BVD on the modern Dairy: The present state of confusion? Tom Shelton MS, DVM Bruce W. Hoffman, DVM

What' s changed in the last 10 years? The advent of molecular biology allowed for the characterization of the biology and pathogenesis of the virus –Viral proteins –Nucleotide sequencing PCR testing Immunohistochemistry Molecular epidemiology

NAHMS 2007 Percentage of operations that normally vaccinate cows for the following diseases. Heifers vaccination Pct. very similar for BVD

Percentage of operations that routinely tested heifers for P.I. by herd size Small <100 Medium Large >500 All Pct Std Error Pct Std Error Pct Std Error Pct Std Error 1.9 (0.5)6.7 (1.1)21.2 (2.4)4.0 (0.4)

Why should we care about BVDV on dairies? Aren’t vaccines protecting us? Detrimental effects include: –Reduced milk production, increased clinical mastitis –Reduced reproductive performance –Growth retardation –Increased occurrence of other diseases –Unthriftiness –Early culling –Increased mortality of young stock Houe H, Biologicals 31 (2003) Estimations of losses at the national level range between million $’s/million calvings –$10-$40 per calving

Evolution of testing program Had previously surveyed calf population for P.I.’s –Similar results of approx. 0.4% positive calves Operation expanded to include a large heifer growing facility with pens of 750 animals/pen From previous survey calculated that 13 of 25 pens would include at least 1 P.I. animal while breeding occurred

Southern Idaho heifer calf ranch Initiated P.I. testing Sept 18, 2007 Data includes numbers through Jan 15, 2008 A total of 18,981 calves tested –Calves tested at API by RT-PCR pooled samples of 28 from a total of 32 dairies –Determined to be P.I. if tested 2X at 3 weeks apart or died between 1 st test and 3 week re- confirm –Transients (2 nd test negative returned to herd)

Summary Data 48 confirmed Positive P.I.’s 52% of the dairies have contributed a P.I..25% about 3/1000 calves arriving are P.I.’s –66% will be dead at 12 months of age –Additional 24% die between 12 and 24 months of age –10% will be alive at 24 months of age Goyal and Ridpath, 2005 –25 pens with 13 P.I.’s at 12 months of age

Too many calves with scours?

Updated numbers 54,260 calves tested with 149 confirmed P.I.’s (0.27%) 9/18/ /2/08 40 samples submitted to Robert Fulton at OSU for typing Plus genetic characterization at the USDA, ARS, Ames, IA by Julia Ridpath

Results 5 BVD 2a’s(12.5%) 34 BVD 1b’s(85%) 1 BVD 1a(2.5%)

1b 2a 1a Vaccine or reference strains NY-1,C24V, Singer, NADL, 296c, 890 BVD dendogram from 40 submitted samples From 5′ UTR

Common Sense Observations What do we do with them? –Euthanize – best –Some resistance, but with feed costs and observed death loss owners agreed Acute infections –Able to identify with PCR –False transmission at collection –Real transmission in fresh pen and transport Needs more observation and study

Common Sense Observations Identified Problem Dairy…but –Difficulty in working with herd veterinarian to identify source and solution Already fixed it We vaccinate Not an economic issue –Difficulty in developing a herd control plan Periodical bulk/string sampling Testing newborns –Don’t buy a PI or send to a heifer raiser that does not assure all animals are BVD PI negative

Final Observations BVD PIs are a problem for the dairy industry Management changes have created increased incidence Need to improve awareness and relationships with herd veterinarians that have a reproduction focus

Best Solution Management is still key to control Vaccination with a MLV type 1 and 2 BVD is a necessary adjunct –Use qualified USDA vaccines with the best reproductive approvals Unless the P.I.’s are eliminated, the current evidence suggests that BVD will continue to circulate within the herd at often sub-clinical levels