As far as is known, Trichomonas vaginalis is only transmitted and acquired sexually. The standard explanation for the apparent exceptions is that the organism can be dormant for months, probably for many years, in both women and men; so that a new diagnosis doesn't necessarily mean it was acquired recently. Contrary to occasional rumor, it is not acquired from toilet seats, shared moist towels, etc.
Another theoretical possibility is that other species of trichomonas (for example, Trichomonas hominis) can be normal in the intestines, and conceivably could get transmitted into the vagina in women because of the proximity of anus and vagina; and under the microscope, the two organisms look similar. However, this is not believed to be a common explanation.
Whatever the reasons, trich does indeed show up from time to time in circumstances that seem to make sexual acquisition unlikely.
Good luck-- HHH, MD
Thank you for following up with that comment Dr. You don't know how invaluable your information has been. I appreciate the Sunday you gave up to deal with my issues :)
Relationship counseling is definitely not what I do. But keep in mind that it's one thing to hang a relationship on an STD for which there are essentially no exceptions to recent sexual transmission, like gonorrhea or chlamydia; but perhaps another when there are uncertainties about how, when, and where--like trichomonas, HPV, and so on.
HHH, MD
I thank you for your timely response and just the overall availability you provide. My relationship hangs on the balance of this. Although it doesn't make my decision making any easier, I really appreciate you guys!!!