Metrics details. It has been presumed that Chlamydia trachomatis is transmitted between men only through anal or oral sex, but no mathematical models have tested this presumption. To test this presumption, we created 20 compartmental mathematical models of different sexual practices that included both oral and anal sex and calibrated these models to the observed rates of Chlamydia trachomatis infection at three anatomical sites from men who have sex with men MSM in Melbourne Sexual Health Centre during β A model that included only oral and anal sex could replicate the observed rates of single-site infection at the oropharynx, urethra and rectum alone, but could not replicate infection at more than one of these sites multisite.
However, if we included transmission from sexual practices that followed one another in the same sexual episode e. Our modelling study suggests that transmission routes other than just oral and anal sex are necessary to explain the high rate of Chlamydia trachomatis infection at more than one site.
Peer Review reports. Chlamydia trachomatis chlamydia is a common sexually transmitted infection in men who have sex with men MSM , and its burden is likely to rise over time as condom use falls in the pre-exposure prophylaxis PrEP era [ 1 , 2 , 3 , 4 ].
If the rates of condom use are to fall, new prevention measures will be needed, and these measures can only be developed if we clearly understand the transmission dynamics of chlamydia among MSM [ 5 , 6 ]. Mathematical models are important for investigating the transmission of infections in populations, particularly when the transmission is complex or may be difficult to study epidemiologically [ 7 , 8 ]. The transmission of chlamydia may be more complex than has been previously appreciated given transmission occurs between three anatomical sites oropharynx, urethra and anorectum , and there are a large number of potential sexual practices that may transmit it.
Indeed recent epidemiological studies have assessed some potential routes such as kissing, rimming oral-anal sex and the use of saliva as a lubricant for anal sex among MSM [ 9 , 10 , 11 ].
