Background: Although men who have sex with men (MSM) are at high risk of sexually transmitted infections (STIs), data on incidence of STIs in this key population is lacking in West Africa. We assessed the incidence of STIs among MSM in four West-African countries.
Methods: We performed a prospective cohort study in MSM followed up between 2015 and 2018 in Abidjan (Côte d''Ivoire), Bamako (Mali), Lomé (Togo) and Ouagadougou (Burkina Faso). Men aged 18 years or older, and reporting at least one episode of anal intercourse with another man within the previous 3 months were offered a quarterly comprehensive HIV intervention including diagnosis and treatment of STIs using the syndromic approach, HIV testing, peer-led support, condoms and lubricants. Pre-exposure prophylaxis (PrEP) for HIV was not available. Data on sociodemographic characteristics and sexual behaviours were collected at enrolment and follow-up visits. Incidence of symptomatic STIs was calculated. Factors associated with STI incidence were investigated using mixed-effect Poisson regression models.
Results: A total of 855 MSM (631 HIV-; 224 HIV+) were included in this analysis, with a total follow-up time of 1327.2 person-years. Baseline prevalence of symptomatic STIs was 14.7% (126/855; 95% confidence interval (CI) 12.5-17.3). It was higher among HIV-positive MSM than among HIV-negative MSM (19.2% versus 13.2%; p=0.028). Three hundred and twenty-four participants (37.9%) reported symptomatic STIs during follow-up; the incidence rate was 45.1 cases per 100 person-years (95% CI 42.5-47.7). In multivariable analyse, study sites (incidence rate ratio (IRR) for Abidjan 1.80, 95% CI 1.23-2.66; IRR for Ouagadougou 5.04, 95% CI 3.53-7.20; Ref: Lomé), level of education (IRR for high level 0.52, 95% CI 0.27-0.98), HIV status (IRR for HIV+ 0.75, 95% CI 0.59-0.96), and follow-up time (IRR 0.96, 95% CI 0.93-0.98) were associated with incident symptomatic STIs.
Conclusions: Incidence of STIs in West-African MSM was high and heterogeneous between the study sites. The decrease over time suggests that the quarterly intervention had a positive impact. These data will be useful for assessing the impact of HIV PrEP which has been implemented in the same study sites from November 2017.

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