Which condition is characterized by vaginal inflammation caused by a protozoan parasite?

The condition characterized by vaginal inflammation caused by a protozoan parasite is Trichomonas. This infection specifically arises from the parasite Trichomonas vaginalis and is known to cause symptoms such as itching, burning, and unusual discharge in the vaginal area.

Trichomonas is distinct because it is a sexually transmitted infection (STI) caused by a living organism, whereas the other conditions mentioned are caused by different factors. Candidiasis is a yeast infection typically caused by Candida species, not a protozoan. Bacterial vaginosis is primarily related to an imbalance in the normal bacterial flora of the vagina, and it does not involve a protozoan parasite. Chlamydia is a bacterial infection, also an STI, caused by the bacterium Chlamydia trachomatis. These distinctions clarify why Trichomonas is the correct answer and highlight its specific etiology as a protozoan-caused condition.