Bovine Viral Diarrhoea (BVD) is believed by many to be the most important viral disease of cattle, responsible for a variety of production losses. It can be hard, however, to associate health problems seen in the herd with the BVD virus or appreciate the prevalence and dangers of the disease.
The effects of BVD in cattle
Economic losses are incurred in a variety of ways:
- Increased levels of infertility
- Extended calving to conception intervals
- Increased services to get cows in calf
- Abortions and neonatal deaths
- Mucosal disease
- Viral diarrhoea
- Deformed calves, e.g. cataracts, brain damage
- Immunosurpression in young calves which can lead to increased severity of scour and pneumonia.
BVD – a complex problem
BVD is a contagious and complex disease and in reality, both beef and dairy herds could possibly make huge strides in productivity by tackling it effectively.
A major source of BVD infection is animals whose dams have been exposed to the virus in early pregnancy i.e. calves born ‘Persistently Infected’ (PI) with the virus. BVD can be spread by nose-to-nose contact, urine, faeces, tears, saliva and, on occasion, semen and embryos.
How to control BVD
BVD can be controlled by implementing strict bio-security on the farm, a controlled BVD vaccination plan and the removal of persistently infected (PI) animals. The cornerstone of BVD control on any farm is detection and removal of PI animals, coupled with vaccination.
Where individual testing has confirmed the presence of Persistently Infected (PI) animals, cull affected PIs immediately as the major source of BVD.
For long term control, reduce the risk of introducing BVD to herds with a Farm Biosecurity Plan focusing on:
Animal introductions to the herd
- Ideally maintain a closed herd (i.e. no introductions to the herd)
- If a closed herd is not possible, test all brought-in animals for BVD prior to movement
- Animals not tested prior to arrival should be quarantined and tested for BVD
- Do not mix or house animals in the same air space with any whose BVD status is unknown
Maintain stock proof boundaries on the farm, ideally to prevent nose-to-nose contact (3m double fencing)
Avoid co-grazing land with other farms and/or other animal species
Visitors and equipment
BVD can be carried in cattle saliva/faeces on clothing and equipment. To reduce the risk of spreading BVD:
- Have well maintained footbaths and ensure all visitors use them
- Ensure all visitors wear clean protective clothing and minimise their contact with stock
- Clean and disinfect trailers and all veterinary equipment
- Do not spread slurry from other farms and avoid grazing land for at least one month where slurry has been spread
- Biting Flies may have a role in disease transmission
- Sheep may act as virus reservoirs, although the significance of this is not fully understood.
Bovidec vaccinations: increase immunity
In herds with little or no immunity to BVD, the effects of the virus spreading through the herd can be devastating.
- To limit the effects, it is advisable to increase the immunity of cattle
- This is especially true in herds that have never been exposed and where there is a high risk of introduction
- A vaccination plan is best implemented to ensure maximum immunity is present at the beginning of the animals’ breeding season.
To effectively control BVD virus it is important to implement the three control measures which are:
- Remove PI’s