Can we eradicate BVD? | Back to Vet Advice
Dr. Andy Acton
"We have the science -- when are we going to use the results?" This title from an article I read years ago concerning humane processing of calves, suits my topic perfectly: bovine virus diarrhea, and the possibility for control and eventual eradication of BVD virus. This article will not discuss all the basic biology of BVDV infection in a herd, which has been well described many times in the veterinary and lay literature. Instead I'll discuss some of the implications of BVD infection and why we need to pay more attention to it as an industry.
What explains all the attention paid to BVD virus at meetings, in articles, or columns such as this? The fact is that BVDV infection is serious, commonplace, and costs our industry millions of dollars annually. One U. S. estimate I read talked about a $2 billion loss from BVDV infection annually. From work done at the Western College of Veterinary Medicine we know BVD-PI (persistently infected) animals are present in more than 10 per cent of cow-calf herds tested in Western Canada. Herds that had BVD virus present in their herd had significantly lower weaning weights, and more overall health problems. The effect BVDV has on herd fertility can vary from a nagging problem to a catastrophe with the potential to devastate a herd in one year. The WCVM's large-scale studies also show beef herds that vaccinate pre-breeding for BVD virus have improved reproductive performance, showing us BVDV infection is a significant reproductive problem.
Once infected calves leave their herd of origin, the problems often intensify. While only three or four calves per thousand are actually persistently infected, they shed such enormous quantities of virus their feedlot pen-mates can't help but come in contact with it. These transient infections don't usually kill an animal, but they do contribute to a lot of the bovine respiratory disease (BRD) seen in our feedlots. Most studies show we can expect a 30 per cent or greater increase in BRD in pens containing BVDV-PI calves.
Can we vaccinate our way out of a BVDV problem? To achieve true control, it appears the answer is no. Vaccination effectively prevents large-scale wrecks, but it does not "cure" PI animals, therefore it does not get at the root of the problem. Many experts believe vaccination must be done in conjunction with a proper test and removal program on PI calves to achieve an adequate level of control.
The good news is we have more accurate, simple, cost-effective BVDV tests than ever before. Eradication and control is within reach of producers willing to test the whole herd and any new animals before they enter the herd, with guidance from their herd veterinarian. The threat of accidental reinfection from outside sources is real, but once a herd is free of the virus, targeted testing could be used to monitor for BVDV.
So what about regional control or eradication of BVDV? There is a concern about deer as a host for BVDV, and more field research is needed to tell us if wildlife would be a large obstacle to eradication programs. Because of our geography and the nature of our cattle business, with large numbers of cattle being shipped regularly over long distances, we would not have an easy time eradicating BVD in Canada.
Four U.S. states currently have voluntary control programs at various stages of development, and an actual eradication program is underway in Michigan's Upper Peninsula. Many European Union countries are at various stages of BVDV eradication. All the analyses I have seen indicates that BVDV eradication, or at least significant control, would be very profitable for the cattle industry, be it the beef or dairy business.
Where should we start? These aren't exactly shiny times economically for the beef business, but I hope that our industry will start taking actual control measures more seriously. The Denver National Stock Show requires all cattle entries to be tested BVDV-free prior to entering their show -- it sets a great example and illustrates to a lot of producers that testing individual cattle is not hard or overly costly. I would encourage producers involved with our major shows to consider similar measures.
Normal healthy animals from reputable herds using BVDV vaccination have a very low risk of bringing BVDV infection to your herd, so I don't want to be a "fearmonger" here. Having said that, I would consider having new entries to your own herd tested for BVD-PI status prior to bringing them to your farm, along with calves born from purchased females. Also consider testing animals offered for sale, especially breeding animals. For details on how to accomplish this, consult your herd veterinarian.
Remember that a whole-herd test, done at the right time, need not test all the animals. You could test calves prior to the start of breeding, as well as all the replacement heifers and bulls. If the calves are negative, there is no need to test the cows. I'll leave the rest of the details of herd testing to your own herd veterinarian, since it is too large a topic for this column.
Will our provincial or national governments get involved with a BVDV control or eradication program? I'd like to think that such a large economic problem warrants some government involvement or funding, but only time will tell if that becomes a reality. Needless to say, BVDV is a huge problem with a lot of science invested in it. I hope we use the results.
-- Dr. Andy Acton is a private practitioner from Ogema, Sask., and is a member of the Western Canadian Association of Bovine Practitioners, which co-ordinates this column. Reprinted from Canadian Cattlemen, December 2008, page 38.
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