Trichomoniasis, often called “trich,” is the most common curable sexually transmitted infection (STI) globally, caused by the protozoan parasite Trichomonas vaginalis. While historically viewed through the lens of women’s health, men are critical to the sustained transmission of the parasite and can be tested for the infection. Effective diagnosis and treatment in male partners are necessary to break the cycle of reinfection and prevent serious health complications.
How Trichomoniasis Affects Men
The clinical presentation of a T. vaginalis infection in men is often subtle or entirely absent. Approximately 70% to 80% of infected men are asymptomatic carriers, meaning they experience no noticeable symptoms but can still transmit the parasite to their sexual partners. This high rate of asymptomatic carriage is a primary reason why the infection remains widespread.
When symptoms do occur, they are typically mild and non-specific, often developing between 5 and 28 days after exposure. Men may experience a mild urethritis, presenting as slight irritation or itching inside the penis. Other potential signs include a burning sensation after urination or ejaculation, or a thin, clear discharge.
Because these symptoms resemble those of other common STIs, trichomoniasis can be easily overlooked or misdiagnosed in men. The lack of clear symptoms means many infected men do not seek testing, unknowingly serving as a reservoir for the parasite and continuing the transmission to others.
Specific Diagnostic Testing for Men
Accurately diagnosing trichomoniasis in men requires highly sensitive laboratory methods because the parasite burden in the male urogenital tract is often low and transient. Traditional diagnostic methods, such as microscopic examination of a wet mount, are highly unreliable for male samples due to their low sensitivity and the organism degrading quickly outside the body.
For this reason, the gold standard for male diagnosis is the Nucleic Acid Amplification Test (NAAT). NAATs detect the specific genetic material (DNA or RNA) of the parasite, offering greater sensitivity compared to older methods. This technology has revolutionized the detection of trichomoniasis in men, revealing that the prevalence is higher than previously estimated.
The preferred sample type for NAAT testing in men is a first-catch urine specimen, which is non-invasive and highly effective for detecting the parasite in the urethra. Urethral swabs or semen samples may also be collected to increase the detection rate. The availability of these sensitive molecular tests allows clinicians to reliably diagnose the infection in men, even when they are asymptomatic.
Health Risks of Undetected Trichomoniasis
Leaving a T. vaginalis infection untreated carries specific health consequences beyond transmitting the parasite to partners. The infection can ascend the urogenital tract, potentially leading to inflammation of the prostate gland (prostatitis). It is also a known cause of non-gonococcal urethritis, inflammation of the urethra.
Trichomoniasis is associated with inflammation of the epididymis (epididymitis), the coiled tube behind the testicle that stores and carries sperm. Persistent infection has also been linked to diminished sperm function and reduced fertility. The parasite can also be observed in the prostate, which may aggravate urinary symptoms in older men.
A significant public health concern is the association between trichomoniasis and human immunodeficiency virus (HIV). The infection causes inflammation in the urogenital lining, which may increase susceptibility to acquiring HIV. For men living with HIV, trichomoniasis can increase the amount of virus present in seminal fluid, potentially increasing the risk of transmitting HIV.
Treatment Protocols and Partner Management
Following a positive diagnosis, the infection is highly curable using specific anti-parasitic medications. The standard treatment involves a course of nitroimidazole antibiotics, such as metronidazole or tinidazole. Treatment is often administered as a single, large oral dose to promote adherence, or as a lower dose taken twice daily for seven days.
Patients should complete the full course of medication as prescribed, even if symptoms resolve quickly. It is important to avoid consuming alcohol during and for at least 24 hours after finishing metronidazole, or for 72 hours after tinidazole, due to the risk of unpleasant side effects. Treatment failure is rare but can occur, sometimes requiring a longer or different regimen.
Simultaneous treatment of all recent sexual partners is necessary to prevent the cycle of reinfection, often called the “ping-pong” effect. Partners should be treated even if they are asymptomatic or test negative because of the difficulty in detection. Both the patient and all partners must abstain from sexual intercourse until the treatment is completed and any symptoms have resolved.