Abstract
Herd-level prevalence of Mycobacterium avium subsp. paratuberculosis (MAP), causative agent of Johne’s disease (JD) and Bovine Viral Diarrhea (BVD) virus were estimated on dairy farms in Utah. Duplicate milks were collected at 3-4 day intervals on 5 dates from each bulk tank on participating farms. Samples were tested at separate laboratories for BVD (real-time, RT-PCR) and for JD/MAP (ELISA and qPCR). 151/209 (72%) eligible dairy farms participated. Farms detected positive were: 58 JD (38%) and 14 BVD (9%); 5 farms had both diseases. Follow up visited farms’ (n=22) means, medians: 778,420 milking cows; 20,052 lbs, 20,311 lbs 305d milk; 175,545/ml, 178,000/ml bulk milk SCC; stalls visibly soiled in rear one-third 37%, 32%, range 5% to 90%. Seventeen of 21 (81%) farms with JD had observed adult cows becoming thin while retaining appetite, 52% had seen adult cows contract diarrhea and subsequently die. Both BVD-positive farms had observed abortions. Free stalls housed milking cows on 91% of farms; dry lots housed dry cows on 55%. Nine farms (41%) had purchased animals within the past year: 27% pregnant heifers, 18% bulls, 9% calves, 14% cows; 9% had purchased only bulls. Whenever animals were last purchased, 14 farms (64%) had performed no disease testing or segregation; 8 farms (36%) utilized at least one biosecurity practice for replacements. Most common were 9-way vaccine including BVD on arrival (27%), 14% segregated replacements for any time, 11% tested for any diseases (none for JD). Fourteen (67%) farms with JD would identify known positive cows; none would segregate positives. Most producers (57%) allowed known JDpositive cows to calve again, farms with BVD were equivocal. No producers would have a separate calving area for JD or BVD-positive cows. Six farms (27%) fed calves only individual cow colostrum and pasteurized milk. All 22 farms vaccinated against BVD.
Highlights
Johne’s disease (JD, paratuberculosis) is an important chronic digestive tract disease of dairy cattle
Sample collection Signed forms authorizing milk sample collection and testing were returned by 151/209 (72%) of the dairy producers in the study area of Utah and adjacent areas of the Intermountain West
Herd-level prevalence of JD Bulk tank milk tested positive for JD at least once from 58/151 dairy herds (38%) in the study area
Summary
Johne’s disease (JD, paratuberculosis) is an important chronic digestive tract disease of dairy cattle. Johne’s disease is associated with increased risk of culling [1,2,3,4,5,6]. Estimated financial losses associated with JD range from $250 million to $1.5 billion annually in the U.S, possibly underestimated [4,6]. Loss estimates in JD-positive cows range from $83 to $380 per infected cow depending on parity/age, $77 in increased culling losses per cow for all cows within a herd, and $49 to $200 per cow for all cows within infected herds [5,7,8,9]
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