Validation of a gauze sponge sampling methodology to detect Tritrichomonas foetus by real-time PCR

Bovine trichomoniasis is a concern for the cattle industry. Advances in testing systems have increased the ability to detect the disease in bulls. However, the greatest limitation is proper collection of an adequate sample. The low repeatability observed with most sample collection techniques can cause false-negative results. The aim of our study was to validate a sample collection technique that increases diagnostic sensitivity and is easier and safer to collect than preputial scraping. Commercial bulls (n = 111) of unknown infection status were sampled for detection of Tritrichomonas foetus using 2 different collection methods: 1) preputial scraping with a dry insemination pipette and 2) penile sponging with a 16-ply gauze sponge. Preputial scraping samples were collected by vigorously scraping preputial and penile mucosa using a rigid insemination pipette while applying negative pressure with a syringe. Penile sponge samples were obtained by swabbing the penile and preputial mucosa with a gauze sponge during full extension of the penis. All samples were processed using a commercial medium and submitted under similar conditions for PCR testing. Positive PCR results were detected in 37 of 111 (33%) bulls using the preputial scraping technique; however, 39 of 111 (35%) were positive using the penile sponging technique. The Newton-Raphson algorithm predicted that the sensitivity of the preputial scraping method was 0.919 (95% CI: 0.689-0.983) and the sensitivity of the penile sponging was 0.949 (95% CI: 0.818-0.987). These data indicate that the penile sponging technique is a reliable alternative to the preputial scraping method.