Alternative trich sampling method

The wiping technique provides a less-invasive means of collecting a sample for trich testing.

Veterinarians at Iowa State University (ISU) have been testing an alternative method for collecting samples from bulls for trichomoniasis (trich) testing. ISU Extension veterinarian Grant Dewell, DVM, MS, PhD, described the technique during a recent Academy of Veterinary Consultants conference.

In infected bulls, the protozoa Tritrichomonas foetus live in the preputial folds of the penis. The typical sampling technique involves a preputial scraping to collect smegma from below the mucosal surface of the prepuce using a rigid pipette. The procedure can be painful to the bull, especially if repeated several times, and if done improperly can cause injury to the bull. The method also creates some safety risk for the veterinarian and can be inconsistent.

In an ISU survey of 50 veterinarians, just 25% felt comfortable with performing preputial scraping while 33% indicated they were uncomfortable with the procedure. To address this issue, the ISU team worked to identify a method that would be easier, safer for the animal and the veterinarian, and consistently sensitive.

The new method uses a 4"-by- 4" gauze sponge to collect the sample during a bull-soundness exam. At the time of electro-stimulation for semen collection, the veterinarian uses the sponge to swab around the glans and the shaft of the penis. Then the veterinarian places the sponge into the upper chamber of the “InPouch” delivery container and pushes fluid up from the lower chamber to saturate the sponge. They can then send the container to a diagnostic lab just as they would with a typical sample from preputial scraping. Other containers can also work, and veterinarians should check with their diagnostic labs for guidance. Dewell notes the veterinarian needs to change gloves after sampling each bull to avoid contaminating samples.

The ISU team conducted a trial comparing the wiping method with traditional preputial scraping on 111 bulls known to be of high risk for trich. The new collection method identified 39 positive samples and 74 negative samples compared with 37 positive and 72 negative for the scraping method.  They conclude the new method provides sensitivity equal to or greater than that for preputial scraping.

At the diagnostic lab, the sample requires one extra processing step, as the technician needs to squeeze the medium from the sponge for standard PCR testing. It is a minor step, but Dewell recommends veterinarians discuss sampling and submission methods with their diagnostic labs before switching. He also notes that some states currently specify testing based on preputial scraping to meet regulatory requirements for inter- or intra-state movement of bulls. Veterinarians can use the wiping method for management and surveillance purposes in client herds but, for now, might need to use preputial scraping to comply with regulations regarding bull sales and movements.