Background Trichomonas vaginalis (TV) is the most common non-viral STI and has been linked to premature membrane rupture, preterm birth, and low birth weight in pregnant women. TV has also been shown to increase vaginal shedding of HIV and, thus, may influence HIV sexual and perinatal transmission. Repeat infection rates among HIV+ women are high. We have shown that bacterial vaginosis (BV) is associated with single dose metronidazole (MTZ) treatment failure in HIV+ women. A recent study in Africa has found that nevirapine is also associated with a higher rate of repeat infections. The purpose of this study is to determine if other ART interferes with single dose MTZ treatment of TV.

Methods A secondary data analysis was performed on a cohort of HIV+/TV+ women who had been randomised to single (2gm) dose or 7 day (500mg BID) dose MTZ. Follow-up visit, including culture, occurred 6–12 days after treatment completion. Data on sexual exposure was collected. Repeat TV infection rates were compared for women on ART at baseline versus not on ART, controlling for BV and treatment arm.

Results Of the 230 women included, 65% were receiving ART: NRTI (95%), NNRTI (31%), PI (58%) and other ART (2%). Those on ART had higher repeat infections than women not on ART [25/150 (16.7%) vs. 6/80 (6.3%), p-value = 0.03]. Controlling for BV status and stratifying by treatment arm, the association was found only in the single-dose arm (p-value = 0.05) and not in the multi-dose arm (p-value = 0.39). Only 5% of the women were sexually re-exposed during follow-up.

Conclusions ART in general is associated with a higher TV repeat infection rate following single dose MTZ treatment but not for multi-dose. These data further support the recommendation that single dose MTZ not be used in HIV+ women.