Perineal Urethrostomy Enables Susceptibility of Bull Calves as a Natural Host Model for Bovine Trichomonosis

<i>Tritrichomonas foetus</i> is a sexually transmitted protozoan that causes early embryonic death in cattle. A challenge in trichomonosis research is that in vivo studies of treatments, diagnostic strategies, and vaccines are severely hampered by the logistical challenge and cost of maintaining adult bulls. Since natural infections are diagnosed in postpubescent animals, the paradigm is that only mature breeding bulls can be infected. In this study, we hypothesized that prepubescent bull calves could be artificially infected with <i>T. foetus</i> trophozoites for the purpose of conducting research trials. Initial attempts to directly infect bull calves with two different parasite isolates resulted in the sporadic and transient detection of parasite DNA but not culturable trophozoites. In vitro and in vivo studies suggested that urine directly inhibited trophozoites, likely by osmotic damage and mechanical flushing action. Studies utilizing a perineal urethrostomy to remove urine flow from the prepuce resulted in the ability to colonize the prepuce, with live organisms being cultured for as long as 15 days post-inoculation. Future studies optimizing this technique have the potential to accelerate the pace of bovine trichomonosis research and may have applications in the study of human trichomoniasis.