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in Journal of the American Veterinary Medical Association

Summary

Fetuses were obtained from 58 cows that were fecal culture-positive for Mycobacterium paratuberculosis, but were not manifesting signs of paratuberculosis. Fetal tissues from 5 of 58 cows were culture-positive for M paratuberculosis. All 5 culture-positive fetuses were from cows that were classified as heavy fecal shedders (5/28; 17.8%). Difference in prevalence of fetal infection between light (< 70 colonies/tube) and heavy fecal shedders was significant (Fisher's exact test, P < 0.05). Association was not evident between serologic status of the dam and prevalence of fetal infection.

In infected cows without signs of paratuberculosis, fetal infection develops with lower frequency than previously reported for cows with clinical signs of the disease. In this study, fetal infection was found only in cows that were heavy fecal shedders.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To compare sensitivity of several methods of bacteriologic culture of pooled bovine fecal samples for detection of Mycobacterium paratuberculosis and evaluate homogeneity in number of M paratuberculosisin pooled fecal samples.

Sample Population—Feces from 10 dairy cows that shed M paratuberculosis at various concentrations and 1 dairy cow known to be free of infection with M paratuberculosis.

Procedure—5 fecal pooling methods, 2 culture methods, and 2 pool sizes were evaluated. Each pooled sample contained 1 infected sample and 4 or 9 uninfected samples.

Results—Sensitivity of detection of M paratuberculosis was greater with smaller pool size (5 vs 10 samples/ pool). Detection sensitivity was also associated with concentration of bacteria in the infected sample. Results indicated that, compared with concurrent bacterial culture of individual infected samples, 37 to 44% of pooled samples with low bacterial concentrations yielded positive culture results and 94% of pooled samples with high bacterial concentrations yielded positive results.

Conclusions and Clinical Relevance—Bacteriologic culture of pooled fecal samples may provide a valid and cost-effective method of detecting M paratuberculosis infection in cattle herds. (Am J Vet Res 2002;63:1207–1211)

Full access
in American Journal of Veterinary Research

Objective

To evaluate clinical findings in cows with recumbency associated with hypokalemia.

Design

Retrospective case series.

Animals

10 adult dairy cows with weakness or recumbency and hypokalemia.

Procedure

Signalment, history, physical examination findings, results of diagnostic tests, and response to treatment were extracted from the medical record of each cow.

Results

8 cows were recumbent on admission and 2 were profoundly weak. All cows had been given isoflupredone acetate as treatment for ketosis prior to admission. All were hypokalemic (serum potassium concentration, 1.4 to 2.3 mEq/L) with no other apparent cause for recumbency. Despite treatment with potassium, plasma potassium concentrations within the reference range were achieved in only 6 of the 9 cows treated. Two cows responded to treatment. Three cows died, 3 were euthanatized, 2 improved clinically and were discharged, 1 was discharged while still recumbent, and 1 was sent to slaughter prior to treatment. Histologic examination of muscle tissue from 2 cows revealed myonecrosis and vacuolation consistent with hypokalemic myopathy.

Clinical Implications

Hypokalemia should be considered in the differential diagnosis for cows that are weak or recumbent, particularly after treatment for ketosis with isoflupredone acetate. Aggressive treatment with potassium salts administered orally is indicated.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the in vitro susceptibility of various field isolates of Mycobacterium avium subsp paratuberculosis (MAP) to gallium nitrate.

Sample—10 isolates of MAP, including 4 isolated from cattle, 2 isolated from bison, 1 isolated from an alpaca, and 3 isolated from humans.

Procedures—The in vitro susceptibility to gallium nitrate was tested by use of broth culture with detection of MAP growth by means of a nonradiometric automated detection method. For each MAP isolate, a series of 7 dilutions of gallium nitrate (concentrations ranging from 200 to 1,000μM) were tested. Gallium nitrate was considered to have caused 90% and 99% inhibition of the MAP growth when the time to detection for culture of the MAP stock solution and a specific concentration of gallium nitrate was delayed and was similar to that obtained for culture of the MAP stock solution (without the addition of gallium nitrate) diluted 1:10 and 1:100, respectively.

Results—Gallium nitrate inhibited MAP growth in all 10 isolates. The susceptibility to gallium nitrate was variable among isolates, and all isolates of MAP were inhibited in a dose-dependent manner. Overall, the concentration that resulted in 90% inhibition ranged from < 200μM for the most susceptible isolates to 743μM for the least susceptible isolates.

Conclusions and Clinical Relevance—Gallium nitrate had activity against all 10 isolates of MAP tested in vitro and could potentially be used as a prophylactic agent to aid in the control of MAP infections during the neonatal period.

Full access
in American Journal of Veterinary Research

Summary

An elisa containing lipoarabinomannan (lam) antigen was used to detect antibodies in milk and serum for diagnosis of Mycobacterium paratuberculosis infection in dairy cattle. In experiment 1, milk and serum samples were obtained from 25 cows, and subjected to lam elisa testing immediately, and after 1 year of storage at −70 C. Milk samples, with and without a commonly used chemical preservative, were tested. There was no significant difference in lam elisa results between fresh and frozen samples or between preserved and unpreserved milk samples. In experiment 2, milk samples were collected daily from 30 cows over a 14-day period. The day-to-day coefficient of variation was 0.19 for milk lam elisa and was 0.15 for serum lam elisa, with no statistically significant time effect detected. In experiment 3, single milk, serum, and fecal samples were obtained from 764 cows. The fecal samples were cultured for M paratuberculosis to identify infected cows, and the serum and milk samples were subjected to lam elisa testing. Results were compared, using the area under the receiver operating characteristic curves. The milk lam elisa had specificity (± 95% confidence limits) of 87 ± 8.1% when the cutoff was set at 50% sensitivity, and specificity of 83 ± 9.1% when sensitivity was set at 60%. The area under the receiver operating characteristic curve was 0.85 ± 0.03 for the milk elisa and 0.75 ± 0.02 for the serum elisa. In this population of cattle, the milk lam elisa had comparable accuracy to serum lam elisa, although the milk lam elisa was slightly less reproducible (higher coefficient of variation).

Free access
in American Journal of Veterinary Research

Summary

Overall, 74% of the tissue specimens that meat inspectors at a large Pennsylvania packing plant identified as lesions of swine mycobacteriosis yielded Mycobacterium avium on bacteriologie culture. Histopathologic lesions compatible with mycobacteriosis were identified in 83% of the specimens; only 12% of the specimens had acid-fast staining organisms.

Free access
in Journal of the American Veterinary Medical Association

Summary

Feces from cows naturally infected with Mycobacterium paratuberculosis was given to 6 uninfected heifers by orogastric intubation, to determine whether ingested organisms could be passively excreted and detected by bacteriologic culture of feces (ie, false-positive result). Heifers were paired, and each pair received a different dose of feces on days 1 and 2. Fecal samples were collected from the heifers 3 times daily. Mycobacterium paratuberculosis was detected in fecal samples of all heifers within 18 hours of being given the first dose of feces. The number of colony-forming units peaked on days 3 or 4, and organisms were no longer detected by day 7. The number of colony-forming units in fecal samples from the heifers was approximately proportional to the dose given. On days 15 and 16, the experiment was repeated with feces from a second infected cow. Results were similar to those in the first experiment. All heifers remained seronegative (agar-gel immunodiffusion test and elisa) and had negative results to the intradermal johnin test throughout the experiment.

Lymph node and intestinal tissues were obtained from all 6 heifers at slaughter on day 28. Mycobacterium paratuberculosis was not isolated from mesenteric lymph nodes from the ileocecal valve region, but was isolated from ileal mucosal samples from each heifer.

Free access
in American Journal of Veterinary Research