Trichomoniasis

Etiology

Trichomoniasis is an infection that is sexually transmitted and is acquired by direct sexual contact. It can live for a few hours in moist environments, but virtually all cases are due to the venereal transmission of the organism.  Risk factors include:

• History of STIs
• New sex partner or multiple partners
• Contact with an infected partner
• Abusing IV drugs
• Not using any type of barrier contraception

Epidemiology

Trichomoniasis occurs more frequently in people with multiple sexual partners who also have other sexually transmitted infections. In one study with 4057 participants, T. vaginalis infection was found in 0.5% of males and 1.8% of females in the study population. They found prevalence among Black study participants to be higher, with 4.2% and 8.9% infection rates noted in males and females, respectively.[1]  

According to another article, the estimated infection rate of Trichomoniasis vaginalis is 3.2%. T. vaginalis infection rates in the United States are higher than those of Neisseria gonorrhoeae and Chlamydia trachomatis infection rates combined. Trichomoniasis is most prevalent amongst women ages 40 to 49, which is starkly different from the rate of chlamydia infections, which peaks in the 19 to 24-year-old age group.[2]

Pathophysiology

Trichomonas is a motile organism with a size comparable to a white blood cell. It has at least 4 flagella that provide undulating motility. The organism resides in the lumen of the urogenital tract. The organism releases cytotoxic proteins that destroy the epithelial lining. During an infection, the vaginal pH usually increases.

In women, T. vaginalis has an incubation period of five to twenty-eight days. Women with trichomoniasis often complain of a foul-smelling yellow or green vaginal discharge, dyspareunia, urinary frequency, dysuria, and/or vulvar pruritus or erythema. In men, it often does not cause symptoms. If a male is symptomatic, the most common symptom is urethritis. Less commonly, men may also develop prostatitis and epididymitis.

History and Physical

Women will often present with a chief complaint similar to other sexually transmitted infections, including vaginal discharge, painful intercourse, urinary tract infection symptoms, vaginal itching, or pelvic pain. Men may be asymptomatic, or on occasion, they may present with symptoms including penile discharge, testicular pain, dysuria, urinary frequency, or cloudy urine. Trichomoniasis can cause urethritis in men and occasionally epididymitis or prostatitis. 

Critical questions to ask when gathering a history include past treatment for STIs, condom use with intercourse, and the presence of foul-smelling discharge.

A physical exam will often include a pelvic exam for women and a urethral swab for men.[3]

A vaginal discharge is common in women; the discharge is thin, frothy, and has an abnormal odor. The genitals are often red and edematous. A strawberry cervix is seen in about 40% of patients. Palpation of the pelvis may reveal mild tenderness.

Evaluation

The most common diagnostic testing performed is wet prep microscopy. Trichomonads are motile organisms with flagella and can be seen moving in the preparation when viewed with a microscope. This test has been shown to be only 40% to 60% sensitive but is typically the most common testing method used due to convenience and low cost.[4]

Nucleic acid amplification tests (NAATs) are gaining favor when testing for Trichomonas vaginalis. They have become the gold standard when testing for gonorrhea and chlamydia. Many of the NAATs available have been shown to have greater than 90% sensitivity and specificity when testing for Trichomonas vaginalis.[2]

Before NAATs and other point-of-care options were developed, the gold standard was a culture when testing for Trichomonas vaginalis with a negative wet prep and a symptomatic patient.

The vaginal pH is usually more than 4.5 in the presence of trichomoniasis, but this is not a specific finding. The whiff test is done by adding drops of potassium hydroxide to a sample of vaginal discharge. This generates a fishy smell.

Treatment / Management

According to the 2021 CDC STI treatment guidelines, a seven-day course of 500 mg metronidazole twice daily is indicated.

In patients with known HIV infection, the recommended treatment regimen is a seven-day course of 500 mg metronidazole twice daily.

According to a study, the percentage of women positive for trichomoniasis on their test of cure was 19% when given a single dose of metronidazole versus 11% when patients completed a seven-day course of metronidazole.[5](A1)

If left untreated, trichomoniasis may remain subclinical or resolve with host immunity.[2]

Pregnant women must be treated. Otherwise, it can result in adverse outcomes. The drug of choice is metronidazole. Women should stop breastfeeding during treatment.

The CDC also recommends performing a test of cure for all women treated for trichomoniasis within three months of treatment. Nucleic acid amplification testing (NAAT) can be completed as soon as two weeks following treatment. NAAT is the recommended method for a test of cure due to the sensitivity of the test.

Many states allow expedited partner therapy (EPT). EPT laws typically enable providers to prescribe treatment to a third party sexual partner without performing a medical examination or establishing a provider/patient relationship with the third party sexual partner of a patient diagnosed with trichomoniasis or other STIs. A list of states and the laws surrounding EPT can be found on the CDC website.

The CDC does not recommend for or against treating for chlamydia and gonorrhea when treating for trichomonas. This is a provider and patient-specific decision. Things to consider when deciding on treatment for chlamydia and gonorrhea are the patient's reliability for follow-up and the risks and benefits of treatment.[6]

When metronidazole fails, the other drug is tinidazole. Patients should be advised not to consume alcohol when these drugs are prescribed. Topical medications have high failure rates and should not be used.

Differential Diagnosis

A provider should always consider other STIs when a patient presents with complaints concerning for trichomoniasis or coinfection when a patient is diagnosed with trichomoniasis. If a female patient presents with complaints and concerns about an STI, the practitioner should always consider pelvic inflammatory disease (PID) in their differential diagnosis. PID has significant morbidity implications, including reduced fertility. Trichomonas is not known to cause pelvic inflammatory disease, so if there is concern for PID, there is a different treatment regimen.[7]

Prognosis

Patients treated with metronidazole have a 90% to 95% cure rate. The cure rates are even higher when the sexual partner is treated. Unfortunately, recurrent infections are common in sexually active individuals. Trichomoniasis is strongly associated with the presence of other STIs, including HIV, gonorrhea, human papillomavirus (HPV), herpes, and chlamydia. Pregnant women are at risk for preterm delivery, low birth weight infants, and premature rupture of membranes. There is also a high risk of developing pelvic inflammatory disease.

Complications

Trichomoniasis causes significant morbidity if infections are not treated during pregnancy, including preterm delivery, low birth weight infants, and premature rupture of membranes.

Research reveals that trichomoniasis increases the risk of HIV and other STIs. In men, complications may include epididymitis, prostatitis, and infertility.