Trichomonas and HIV infection

Infection with Trichomonas vaginalis significantly increases a woman's risk of becoming infected with HIV, according to a study published in a recent edition of The Journal of Infectious Diseases.

It is well known that sexually transmitted infections (STIs) increase the risk of transmitting and acquiring HIV. Researchers from the University of Washington, USA and from Mombasa, Kenya, thought there might be a link between T. vaginalis infection and an increased risk of acquiring HIV and carried out an 11 year prospective study of sex workers in Mombasa, running between 1993 and 2004. The study involved 1 335 female sex workers, who were HIV negative at baseline. The women were seen monthly, when they provided information about their general medical, gynaecological and sexual health. They also had physical examinations and were screened for HIV, as well as other STIs, including T. vaginalis.

During the study, researchers recorded 806 infections with T. vaginalis and 265 women became infected with HIV. Infection with T. vaginalis significantly increased the risk of HIV infection, even after adjusting for possible confounding factors. T. vaginalis infection itself was significantly associated with a shorter duration of sex work, less than 8 years of eduction and concurrent cervicitis and bacterial vaginosis. Women who used condoms 100% of the time, as well as those who used progesterone-only contraceptives, had a lower risk of T. vaginalis infection.

Researchers suggest several possible reasons why infection with Trichomonas vaginalis increases the risk of HIV acquisition:
• T. vaginalis leads to inflammation, resulting in cells vulnerable to HIV infection being present in the vaginal and cervical mucosa.
• T. vaginalis could cause mucosal haemorrhage, damaging natural defences against infection.
• T. vaginalis undermines a process that can prevent HIV's attachment to cells.
• T. vaginalis increases the risk of HIV by increasing susceptibility to vaginal infections or the persistence of abnormal vaginal flora.

McClelland RS et al. J Infect Dis 2007;195: 698-702 (online edition)