Causal Agent:    
Trichomonas vaginalis, a flagellate, is the most common pathogenic protozoan of humans in industrialized countries.

Life Cycle:

Trichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate , where it replicates by binary fission .  The parasite does not appear to have a cyst form, and does not survive well in the external environment.  Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse .

Geographic Distribution:     
Worldwide.  Higher prevalence among persons with multiple sexual partners or other venereal diseases.

Clinical Features:        
Trichomonas vaginalis infection in women is frequently symptomatic.  Vaginitis with a purulent discharge is the prominent symptom, and can be accompanied by vulvar and cervical lesions, abdominal pain, dysuria and dyspareunia.  The incubation period is 5 to 28 days.  In men, the infection is frequently asymptomatic; occasionally, urethritis, epididymitis, and prostatitis can occur.

Laboratory Diagnosis:         
Microscopic examination of wet mounts may establish the diagnosis by detecting actively motile organisms.  This is the most practical and rapid method of diagnosis (allowing immediate treatment), but it is relatively insensitive.  Direct immunofluorescent antibody staining is more sensitive than wet mounts, but technically more complex.  Culture of the parasite is the most sensitive method, but results are not available for 3 to 7 days.  In women, examination should be performed on vaginal and urethral secretions.  In men, anterior urethral or prostatic secretions should be examined.

Diagnostic findings

  • Microscopy

Treatment should be implemented under medical supervision, and should include all sexual partners of the infected persons.  The drugs of choice for treatment are metronidazole and tinidazole; therapy is usually highly successful.  Strains of Trichomonas vaginalis resistant to both drugs have been reported.