VECTOR-BORNE DISEASES,SURVEILLANCE,PREVENTION Microdistribution of Sylvatic Triatomine Populations in Central-Coastal Ecuador VICTORIA SUAREZ-DAVALOS, 1 OLIVIER DANGLES, 2,3 ANITA G. VILLACIS, 1 AND MARIO J. GRIJALVA 1,4 Center for Infectious Disease Research, PontiÞcal Catholic University of Ecuador, Quito, Ecuador J. Med. Entomol. 47(1): 80Ð88 (2010) ABSTRACT Chagas disease is a serious public health problem in Ecuador, where nearly 230,000 individuals show Trypanosoma cruzi infection. Sylvatic T. cruzi transmission is a threat to current control strategies. This is because of the possibility of house reinfestation by sylvatic triatomines after insecticide treatment. This work quantiÞed the spatial distribution of triatomines in sylvatic habitats and its relationship with nearby human dwellings. A simple random sampling design using live-baited traps and manual searches for triatomines was used in areas near human communities in Manabõ ´ province, Ecuador, during June and July 2007. We identiÞed risk factors associated with triatomine density using generalized linear models, and developed predictive maps for triatomine density interpolation. There were 345 triatomines belonging to the species Rhodnius ecuadoriensis and Panstrongylus howardi collected in sylvatic areas. Spatial analyses revealed an aggregated distribution pattern of the sylvatic triatomine populations (clustered mostly at a distance smaller than 100 m). Generalized linear models showed that the distance from the nearest house, nest type, and height from ground level were the main factors explaining triatomine densities. Squirrel nests (Sciurus stramineus), located in plants other than palms, above 5 m and close to the domicile presented higher infestation. Interpolation maps of triatomine microdistribution are presented as potential tools to predict triato- mine occurrence. The presence of sylvatic populations and the synanthropic tendency of the vectors highlight the need for continuous active and passive entomological surveillance for the long-term control of Chagas disease. KEY WORDS Chagas disease, random sampling, sylvatic habitat, triatomine ecology, Ecuador In Ecuador, around 3.8 million people are at risk of acquiring Chagas disease (American trypanosomi- asis) and 230,000 individuals are currently in- fected with the disease making it a serious public health issue (World Health Organization [WHO] 2002). Sixteen species of insect vectors (Hemiptera: Triatominae) have been reported in Ecuador (Abad-Franch et al. 2001; Lent and Wygodzinsky 1979). Triatoma dimidiata, thought to be an intro- duced species, is considered the main vector, and Rhodnius ecuadoriensis is considered the second most important vector in the country. T. dimidiata seems to be exclusively domestic in Ecuador, but R. ecuadoriensis presents domiciliary and peridomicili- ary infestations, and abundant sylvatic populations in the central coastal region where it is associated with the endemic palm species Phytelephas aequa- torialis (Abad-Franch et al. 2001, Grijalva et al. 2005). Several other triatomine species have also shown capacity to colonize houses and to transmit Trypanosoma cruzi, including Panstrongylus howardi in dry areas of Manabõ ´ province, and P. rufotuber- culatus in the Coastal region and Interandean val- leys. In the Amazon region of Ecuador, the sylvatic vectors R. pictipes, R. robustus, and P. geniculatus are responsible for most of the T. cruzi infections, trans- mitting the parasite without establishing colonies in human environments (Aguilar et al. 1999), but little information exists regarding the ecology of most triatomine species in Ecuador. The main objectives of the current study were to develop a better-standardized method for sampling sylvatic triatomine populations and to evaluate the efÞcacy of live-baited traps compared with manual searches. We also sought to identify environmental factors that may inßuence the distribution pattern of these sylvatic populations, and to model the spa- tial distribution of sylvatic triatomine populations in relation to their location near human dwellings. 1 Center for Infectious Disease Research, PontiÞcal Catholic Uni- versity of Ecuador, Quito, Ecuador (e-mail: grijalva@ohio.edu). 2 Laboratory of Entomology, PontiÞcal Catholic University of Ec- uador. 3 IRD UR072, LEGS UPR 9034, CNRS 91198 Gif-sur Yvette Cedex and Universite ´ Paris-Sud 11, France. 4 Tropical Disease Institute, College of Osteopathic Medicine, Ohio University, Athens, OH 45701. 0022-2585/10/0080Ð0088$04.00/0  2010 Entomological Society of America