Trichomonas vaginalis infection: testing and treatment from A to E

Trichomonas vaginalis (TV) is a very successful protozoan pathogen. It is responsible for one of the most common sexually transmitted infections and affects 180 million females worldwide each year.1 It does infect men but it tends to be short-lived and harder to detect. It has the ability to adapt easily to its environment and produces an array of glycosidases2 and cysteine proteinase enzymes.3 It harvests host proteins and DNA for metabolism and destroys the protective host mucosa. Consequently, while it is estimated that 50% of infected people are asymptomatic, it can cause lesions, vaginitis and acute inflammation.

There are two subtypes of TV. Type I can produce an antibody surface binding protein, tends to cause subclinical or asymptomatic infection, and is usually found in younger women. Type II produces and secretes the antibody surface binding protein. Type II is infected with a double-stranded RNA virus that causes this up-regulation, synthesis and surface expression. It tends to be more common in older women and is associated with more symptomatic infection.4 

Traditionally, TV infection has not given too much cause for concern. In general it is sexually transmitted but there are a few exceptions, and it is treated easily with metronidazole. However, attitudes towards it have changed following its implication in adverse pregnancy outcome,5,6 increased risk of human immunodeficiency virus (HIV)7 and hepatitis C virus (HCV)8 transmission, and its link with a three-fold increase in the risk of cervical cancer.4 The emergence of metronidazole-resistant TV is also a cause for concern, with estimates for TV resistance varying between 1.2%9 and 5%.10,11