LETTERS Buruli Ulcer respectively) (3,5). On the basis of rou- Songololo was high, the nearby broad tine data collected during 2005–2009, Bangu plateau, ≈300 meters higher Prevalence and we calculated the prevalence of BU in than Songololo, was devoid of BU Altitude, Benin each village of these districts and corre- (D.M. Phanzu, unpub. data). Soil and To the Editor: Buruli ulcer (BU), lated it with the altitude of the village, geologic features (e.g., chemical com- caused by Mycobacterium ulcerans, is fi rst by mapping with Healthmapper position of substrata; vegetation, fauna, one of 13 recently classifi ed neglected 4.3.2 (http://healthmapper.software. and pH of swamps) were raised as en- tropical diseases (1). Little is known informer.com) and then with statistical vironmental factors that might explain about factors infl uencing its focal dis- analyses by using Epi Info 3.5.1 (Cen- this focal distribution (8,9). The focal tribution. In Benin, altitude may play a ters for Disease Control and Preven- distribution of BU was also described role in such distribution of BU. tion, Atlanta. GA, USA). by Johnson et al., who found an inverse Incidence, prevalence, and other We found that highly BU-endemic relationship between the prevalence of health-related data are usually report- villages are located most often in low- the disease in Lalo District villages and ed at national or district levels. These land areas (online Appendix Figure; distance from the Couffo River (4). data convey the importance of the dis- www.cdc.gov/EID/content/17/1/153- Few studies have investigated ease but do not show the wide varia- appF.htm). The mean prevalence of environmental risk factors (other than tions existing at the village level. Data BU was 60.7/10,000 inhabitants in water-related) possibly related to the from the surveillance system (2) and villages with elevations <50 m, which prevalence of BU. In 2008, Wagner et surveys (3–6) in Benin have shown was signifi cantly higher than the prev- al. suggested that villages with higher that BU-endemic areas are confi ned to alence in villages with elevations 50– prevalence rates were located in areas the southern regions. Substantial vari- 100 meters (10.2/10,000 inhabitants) of low elevation. They associated the ability in endemicity levels have been and that of villages with elevations high prevalence of BU with farming detected from 1 department to another, >100 meters (5.4/10,000 inhabitants) activities that occurred primarily at at the district and village levels, and (p = 0.0003; Kruskal-Wallis test). low elevations (10). Our results are from year to year (2–5). In addition, we performed a sim- similar, but we have provided addi- However, some districts (Lalo in ple linear regression, including all vil- tional quantifi cation of the relation- the Mono-Couffo Department, Ouinhi lages (model A) and only BU-endemic ship between prevalence and altitude. in the Zou Department; Zê in the At- villages (prevalence ≠ 0) (model B). One reasonable explanation for lantique Department; and Adjohoun, Model A showed that at 0 altitude, the relationship between altitude and Bonou, and Dangbo in the Oueme De- the expected prevalence of BU was BU prevalence is that because low- partment) remain the most persistently 26.7/10,000 inhabitants. This preva- lands tend to be wetter than higher BU-endemic from year to year. In ad- lence decreased by 0.1/10,000 inhab- grounds, they provide more favorable dition, these BU-endemic districts are itants for each meter of increase in conditions for the proliferation and all located at the same latitude. A map altitude (correlation coeffi cient 0.20; spread of the etiologic agent. Further- of these districts can be superimposed coeffi cient of determination 4%). Mod- more, persons are more apt to frequent on the Lama depression (a median el B demonstrated that at 0 altitude, the these wetter lowlands to plant and tend band, oriented from west to east, that expected prevalence was 89.6/10,000 their crops, thus becoming vulnerable forms a large area at a low elevation, inhabitants. This prevalence decreased to infectious agents in the area. 130 km long with a width from 5 km by 0.7/10,000 inhabitants for each me- An extension of this study to all in the area of Tchi in Lalo to 25 km ter of increase in altitude (correlation BU-endemic villages is needed to fur- in the area of Issaba in Pobê) (7). coeffi cient 0.50; coeffi cient of deter- ther refi ne our results. The endemicity This factor prompted us to investigate mination 25%). Therefore, we con- of BU is multifactorial; however, our whether variations in altitude correlate clude that a low but signifi cant linear results suggest that altitude should be with BU prevalence. relationship exists between altitude included in future analytical models Using a Garmin eTrex global po- and BU prevalence in disease-endemic of environmental risk factors for this sitioning system (Olathe, KS, USA), villages. Thus, altitude may be 1 factor disease. we collected precise geographic coor- in determining variations in prevalence dinates, including altitude, for each vil- (4% for all villages and 25% for BU- Acknowledgments lage in 2 persistently BU-endemic dis- endemic villages). We are grateful to all the partici- tricts of the Atlantique Department. We The focal distribution of BU was pants in this study, the staff of Centre de chose districts where BU endemicity discussed in 1974 by Meyers et al. in Dépistage et de Traitement de l’Ulcère de was high (Zê) and low (Toffo) (preva- Zaire (8). In the Bas-Congo Province, Buruli d’Allada, and partners who support lences 52.0 and 7.8/10,000 inhabitants, although the concentration of BU in the Programme National de Lutte contre Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 1, January 2011 153 LETTERS la Lèpre et l’Ulcère de Buruli, in particu- 4. Johnson RC, Makoutode M, Sopoh GE, coastal, brackish and riverine waters lar, the following: Government of Benin; Elsen P, Gbovi J, Pouteau LH, et al. Buruli in cholera-endemic and cholera-free ulcer distribution in Benin. Emerg Infect Raoul Follereau Foundation of Luxem- Dis. 2005;11:500. areas supports the view that autoch- bourg; Burulico Project (European Union), 5. Sopoh GE, Adinsi V, Johnson RC, Barogui tonous V. cholerae is involved in the project INCO-CT-2005-051476; Stop Bu- YT, Dossou A, Van der Werf TS, et al. Dis- introduction of cholera (3,4). To our ruli Project (UBS Optimus Foundation), tribution de l’UB dans la commune de Zê. knowledge, cholera has not been re- Med Trop (Mars). 2010;70:379–83. Geneva, Switzerland; Directorate-General 6. Debacker M, Aguiar J, Steunou C, Zinsou ported in Papua New Guinea, despite for Development and Cooperation, Brus- C, Meyers WM, Guédénon A, et al. Myco- social and environmental conditions sels, Belgium; and the World Health Orga- bacterium ulcerans disease (Buruli ulcer) likely to facilitate transmission and the nization, Geneva, Switzerland. in a rural hospital, southern Benin, 1997– nation's close proximity to cholera-en- 2001. Emerg Infect Dis. 2004;10:1391–8. 7. Kolawolé SA, Boko M. Le Benin [French] demic countries (5,6). Ghislain Emmanuel Sopoh, Cotonou (Benin) and Paris: EDICEF; On August 6, 2009, a physician Roch Christian Johnson, 1983. p. 95. who visited the coastal village of 8. Meyers WM, Connor DH, McCullough B, Lambutina reported an outbreak of Séverin Yehouénou Anagonou, Bourland J, Moris R, Proos L. Distribution Yves Thierry Barogui, of Mycobacterium ulcerans infections in acute watery diarrhea that was associ- Ange Dodji Dossou, Zaire, including the report of new foci. ated with the death of his father and 4 Jean Gabin Houézo, Ann Soc Belg Med Trop. 1974;54:147– other persons from this and a neigh- 57. boring village. The outbreak began in Delphin Mavingha Phanzu, 9. Portaels F. Epidemiology of mycobacterial Brice Hughes Tente, diseases. In: Schuster M, editor. Mycobac- the village of Nambariwa and spread Wayne M. Meyers, terial diseases of the skin. Clin Dermatol. to neighboring Lambutina, Morobe and Françoise Portaels 1995;13:207–22. Province. From August 13, multidis- 10. Wagner T, Benbow EM, Brenden OT, Qi ciplinary teams worked with the com- Author affi liations: Centre de Dépistage et J, Johnson RC. Buruli ulcer disease preva- de Traitement de l’Ulcère de Buruli d’Allada, lence in Benin, West Africa: associations munity to reduce the number of deaths Allada, Bénin (G.E. Sopoh, A.D. Dossou, with land use/cover and identifi cation through early identifi cation and treat- of disease clusters. Int J Health Geogr. J.G. Houezo); Programme National de Lutte ment of case-patients. The teams also 2008;7:25. DOI: 10.1186/1476-072X-7- worked to limit transmission through Contre la Lèpre et l’Ulcère de Buruli, Coto- 25 nou, Bénin (R.C. Johnson); Laboratoire de improvements to the water and sanita- Référence des Mycobactéries, Cotonou Address for correspondence: Françoise Portaels, tion infrastructure and by encouraging (S.Y. Anagonou); Centre de Dépistage et Department of Microbiology, Institute of better hygiene practices among the de Traitement de l’Ulcère de Buruli de Lalo, Tropical Medicine, Nationalestraat 155, B-2000 villagers. A suspected case of cholera Lalo, Bénin (Y.T. Barogui); Institut Médical Antwerp, Belgium; email: [email protected] was defi ned as acute watery diarrhea Evangélique, Kimpese, Bas-Congo, Demo- or vomiting in a resident of Lambutina cratic Republic of Congo (D.M. Phanzu); or Nambariwa villages since July 22, Université d’Abomey-Calavi, Bénin (B.H. 2009.