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  • Author or Editor: Kevin D. McSweeney x
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Abstract

Objective—To estimate seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) infection among adult dairy cows in Colorado and determine herd-level factors associated with the risk that individual cows would be seropositive.

Design—Cross-sectional observational study.

Animals—10,280 adult (≥ 2 years old) dairy cows in 15 herds in Colorado.

Procedure—Serum samples were tested with a commercial ELISA. A herd was considered to be infected with MAP if results of mycobacterial culture of ≥ 1 individual cow fecal sample were positive or if ≥ 1 culled cow had histologic evidence of MAP infection.

Results—424 of the 10,280 (4.12%) cows were seropositive. Within-herd prevalence of seropositive cows ranged from 0% to 7.82% (mean, 2.6%). Infection was confirmed in 11 dairies. Cows in herds that had imported ≥ 8% of their current herd size annually during the preceding 5 years were 3.28 times as likely to be seropositive as were cows in herds that imported < 8%. Cows in herds with ≥ 600 lactating cows were 3.12 times as likely to be seropositive as were cows in herds with < 600 lactating cows. Cows in herds with a history of clinical signs of MAP infection were 2.27 times as likely to be seropositive as were cows in herds without clinical signs.

Conclusions and Clinical Relevance—Annual importation rate, herd size, and whether cows in the herd had clinical signs typical of MAP infection were associated with the risk that individual cows would be seropositive for MAP infection. (J Am Vet Med Assoc 2004;225:97–101)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the incidence of bacteremia in dairy cows with naturally occurring acute coliform mastitis (ACM) with a wide range of disease severity.

Design—Cohort study.

Animals—144 dairy cows with ACM from 6 herds.

Procedure—Cows were examined at time of identification of ACM (time 0) and classified as having mild, moderate, or severe mastitis on the basis of rectal temperature, hydration status, rumen contraction rate, and attitude. Cows were reexamined at 24 or 48 hours. Bacteriologic culturing of milk and blood (30 ml), CBC, and serum biochemical analysis were performed at each time point. Appropriate samples were obtained at a single point from herdmates without mastitis (controls) that were closely matched for lactation number and days since parturition. Blood culture results were compared among severity groups and controls by use of χ2 tests, as was outcome of an ACM episode for cows grouped by blood bacterial isolates.

Results—Bacteria were isolated from 52 blood samples from 46 of 144 (32%) cows with ACM, which was significantly more than control cows (11/156; 7.1%). Group-1 isolates (Escherichia coli, Pasteurella multocida, Mannheimia haemolytica, Klebsiella pneumoniae, Enterobacter agglomerans, and Salmonella enterica serotype Typhimurium) were identified in 20 of 144 (14%) cows with ACM and 0 of 156 control cows. Group-1 isolates were identified in 4.3, 9.1, and 42% of cows classified as having mild, moderate, and severe ACM, respectively. Escherichia coli and K pneumoniae milk and blood isolates obtained from the same cow were of the same genotype. Bacillus spp were identified in 21 of 144 (15%) cows with ACM, which was significantly more than control cows (3/156; 1.9%). Thirty-five percent of cows with a group-1 isolate died during the mastitis episode.

Conclusions and Clinical Relevance—Results suggest that bacteremia develops in a substantial proportion of cows with ACM. Classification of severity of disease is important for establishment of effective treatment protocols; parenteral antimicrobial treatment may be indicated in cows with ACM. (J Am Vet Med Assoc 2001;219:976–981)

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in Journal of the American Veterinary Medical Association