A protozoon normally present in the VAGINA of about 30–40 per cent of women. It sometimes becomes PATHOGENIC and causes inflammation of the genital passages, with vaginal discharge. A man may become infected as a result of sexual intercourse with an infected woman and suffer from a urethral discharge; it may also cause prostatitis (see under PROSTATE GLAND, DISEASES OF). METRONIDAZOLE is usually an effective treatment, and to obtain a satisfactory result it may be necessary to treat both partners. An alternative treatment is tinidazole.