Is trichomoniasis (trich) a sexually transmitted infection (STD)?

Is Trichomoniasis a Sexually Transmitted Infection?

Yes, trichomoniasis is definitively a sexually transmitted infection (STI/STD) caused by the protozoan parasite Trichomonas vaginalis, transmitted through sexual contact with an infected partner. 1, 2, 3, 4

Transmission Mechanism

• Trichomoniasis is contracted exclusively through sexual intercourse with an infected partner. 1, 4
• The CDC explicitly classifies trichomoniasis among diseases characterized by vaginal discharge in their sexually transmitted diseases treatment guidelines. 5
• Trichomonas vaginalis is site-specific for the genitourinary tract and has been isolated from virtually all genitourinary structures. 3
• Transmission via fomites (non-sexual objects) is extremely rare and not a clinically significant route. 4

Epidemiologic Significance

• Trichomoniasis is the most common non-viral sexually transmitted infection worldwide, with the WHO estimating 276 million new cases annually and a prevalence of 187 million infected individuals. 4, 6, 7
• In the United States, aside from human papillomavirus, trichomoniasis is the most common sexually transmitted infection. 7
• The infection is highly contagious between sexual partners, which is why the CDC mandates simultaneous treatment of all sexual partners to prevent reinfection. 1, 2

Clinical Presentation Supporting Sexual Transmission

• Most infected men are asymptomatic carriers, making them unknowing vectors of transmission to female partners. 1, 2
• Up to 50% of infected women are also asymptomatic, though symptomatic women typically develop diffuse, malodorous yellow-green vaginal discharge with vulvar irritation. 1, 2
• The asymptomatic nature in both sexes explains why partner treatment is essential even without confirmed testing—untreated partners will reinfect treated patients. 1

Key Distinction from Other Vaginal Infections

• Unlike bacterial vaginosis (BV), which is associated with sexual activity but not considered exclusively an STD, trichomoniasis is definitively sexually transmitted. 5
• Women who have never been sexually active are rarely affected by trichomoniasis, confirming its sexual transmission route. 5
• The CDC requires that all sexual partners be treated simultaneously with the same metronidazole regimen, regardless of symptoms, because untreated partners are the leading cause of treatment failure. 1

Public Health Implications

• Trichomoniasis is a reportable sexually transmitted infection that requires evaluation and treatment of all recent sexual contacts. 1
• The infection facilitates HIV transmission and acquisition, causes adverse pregnancy outcomes (premature rupture of membranes, preterm delivery, low birth weight), and has potential links to cervical cancer. 2, 7
• Patients must abstain from sexual intercourse until both partners complete treatment and are asymptomatic to prevent reinfection. 1, 2

Common Pitfalls

• Do not confuse trichomoniasis with bacterial vaginosis—while BV is associated with sexual activity, it is not exclusively an STD and partner treatment is not beneficial for BV. 5
• Do not fail to treat sexual partners simultaneously—this is the most common cause of treatment failure and reinfection. 1
• Do not assume symptomatic presentation is required for transmission—asymptomatic carriers efficiently transmit the infection. 1, 2