Migration and the Emergence of Chagas Disease Vectors in the Growing City of El Pedregal, Peru

The city of El Pedregal grew out of a desert, following an agricultural irrigation project in Southern Peru. We conducted door-to-door entomological surveys to document the emergence of triatomines and bed bugs into this new urban environment. We inspected 5,191 households for Triatoma infestans (known locally as the Chirimacha); 21 (0.41%) were infested. These were extremely spatially clustered (Ripleys K p-value <0.001 at various spatial scales). Using remote sensing we compared the year of construction of infested to un-infested households and found that infested houses were older than controls (Wilcoxon rank-sum: W=33; p=0.02). We confirmed infestations through a subsequent bed bug specific inspection in 34 households. These households were more spatially disperse across El Pedregal. To gain a better understanding of the context surrounding triatomine infestations, we conducted in-depth interviews with residents to explore their migration histories and previous experiences with Chirimachas. Main reasons for migration includes searching for work on land, opportunity to buying a house, and scape adverse climate effects. Permanent migration flow and poor housing conditions create suitable environment for emergence triatomine infestation. We discuss how changes in the landscape could potentially heighten vulnerability to vector-borne illnesses. Author summaryLarge-scale irrigation and changes in land-use have been linked with emergence of infectious disease worldwide. In El Pedregal, Southern Peru, the Majes-Siguas irrigation was designed to supply water to agribusiness companies installed in a desert area. This project has propelled a constant migration flow and the growth of this new city, promoting conditions to emergence of Triatoma infestans, an insect vector of Chagas disease, as well as bed bugs. Triatomine infestation presented a clustered pattern, its dispersion limited by unoccupied houses. Triatomine infested houses tend to be older than other houses. Bed bug infestations were more spread out, and not related to construction age. Householders stories of migration shed light on some of the socioeconomic determinants that promote conditions for infestation. Amongst these, living in poor housing conditions, and the constant migration flow; driven by seeking opportunities to work, to buy a house, or to escape from adverse climate effects in other farming regions. Environmental and socioeconomic impacts of large-scale development disproportionately affect vulnerable populations. Design of surveillance systems that account for these contexts is urgently needed to support early detection and control of emergence of vector-borne diseases.