Estimating the Number of Male Sex Workers with the Capture- Re-capture Technique in Nigeria

Sylvia B. Adebajo, George I. Eluwa, Jack U. Tocco, Babatunde A. Ahonsi, Lolade Y. Abiodun, Oliver A. Anene, Dennis O. Akpona, Andrew S. Karlyn, Scott Kellerman


Estimating the size of populations most affected by HIV such as men who have sex with men (MSM) though crucial for structuring responses to the epidemic presents significant challenges, especially in a developing society. Using capture-recapture methodology, the size of MSM-SW in Nigeria was estimated in three major cities (Lagos, Kano and Port Harcourt) between July and December 2009. Following interviews with key informants, locations and times when MSM-SW were available to male clients were mapped and designated as “hotspots”. Counts were conducted on two consecutive weekends. Population estimates were computed using a standardized Lincoln formula. Fifty-six hotspots were identified in Kano, 38 in Lagos and 42 in Port Harcourt. On a given weekend night, Port Harcourt had the largest estimated population of MSM sex workers, 723 (95%CI: 594892) followed by Lagos state with 620 (95%CI: 517-724) and Kano state with 353 (95%CI: 332-373). This study documents a large population of MSM-SW in 3 Nigerian cities where higher HIV prevalence among MSM compared to the general population has been documented. Research and programming are needed to better understand and address the health vulnerabilities that MSM-SW and their clients face. Afr J Reprod Health 2013 (Special Edition); 17[4]: 83-89).


Keywords: Male sex worker, Capture-recapture, size estimation, population estimates, Men who have sex with men, Nigeria, Lagos, Kano, Port Harcourt.





Estimer la taille des populations les plus touchées par le VIH, comme les hommes ayant des rapports sexuels avec des hommes (HSH) bien que  crucial pour la structuration des réponses à l'épidémie, présente des défis importants, surtout dans une société en développement. En utilisant la méthode de capture-recapture, le nombre  des prostitués hommes-HSH au Nigeria a été estimé dans trois grandes villes (Lagos, Kano et Port Harcourt) entre juillet et décembre 2009. Grâce à des entretiens avec des informateurs clés, les emplacements et les heures où les hommes prostitués-HSH étaient à la disposition des clients masculins ont été élaborés et désignés comme « points chauds».  Des  comptages ont été effectués pendant deux week-ends consécutifs. Les estimations de population ont été calculées en utilisant une formule de Lincoln standardisée. Cinquante- six points névralgiques ont été identifiés à Kano, 38 à Lagos et 42 à Port Harcourt.  Une nuit d’un week-end donné, Port Harcourt avait la plus grande population estimée des hommes prostitués-HSH, 723 (CI : 594 -892 95 %), suivi de l'Etat de Lagos avec 620 (CI : 517 -724 95%) et l'Etat de Kano avec 353 (95 % CI : 332 -373). Cette étude documente une grande population des hommes prostitués-HSH dans 3 villes nigérianes où la prévalence élevée du VIH parmi les HSH par rapport à la population générale a été documentée. La recherche et la programmation sont nécessaires pour mieux comprendre et aborder les vulnérabilités de la santé auxquelles font face les prostitués-HSH et leurs clients. Afr J Reprod Health 2013 (Edition Spéciale); 17[4]: 83-89).


Mots-clés: hommes prostitués,  capturer-recapturer, estimation de l’ampleur,  estimations de la population, les hommes qui ont des rapports sexuels avec des hommes, Nigeria, Lagos, Kano, Port Harcourt.

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National AIDS/STI Control Programme, Federal Ministry of Health. HIV/STI Integrated Biological and Behavioral Surveillance Survey (IBBSS) Nigeria: Federal Ministry of Health 2007.

Merrigan M, Azeez A, Afolabi B, Chabikuli ON, Onyekwena O, Eluwa G, Aiyenigba B, Kawu I, Ogungbemi K, Hamelmann C. HIV prevalence and risk behaviours among men having sex with men in Nigeria. Sex Transm Infect 2010; 87(1):65-70.

Allman D, Adebajo S, Myers T, Odumuye O, Ogunsola S. Challenges for the Sexual Health and Social Acceptance of Men Who have Sex with Men in Nigeria Culture, Health and Sexuality 2007; 9(2):153168.

Geibel S, van der Elst EM, King'ola N, Luchters S, Davies A, Getambu EM, Peshu N, Graham SM, McClelland

RS, Sanders EJ. 'Are you on the market?': A CaptureRecapture Enumeration of Men who sell sex to Men in and around Mombasa, Kenya. AIDS 2007;21(10):1349-1354

Okal J, Luchters S, Geibel S, Chersich MF, Lango D, Temmerman M. Social context, sexual risk perceptions and stigma: HIV vulnerability among male sex workers in Mombasa, Kenya. Culture, Health & Sexuality 2009; 11(8):811 - 826.

Berchenko Y, Frost SD. Capture-recapture methods and respondent-driven sampling: their potential and limitations. Sex Transm Infect 2011; 87. doi: 10.1136/sti.2011.049171.

Magnani R, Sabin K, Saidel T, Heckathorn D. Review of sampling hard-to-reach and hidden populations for HIV surveillance. AIDS 2005; 19:S67-S72.

Semaan S, Lauby J, Liebman J. Street and network sampling in evaluation studies of HIV risk-reduction interventions. AIDS Rev 2002; 4:213-23.

Paz-Bailey G, Jacobson J, Guardado M, Hernandez FM, Nieto AI, Estrada M, Creswell J. How many men who have sex with men and female sex workers live in El Salvador? Using respondent-driven sampling and capture-recapture to estimate population sizes. Sex Trans Infect 2011; doi: 10.1136/sti.2010.045633.

Cojocaru C, Mihaescu T. Capture-Recapture Method: an Instrument for estimating TB Prevalence.

Pneumologia. 2006;5(4):213-223.

Kleis GW, Salisu AA. Masculine power and gender ambiguity in urban Hausa society. African Urban Studies 1983; 16:39-54.

Vuylsteke B, Vandenhoudt H, Langat L, Semde G,

Menten J, Odongo F, Anapapa A, Sika L, Buve A,

Laga M. Capture-recapture for estimating the size of the female sex worker population in three cities in Côte d'Ivoire and in Kisumu, western Kenya. Trop Med Int Health 2010; 15:1537–1543.

Luan R, Zeng G, Zhang D, Luo L, Yuan P, Liang B, Li Y. A study on methods of estimating the population size of men who have sex with men in Southwest China. Eur J Epidemiol 2005; 20(7):581-585.

Gaudio RP. Allah made us: sexual outlaws in an Islamic African city. Malden, MA: Wiley-Blackwell 2009:23.

Pittin R. Houses of women: a focus on alternative lifestyles in Katsina City. In Female and Male in West Africa. London, Oppong C, ed.; Boston: Allen & Unwin 1983; 291-302.

Aina TA. Patterns of Bisexuality in Sub-Saharan Africa. In Bisexuality and HIV/AIDS 1991.

Tielman, M. Carballo, and A. Hendriks, eds.; Buffalo: Prometheus 1991; 81-90.

Lowndes CM, Alary M, Belleau M, Bosu WK, Kintin DF, Nnorom JA, Seck K, Victor-Ahuchogu J, Wilson D. West Africa HIV/AIDS Epidemiology and Synthesis

Response. World Bank Global HIV/AIDS Program Report. 2008.

The Lincoln Index.

Seber, G.A.F., The Estimation of Animal Abundance and Related Parameters. Caldwell, New Jersey: Blackburn Press. ISBN 1-930665-55-5

NACA. UNAIDS, World Bank. Modes of Transmission in Nigeria: Analysis of the Distribution of New HIV infections in Nigeria and Recommendations for Prevention. 2008.

Grulich AE, Zablotska I. Probability of HIV transmission through anal intercourse. Int J Epi 2010; 10:1-2

Law of the Federation of Nigeria. Criminal Code Act Part

III. Chapter 21. http://www.nigeria- (accessed February 2012).

Adebajo, S. B., Eluwa, G., Allman, D., Myers, T., Ahonsi, B., (2012). "Internalized Homophobia Prevalence of internalized homophobia and HIV associated risks among men who have sex with men in Nigeria. African Journal of Reproductive Health. 16(4).

Cáceres C, Konda K, Pecheny M, Chatterjee A, Lyerla R. Estimating the number of men who have sex with men in low and middle income countries. Sex Transm Infect 2006;82:iii3-iii9.

National AIDS/STI Control Programme, Federal Ministry of Health. HIV/STI Integrated Biological and Behavioral Surveillance Survey (IBBSS) Nigeria: Federal Ministry of Health 2010.

National AIDS and STI Control Program, Enhancing National Response Program. Prevalence of Sexually Transmitted Infections among Men who have Sex with Men and Injecting Drug Users & Validation of Audio Computer-Assisted Self Interview (ACASI) in Abuja, Lagos, and Ibadan, Nigeria. Technical Report 2010.


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