Risk profiling of cattle farms as a potential tool in risk-based surveillance for Mycobacterium bovis infection among cattle in tuberculosis-free areas.

OBJECTIVE To develop a cattle herd risk-profiling system that could potentially inform risk-based surveillance strategies for Mycobacterium bovis infection in cattle and provide information that could be used to help direct resource allocation by a state agency for this purpose. DESIGN Cross-sectional study. SAMPLE Records for any size movement (importation) of cattle into Minnesota from other US states during 2009 (n = 7,185) and 2011 (8,107). PROCEDURES Data from certificates of veterinary inspection were entered into a spreadsheet. Movement data were summarized at premises and county levels, and for each level, the distribution of cattle moved and number of movements were evaluated. Risk profiling (assessment and categorization of risk for disease introduction) for each import movement was performed on the basis of known risk factors. Latent class analysis was used to assign movements to risk classifications with adjustment on the basis of expert opinions from personnel knowledgeable about bovine tuberculosis; these data were used to classify premises as very high, high, medium, or low risk for disease introduction. RESULTS In each year, approximately 1,500 premises imported cattle, typically beef and feeder types, with the peak of import movements during the fall season. The risk model identified 4 risk classes for cattle movements. Approximately 500 of the estimated 27,406 (2%) cattle premises in Minnesota were in the very high or high risk groups for either year; greatest density of these premises was in the southeast and southwest regions of the state. CONCLUSIONS AND CLINICAL RELEVANCE A risk-profiling approach was developed that can be applied in targeted surveillance efforts for bovine tuberculosis, particularly in disease-free areas.

Mannosylated lipoarabinomannan in serum as a biomarker candidate for subclinical bovine tuberculosis.

BACKGROUND: Early and unambiguous detection of bovine tuberculosis (bTB), a significant disease of cattle worldwide, is necessary to control the spread of infection to other animals and humans. Current testing strategies are laborious, time consuming and heavily reliant on host responses that do not distinguish bTB from other mycobacteria. We report the presence of a pathogen signature, liparabinomannan (LAM), as a potential biomarker for bTB infection. FINDINGS: Fifty-five animals (uninfected [n = 33], bTb [n = 10] and exposed cases [n = 12]) from a well characterized bovine serum repository were screened for the presence of LAM using a commercially available ELISA. Analysis showed that LAM had a sensitivity of 100% and a specificity of 91.7% for bTB detection (bTB positive versus bTB exposed animals). CONCLUSION: LAM detection easily separated bTB infected animals from bTB exposed and negative controls. We propose that pathogen related markers, such as LAM, should be included with current testing strategies as a battery diagnostic for bTB.

Circulating Mycobacterium bovis peptides and host response proteins as biomarkers for unambiguous detection of subclinical infection.

Bovine tuberculosis remains one of the most damaging diseases to agriculture, and there is also a concern for human spillover. A critical need exists for rapid, thorough, and inexpensive diagnostic methods capable of detecting and differentiating Mycobacterium bovis infection from other pathogenic and environmental mycobacteria at multiple surveillance levels. In a previous study, Seth et al. (PLoS One 4:e5478, 2009, doi:10.1371/journal.pone.0005478) identified 32 host peptides that specifically increased in the blood serum of M. bovis-infected animals). In the current study, 16 M. bovis proteins were discovered in the blood serum proteomics data sets. A large-scale validation analysis was undertaken for selected host and M. bovis proteins using a cattle serum repository containing M. bovis (n = 128), Mycobacterium kansasii (n = 10), and Mycobacterium avium subsp. paratuberculosis (n = 10), cases exposed to M. bovis (n = 424), and negative controls (n = 38). Of the host biomarkers, vitamin D binding protein (VDBP) showed the greatest sensitivity and specificity for M. bovis detection. Circulating M. bovis proteins, specifically polyketide synthetase 5, detected M. bovis-infected cattle with little to no seroreactivity against M. kansasii- and M. avium subsp. paratuberculosis-infected animals. These data indicate that host and pathogen serum proteins can serve as reliable biomarkers for tracking M. bovis infection in animal populations.

Evaluation of the effects of a killed whole-cell vaccine against Mycobacterium avium subsp paratuberculosis in 3 herds of dairy cattle with natural exposure to the organism.

OBJECTIVE: To evaluate effects of vaccination with a killed whole-cell vaccine against Mycobacterium avium subsp paratuberculosis (MAP) on fecal shedding of the organism, development of clinical paratuberculosis (Johne's disease [JD]), milk production, measures of reproduction, and within-herd longevity of dairy cattle naturally exposed to MAP. DESIGN: Controlled clinical trial. ANIMALS: 200 vaccinated and 195 unvaccinated (control) dairy cows from 3 herds in Wisconsin. PROCEDURES: Every other heifer calf born in each herd received the MAP vaccine; 162 vaccinates and 145 controls that had ≥ 1 lactation were included in analyses. Bacteriologic culture of fecal samples for MAP was performed annually for 7 years; results were confirmed via histologic methods and PCR assay. Production records and culture results were evaluated to determine effects of vaccination on variables of interest in study cows. Annual whole-herd prevalence of MAP shedding in feces was also determined. RESULTS: Vaccinates had a significantly lower hazard of testing positive for MAP via culture of fecal samples than did controls over time (hazard ratio, 0.57; 95% confidence interval, 0.34 to 0.97). Fewer vaccinates developed clinical JD than did controls (n = 6 and 12, respectively), but these differences were nonsignificant. Overall within-herd longevity, total milk production, and calving-to-conception intervals were similar between vaccinates and controls. In all herds, prevalence of MAP shedding in feces decreased over time. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination with a killed whole-cell MAP vaccine appeared to be an effective tool as part of a program to control the spread of JD in dairy cattle.