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CASE STUDY
AUTUMN 2012 ISSUE
LIVESTOCK MATTERS
14
Case Study
In January 2011 Clyde Vet Group received
a call from one of their farm clients as a
group of home-bred store calves were
looking quite poorly and one of them had
died that morning. The farmer requested
a visit to investigate and Neil Laing from
the practice attended.
Neil comments: ‘The group of calves were
indeed in poorer condition than would be
expected and had not really done well
since they were weaned and housed in
early November. Feeding rates seemed to
be appropriate and there were no obvious
signs of infection in the group. Plus, there
was no history of pneumonia on the farm.
‘I performed a post-mortem on the dead
calf and found chronic liver fluke infection
in the liver. The liver was badly damaged
and scarred and there were quite a lot of
adult fluke in the bile ducts,’ he says.
It is known to be a wet farm; which
provides an ideal habitat for both fluke and
the mud snails to exist. There are sheep on
the farm too, which are routinely treated for
liver fluke, but it had never been perceived
as a big issue. The farmer was surprised
at the diagnosis as he had treated all the
calves with a combination fluke and worm
product at housing. ‘It appeared the
product the farmer had bought from his
merchant had been used in accordance
with the data sheet, although he did
comment that he had estimated weights
of the group to be treated,’ says Neil.
With this in mind, Neil advised a fluke
treatment with Nitroxynil injection for
the rest of the calves and they quickly
picked up. Trace element profiles
showed no obvious deficiencies that
would compromise the immune system
of the calves.
So what went wrong?
l
The autumn of 2010 was relatively
dry, but it followed a wetter than normal
summer where conditions were ideal for
fluke to multiply rapidly.
l
With the good autumn weather, the
calves were out for longer than usual
so probably picked up more fluke
larvae than normal.
l
The combination product the farmer
used only kills immature fluke at more
than eight weeks of age, which doesn't
make it the ideal product to use at
housing, as not all the fluke in the calves
would be killed at this time.
In a normal year the problem could have
easily gone unnoticed, as a small number
of surviving fluke might well not cause
obvious production losses, but due to the
circumstances in this particular year there
were probably more larvae than normal
in the calves, which led to the problems we
saw. ‘The lessons to learn from this case
are twofold; firstly, make sure the product
you use is appropriate for the purpose
you are using it for and secondly, plan the
timing of your treatment to kill as many fluke
as possible,’ advises Neil. ‘Combination
products are very convenient to use, and
this is an advantage where time and
manpower are short. However, as this case
demonstrates, they may not always be the
most effective product for both purposes.
‘In this instance, delaying application of
the product until at least eight weeks
after housing would have been more
advantageous. By doing this all fluke would
then be at an age where the product
would kill them. Alternatively, if treatment
is to be undertaken at housing again, a
product that that kills early immature larvae,
such as Triclabendazole, should be used.
Having said this, in situations such as
with this case where lungworm is also
a concern, it might be more appropriate
to use a wormer at housing and then
administer a separate flukicide later in
the winter.
‘This case highlights that there can be
several treatment routes available, even for
a single farm, but consideration must be
given to the products and their capabilities
and advice sought before commencing any
treatment programme,’ concludes Neil.
With such a wide range of products
available to treat liver fluke, plus all the
combination products offering fluke and
worm control, it can be confusing to know
which is the most suitable. To complicate
matters further, as we've seen above the
different flukicides have varying degrees of
effectiveness against the different stages of
fluke. So before using an anthelmintic on
your cattle at housing time speak to your
local XLVets practice. They will be able
to help ensure you are using the most
appropriate product, based on your
individual circumstances and will also
discuss the optimum timing of your
treatment to ensure the most effective
control of liver fluke this winter.
Treatment is very effective but needs to
be targeted to the fluke season and to
recognise the variable efficacy of products
for the different stages of fluke; early
immature, immature and adult. Also the
milk withhold must be considered and
often means treatment must be targeted in
the dry period. Fluke treatments come as
drenches and injections, and are also
available in combination with wormers.
The recognition of fluke and a strategic
approach to treatment should be a
component of herd health plan reviews.
A little investment in health will go a long
way to alleviating the production loss
which is the hidden cost of fluke infection.
Fluke diagnosis is not straightforward and
needs careful interpretation so speak to
your XLVets practice. Fluke egg counts from
faecal samples indicate infection but fluke
egg production is sporadic and therefore
this test can be unreliable to detect the
presence of fluke. Blood sampling a
random group (often young home-bred
stock are a good indicator) can reveal
the foot-print of fluke infection. Post
mortem/slaughterhouse feedback provides
a direct report of fluke level in condemned
livers and many more abattoirs are
doing this now. Bulk milk testing is also
available to detect the presence of fluke
within a dairy herd.
Diagnosis
The larvae multiply in the snails and emerge
to attach to the grass as cysts. The grazing
animal ingests the cyst where it breaks out
as an immature fluke to make its way to the
liver. The fluke tunnel through the liver and
if conditions favour, will mass hatch and
this infection can cause severe and
permanent damage.
Adult fluke live in the bile ducts of the liver
where they feed on blood. This can amount
to half a millilitre per adult fluke per day,
which explains the anaemia exhibited by
infected animals.
Figure 2: Liver fluke is a large parasite that can
grow up to 3.5cm in length
Figure 3: Liver fluke can result in condemned
livers at the abattoir
Treatment