Control of Bovine Viral Diarrhoea on a Farm
The history of Bovine Viral Diarrhoea (BVD) virus dates back as far as the late 1940’s. Olafson and associates described a gastro-enteritis with severe diarrhoea in dairy herds in New York State in 1946. Today BVD infections are seen in all ages of cattle throughout . . .
The history of Bovine Viral Diarrhoea (BVD) virus dates back as far as the late 1940’s. Olafson and associates described a gastro-enteritis with severe diarrhoea in dairy herds in New York State in 1946.
Today BVD infections are seen in all ages of cattle throughout the world and have major economic impact due to productive and reproductive losses. Over the past years, advances in molecular genetic research have helped increase the understanding of the wide range of clinical diseases associated with BVD. The biggest challenge is how to control the spread of the virus.
The role of Persistently Infected (PI) calves in the spread of BVD virus
An important aspect of Bovine Viral Diarrhoea is that the virus in the blood of an infected cow can cross the placenta and infect the unborn foetus. Foetuses infected during this period can often be carried to full term and are then born as the so-called Persistently Infected (PI) calves. These calves are consistently shedding considerable amounts of virus into the environment through nasal discharges, urine and faeces. Therefore, it becomes clear that the detection and elimination of persistently infected animals is the key to control of BVD on a farm.
Does vaccination against BVD virus protect against infection?
It is important to understand that vaccination against BVD virus only protects against the clinical effects of the disease in the animal, but does not protect against infection. Vaccinated animals will still get infected and develop a viraemic state and may continue to shed virus to the environment. This means pregnant animals in a viraemic state, whether vaccinated previously or not, have the potential to infect the foetus with virus. Depending on their stage of pregnancy at the time of infection, can lead to birth of persistently infected calves. Therefore vaccination does not necessarily equal foetal protection.
Has vaccination against BVDV been successful?
BVD vaccination programmes have not always been 100% successful. Live vaccines induce reasonably good immunity against field infections, preventing clinical manifestation of BVD as well as foetal protection. However, there is always a concern about the risk associated with the use of live vaccines in pregnant animals and also the possibility of spread of vaccine virus from vaccinated animals to susceptible ones. Inactivated vaccines are generally safe, but the immunity they offer does not offer reliable foetal protection against virulent field strains.
Foetal protection the cornerstone of BVD control
Prevention of transmission of virus from infected pregnant cow to the unborn calf is important in breaking the cycle of BVD virus infections in a herd. This means that the continuous re-infection of cows by persistently infected animals can be blocked in this way. Vaccinating a herd with Bovilis BVD-MD will induce active immunity within the vaccinated animals themselves and is safe to use in pregnant cows. It also provides protection of the unborn foetus from infection. Therefore, no more PI calves to infect the rest of the herd.
Animals vaccinated with Bovilis BVD-MD have shown a reduction in the shedding of virus after challenge as compared to unvaccinated ones. Therefore vaccination of a herd with Bovilis BVD can reduce transmission and perpetuation of virus in a herd. In the same way, the infection pressure of BVD virus infection for the whole herd will be drastically reduced.
Benefits of vaccination with Bovilis BVD-MD
- Prevents trans-placental transmission of BVDV and hence offers foetal protection
- Drastically reduces shedding of challenge virus from the nostrils in BVDV infected animals
- Safe to use in pregnant animals
- Protects against type 1 and type 2 BVDV
- Has no negative effect on milk yield