Infection of prepubertal heifer calves as a natural host model for Tritrichomonas foetus

Katy A. Martin¹Sara Reece¹Jeba Jesudoss Chelladurai²Tyler A Harm¹Jodi D. Smith¹Courtney N Blake³Douglas Jones¹Kris Kovach¹Krysta McMahan¹Erica Moscoso¹Morgan Ostrander¹Matthew T Brewer^1*

• ¹Iowa State University, Ames, United States
• ²Auburn University, Auburn, AL, United States
• ³Practical Livestock Services, Casey Iowa, United States

Tritrichomonas foetus is a sexually transmitted protozoan parasite that causes economic loss in the cattle industry throughout the world. In the United States, there are no approved treatments for the parasite. Owing to its transmission strategy, T. foetus typically infects cattle of breeding age. However, in vivo studies of treatments, diagnostic strategies, and vaccines are severely hampered by the maintenance and cost of maintaining adult cattle in research settings. In this study, we investigated the utility of infecting pre-pubescent heifer calves with T. foetus. Our experiments revealed that despite being in anestrus, these calves were amenable to infection with trophozoites for as long as 42 days post-infection as determined by PCR and culture of the organism. Histopathology of infected reproductive tracts revealed inflammation throughout the reproductive tract of infected calves. Infection resulted in endometritis with lymphoplasmacytic infiltration and demonstrated that trophozoites could pass through the cervix even during anestrus in prepubescent heifers. In addition, immunohistochemistry of the vagina, cervix, and uterus demonstrated robust expression of galectin-1, a putative receptor for T. foetus adhesion. Our results demonstrate that prepubertal heifer calves are a suitable natural host model for bovine trichomonosis. This is a significant breakthrough in the field and also has potential for advancing the human trichomoniasis research agenda.