Herd-level prevalence of Johne's disease in Utah and adjacent areas of the intermountain west as detected by a bulk-tank milk surveillance project

Abstract

The objectives of this study were to estimate the dairy herd-level prevalence of Johne's disease (JD) in Utah and nearby areas of the intermountain west and to estimate the sensitivity of a single bulk-tank milk test for JD detection. Two milk samples from all bulk tanks on the study farms were collected 1 mo apart. Samples were frozen and shipped to a laboratory for JD testing. An ELISA to measure total IgG antibody specific against Mycobacterium avium ssp. paratuberculosis, the etiological agent that causes JD, and a quantitative real-time PCR to detect M. avium ssp. paratuberculosis DNA were used; both tests were designed for bulk milk. Of the dairy farms in the study area, 170/246 (69%) participated. Positive JD results were found in bulk milk from 67/170 (39%) of dairy farms in Utah and adjacent areas. There were 138 JD-positive bulk-tank results from 241 bulk-tank samples from the 67 positive herds. The sensitivity of the bulk milk testing for detection of JD was 138/241(57%). From the 103 JD-negative farms, 235 bulk-tank samples tested negative for JD. The probability of false-negative results on a single bulk-milk sample was (1 - 0.57) = 0.43. For farms with 1 bulk tank, 2 samples collected 1 mo apart, with both samples testing negative (by both ELISA and quantitative real-time PCR) for JD, the true-negative probability was [1 - (0.43)(2)] = (1 - 0.18) = 82%. For farms with at least 2 bulk tanks, at least 4 samples tested, with all results negative for JD, the true-negative probability was at least 97%. Results support other estimates that prevalence of JD has increased over the last 15 to 20 yr. However, the prevalence detected was 3 times that from a recent report where 13% of dairy herds in the western US were positive. The increase in JD suggests that current control programs, at least as applied, are not effective. Bulk milk testing is a practical way to screen dairy herds for presence of JD. Studies are needed regarding the use of individual cow milk tests for accuracy, practicality, and effectiveness in reducing the prevalence of JD in dairy herds.

Associations between Mycobacterium avium subsp. paratuberculosis antibodies in bulk tank milk, season of sampling and protocols for managing infected cows

“…The Parachek commercial ELISA tests have been found to have a high specificity and a sensitivity ranging from 21 to 67% on individual milk samples [8]. When used on bulk tank milk, the Pourquier ELISA test had a sensitivity of 57% [9]. Additionally, van Weering et al [10] demonstrated that certified MAP-negative herds had a low sample/positive (S/P) ratio on bulk milk Pourquier ELISA tests and they showed that the likelihood of a herd having a MAP-infected animal increased with increasing bulk milk ELISA S/P ratio.…”

The herd-level prevalence of antibodies against Mycobacterium avium subspecies paratuberculosis in the Gyeonggi and Chungbuk of Korea, as detected by bulk tank milk ELISA

“…The antibody prevalence of MAP was estimated as 10% by serum ELISA from previous sets of unpublished data from the QIA. Based on this estimated prevalence, the sample had to consist of at least 138 herds in order to obtain a relative of 5 percent with 95% confidence (Wilson et al, 2010).…”

Johne’s disease, Mycoplasma and BVD in Utah-Bulk Tank Milk Testing and Comparison to Previous Regional Prevalence and Individual Herd Results over Time

“…Using the same tests as in the current study, the same dairy region was surveyed previously for JD in 2009, with 67/170 (39%) of dairy herds detected with JD [32]. However, the previous study collected 2 samples from every bulk tank while the current study collected 5 samples per tank.…”

“…At Antel BioSystems, 2 separate analyses were performed on each bulk tank sample as previously described [32,34]. Briefly, each bulk tank sample was analyzed for MAP-specific IgG antibody by ELISA and for presence of MAP organism by real-time PCR.…”

“…in 7% of Utah dairy herds in 2009 and 2007, respectively [32,33]. Objectives of the study reported here included estimation of the dairy herd-level prevalence of JD, Mycoplasma spp., and BVD virus in Utah and the nearby Intermountain West using a repeated sampling scheme.…”