Trichomonas Transmission from One Sexual Interaction
Yes, Trichomonas vaginalis can absolutely be transmitted from a single sexual encounter, as it is a sexually transmitted infection with high transmission efficiency between partners. 1, 2
Transmission Characteristics
Trichomoniasis is transmitted through sexual intercourse, making it one of the most common non-viral sexually transmitted diseases worldwide with an estimated 276 million new cases annually. 2
Transmission via fomites (contaminated objects) is rare, with sexual contact being the primary route of spread. 2
The infection is highly contagious between sexual partners, which is why CDC guidelines explicitly recommend simultaneous treatment of all sexual partners to prevent reinfection. 1, 3
Clinical Presentation After Exposure
Most men infected with T. vaginalis are asymptomatic, making them efficient vectors for transmission without knowing they are infected. 1
Many women are also asymptomatic (up to 50% may not report symptoms), though symptomatic women typically develop diffuse, malodorous, yellow-green discharge with vulvar irritation. 1
The asymptomatic nature in both sexes facilitates ongoing transmission, as infected individuals may not seek treatment and continue sexual activity. 4
Evidence Supporting Single-Encounter Transmission
CDC guidelines emphasize treating asymptomatic sexual partners even when cultures are negative or not performed, specifically because "a woman may become reinfected if her consort is not treated." 3
The difficulty in isolating the organism from asymptomatic male carriers means negative tests cannot be relied upon, yet transmission still occurs from these individuals. 3
Treatment of both patient and sex partner is required for "reduction of transmission," indicating the high likelihood of partner-to-partner spread. 1
Important Clinical Pitfalls
Reinfection is extremely common when partners are not treated simultaneously, which is why patients must abstain from sex until both they and their partners complete treatment and are asymptomatic. 1, 5
High rates of retest positives occur after treatment (7-10% treatment failure, even higher in HIV+ women), often due to reinfection from untreated partners rather than true treatment failure. 6
The infection has serious health consequences beyond transmission, including facilitation of HIV transmission and acquisition, adverse pregnancy outcomes (premature rupture of membranes, preterm delivery, low birth weight), and potential links to cervical cancer. 1, 2, 7