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I BR CONTROL
Veterinary Surgeon
Tom Wright
XLVets Practice
Lambert, Leonard
& May
IBR
- relatively cheap to
control, but potentially
expensive to ignore...
AUTUMN 2012 ISSUE
LIVESTOCK MATTERS
10
TOM WRIGHT,
LAMBERT, LEONARD & MAY
IBR (Infectious Bovine Rhinotracheitis)
is one of the four main
infectious cattle diseases. It is caused by the bovine herpes virus
(BHV), and infection can lead to acute respiratory disease
(‘classic IBR’) or a sub-clinical syndrome characterised by poorer
health and fertility, and a reduction in milk production.
XLVets’ Tom Wright of Lambert Leonard and
May Farm Vets explains: ‘The bovine herpes
virus is similar to the herpes or cold sore virus
in humans. IBR outbreaks are often triggered
by stress or the introduction of infection into a
naive group of animals.
‘The main clinical signs of an acute infection
in a naive animal can be spectacular: nasal
and ocular discharge that becomes pus-filled,
red eyes, coughing, increased respiration
rate, high rectal temperature and a decreased
feed intake and milk drop.
‘After initial infection, the virus remains dormant
within the animal’s nerve cells for the rest of its
life. But it can be re-activated in further times of
stress, e.g. at calving, due to poor nutrition, or
hot weather which will lead to further bouts of
virus shedding.
‘So what is commonly seen in herds where the
disease is endemic, is a sub-clinical syndrome
characterised predominantly by production loss
and poor fertility.’
A range of vaccines and administration
programmes are available which reduce the
clinical signs of the disease and help prevent
virus shedding.
Tom explains: ‘Vaccination for IBR differs from
that of BVD and leptospirosis as it doesn’t
actually stop the animal becoming infected
with the bovine herpes virus. Instead, it helps
protect animal health by reducing the clinical
signs. And when a virus outbreak has been
triggered, it reduces the shedding of the virus,
thereby reducing the spread of infection.
‘IBR and the BHV have not historically received
a lot of publicity. However the effects on cattle
health and performance are still significant.
Moreover, IBR vaccines are relatively cheap,
and so it is far better to vaccinate than to
allow the virus in infected herds to depress
production and health.’
Bulk tank milk tests can indicate the presence
of the bovine herpes virus in a herd. A recent
survey of herds in south Wales, carried out
by XLVets’ Rob Davies of ’Allen and Partners
practice, revealed nearly 80% were positive
for IBR.
Types of IBR vaccine
There are a number of vaccines on the
market which protect cattle against IBR. They
fall into two types:
‘live’
or
‘inactivated’
(sometimes referred to as ‘dead’). Both reduce
the clinical signs of disease and reduce virus
shedding - but neither of them stop the animal
becoming infected.
Tom explains: ‘Live vaccines are best used on
animals which are naive to the disease, i.e.
those that have never been exposed to the virus.
This is because live vaccines are better at pre-
venting clinical signs of the disease. So typically,
live vaccines are used on calves and heifers.
‘Once an animal is considered to have
encountered the virus and be carrying latent
infection, then using an inactivated vaccine
might be better. This is because there is some
evidence to suggest that these vaccines may
be more effective at reducing virus re-activation
and shedding, and so could help to reduce
the spread of infection in the herd.
Frequency of vaccination
Tom explains: ‘The programmes for booster
vaccinations may be for 6-monthly, or annual,
injections. The most appropriate frequency will
depend on each herd’s individual situation.
‘In fact, in the control of IBR on a farm, every
situation is different and this is very much an
area which farmers should discuss with their vet.
‘The choice of vaccine - manufacturer, live
or dead - and the frequency of booster
vaccinations, need to be decided based on
each farm’s system, stress factors, levels of
disease challenge, and herd health history.
Simply opting for an ‘off the peg’ vaccination
programme that may appear to be a
cost saving may in fact not be appropriate
for the circumstances, and end up costing
dearly in terms of lost productivity.’
Tom adds: ‘Whatever the vaccine and
programme that’s adopted, it’s just as
important to also ensure that all at-risk animals
are treated, and that booster injections are
not allowed to lapse.’