Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/3/1995
Publication Date: N/A
Technical Abstract: Purified protein derivatives (PPDs) for skin testing cattle in tuberculosis eradication programs in Canada, Mexico, and the United States were compared in side-by-side caudal fold skin tests (CFT) in over 300 cattle from a known infected herd in Mexico. Cattle were randomly assigned to PPD combination groups (Canada/Mexico, Canada/US, and Mexico/US). CFT results in individual cattle agreed (both positive or negative) or were discrepant (one positive, one negative). Samples for culture and histopathology were collected at slaughter for a subpopulation of tested cattle. CFT results agreed in 76-85% of the cattle in various PPD combination groups. Some discrepant CFT results were observed in each PPD combination group, but reached statistical significance only in the Mexico/US PPD group, most Mexico positive-US negative. The amount of agreement between PPDs observed in this study would ensure comparable results for identifying a herd of high prevalence, but may or may not be comparable for identifying low prevalence herds or infected individuals within a herd. Further interpretation of the data should be made cautiously, with limitations of tuberculosis diagnostic techniques in mind. Implications of this data for import/export activities will be left to eradication program staff in each participating country.