Read about the symptoms and causes of Bovine Virus Diarrhoea Virus (BVDV; also known as Bovine Pestivirus) and how you may control the risk of this disease.
What to look for
- Most cattle become transiently infected (TI) then eliminate the virus and develop long lasting immunity. BVDV infection (outside of early pregnancy) decreases calf and cow immunity but has few obvious signs.
- Females without prior immunity that become infected in the mating period/early pregnancy may suffer lower fertility or abortion.
- BVDV can occasionally cause mass abortions and infertility. Outbreaks can also result in large numbers of persistently infected (PI) calves being born. These calves do not develop immunity, and may have poorer health and growth rates.
Cause - a viral infection (Bovine Pestivirus)
PI animals continue to shed large amounts of virus throughout life and are the main reservoir of viral infection.
Animals likely to be affected
All classes of cattle are susceptible to transient infection but only animals infected in utero become PI.
Other diseases with similar signs
Other infectious causes of abortion in cattle
Spread of the disease
Animals are usually infected with BVDV by direct contact with PI animals or their body secretions. Herds that have eradicated BVDV are at high risk of re-infection unless specific actions are taken to manage this risk. Modelling of BVDV infection within dairy herds suggests that a 7–10 year virus eradication and re-introduction cycle is typical when no BVDV controls (including no BVDV-specific biosecurity measures) are undertaken.
Herd size and calving system also have effect on the impact of BVDV. Larger herds and year-round calving herds tend to have more prolonged periods with circulating virus than similar sized seasonal or split calving herds, as there is more likely to be a PI animal present in the herd.
Confirming the diagnosis
The tests available have high diagnostic sensitivity and specificity. Blood tests can determine if individual animals have been infected with the BVDV. A bulk milk ELISA test can be used to gauge the immunity of the milking herd. BVDV antigen tests are required to detect PI animals. Herd immunity should be tested at least 8–10 weeks before mating to allow time to implement controls if required.
None. Animals with BVDV are not treated. Infected herds, and smaller management groups of cattle within herds, often self-eradicate the virus when all persistently-infected cattle (including infected foetuses) are removed (culled or die) and all transiently infected cattle recover or are removed.
Risks to people
Numerous BVDV control strategies are available, consisting of one or more activities. The complexity and cost of different strategies varies and must be weighed up against the expected benefits to the farm business. Your veterinarian can assist in developing a suitable strategy to control BVDV risks.
A vaccine is available. Removal of PI animals from a herd (including all infected foetuses) typically leads to rapid eradication of virus from the herd. However, once the virus is gone, a growing proportion of animals in the herd start to become susceptible to infection again.
BVDV in Australian dairy herds fact sheet (PDF, 512KB)
Bovine Virus Diarrhoea Virus (BVDV) - Control guidelines for farmers (PDF, 1.16MB)