Agent/Cause
- BVD is caused by a virus, bovine viral diarrhoea virus (BVDV)
Disease
- Infection can result in a wide range of clinical signs including:
- Weakening of the immune system, leaving cattle more susceptible to other
infections
- Scours and pneumonia in calves
- Reproductive problems,
including failure to conceive, abortion and birth defects in older
cattle
- Calves that survive infection during early pregnancy are born persistently
infected (PI)
with the virus. Many will develop a fatal condition called mucosal disease in the first two years of
life
Introduction and Spread
- Purchase of PI cattle (possibly as unborn calves in pregnant cattle) is
the most important means of introduction.
- PI calves are the main transmitters of
virus to other cattle.
Impact
- Economic losses can be very high.
- Persistently infected bulls are excluded from AI centres due to the presence of BVDV in
their semen.
- Possible future restriction on live exports.
Control
Program
- Test program using blood and milk samples.
- Identification
and removal of PI animals is recommended, coupled with biosecurity measures
to prevent re-infection.
- Vaccination with killed vaccine may be used within any of the
programmes,
but it is mandatory in the Vaccinated Monitored Free (VMF) program.
- Double fencing
3 meters wide mandatory for the BVD accredited programme. Not mandatory on the VMF programme.
- Added
animals from non-accredited herds must be placed in isolation and tested for BVD
Test
Types
- Bulk tank milk test (BTM)
- First lactation
test (FLT): Individual milk samples from all first lactation cows
- Check test: test
for BVD antibodies in sentinel group of the 5 homebred cattle in each separately managed group of cattle
aged 9-18 months. See technical document for details (CHeCS Technical Document)
These
are used in a structured way in:
