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  • Author or Editor: R. F. Rohde x
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A retrospective study of the results of 12,549 agar gel immunodiffusion tests for bovine leukemia virus, conducted on 1,296 dairy bulls over an 8-year period, was performed to estimate the sensitivity and specificity of the test. The number of tests performed on each bull ranged from 5 to 35, with a mean of 9.7 tests per bull.

Bulls were categorized by their agar gel immunodiffusion test responses; 1,069 (82.5%) were non-infected and 227 (17.5%) were infected. Eighteen false-positive results were reported from the noninfected bulls. Test specificity was estimated to be 99.8%. Thirty-one false-negative results were reported from the infected bulls. Test sensitivity was estimated to be 98.5%.

Fifty-six bulls had 1 or more positive responses when < 6 months old. In 26 (46%), these results were thought to be attributable to colostral immunity.

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in Journal of the American Veterinary Medical Association


To establish whether Mycobacterium paratuberculosis could be cultured from Dulbecco phosphate-buffered saline solution (dpbss) and to test 3 sampling methods, dpbss supplemented with 2% fetal bovine serum was inoculated with M paratuberculosis at concentrations of 104, 103, 102, 101, and 100 colony-forming units/ml. The inoculated media was sampled after mixing, after centrifugation, and after centrifugation and decontamination with 0.75% hexadecylpyridinium chloride. The samples were inoculated onto 3 slants of Herrolds egg yolk medium supplemented with sodium pyruvate and mycobactin J and 1 slant without mycobactin J. Mycobacterium paratuberculosis was isolated following all 3 sampling methods for all concentrations. Treatment with hexadecylpyridinium chloride decreased the number of colonies isolated.

To test the efficacy of a 10-step wash procedure for removing M paratuberculosis from bovine ova, washed zona pellucida intact bovine ova were incubated in dpbss supplemented with 2% fetal bovine serum containing concentrations of 104, 103, 102, 101, and 100 colony-forming units of M paratuberculosis/ml for 12 hours at 22 C. Ten zona pellucida intact ova were removed from each concentration and washed by passing through 10 changes of dpbss supplemented with 15% fetal bovine serum. The media from each wash step was inoculated onto slants of Herrolds egg yolk medium. The ova were included with the tenth wash step. Mycobacterium paratuberculosis was isolated from 1 of 10 tenth-wash steps at the 104 concentration and 5 of 10 tenth-wash steps at 103.

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in American Journal of Veterinary Research