• • In women, findings include motile trichomonads visible on vaginal wet mount, positive culture for Trichomonas vaginalis, and Pap smear result that is positive for trichomonads.
  
• • In men, diagnosis is often presumptive, after failure to respond to standard treatment for nongonococcal urethritis (NGU).

Trichomoniasis is one of the three major causes of symptomatic infectious vaginitis, along with candidiasis and bacterial vaginosis, and is the only one known to be sexually transmitted. Despite being a readily diagnosed and treated infection, trichomoniasis is not a reportable one, and control of the infection has received relatively little emphasis from public health control programs for sexually transmitted diseases (STDs). The annual incidence of Trichomonas vaginalis infections in the United States has been estimated at 5 million cases. The World Health Organization has estimated that this infection accounts for almost half of all curable STDs worldwide.

Trichomoniasis is the exception to the rule that applies to most STDs in that it is more difficult to diagnose in men than in women. Currently available diagnostic methods for trichomoniasis in men lack sensitivity and availability. Therefore, most men are treated either as a result of sexual exposure to an infected woman or as part of an algorithm for persistent NGU.

T vaginalis, a flagellated parasite, is the causative agent of this infection. Although two other species of Trichomonas infect humans (Trichomonas tenax and Trichomonas hominis), T vaginalis is the only one that infects the urogenital tract. Trichomonas infects the squamous epithelium of the vagina and ectocervix and often causes an inflammatory response in the host manifested clinically by purulent discharge. The pathogenesis in men is poorly understood.

As with any STD, unprotected sex is a risk factor for acquisition of infection. Limiting the number of sex partners or using condoms helps to prevent infection.

Symptoms and Signs

Symptoms of trichomoniasis in women include vaginal discharge, irritation, and pruritus; however, about half of all women infected with T vaginalis are asymptomatic. Occasionally women report vague lower abdominal pain. Signs of infection in women include vaginal discharge, odor, and edema or erythema, but these may be absent. Occasionally, erythematous, punctuate lesions may be seen on the ectocervix, the so-called “strawberry cervix.”

In men, the prevalence and spectrum of disease is far less well characterized; the infection usually appears to be asymptomatic; however, it has been suggested as an increasingly important cause of NGU.

Laboratory Findings

Diagnosis of trichomoniasis in women is usually accomplished via direct microscopic examination of the vaginal fluid (wet mount); however, even when performed by skilled diagnosticians the sensitivity of this test is only 60% overall and may be less in asymptomatic women. In addition to motile trichomonads, white blood cells may be present. The vaginal pH may be elevated or normal. (Normal pH is generally associated with a low number of trichomonads.) Bacterial vaginosis is a frequent coinfection with trichomoniasis. Culture media is commercially available and is currently the “gold standard” for diagnosis (InPouch TV, BioMed Diagnostics, White City, OR). Polymerase chain reaction (PCR) techniques are under development but have thus far shown variable results.

Diagnosis in general is much more difficult in men, and the best culture results are obtained by combining urethral swabs and urine sediment for culture. Nonetheless, it is highly likely, as suggested by PCR results, that this approach lacks sensitivity.