Pathogenesis of Trichomoniasis

Trichomonads on vaginal epithelial cells.

Courtesy of John Alderete, Ph.D.

Although trichomoniasis is the most common non-viral sexually transmitted disease, the pathogenicity of T. vaginalis is not thoroughly understood. Trichomonads participate in a host-parasite relationship, causing them to adhere to epithelial cells. The ability of trichomonads to adhere is affected by time, temperature, and pH level. T. vaginalis grows best in an anaerobic environment with a pH > 6.¹

Binding of T. vaginalis to vaginal epithelial cells for colonization and infection is dependent upon specific parasite surface proteins. Parasites treated with tinidazole, metronidazole or other nitroimidazoles lose their ability to adhere, making them ineffective disease agents. Hemolysis, the destruction of red blood cells such that hemoglobin is released, is also correlated with virulence. Trichomoniasis has been seen to increase in severity during or slightly after menstruation.²

The relationship between T. vaginalis growth and protective lactobacilli is a complex one. It is currently unknown whether T. vaginalis infection alters the vaginal environment by creating an anaerobic situation, or if anaerobes in the vagina precede T. vaginalis growth. The vagina contains glycogen, and vaginal glycogen levels are elevated in women of reproductive age. Glycogen is broken down into glucose, a nutrient T. vaginalis requires for growth.³