For nearly 50 years, scientists and veterinarians from around the world have been trying to get a grasp on the bovine virus diarrhea (BVD) virus. Because of the wide variety of disease syndromes that can occur, the virus is often blamed for many disease problems — without diagnostic evidence that it's actually the culprit.
Conversely, bovine virus “diarrhea” is a bit of a misnomer.
“Of the disease problems caused by the BVD virus, diarrhea is often not seen,” says Hana Van Campen, DVM, PhD, a Colorado State University Veterinary Diagnostic Laboratory scientist in Fort Collins.
“The main effects of BVD viral infection in the U.S. today are associated with respiratory disease outbreaks in feeder animals and reproductive disease in pregnant cows,” she says. “The virus has mutated into dozens of strains that can infect a variety of organ systems ranging from the digestive to the respiratory to the reproductive tract.”
And, the virus will continue to mutate, Van Campen says.
The BVD virus is especially troublesome because it can lead to in-utero infections that result in permanent infection of the fetus. When born, these persistently-infected (PI) animals shed large numbers of the virus and are often the primary source of BVD disease in beef herds.
“While the BVD virus may not kill an animal directly, immunosuppression allows other infectious disease agents to do serious injury or cause death,” Van Campen adds.
Julia Ridpath, PhD, is lead scientist for the BVD Detection and Control Project at the National Animal Disease Center in Ames, IA. She says the changing nature of BVD is illustrated by the observation that despite widespread vaccination the rate of fetal infections has not decreased.
“This pattern suggests that field strains may be antigenically different from vaccine strains,” she says, “Many vaccines contain BVD type 1 strains that were isolated more than 20 years ago. Today we are detecting a predominance of Type 1 variants and Type 2 BVD in the field that do not look like the old Type 1 vaccine strains.”
Control BVD — how?
BVD virus infection revolves around several core elements that need to be taken into account if control and eventual eradication of the disease is to be successful. To further establish these elements in the persona of the U.S. cattle industry, Van Campen and Ridpath have organized a two-day conference in Denver for scientists and cattle producers (see sidebar on page 44).
They both feel that control of BVD-associated diseases in beef cattle ultimately depends on the identification and removal of PI animals from the cowherd prior to the breeding season.
“This strategy has been outlined by the Academy of Veterinary Consultants and is the basis of a voluntary BVD control and eradication program in Colorado,” Ridpath says. “We'll include a discussion of Colorado's program in the producer session on Jan. 31.” (See “Battling BVD” — November 2004 BEEF.)
The key to such programs is the presence, and availability for field application, of diagnostic technologies to identify PI animals. Subsequently, the success of such programs depends on industry's realization of the added value benefits to ranchers who attain BVD-free herds.
“We're hoping that with this program, we can initiate a new round of attention to BVD and energize producers into adopting market-enhancing BVD control programs,” Van Campen says.
Ultimately, Van Campen and Ridpath say their goal is to see BVD eradicated. But, first, producers must recognize eradication will involve a systematic control program utilizing diagnostic testing strategies to find and remove PI cattle, vaccination to increase fetal protection from infection, and biosecurity to reduce the risk of exposure to animals persistently (or transiently) infected with the virus, they say.
January session will focus on BVD
A two-day BVD seminar is set for Jan. 30-31, 2006, at the Adams Mark Hotel in Denver, CO. It will be held in conjunction with the 2006 Cattle Industry Annual Convention and Trade Show, Feb 1-4 at the Colorado Convention Center.
The seminar's sessions are broken into two parts — the first looking at the science behind BVD, the second at producer concerns with the disease.
BVD scientific session
A day-long scientific program on Jan. 30 will focus on BVD diagnosis and surveillance. Included will be discussions on future BVD control strategies and eradication programs.
Paul Steinar Valle, DVM, Olso, Norway, will outline a Norwegian “user-defined” research project that evaluates the cost-efficiency of BVD control.
Valle says in Europe there are two main approaches for BVD control:
- vaccination; and
- sanitary control and biosecurity measures.
Valle will outline control options and/or combinations of the European BVD control network, a four-part package:
Diagnostic tools and procedures, and aspects of the genome.
Epidemiology and the assessment of risk factors in different settings.
Vaccines and vaccination strategies.
The socio-economic assessment of the different control options.
Valle will also address the Jan. 31 producer session.
BVD session for producers
This 1-5 p.m. session on Jan. 31 will be moderated by Bob Smith, DVM, PhD, and chairman of the National Cattlemen's Beef Association's Cattle Health and Well-being Committee. Among the topics are:
Why control BVD?
Economic and production costs and tools.
The BVD virus — what do we need to know?
Tests and test interpretations.
BVD control plans — components, setting and achieving goals.
Results of Europe's BVD control efforts.
Potential and benefits for statewide BVD control programs.
Current BVD control in beef operations:
Seedstock — Mark Gardiner and Randall Spare, DVM.
Commercial cow-calf — Dan Goehl or Phil Kesterson.
Feedlot and backgrounding — Lucy Rechel.
Biosecurity and merchandising aspects — Patsy Houghton.
Panel discussion and wrap up.
For more information go to www.nadc.ars.usda.gov/events/BVDV%202005/Index.asp.