What Is Trichomoniasis?
Trichomonads are single-celled eukaryotic microorganisms classified as protozoa. One species, Trichomonas vaginalis, causes trichomoniasis, a sexually transmitted infection (STI) affecting the urogenital tract.
In women, the parasite primarily infects the vagina, cervix, and urethra, while in men, it mainly affects the urethra.
Unlike other sexually transmitted infections, such as chlamydia and gonorrhoea, trichomoniasis is caused by a protozoan parasite rather than a bacterium.
According to the World Health Organization (WHO), approximately 156 million new Trichomonas vaginalis infections were estimated worldwide in 2020 among people aged 15–49.
This makes trichomoniasis the most common non-viral sexually transmitted infection globally. [1]
How Is Trichomoniasis Transmitted?
Trichomoniasis is primarily spread through sexual contact with someone who carries the parasite.
Transmission can occur during vaginal sex without a condom, through direct genital-to-genital contact, or by sharing sex toys without proper cleaning or protection.
The parasite can be transmitted from men to women, from women to men, and between women.
Importantly, transmission can occur even when an infected person has no symptoms. [2,3]
Can You Get Trichomoniasis from a Swimming Pool or Toilet?
Sexual contact is the main, well-established route of trichomoniasis transmission.
Transmission through swimming pool water or contaminated objects is considered uncommon and is not an established route of infection in everyday settings.
However, some laboratory studies have shown that Trichomonas vaginalis can remain viable in moist environments for a certain period under specific conditions.
This does not, however, demonstrate that transmission occurs effectively under real-world conditions.
The available evidence therefore does not support swimming in a pool as a route of trichomoniasis transmission. [8,9]
What Are the Symptoms of Trichomoniasis?
Trichomoniasis often causes no noticeable symptoms.
According to the CDC, approximately 70% of people with trichomoniasis do not experience symptoms.
When symptoms do occur, they typically appear 5–28 days after infection, although they may develop later in some cases. [2,3]
Symptoms in Women
In women, trichomoniasis can cause vaginitis and may lead to:
- Increased vaginal discharge, which may be yellowish or greenish and sometimes frothy.
- An unpleasant odour from vaginal discharge.
- Itching, irritation, or a burning sensation in the genital area.
- Pain or discomfort during sexual intercourse.
- Pain or a burning sensation when urinating.
- Less commonly, lower abdominal pain.
Symptoms in Men
In men, trichomoniasis is often asymptomatic.
When symptoms develop, they may include discharge from the urethra, a burning sensation during urination or ejaculation, and irritation inside the penis.
In some cases, the parasite may be associated with urethritis or prostatitis. [5,6]
The absence of symptoms does not rule out infection. [2,3,4]
How Is Trichomoniasis Diagnosed?
Trichomoniasis cannot be diagnosed based on symptoms alone.
This is because some of its symptoms, including vaginal discharge, itching, and burning, can also occur with other conditions, such as bacterial vaginosis and vulvovaginal candidiasis.
Laboratory testing is therefore needed to confirm the infection.
Molecular Tests (NAAT/PCR)
Nucleic acid amplification tests (NAATs), which include PCR-based methods, are highly sensitive diagnostic tests.
Depending on the test available, vaginal or cervical samples, as well as urine samples, may be used.
Molecular tests can detect infections even in people who have no symptoms.
Microscopic Examination
Direct microscopic examination of a wet-mount preparation can reveal motile parasites.
However, this method has significant limitations.
According to the CDC, the sensitivity of wet-mount microscopy ranges from approximately 44% to 68% and decreases considerably when there is a delay in examining the sample.
Therefore, a negative microscopy result does not rule out trichomoniasis.
Culture
Culture is another available diagnostic method. However, it takes longer to produce results and generally has lower sensitivity than modern molecular tests.
It is also important to note that a Pap smear is not an appropriate diagnostic test for trichomoniasis.
If findings suggestive of Trichomonas vaginalis are detected incidentally during cervical cytology, confirmation with an appropriate diagnostic test is recommended. [4,8]
How Is Trichomoniasis Treated?
Trichomoniasis is a curable infection.
Treatment involves medications from the nitroimidazole class, primarily metronidazole and, in some cases, tinidazole.
Treatment recommendations vary slightly between international health organisations.
Alternative treatment regimens may be used depending on the clinical circumstances. However, tinidazole should be avoided during pregnancy. [4,5]
The choice of medication and dosage should always be determined by a healthcare professional.
Why Is Treating Sexual Partners Important?
Successfully treating trichomoniasis involves more than treating the person who has been diagnosed.
Sexual partners should also be assessed and receive appropriate treatment, even if they have no symptoms.
Otherwise, there is a significant risk of reinfection.
People are advised to avoid sexual contact until they and their sexual partners have completed treatment and any symptoms have resolved.
In addition, the CDC recommends that sexually active women be retested approximately three months after initial treatment, due to the high rate of reinfection. [4]
What Are the Possible Complications of Trichomoniasis?
Although trichomoniasis can be treated effectively, the infection should not be left untreated.
Trichomonas vaginalis infection has been associated with an increased risk of acquiring HIV. According to the WHO, this risk is approximately 1.5 times higher in people with trichomoniasis. [7]
The infection has also been associated with inflammatory conditions affecting the reproductive system, including pelvic inflammatory disease (PID), particularly among women living with HIV.
During pregnancy, trichomoniasis has been linked to adverse pregnancy outcomes, including preterm birth, premature rupture of membranes, and low birth weight. [1,4]
Trichomoniasis During Pregnancy
Pregnant women experiencing symptoms suggestive of trichomoniasis should undergo appropriate diagnostic testing and receive treatment if the infection is confirmed.
Based on the available evidence, metronidazole is considered to pose a low risk to the developing fetus.
However, treatment should always be carried out under medical supervision.
There is currently insufficient evidence to establish the benefits of universal screening for trichomoniasis in all asymptomatic pregnant women. [4]
How Can Trichomoniasis Be Prevented?
Preventing trichomoniasis largely involves practising safer sex.
Correct and consistent condom use reduces the risk of transmission.
Other important preventive measures include avoiding the sharing of sex toys without appropriate cleaning or protection, informing sexual partners following a diagnosis, and seeking prompt medical assessment after a possible exposure.
In addition, people diagnosed with trichomoniasis are advised to undergo testing for other sexually transmitted infections, including HIV, syphilis, gonorrhoea and chlamydia.
Early diagnosis and the simultaneous treatment of sexual partners play an important role in preventing further infections. [1,4]