WHAT IS BVD?
Bovine Viral Diarrhoea is a contagious virus that can be the underlying cause of many cattle health problems. We often liken the effect of BVD on cattle to that of AIDS in humans as both diseases lower immunity, increase susceptibility to other diseases and leave the victim with reduced defences which may result in an increased use of treatment drugs and possible death. Problems such as scour and pneumonia can become significant (especially dangerous for young calves), it can lead to mucosal disease, infertility, abortion, calf deformity and a reduction in overall herd performance. In short, it is something you will be much better off without!
A random survey of members that had had BVD in their herds was carried out in 2005. They all agreed that since eradicating the disease the performance of the herd had improved, weight gain had increased, calvings (in general) had improved, less time was being spent nursing and treating stock, significantly less was being spent on treatment drugs and an average of 3-4 animals per year were being reared, with one farm stating an increase of 10-15. They unanimously agreed that BVD eradication was very worthwhile.
COLOUR CODE
We adopted a colour code which is used by our members when relating to the status of their cattle:-
- White - Antibody Negative and Virus/Antigen Negative. Animals that have not been exposed to the disease.
- Green - Antibody Positive. Animals that have been exposed to BVD.
- Red - Virus/Antigen Positive. Animals infected in the womb. Continue to shed virus after birth. Commonly referred to as Persistently Infected (PI's).
HOW DO I KNOW IF I HAVE BVD IN MY HERD?
The best way to determine your BVD status is to carry out a screen test of 10 youngstock, preferably aged between 9 and 18 months old. A BVD screen test is simple inexpensive procedure that involves your vet taking blood samples from your 10 randomly selected animals. These must have intermingled since birth. If you keep separate groups you will need to do screen each group separately. You may think that only testing 10 animals is rather few especially in larger herds but we know that if BVD is in your herd it does a very good job of spreading and the screen test is a proven indicator.
We also recommend that you get any abortions checked out as it can be helpful to know of any potential problems as soon as they arise. This should also involve sampling the dam.
We issue reminders for tests due based on previous testing dates but it is up to you to telephone your vet to book any veterinary procedures including health planning.
RESULTS
The laboratory will send your results to you, your vet and to OLA. The vets at the laboratory usually give written comment on the results, but if you require further advice you can contact them, your vet or OLA.
Negative Screen
This shows that no BVD infection was in your herd during that calving season. Consider vaccinating your breeding stock to prevent future infection, especially if your boundaries are less than 3 metres from neighbouring stock.
BVD Accreditation
BVD Accreditation is awarded following two consecutive annual clear screen tests. The laboratory will issue you with certificates.
Positive Screen
This tells you that BVD may be active in your herd and you should test all cattle on your holding over 9 months to identify any "Red" animals. These should then be isolated or culled. Breeding cattle that are "White" should be vaccinated to protect them from any "Reds" that have or are due to be born. Breeding cattle that are "Green" are naturally immune and do not require vaccination but may have a "Red" calf in the womb or at foot (unless you know they were "Green" before that pregnancy) or in the case of bulls may produce infected semen for up to 20 weeks after infection.
If you are to carry out a whole herd test you may also test for other diseases at the same time. It may be worthwhile to check if your TB test is due too but ensure that samples are taken before tuberculin is injected as it can affect results for some tests.
Ear Tag Test
We can now offer ear tag testing which involves tagging cattle in the usual way except using special pliers and tag. The plier deposits a small skin sample into a collection pot at the back of the tag which is then removed and sent to the laboratory for testing.
This test is very useful for using on young calves that are too young to blood sample so is proving beneficial to members that buy in replacement calves and holdings that know they have BVD in their herd and want to identify any "Red" calves before turnout.
Pliers and tags are available from the office on loan or may be purchased to order.
PURCHASING STOCK
This has become easier with the increase of BVD known status sales. However we still recommend that you isolate and test all cattle purchased - especially if they came from a holding of unknown or inferior status to your own or an auction where all classes of cattle are sold regardless of status.
RULES FOR MEMBERS PARTICIPATING IN BVD ERADICATION SCHEME
- A herd is defined as cattle that are under a unified management system, not necessarily on the same premises, but intermingle periodically throughout the year. A member who keeps groups of cattle separate can join as one membership, but has to screen test the groups individually.
- When a member's herd screen tests positive, they have to carry out the whole herd test and make every effort to eradicate the disease.
- Farm boundaries must prevent cattle from straying off or on to the farm, and must prevent nose-to-nose contact over fences or walls. Double fencing with a space of at least 3 metres between their cattle and neighbouring cattle of a poorer or unknown status is required for BVD and IBR programmes. Where this is impractical, members should vaccinate all BREEDING cattle in uninfected herds. On infected holdings that carry out the whole herd test, members should vaccinate all the "WHITE" BREEDING cattle in the herd. Members should avoid vaccinating young animals under 15 months of age as this would jeopardise the result of the screen test - hence the accredited status.
- WHITE coloured animals mean animals that have not been exposed to the disease.
- GREEN coloured animals are the animals that are antibody positive, have been exposed the disease, and are effectively naturally vaccinated.
- RED coloured animals are the persistently infected animals that are virus positive and the main carriers of the disease, commonly referred to as "PI's".
- Purchased cattle that are of an inferior health status either from within or out-with the scheme MUST be quarantined in suitable facilities until the appropriate test results of that particular animal are received.
- Suitable quarantine facilities are in the form of pens or paddocks that do not allow contact with other livestock. These must be available for cattle coming in to the herd.
- Equipment, livestock trailers and handling facilities that are shared between health scheme cattle and other livestock or cattle of a poorer or unknown status, must be cleaned and disinfected before used by health scheme cattle.
- Blood samples can only be collected by a veterinary surgeon, someone designated by a veterinary surgeon, or in the case of milk samples, by a milk recorder. Where the herd uses more than one bulk tank, representative samples must be taken from each tank.
- PI's (red animals) must be culled or strictly quarantined in a facility where there can be no danger to any other animals either on that farm, or any other farm. They should be slaughtered as quickly and as practically as possible. They should not be moved off the holding other than directly to slaughter facilities. Veterinary advice should be sought regarding the best option to take.
- SHOWS AND SALES - Only animals of a known health status should be shown. Unless the animal is GREEN, it should be vaccinated before it attends the show and quarantined for 3 weeks after the event. This vaccination and quarantine policy will also apply to live cattle sales where there is a possibility of the cattle returning home. Particular attention must be paid to pregnant animals, as it is paramount that the foetus is protected.
- Avoid introduction of infection on clothing or footwear, (e.g. AI technicians, vets, neighbours, hoof trimmers, lorry man etc) or equipment (e.g. vehicles, crushes, dosing equipment etc). Dedicated clothing, footwear and equipment for a particular farm is the safest option. A less secure but acceptable alternative is thorough cleaning and disinfecting of clothing, footwear and equipment before use on the farm at risk. (Waterproof overalls are more hygienic than boiler suits). Vehicles should be cleansed and disinfected before they are used for health scheme cattle, unless they are moving direct to a slaughter house. Particular effort should be made to clean and disinfect equipment likely to be contaminated by blood (e.g. hoof knives, instruments for castrating, dis-budding and de-horning). Injection equipment should never be shared among farms or species. Veterinary and surgical equipment must not be shared between farms unless it is sterilised before use.
- Limit farm access to those people deemed essential.
- Use piped mains water rather than natural water sources whenever possible.
- Prevent access of vermin and wild life to feed, bedding stores and the cattle whenever possible.
- Purchased feed and bedding constitute a risk of introducing infection, so it is important to use reputable suppliers.
- Embryos and semen should be from donors of certified disease free status.
- Sheep can harbour some of the diseases that affect cattle. Contact between sheep and cattle should be avoided as much as possible.
- When joining the scheme you have to produce an annual veterinary health plan with your vet. This will monitor and evaluate your cattle health status, as well as act as our inspection to make sure members adhere to our rules. Any breach of the rules will lead to the member losing their accredited status, and OIC would have the right to recover the laboratory testing costs from the member to whom the breach of the rules applies. If challenged the decision would be arbitrated by Hi Health's Independent vet.