Are you the same person as rbalek? Multiple usernames are not allowed on MedHelp.
Pap smears usually miss trichomonas, especially in chronic carriers with low levels of infection.
I should have also said that you should run my reply past your gynecologist. I'll bet s/he has seen other cases like yours, and that s/he will agree with my reply.
And by the way, that your trich was diagnosed by culture, and not by microscopic exam of your vaginal fluid (which is done the same day), suggests the organism was present in small amounts. This is consistent with chronic carriage, i.e. you might have had it for many years. Also, the trich might not be the cause of the symptoms that originally brought you to seek care. It is possible you really had yeast and the trich had nothing to do with it. You'll get a clue based on whether the symptoms clear up after treatment of the trichomonas.
Welcome to the STD forum. I'll try to help. The bottom line is that your husband has not necessarily had other partners.
There are many open questions about the transmission and overall epidemiology of trichomonas. It has been considered a minor STD, an inconvenience more than a significant health problem (although that perspective is beginning to change), and therefore not much research has been done. Although clealry sexually acquired in most cases, there have always been mysterious cases.
If I could show you a graph that showed frequency of trich by women's age at diagnosis, you would see a double peak -- in the early 20s and around age 40-50. The second peak doesn't fit with overall risks for STD, but it does match an age at which gynecological symptoms increase (menopause related) and when some women "catch up" on previously delayed pap smears. That second peak might apply to you. The assumption has always been that most of those infections represent reappearnce of latent infections originally acquired many years earlier. Others might represent nonsexually acquired cases, perhaps from a reservoir in the rectum -- there are certain trich species that normally inhabit our intestines.
Of course, I cannot rule out the possibility that your husband in fact has had other partners recently. But stories like yours are very common, and in many cases neither member of the couple has had sex with other people. You are the best judge of your relationship, but if there is no other reason for doubt about his fidelity, you should trust him. However, he still needs to be treated. Regardless of when and where you were infected, you should assume your husband now also carries the trich; if he isn't treated, you are likely to be reinfected.
I hope this helps. Best wishes-- HHH, MD