As discussed in the last post on BVD, Persistently Infected Cattle are the main source of BVD infection.
So in order to control BVD, you need to find and eliminate these PI cattle from the herd.
You then need to make sure that no new PI's enter the herd or naive cattle have a chance to become infected.
You do this by monitoring, culling, practising biosecurity on the farm and vaccinating for BVD.
To monitor for BVD, you would test for antibodies and virus in the blood. If any of your animals are shown to have virus or antibodies in their blood, it would mean they've been exposed to the virus in the last few years.
With antibodies, the higher the levels of antibody, the more recent the exposure has been. Anything over SP:75 means that there could be a PI in contact with the herd at the moment and there is an active infection.
If you were monitoring for virus in the blood and the animal actually has virus in the blood, it means the animal is a PI it may have been exposed to the virus for the first time as a naive animal and hasn't yet got rid of the infection (TI).
The vet will help decide if the animal should be isolated and retested or if it's a PI.
If the animal is a PI it will need to be culled as it will always be the source of infection for other cows and will never stop spreading the virus.
When should you test for BVD?
It is recommended to do a bulk milk antibody test twice or three times a year for dairy herds. If the antibody levels go up between tests, then you would do a test for the BVD virus to see if there is a PI in the herd. The vet will look at all records for milk sampling and records of cows who have entered the herd since the last negative test to find out which cow is the likely source of infection.
If your antibody or virus is high, you will need to work with your vet to find and eliminate the PI, especially before mating since it will affect the reproductive health of cows and could lead to abortions and more PI calves being born.
To prevent BVD from entering the herd you will need to:
Virus test replacement calves and cull any PIs
Virus test all purchased animals before they arrive
Make sure all bulls are virus test negative and are vaccinated.
Eliminating BVD in your farm
Good biosecurity plans should be in place. This involves keeping accurate records of every animal entering or leaving the farm and ensuring that any animal coming into the farm is BVD negative.
Because BVD can be spread from direct contact (touching an infected animal) and indirect contact (through excretions that can be carried indirectly), hygiene is key. People who are coming into the farm should adhere to personal disinfection, such as cleaning boots, clothes and equipment.
Keeping boundary fencing metres apart from neighbouring farms or groups of cattle will help to prevent direct contact.
Vaccinating animals is also critical.
BVD Eradication Programme in Ireland
The BVD Eradication programme is supported by legislation in Ireland.
Key points include:
• All calves born from 1st January 2013 onwards must be tested for BVD.
In May 2020, legislation was amended to provide for the compulsory BVD testing of all cattle, including those born before the 1st of January 2013. This excludes female animals that have not had one or more calves that tested negative for BVD.
• Calves cannot be sold without a negative result
• Follow up testing where PIs (persistently infected animals) are identified
In Ireland, eradicating BVD is a key goal by 2023 and is making progress. Quoted from a recent press release, Minister Charlie Mc Conalogue, T.D said he was satisfied with the progress being made.
"The Minister expressed his satisfaction with the ongoing progress being made in the eradication of BVD. The Minister noted that substantial savings are being achieved by farmers, with the incidence of BVD positive animals decreasing this year to just 0.03 % from 0.66 % in 2013 – the first year of the compulsory phase of the Eradication Programme."
For any specific queries in relation to BVD, always ask your vet.