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Blue Tongue Disease
Sarah and Mark recently attended a vets meeting on
blue tongue virus (BTV) in Cheshire and although there
have been local farmers meetings discussing the subject,
we thought that it was worth giving you some of the
important points again.
Blue Tongue is a viral infection spread between ruminant
species by certain species of midge, which can travel
on average 10-15km per day.
There are 24 distinct serotypes of BTV and immunity
to one does not convey protection against the others.
BTV 8 is the serotype present in Northern Europe and
the UK. It is considered to be one of the most virulent
strains. The other serotypes are not a threat to the
UK in the short term.
In 2007, 27% of Belgian sheep flocks showed signs of
disease. Of the individual sheep that showed clinical
signs, 50% died. The rest showed loss of weight and
took at least six weeks to recover. Infected rams and
bulls become infertile and it is unlikely they ever
recover. This may be very pertinent to this area as
BTV is predicted to reach here in September. Many pregnant
animals either abort or produce weak offspring.
Cattle are less likely to show clinical signs but do
become infected and produce a lot of virus and so are
important in the spread of BTV.
As it is viral, treatment options are limited. Due to
sore mouths, animals have difficulty eating and drinking,
therefore fluid therapy, anti-inflammatories and TLC
are required. Antibiotic treatment is necessary to prevent
secondary bacterial infections.
Under EU law, vaccination against BTV is only allowed
in Protection Zones (PZ). This is because antibody tests
cannot distinguish between a vaccinated and infected
animal. It may also be because unlike the present vaccine,
vaccines in the past have been live and capable of reverting
to wild strains and so causing disease. The present
vaccine is a dead vaccine and not able to cause disease.
This also makes its use in pregnant animals safe unlike
the live vaccines which could not be used in pregnancy.
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