Background Trichomonas vaginalis (TV) infection is a prevalent parasitic STD that may increase the risk of acquiring other STI including HIV. Trichomoniasis has been increasingly reported in older female populations. Detection methods include the InPouch culture system and GenProbe’s APTIMA Trichomonas vaginalis nucleic acid amplification test (NAAT). Both systems detect TV (viable or genetic material, respectively) from vaginal swabs. In addition to comparing TV detection technologies, this study attempted to look at infection status in younger versus older macaque populations.

Methods 24 sexually mature female pigtailed macaques were challenged with TV (ATCC 50148, human isolate), and followed weekly for five weeks, before metronidazole treatment. The reproductive age span for pigtailed macaques is approximately 4 to 18 years of age. Twelve animals aged 4–7 and twelve animals older than 13 years were enrolled. Paired vaginal swabs were collected weekly from each animal for culture and NAAT detection assays.

Results Each TV-challenged macaque developed trichomoniasis. Of 199 matched samples (culture and NAAT), 13 had discrepant results. Six of these were likely due to false culture results. Four samples represented the transition time from positive to negative status in three animals. It is plausible that organisms detected by NAAT were no longer viable (thus culture-negative). There is no obvious explanation for the three remaining discrepant results.

Trichomoniasis infection was self-limited (resolved prior to metronidazole treatment) in eight animals: two older and six younger macaques. Two of these younger macaques experienced intermittent discrepant results after testing negative by both methods for two consecutive weeks.

Conclusions NAAT detection appears to be more sensitive and less prone to erroneous results in this laboratory’s experience. There may be a trend for younger animals to self-clear TV infection faster than older animals, which might explain the increased TVinfection rates noted in older women.