Trichomonads are small unicellular organisms that can be detected in many wild and domestic animals. Most of these Trichomonads are non-pathogenic commensals or cause mild disease. A clinically significant member of this group is the species Tritrichomonas (T.) fetus, the causative agent of bovine trichomonosis. The pathogen is transmitted during mating. While the infection in the bull is usually asymptomatic, it can lead to vaginitis, endometritis and abortions in cows. Bulls play an important role in the transmission of trichomonads, as they can be carriers of the parasite and may excrete the parasite lifelong. The diagnosis is made by direct microscopic detection of the pathogen in rinse samples or other samples suitable for the examination (for example aborted fetuses, fetal membranes, vaginal secretions). Furthermore, cultivation is possible. However, as already mentioned, a morphological differentiation of the animal-relevant pathogen T. fetus from other Trichomonads is difficult and not always successful. This also applies to Giemsa stained smear preparations, as the number of flagella can vary within the same species. Therefore, molecular methods are more suitable for differentiation than the application of morphological criteria. PCR with specific primers allows differentiation of T. fetus. Thus, it is possible to check isolates and to avoid false positive results. The PCR can also be used on native samples. Therefore, as a complementary method, PCR should be included in animal disease control legislation and used regularly to differentiate Trichomonads spp. In cats, a molecular-genetically different, under field conditions host-specific T. fetus genotype causes diarrhea after fecal-oral infection, in pigs there are no signs of disease.