Irrigation, migration and infestation: a case study of Chagas Disease Vectors and bed bugs in El Pedregal, Peru

Background: The city of El Pedregal grew out of a desert, following an agricultural irrigation project in Southern Peru. Objective: To describe infestation patterns by triatomines and bed bugs and their relationship with migration and urbanization. Methods: We conducted door-to-door entomological surveys for triatomines and bed bugs. We assessed spatial clustering of infestations and compare the year of construction of infested to un-infested households. To gain a better understanding of the context surrounding triatomine infestations, we conducted in-depth interviews with residents to explore their migration histories, including previous experiences with infestation. Results: We inspected 5,164 households for Triatoma infestans (known locally as the Chirimacha); 21 (0.41%) were infested. These were extremely spatially clustered (Ripley’s K p-value <0.001 at various spatial scales). Infested houses were older than controls (Wilcoxon rank-sum: W=33; p=0.02). We conducted bed bug specific inspections in 34 households; 23 of these were infested. These were spatially dispersed across El Pedregal, and no difference was observed in construction age between Cimex infested houses and control houses (W=6.5, p=0.07). Reasons for migration included searching for work, opportunity to buy a house, and to escape adverse climate effects, such as flooding. We discuss how changes in the landscape could potentially heighten vulnerability to vector-borne illnesses.