Introduction The pigtailed macaque model for trichomonal infection was used to compare T. vaginalis (TV) detection technologies, to describe infection status in younger versus older populations, and to test whether TV reinfection after antibiotic clearance is possible in this model.

Methods Thirty-six macaques received a single vaginal TV inoculation (ATCC 50148; ~6E5), followed by five weekly visits to document infection. Eighteen animals were 4–7 years old; eighteen were over 13 years old. Infection status was documented by culture (InPouchTV) and by NAAT (AptimaTV). Colposcopy was performed to assess tissue reaction to infection. Animals underwent antibiotic treatment (metronidazole) and test-of-cure. Five macaques from the younger cohort were later re-inoculated with the same TV strain and followed for three weeks to document reinfection.

Results All but one (older) animal were successfully infected after the initial vaginal challenge. Among 295 matched samples (culture/NAAT), 22 did not share confirmatory results. In this experimental setting, with weekly vaginal swabs providing a timeline of trichomonal presence in each animal, we can infer infectious status for some discrepant samples. It is likely that 10–12 instances can be attributed to false culture readings, and 3–5 to false NAAT results. Self-limited infections were noted more frequently among younger macaques. Friable tissue was noted more frequently among older animals. Four of the five animals that were re-challenged with TV developed infection.

Conclusions The NAAT gave fewer false results, when we had the luxury of a timeline of serial samples to refer to for determining test accuracy. Similar infection rates were observed in both age cohorts. Older animals had a greater incidence of cervicovaginal irritation evidenced primarily by friability in this study, and younger animals tended to self-clear T. vaginalis infection faster than older animals. Finally, TV re-infection is possible in the macaque model.

Disclosure of interest statement This research was supported by NIH Contract Number HHSN266200700013C and by the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health through Grant Number P51 OD010425 Washington National Primate Research Centre. No pharmaceutical grants were received in the development of this study.