Comparison of two sampling tools for diagnosis of Tritrichomonas foetus inbulls and clinical interpretation of culture results

Objective-To compare sensitivity for diagnosing Tritrichomonas foetus infec tion in bulls using 2 sampling tools and to calculate negative predictive v alues for infection. Design-Randomized clinical trial. Animals-30 Bos taurus bulls naturally or experimentally infected with T foe tus. Procedure-Preputial scrapings were obtained once/wk for 6 weeks using an ar tificial insemination pipette and a metal brush; which tool was used first for each bull was randomly determined. Samples were collected first from th e left side of the prepuce and then from the right side and placed in comme rcially available transport media. chi(2) Values and confidence limits were adjusted for effect of clustering of results by bull. Results-Significant differences in sensitivity of results were not found be tween samples collected using the brush or pipette. Using the pipette, sens itivity was estimated to be 91.6% (95% confidence inter val, 84.3 to 95.7%) ; negative predictive values ranged from 41 to 99% for prevalence of infect ion of 90 to 5%, respectively. Sensitivity was 88.8% for first sample obtai ned and 96.1% for second sample obtained. Conclusions and Clinical Relevance-Collection of preputial scrapings with a n artificial insemination pipette or a metal brush and use of a commerciall y available culture system can provide a sensitive diagnostic test for T fo etus infection in bulls. Calculated negative predictive values indicated th at 1 or 2 tests would suffice in most clinical situations. For bulls from h erds in which T foetus is endemic, 2 to 4 tests/bull may be required to ens ure that each bull is not infected.