In BC, syphilis rates among men who have sex with men have seen a fourfold increase between 2010 to 2014. Researchers have also noticed that the number of people contracting HIV and syphilis simultaneously has increased. Similar trends have been occurring in the US and the UK.
Dr. Michael Rekart, a clinical professor at UBC’s School of Population and Public Health, became aware of this trend while reading an AIDS conference newspaper, and decided to investigate. After reading through the literature, he was convinced that the accepted explanation known as “HIV treatment optimism” was based on weak evidence and was unsatisfactory. HIV treatment optimism states that since anti-HIV drugs reduce the amount of the virus in a patient’s blood to non-detectable levels, people stop using condoms because they don’t think HIV poses a risk anymore.
“Of course, if you don’t use condoms, even if you’re not risking HIV, you’re risking other STDs. It hoists the entire problem on the gay male population,” said Rekart. “There is maybe an implication that [gay men] are immoral and they don’t care about their partners, and you know, they just [want to] have fun. I never found that to be true.
“Gay men and lesbians care about their partners — they don’t want to infect other people. They’re responsible, they work hard, they vote, they go to church. I always didn’t like the explanation,” said Rekart.
Frustrated by a theory so many had accepted, Rekart tried to answer the question, “what do the majority of HIV-positive people have in common?” The answer was the predominant treatment for HIV — Highly Active Antiretroviral Therapy (HAART). Rekart also noticed that although syphilis rates were on the rise, other types of STIs were not increasing at a similar rate. He contacted Dr. Caroline Cameron, a syphilis researcher at the University of Victoria, who confirmed that there was a possibility HAART was causing the rise in syphilis.
“Antiretroviral drugs actually impair immunity in the area where syphilis is most important and that is phagocytosis. Unlike other STDs, syphilis is extracellular, so the body’s immune reaction is to send macrophages there and to gobble up the bacteria and destroy it,” said Rekart. “For intracellular bacteria, like chlamydia and gonorrhoea, that’s not the mechanism of immunity because they’re inside the cell. [There’s a] particular kind of immunity called opsonophagocytosis — that’s what syphilis immunity relies on and that’s the area where HAART can impair immunity.”
Rekart, Cameron and their team of researchers created a mathematical model that not only showed that HIV treatment optimism alone would not explain the trend in syphilis rates, but that a combination of that theory and the suggested effects of HAART would create exactly the rise in syphilis rates we are seeing now.
In their paper, they suggested several avenues of future research to verify the hypothesis — run experiments on a specific type of monkey, look at immunity in the laboratory for people on HAART or look at the data.
“There’s a lot of data in the world about who’s on HAART and there’s a lot of data about who gets syphilis. The problem is these two databases are separate in most cases. So if those databases could be collated in an ethical way, you might be able to come up with the answer right away.”
While we wait for the results of future research on the link between HAART and syphilis, Rekart urges people with HIV to continue to use protection and to not forego their HAART treatments.
“HAART is life-saving and syphilis is curable,” said Rekart.
He also stated that until there is conclusive evidence linking HAART to syphilis, those undergoing HAART should be made aware of their potentially increased risk of contracting syphilis, and that healthcare professionals should consider screening people on HAART for syphilis more often.