Objectives Recently developed genotyping tools allow better understanding of Trichomonas vaginalis population genetics and epidemiology. These tools have yet to be applied to T vaginalis collected from HIV⁺ populations, where understanding the interaction between the pathogens is of great importance due to the correlation between T vaginalis infection and HIV transmission. The objectives of the study were twofold: first, to compare the genetic diversity and population structure of T vaginalis collected from HIV⁺ women with parasites from reference populations; second, to use the genetic markers to perform a case study demonstrating the usefulness of these techniques in investigating the mechanisms of repeat infections.

Methods Repository T vaginalis samples from a previously described treatment trial were genotyped at 11 microsatellite loci. Estimates of genetic diversity and population structure were determined using standard techniques and compared with previously reported estimates of global populations. Genotyping data were used in conjunction with behavioural data to evaluate mechanisms of repeat infections.

Results T vaginalis from HIV⁺ women maintain many of the population genetic characteristics of parasites from global reference populations. Although there is evidence of reduced diversity and bias towards type 1 parasites in the HIV⁺ population, the populations share a two-type population structure and parasite haplotypes. Genotyping/behavioural data suggest that 36% (12/33) of repeat infections in HIV⁺ women can be attributed to treatment failure.

Conclusions T vaginalis infecting HIV⁺ women is not genetically distinct from T vaginalis infecting reference populations. Information from genotyping can be valuable for understanding mechanisms of repeat infections.