Background:  The Lagos (Nigeria) to Cotonou (Benin) international route is known for illegal trade activities and also harbors cohorts of female sex workers (FSW) and intravenous drug users (IDU). Our objective was to compare the effect of a novel behavioral intervention to promote condom use in 2 groups:  FSW who injected drugs and those who did not inject drugs.

Methods:  We recruited 643 adult FSW (>18 years) who had unprotected sex with >1 client from motels, shanty towns, parks, beauty parlors, club houses, and restraints in towns and villages along Lagos–Cotonou international route. None of them was known to have HIV infection and all were recruited via outreach. The participants were randomized into a control group and an intervention group. The intervention group was treated to motivational counseling and theoretical principles of behavioral change. Both groups were followed for 6 months. At baseline and at 6 month, HIV testing, antibody testing for syphilis and ligase chain reaction tests on vaginal swab for gonorrhea, were done for all participants.

Results:  Of the initial 643 FSW, 96 (15%) were IDU. The follow-up rate at 6 months was 86.6%. At baseline, the prevalence of HIV (18.7% vs 8.8%, p <0.001), syphilis titre >1:8 (20.8% vs 12.2%, p = 0.022), and gonorrhea (22.9% vs 11.5%, p <0.001) was significantly higher among FSW IDU than non-IDU. There was significant decline in HIV (0/100 person-years vs 3/100 person-years, p = 0.031), syphilis (5% vs 10%, p = 0.018), and gonorrhea (7% vs 11%, p = 0.022) between intervention and control groups. The non-IDU demonstrated more significant decrease in total number of unprotected sex acts with clients (intervention:  –13; control: –5; p <0.001) when compared with FSW IDU (intervention:  –9; control:  –4; p = 0.032). Also, non-IDU had increased positive outcome expectancies (p = 0.044) and improved attitudes on HIV and sexually transmitted infection prevention (p = 0.038) when compared with FSW IDU (p = 0.6 and 0.42, respectively).

Conclusions:  The study shows that this novel behavioral intervention to promote condom use has significant positive influence on FSW, particularly those who are not IDU. It also demonstrates a need for intervention that focuses on addressing issues specific to FSW IDU and sharing of injection equipments using effective culturally sensitive methods. Thus, there is urgent need for holistic approach to curbing the dual problems of HIV and intravenous drug use among FSW in Nigeria and Benin.