Grant: Project Grant

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Over the last decade, syphilis has seen a resurgence in many parts of the world, including Canada, with the bulk of infections seen in major urban centres. More recently, these increases have been even more significant, with a 30-40% rise in Vancouver and Toronto syphilis rates in 2015 compared to 2014. These infections have primarily affected men who have sex with men (MSM). Further, HIV-positive MSM are disproportionately affected by syphilis infections. In addition to playing a role in enhanced transmission of HIV, syphilis also places HIV-positive individuals at higher risk of complications and more severe disease. A recently published, small pilot study found that doxycycline - an inexpensive, relatively well-tolerated antibiotic - given daily may prevent new syphilis infections, along with other bacterial STIs such as chlamydia and gonorrhoea. This study will examine the use of doxycycline as daily preventative therapy for syphilis and other STIs in HIV-positive MSM.