Background Lymphogranuloma venereum (LGV) infection is now endemic among men who have sex with men (MSM) in the UK. Control of the outbreak has relied on LGV typing and treating of symptomatic patients since previous UK data indicated only 6% of cases were asymptomatic. However, emerging evidence suggests there may be a significant reservoir of asymptomatic infection.

Methods Twelve UK Genitourinary Medicine clinics that routinely screen all MSMs for Chlamydia trachomatis (CT) at the pharynx, urethra and rectum participated in a case-finding study. All CT-positive specimens in MSMs during the study period (24/09/12 – 07/12/12) were referred for LGV typing and clinical data collected. Descriptive and logistic regression analyses were done.

Results 71 (9%) LGV and 742 (91%) non-LGV CT serovars were confirmed. Clinical data were available for 49 (69%) LGV and 545 (73%) non-LGV cases. LGV detection was higher in Brighton (10%), London (10%) and Manchester (11%) than in Glasgow (4%).

11/49 (22%) LGV infections detected were asymptomatic at first presentation; 91% (n = 10) of these were rectal. 3/11 (27%) LGV infections were ‘pre-symptomatic’ (asymptomatic at first attendance but symptomatic by the second attendance for treatment). Compared to non-LGV cases, LGV cases were older (median age 39 vs 32 years), more likely to have rectal infection (87% vs 60%; urethral 4% vs 28%; pharyngeal 4% vs 23%) and to be symptomatic (78% vs 44%). In univariate analysis, older age (OR = 16.9, p < 0.01; 35–44 vs 18–24 years), rectal infection (OR = 5.98, p < 0.0001) and symptomatic infection (OR = 4.20, p < 0.0001) were significantly associated with being an LGV case.

Discussion Asymptomatic rectal LGV is considerably more common than previously reported in the UK. This could reflect changing screening practises for MSM, or evolving LGV epidemiology. LGV typing in asymptomatic rectal CT may be warranted to reduce ongoing transmission. The effectiveness of current CT treatment regimens in asymptomatic LGV needs assessment