Trichomoniasis is a common sexually transmitted infection (STI) caused by the single-celled parasite Trichomonas vaginalis. This protozoan infects the urogenital tract and is one of the most prevalent non-viral STIs globally. While many infected individuals experience no symptoms, the infection often causes noticeable changes, particularly in vaginal or penile discharge.
Characteristics of Trichomoniasis Discharge
The discharge associated with a Trichomonas vaginalis infection is frequently described as having a strong, unpleasant, or foul odor, often characterized as “fishy.” This distinct smell results from the parasite’s metabolic activity, which produces volatile organic compounds known as amines. The presence of these amines is so characteristic that the “whiff test” involves adding a potassium hydroxide solution to a discharge sample to intensify the odor for detection.
The discharge typically exhibits a thin consistency and is often frothy, foamy, or bubbly. This unusual texture is caused by gases released by the parasite as it metabolizes materials. The volume of discharge may also be significantly increased compared to normal physiological discharge.
The color of the discharge is another defining characteristic, commonly appearing as yellowish-green or grey. While these physical properties are indicative of trichomoniasis, symptoms can overlap with other conditions, such as bacterial vaginosis. Therefore, professional testing is necessary for a definitive diagnosis.
Additional Signs of Infection
While abnormal discharge is a primary symptom, the parasite can trigger significant localized irritation in the genital area. This irritation often manifests as intense itching, burning, soreness, or redness of the vulva, vagina, or penis.
Discomfort during urination, medically termed dysuria, is another common symptom. The infection can cause an inflamed urethra, leading to a burning feeling or pain when passing urine, or a frequent urge to urinate. Pain or discomfort during sexual intercourse (dyspareunia) may also occur due to the inflammation of the genital tissues.
A substantial number of people, particularly those with a penis, may remain asymptomatic carriers of the infection. When symptoms occur in men, they are often milder, including transient urethritis, a slight penile discharge, or burning after ejaculation. Even without obvious symptoms, an infected person can still transmit the parasite to sexual partners.
Medical Diagnosis and Treatment
Anyone experiencing symptoms suggestive of trichomoniasis should consult a healthcare provider for evaluation. Diagnosis typically begins with a physical examination and the collection of a sample of discharge or urine for laboratory testing. The most accurate method involves Nucleic Acid Amplification Tests (NAATs), which are highly sensitive for identifying the parasite’s genetic material.
Once confirmed, the infection is highly curable with prescription oral antibiotics from the 5-nitroimidazole class, such as metronidazole or tinidazole. The standard course for women is often metronidazole 500 mg twice daily for seven days, while men are typically prescribed a single 2-gram dose. Patients must complete the full course of medication exactly as prescribed, even if symptoms resolve quickly.
Simultaneous treatment of all sexual partners is necessary to prevent reinfection. Untreated trichomoniasis carries significant health risks, including increased susceptibility to acquiring or transmitting HIV. In pregnant individuals, the infection is also associated with complications such as premature rupture of membranes, preterm labor, and low birth weight.