Wednesday, January 18, 2017

Antiretrovirals and Syphilis

A new review published in Sexually Transmitted Infections questions whether the antiretroviral therapy common in treating HIV infection is contributing to a higher incidence of syphilis infection.  The authors, Michael Rekart and Wilfred Ndifon among others, began examining this line of reasoning after noticing that the rate of syphilis was increasing much more than that of other STIs (90.6% increase versus 39.9% for chlamydia in the same time period in British Columbia), and that the majority of the syphilis cases were found in men, especially men who have sex with men (MSM).  This coincided with a coinfection rate of syphilis and HIV in MSM of 50-75%.  Similar trends were also seen in the US and UK.

This led the researchers to begin examining why such a high coinfection rate could be seen.  Because many HIV positive individuals are on medication to treat their infection, the researchers began to look at the highly active antiretroviral therapy (HAART) to see if it may have an effect on syphilis acquisition.  They initially looked at the possibility that those on HAART may simply have riskier sexual behaviors that would lead to these numbers, but this didn’t seem to be supported.  What they did find via mathematical modeling is that sexual behavior change along with HAART use could definitely explain some of the increase in prevalence of syphilis among this population.  They hypothesize that HAART may play a role in this increase by ‘dampening the immune system’ and making individuals more susceptible to other infections, such as syphilis.  While obviously more research is needed to examine this hypothesized link, the researchers recognize that if it is proved to be true, action will need to be taken to protect those on HAART from the possible infectious agents that they are extra susceptible to.


- Devon Z.

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