High prevalence of anal chlamydia in Swiss HIV-positive gay men

A large proportion of HIV-positive gay men in Switzerland have anorectal infection with chlamydia, investigators report in the November 15^th edition of Clinical Infectious Diseases. The researchers suggest that undiagnosed anal chlamydia infections could be contributing to the continued spread of HIV amongst gay men in Switzerland.

Gay and other men who have sex with men remain the group most affected by HIV in many industrialised countries, including Switzerland. Sexually transmitted infections also disproportionately affect gay men. If left untreated these infections, including chlamydia, can significantly increase the risk of acquiring HIV. As reported on aidsmap.com UK investigators found that many chlamydia infections in gay men were in the rectum, and that HIV-positive gay men were disproportionately affected by rectal chlamydia

Investigators from the Swiss HIV cohort therefore postulated that anorectal chlaymdia infection could be contributing to the ongoing HIV epidemic amongst gay men in the country.

They therefore screened 147 HIV-positive men who reported unprotected receptive anal sex in the previous two years for the infection. The aims of their study were to determine the prevalence and symptoms of anorectal chlamydia, and to see if they could identify any risk factors associated with the infection.

The study was conducted over a twelve month period in 2007 and 2008. Anorectal samples were obtained from the men during routine HIV clinic visits.

A total of 16 samples (11%) tested positive for chlamydia. One of these infections involved lymphomgranuloma venereum which is caused by a strain of chlamydia. In addition, four men had anorectal gonorrhoea.

Only three of the men diagnosed with chlaymdia reported symptoms of proctitis (for example pain, discharge, blood stools, or constipation). LGV is associated with unpleasant symptoms, and the patient with this infection reported a week long history of pain, blood stools and cramps.

The only factor that the investigators were able to identify as being associated with anoectal infection with chlamydia was a greater number of sexual partners. Men who reported two or more partners in the previous two years were significantly more likely to be diagnosed with the infection than men reporting fewer partners (p = 0.001).

“The high prevalence together with a strong association with multiple sex partners…suggest a possible role for anorectal chlamydial infection in sustaining the ongoing HIV epidemic among men who have sex men in Switzerland”, comment the investigators.

Noting that tests for the infection were easy to perform, they suggest that their findings “underscore a potential role fir expanded rectal chlamydial screening” as part of routine HIV care. They recommend that tests for the infection should be offered even if patients do not report any symptoms suggestive of the infection.