T vaginalis is often harbored asymptomatically. For women with symptomatic disease, after an incubation period of 5 days to 4 weeks, a vaginal discharge develops, often with vulvovaginal discomfort, pruritus, dysuria, dyspareunia, or abdominal pain. Examination shows a copious discharge, which is usually not foul smelling but is often frothy and yellow or green in color. Inflammation of the vaginal walls and cervix with punctate hemorrhages are common. Most men infected with T vaginalis are asymptomatic, but it can be isolated from about 10% of men with nongonococcal urethritis. In men with trichomonal urethritis, the urethral discharge is generally more scanty than with other causes of urethritis.
Diagnosis is traditionally made by identifying the organism in vaginal or urethral secretions. Examination of wet mounts will show motile organisms. Tests for bacterial vaginosis (pH > 4.5, fishy odor after addition of potassium hydroxide) are often positive with trichomoniasis. Newer point-of-care antigen detection and nucleic acid probe hybridization tests and nucleic acid amplification assays offer improved sensitivity compared to wet mount microscopy and excellent specificity.