Sexually Transmitted Infections: Trichomonas Vaginalis

Introduction

• Description: Infection by the anaerobic flagellate protozoan Trichomonas vaginalis is most often acquired by sexual contact with an infected person.

• Prevalence: Approximately 3.7 million cases per year in the United States (2.1% of women); accounts for 25% of “vaginal infections.” The most common nonviral sexually transmitted infection (STI).

• Predominant Age: 15–50 years, but it may occur at any age. One study found a peak rate at ages 47–53 years.

• Genetics: No genetic pattern.

Etiology and Pathogenesis

• Causes: T. vaginalis, an anaerobic flagellate protozoan. The incubation period for Trichomonas infections is considered to be between 4 and 28 days. Humans are the only natural host.

• Risk Factors: Multiple sexual partners, vaginal pH that is less acidic. Blood, semen, or bacterial pathogens increase the risk. Of asymptomatic partners of women with Trichomonas infections, 30%–80% have a positive culture. Trichomonas has been reported (rarely) in virginal patients, supporting the possibility of nonsexual transmission. Transmission from woman to woman is possible, but transmission among men is uncommon.

Signs and Symptoms

• 70% to 85% may be asymptomatic; a carrier state may exist for many years

• Vulvar itching or burning

• Copious discharge with a rancid odor (generally thin, runny, and yellow-green to gray in color, “frothy” in 25%)

• “Strawberry” punctation of the cervix and upper vagina (15%)

• Dysuria

• Dyspareunia

• Edema or erythema of the vulva

Diagnostic Approach