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Objective

To determine the validity of a 5-antigen ELISA for detection of tuberculosis in cattle and Cervidae.

Design

Cross-sectional observational study.

Sample Population

Serum samples collected from 5,304 cattle in 23 herds and 1,441 Cervidae in 12 herds.

Procedure

Discriminant analysis was used to determine the linear combination of antigens that accurately predicted the true Mycobacterium bovis infection status of the most animals. The resulting classification functions then were used to calculate the percentage of animals that were correctly classified (ie, sensitivity and specificity). The kappa statistic was calculated to evaluate different combinations of test results,

Results

Of the 23 cattle herds, 4 dairy and 2 beef herds were considered infected. Of the 12 Cervidae herds, 5 were considered infected. For cattle, the specificity and sensitivity of ELISA, using the discriminant function, were 56.4 and 65.6%, respectively. For Cervidae, the specificity and sensitivity of ELISA, using the discriminant function, were 78.6 and 70.0%, respectively.

Clinical Implications

Results suggest that the 5- antigen ELISA would not be a good test for tuberculosis, especially in cattle, if used alone. However, when results of the ELISA and tuberculin test were interpreted in parallel, sensitivity of the combination was greater than sensitivity of either test alone. Similarly, when results of the 2 tests were interpreted in series, specificity of the combination was greater than specificity of either test alone. (J Am Vet Med Assoc 1996; 209:962-966)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess phylogenetic relationships among Mycobacterium bovis isolates by use of random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) fingerprinting and to relate genetic profiles of isolates to epidemiologic characteristics.

Animals—400 cattle with tuberculosis.

ProcedureMycobacterium bovis was isolated from various organs of cattle slaughtered in 6 geographic regions of Mexico. Most cattle were adult Holsteins from large herds that did not participate in a tuberculosis control program. Four random primers and 2 selected primers were used in RAPD-PCR fingerprinting of 88 isolates. Pairwise genetic distance between isolates was obtained and subjected to cluster analysis with bootstrapping to test for levels of support.

Results—98 different fragments were obtained; there was broad genetic diversity among isolates, and each isolate had a unique RAPD-genotype, including those originating from the same herd. Clustering by geographic location, affected organ, or severity of lesion was not detected. Linkage disequilibrium analysis suggested that M bovis was highly clonal and that mutations develop at a rapid rate among isolates.

Conclusions and Clinical Relevance—Use of RAPDPCR could not differentiate M bovis isolates by epidemiologic characteristics or identify common sources of infection. (Am J Vet Res 2000;61:90–95)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe time-dependent changes in plasma concentrations of 3-methylindole (3MI) and blood concentrations of 3-methyleneindolenine (3MEIN)-adduct in feedlot cattle.

Animals—64 yearling steers.

Procedures—Steers were assigned to 2 groups (32 steers/group). During the first 8 weeks, blood samples were collected from group 1 before the morning ration was fed, whereas samples from group 2 were collected 2 to 3 hours after the ration was fed. Blood samples were collected from all steers approximately 4 times/wk for 3 weeks and 3 times/wk for the subsequent 5 weeks. Samples were collected at the same time for all steers for an additional 10 weeks. Plasma samples were analyzed for 3MI concentrations. Blood samples collected from cattle in group 2 during the first 8 weeks were analyzed for 3MEINadduct concentrations.

Results—Mean blood concentration of 3MEINadduct increased to a maximum value on day 33 (0.80 U/μg of protein) and then decreased to a minimum on day 54 0.40 U/μg of protein). Plasma 3MI concentrations initially decreased and remained low until after day 54. Group-1 cattle had lower plasma 3MI concentrations, compared with concentrations for group-2 cattle. Blood 3MEIN-adduct concentrations and plasma 3MI concentrations were not associated with deleterious effects on weight gains.

Conclusions and Clinical Relevance—Blood 3MEIN-adduct concentrations peaked during the period of greatest risk for development of bovine respiratory disease complex. Conversely, plasma 3MI concentrations decreased during the same period. Animal-to-animal variation in metabolic capacity to convert 3MI to 3MEIN may be of more importance than differences in plasma 3MI concentration. Am J Vet Res (2002;63:591–597).

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate 2 polymerase chain reaction (PCR)-based methods for differentiating cytotoxic and noncytotoxic Pasteurella trehalosi from Rocky Mountain bighorn sheep (Ovis canadensis canadensis).

Sample Population

23 isolates of P trehalosi from bighorn sheep in Colorado, including 18 from free-ranging herds and 5 from a captive herd.

Procedure

Using a sequence of the leukotoxin gene region of P haemolytica serotype 1, 7 PCR primers were designed. A PCR amplification was performed on a sample of bacterial cell suspensions from pure cultures of P trehalosi with known in vitro cytotoxic effects. The 2 most promising primer pairs were used in a study of 23 P trehalosi isolates. Results were analyzed for association with cytotoxicity and 3 distinct ribotypes (ECO, ACO, and BCO).

Results

Significant associations were observed between in vitro cytotoxicity and PCR results for coding region, between ribotype ECO classification and PCR results for coding region, and between ribotype ECO classification and PCR results for promoter region. There was a negative association between ribotype ACO classification and PCR results for coding and promoter regions.

Conclusions and Clinical Relevance

The PCR for the leukotoxin A coding region may be useful in differentiating cytotoxic from noncytotoxic P trehalosi isolates recovered from bighorn sheep. It may be useful for studying epidemiologic features of pasteurellosis in bighorn sheep and for designing vaccines to protect wild sheep against pneumonia caused by P trehalosi and P haemolytica. (Am J Vet Res 1999;60:583–588)

Free access
in American Journal of Veterinary Research