Over a third of gay men with anal infections reported no unprotected anal sex

Sexual practices other than unprotected anal sex appear to be risk factors for anal infection with gonorrhoea and chlamydia, according to an Australian study published in the online edition of Sexually Transmitted Infections. Investigators from the HIM study in Sydney found that over a third of gay men with anal gonorrhoea or chlamydia infections reported no unprotected anal sex, but had engaged in other sexual practices involving the anus, such as rimming, fingering, fisting, or the use of sex toys.

The investigators suggest that their findings have important implications for sexual health screens for gay men, and that all gay men should have swabs for anal infections regardless of whether they report unprotected anal sex.

In countries like the United Kingdom, United States, and Australia there was a marked and rapid fall in the incidence of gonorrhoea amongst gay men after the onset of the HIV epidemic. In recent years, however, there has been a steady increase in the number of new diagnoses of sexually transmitted infections (STIs), including gonorrhoea and chlamydia, involving gay men across the industrialised world.

Some sexually transmitted infections are thought to increase the risk of HIV transmission and infection, and this is one of the reasons why sexually active gay men are encouraged to attend for regular sexual health screens so they can receive appropriate treatment for infections and thereby reduce the risk of HIV transmission or infection.

Between June 2001 and late 2004, investigators from the HIM study in Sydney, Australia, conducted a prospective study to determine the incidence of and risk factors for anal and urethral infection with gonorrhoea and chlamydia.

A total of 1,427 gay men were included the study. All were HIV-negative on entry to the study. Every year, they had a face-to-face interview about their sexual activity and underwent a sexual health screen which included both anal and urethral swabs for gonorrhoea and chlamydia. Every six months, they had a telephone interview where they provided details about their sexual activities and any diagnoses with anal or urethral gonorrhoea or chlamydia since the last study visit. The men had a median age of 35 years, and 95% identified as gay.

At baseline, 6% of men reported a diagnosis of urethral gonorrhoea in the previous twelve months, with 2% reporting anal gonorrhoea in the previous year. The baseline sexual health screen revealed that 0.33% of men had undiagnosed and untreated urethral gonorrhoea and 1% of men had undiagnosed and untreated anal gonorrhoea. The prevalence of urethral chlamydia at baseline was 1%, and the prevalence of anal chlamydia was 4%.

During the study, the overall incidence of gonorrhoea was 5.9 cases per 100 person years. The incidence of chlamydia was 11.55 cases per 100 person years. A third of the cases of anal gonorrhoea and over 50% of the incidence cases of anal chlamydia were diagnosed at the annual study visits.

Risk factors

Significant risk factors for urethral gonorrhoea were younger age (p = 0.04), sexual contact with somebody known to have gonorrhoea (p = 0.001), increasing number of casual sexual contacts in the previous six months (p = 0.016), and unprotected insertive anal sex with a partner known to be HIV-positive (p = 0.032).

The risk factors for urethral chlamydia were broadly similar, and included younger age (p = 0.01), sex with an individual known to have chlamydia (p = 0.001), increasing number of casual sexual partners in the previous six months (p = 0.010), unprotected insertive anal sex (p = 0.029), and insertive oral sex to ejaculation (p = 0.007).

Attention then shifted to the risk factors for anal infections. Anal gonorrhoea was significantly associated with younger age (p = 0.001), sex with a person known to have gonorrhoea (p = 0.001), receptive unprotected anal sex (p = 0.001), and frequent receptive fingering with a casual partner (p = 0.001).

The risk factors for anal chlamydia were similar including sexual contact with an individual known to have chlamydia (p = 0.001), increasing number of casual sexual partners in the previous six months (p = 0.019), receptive unprotected sex (p = 0.001), and receptive rimming (p = 0.004).

Anal infections but no reported unprotected anal sex

Finally, the investigators looked for risk factors for anal infections in patients who received this diagnosis but who did not report unprotected anal sex. The investigators emphasised that 34% of diagnoses of anal gonorrhoea and 36% of diagnoses of anal chlamydia occurred in men who said that they had had not receptive unprotected anal sex. Fingering, fisting, and rimming were associated with anal gonorrhoea and fingering and the use of sex toys were associated with anal chlamydia.

“We have demonstrated for the first time in a prospective epidemiological study that sexual activities other than penile-anal intercourse were associated with infections in each site”, comment the investigators. They add, “the independent association of anal infections with non-intercourse anal sexual practices suggests that comprehensive sexual health screening, particularly anal screening, should occur in all sexually active gay men, not just those who report unprotected anal sex.”