence, it’s the right thing to do.
I would be intrigued to know how free the Zim
dairy herds are of EBL. From what I recall many
countries including many states in the USA have
called time-out on EBL eradication and focused
on other issues. However, this Ruralvet being
an open forum I won’t be offended to receive
alternate viewpoints. Even within our practice
we have slightly varying opinions.
DM - 12 Nov 2014
EBL (Enzootic Bovine Leucosis, caused by Bovine
Leucosis Virus or BLV) appears to be a problem
in SA dairy herds at the moment. The Department
of Production Animal Studies at the Faculty is
currently busy with some surveillance work on
this disease which may shed some more light,
although support from the industry has not been
forthcoming. What I understand is that you will
find it quite hard to get BLV sero-negative herds
nowadays. Please keep in mind:
1. If you find some animals in a herd seropositive
to BLV using the AGID test (not the most
sensitive test) you can be pretty sure that the
virus is in the herd.
2. Serological status is not equal to infection
status and is not equal to clinical EBL status:
There could very easily be infected animals
that have not seroconverted yet, and there
are definitely infected, seroconverted cows
that will take up to a number of years before
they get clinical signs of EBL. For these
reasons you should not export ANY animals
from the herd because the INFECTION status
of individual cows within an infected herd is
not detectable with a serological test.
3. The dairy where I am involved is milking
>70% BLV positive cows successfully with
daily milk yields up to 50kg, some cows being
in their 5th and 6th lactations, having been
seroconverted for years. I am of the opinion
that this is happening in other herds as well,
and this fact resulted partly in the ostrich-
strategy of the industry. Scientific evidence is
not convincing on the impact of the disease
Figure 02: Cattle farmers can monitor the incidence of EBL in their herd through co-operation with abattoirs.
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