It is common for people who have genital chlamydia to also develop rectal chlamydia. In heterosexual cisgender women, this is more often caused by autoinoculation. They don’t have to engage in anal sex, the infection can simply pass from the vagina to the rectum.
The situation is less clear for straight cis men. Their development of rectal chlamydia is considerably less likely to happen just by autoinoculation, so researchers were interested in working out if there might be other methods of contagion. As reported in the journal Sexually Transmitted Diseases, chlamydia might spread to the rectum via oral sex.
A team led by Dr David Nelson from Indiana University in Bloomington enrolled 197 cis men at high risk of this sexually transmitted infection, who went to an STI clinic in Indianapolis, Indiana. Some of them had inflammation of the urethra, others didn’t. They produced urine samples and received a rectal swab. These were tested for chlamydia, as well as gonorrhea and another STI known as mycoplasma genitalium.
The 197 participants in this study completed a questionnaire that asked about their symptoms, sexual orientation, and both their recent oral and anal sexual behavior as well as throughout their lifetime. In the group, there were 135 straight men.
Out of these, 84 reported to have performed cunnilingus but have never experienced any type of anal receptive behavior. Only two people in this group had a rectal infection of chlamydia, and given their sexual history, the team argues that oral sex might be a risk factor when it comes to rectal chlamydia.
It could be argued that given the self-reported nature of the questionnaire, it's possible that the two people who contracted the infection were less than sincere. Many heterosexual men tend to be shy when it comes to their enjoyment of many forms of anal play, whether it is rimming, fingering, or even pegging.
While it is impossible to confirm if they were 100 percent sincere, the team did not find rectal gonorrhea or mycoplasma genitalium in straight men. The statistics were slightly different for the remaining 62 people, who either identified as gay or bisexual. These men partake in anal receptive behavior over their lifetime and they had a higher prevalence of all three infections.
It is also important to consider that it's long been suspected that chlamydia can survive in the gastrointestinal tract, which strengthens the idea put forward in this study.
[H/T: New Scientist]