Anorectal lymphogranuloma venereum (LGV) circulation dynamics in Buenos Aires: Nine-year surveillance and therapeutic implications

Background Lymphogranuloma venereum (LGV), caused by Chlamydia trachomatis L-genotypes, has re-emerged as a major anorectal infection in men who have sex with men (MSM), especially in people living with HIV. Distinguishing LGV from non-LGV C. trachomatis is essential because LGV requires 3 weeks of doxycycline. Long-term Latin American data are lacking. Methods Anorectal swabs from patients with suspected anorectal sexually transmitted infections were studied in a cross-sectional study conducted at two Buenos Aires coloproctology referral centers (August 2017–November 2025). Anorectal swabs were tested for C. trachomatis by NAAT and positive samples were genotyped by PCR-RFLP targeting ompA . Monthly LGV positivity was analyzed using the modified Farrington algorithm to detect epidemic peaks and seasonality, with sensitivity analysis excluding months with <7 samples. Results Of 700 anorectal swabs, 285 (41%) were C. trachomatis positive. Among public-hospital samples with conclusive genotyping, 148/179 (83%) were LGV; in the private center, 78 additional LGV cases were confirmed, totaling 226 LGV cases. HIV coinfection was 78% in LGV versus 100% in non-LGV cases ( p = 0.0016). Concurrent T. pallidum or N. gonorrhoeae infection occurred in 25% of cases and was associated with LGV. The endemic baseline was approximately 32% (range 28–36%), with no seasonal pattern or trend. Pandemic-era epidemic alarms disappeared after excluding low-volume months. Conclusions Anorectal LGV is endemic in Buenos Aires, with no seasonality, and a ∼32% pre-test probability among symptomatic patients at specialized clinics. This supports considering empirical 3-week doxycycline for MSM with rectal symptoms and C. trachomatis infection when genotyping is unavailable, until further trials confirm the non-inferiority of proposed shortened regimens. Biovar-specific testing remains the goal for targeted therapy.