Tritrichomonas foetus is a flagellated protozoan that causes bovine trichomonosis, a venereal disease that can lead to fetal loss (BonDurant, 1997). T. foetus colonizes the bull's lower genital without causing clinical signs or gross pathological changes (Cobo et al., 2009). The protozoan is transmitted to the cow during intercourse. The infection rarely lasts more than four months, but may be associated with genital inflammation and early fetal loss. In general, T. foetus colonizes the cervix, reaches the uterus and can invade the fetal cavities (Parsonson et al., 1976). Colonized organs may show some deterioration of epithelial integrity that has been associated to the raise of immune response (Parsonson et al., 1976).

T. foetus can be grown from Cervical vaginal mucus (CVM) or preputial lavage and in each case presents as a motile cell with four flagella originating at the anterior pole, one of them curved backwards along the body forming an undulating membrane (Tachezy et al., 2002). The multiflagellate trophozoite presents with well-characterized run-and-tumble movements (Lenaghan et al., 2014). Exposure of the protozoan to low temperatures or to certain drugs allows to see an endoflagellate (non motile) form (Pereira-Neves et al., 2014). These studies have suggested that the endoflagellar form could be important in pathogenesis.

Many aspects of the biology of T. foetus are still unknown. It is not clear how T. foetus multiplies in the host, whether it modifies the environment in which it develops, or how it prepares for the next sexual contact. Part of this ignorance translates into the absence of vaccines that help prevent infection (Baltzell et al., 2013; Martinez et al., 2018).

The CVM is a viscoelastic fluid that changes in response to ovarian function (Macdonald, 1969). Under the influence of estrogens the mucus is clear, elastic and abundant, whereas with progesterone, shortly after ovulation, it becomes thick and sticky. In an estrous period, the CVM volume can vary 10-fold while remaining isotonic. Biophysical changes respond to a large number of chemical compounds influenced by changes in the expression of many genes (Pluta et al., 2012; Pommerenke and Viergiver, 2017).

Here, we have set out to grow T. foetus on CVM in the laboratory. In particular, we have sought to know whether T. foetus can grow in the absence of living host cells, whether T. foetus presents the same appearance in CVM as in routine culture medium, and whether T. foetus proliferates similarly in mucus obtained at different stages of the estrous cycle.