Bovine trichomoniasis is a disease of the reproductive tract caused by Tritrichomonas foetus, a flagellate protozoan that is transmitted through coital contact between a bull and a heifer. In cows, infection leads to embryonic and early fetal death, abortion, fetal maceration, pyometra, and transient or permanent infertility. The disease is found in all cattle-producing countries in the world and in some, it still causes major economic loss due to abortion, infertility, and the culling of carrier bulls. Infection of T. foetus in bovines does not develop prominent immune responses and can be diagnosed by ELISA, direct smears or culture, or by PCR of preputial washings, vaginal material, or aborted tissues.