Population Council Research that makes a difference

16th International Conference on AIDS
and Sexually Transmitted Infections in Africa (ICASA)
4–8 December 2011

Abstract

"Estimating the population of male sex workers (MSW) in Nigeria using capture-recapture method"
George Ikechi Eluwa, Sylvia Adebajo, Lolade Abiodun, D. Akpona, A. Anene, I. Apera, Babatunde Ahonsi, and Andrew Karlyn

Background
Accurate rates, though fundamental to epidemiology, are often very difficult to obtain. Estimation of the size of the population most at risk to HIV is crucial for structuring the response to the epidemic, however measuring the size of populations most at risk to HIV, such as men who have sex with men (MSM) presents significant challenges, as these populations are often hidden or hard to reach. Male sex workers (MSW) are a more hidden high risk group thus, posing a bigger challenge to engage in research and HIV prevention intervention. This is the first attempt at determining the population size of male sex workers (MSW) in three states in Nigeria.

Methods
Using capture-recapture methodology, the population size of MSW in three major cities in Nigeria—Lagos, Kano and Port Harcourt, was estimated between July and December 2009. Following interviews with key informants, the location and peak times of activities when MSW meet were mapped and designated as "hotspots". MSW was defined as any male ≥ 18 years who engaged in oral or anal intercourse with another man in exchange for money or gifts. In each city the enumeration involved conducting two counts on two consecutive weekend nights. The first count ("capture") contacted men engaged in transactional sex with other men and tagged them with key chains. The second count ("recapture"), conducted one week later counted men who were tagged the previous week, as well as newly "captured" men. Data were captured in a register designed for the enumeration. Population estimates were computed using standardized formula.

Results
A total of 56 hotspots were identified in Kano, 38 in Lagos and 42 in Port Harcourt with varying yield of MSW. Overall, Lagos state had the highest estimated population of male sex workers, 865 (95% CI: 707-1023) followed by Kano 642 (95% CI: 577-705), and Port Harcourt 358 (95% CI: 173-543).

Conclusion
There is a diverse spread of MSW in Nigeria. MSM are a high risk group and MSW a higher risk group. HIV prevention interventions must be target driven, relevant and appropriate to yield more impactful and cost effective outcomes. Further research on MSW is needed to better understand their risk profile and design appropriate HIV interventions.

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