MSM are becoming increasingly important in HIV epidemics in Africa and their population is growing in Nigeria. However, there's paucity of data on HIV epidemics in MSM in Nigeria and West Africa region. Though HIV transmission in Africa is mainly heterosexual, interactions between HIV epidemics in MSM and heterosexual populations are not well understood. Objective was to describe female clients and partners of MSM sex workers (MSM-SW) in Lagos and to determine risk factors for unprotected sex between women and MSM-SW.

Methods MSM were recruited through respondent driven sampling, a novel methodology designed to access hidden populations. MSM-SW were identified through self-reporting and consent was obtained. Participants completed a pre-tested questionnaire and a behaviour diary. The questionnaire included questions on details of each sexual partner for 4 weeks; each sexual encounter with each partner; and the three most recent partnerships. Data were summarised as proportions and compared using chi square test.

Results 62 MSM-SW participated in the study and concluded the self-reported questionnaire and behaviour diary. MSM-SW recorded 311 partners, out of which 66(21.2%) were female and aged between 16 and 38 years. Thirty-two (10.3%) were recent female partners. Of the recent female partners, 17 (53.1%) were unmarried, 14 (43.8%) married and one was a spouse of MSM-SW. 60 (90.1%) of female partners of MSM-SW paid or were paid for sex (39/60,65% paid MSM-SW while 21/60, 35% were paid by them). There were 52 single episode sexual contacts and 14 regular partnerships. Of the 50 new transactional contacts, more than half (56%) met in the bars, restaurants, clubs, motels and beaches. All the sexual encounters between MSM-SW and their female partners involved penetrative sex—vaginal sex (VS)(53, 80%); anal sex (AS)(39, 59%); and both (31, 47%). Unprotected sex was significantly more frequently associated with sex with regular partner than with single episode sexual contact (79% vs 52%; p=0.02, OR=3.0) and non-transactional sex than sex paid for by the female partners (71% vs 46%; p=0.029,OR=2.8).

Conclusion MSM-SW in Nigeria have a lot of female clients and partners and frequently engage in transactional and unprotected sex with them. Majority of these female partners are in heterosexual married relationships. Understanding these interactions between MSM and heterosexual populations is very crucial to any HIV intervention targeted on MSM and by extension the general population.