Trichomoniasis, often called “trich,” is a common sexually transmitted infection (STI) caused by the microscopic parasite Trichomonas vaginalis. This protozoan is the most prevalent non-viral STI globally, responsible for an estimated 156 million new infections worldwide each year. Despite its high rate of occurrence, most people who contract the infection never develop noticeable symptoms. This article clarifies how the infection spreads and addresses common misunderstandings about its transmission.
What Causes Trichomoniasis and How It Spreads
The infection is caused exclusively by the parasite Trichomonas vaginalis, which thrives in the warm, moist environment of the human urogenital tract. The primary and almost universal method of transmission is through sexual contact, specifically skin-to-skin or mucosal contact between partners. The parasite is typically transferred when fluids are exchanged during penis-to-vagina or vagina-to-vagina contact. In women, the parasite most commonly infects the lower genital tract, including the vagina, urethra, and cervix. For men, the infection usually resides in the urethra and sometimes the prostate.
Survival Outside the Body: Addressing Environmental Transmission
The question of whether Trichomonas vaginalis can be contracted from communal water sources, such as a hot tub, is a persistent concern, but the scientific evidence indicates this is extremely unlikely. The parasite is highly fragile and requires specific conditions to survive outside a human host. T. vaginalis lacks a protective cell wall, making it vulnerable to changes in temperature, pH, and chemical disinfectants. Hot tubs and swimming pools contain chemical disinfectants like chlorine, which are rapidly lethal to the parasite. Therefore, contracting trichomoniasis from a hot tub, swimming pool, or even a toilet seat is not considered a practical risk for transmission.
Recognizing the Signs and Symptoms
While most infected individuals remain asymptomatic, symptoms typically appear between five and 28 days after exposure. In women, the infection can cause a yellow-green or grayish vaginal discharge that is often frothy and may have a foul odor. Other symptoms include vulvar and vaginal itching, burning, and discomfort during urination or sexual intercourse. Men are far more likely to be asymptomatic, but when symptoms are present, they are usually mild, such as minor irritation inside the penis or a burning sensation following urination. Regular screening is important for sexually active individuals, as the infection will not resolve on its own.
Diagnosis and Treatment
Diagnosis begins with a healthcare provider collecting a sample of vaginal fluid or a urine sample. The most accurate method is a Nucleic Acid Amplification Test (NAAT), which detects the parasite’s genetic material. A less sensitive method is the wet mount, which involves analyzing the fluid sample under a microscope to identify the motile parasite. Once diagnosed, the infection is curable with a course of oral antibiotics, typically metronidazole or tinidazole. To prevent reinfection, all sexual partners must receive treatment simultaneously and patients must abstain from sexual activity until symptoms have fully resolved.