Temperature and relative humidity affect the selection of shelters by Triatoma infestans, vector of Chagas disease

The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects p referred refuges at a temperature of 34 degrees C rather than 26 degrees C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperatur e and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an i nner climate favourable to T. infestans. Typical refuges in adobe walls sho wed strongly damped fluctuations in minimum and maximum temperatures, and d elayed changes in these parameters when compared with an external reference . Similarly, the jarilla (Larrea sp.), a plant used for constructing roofin g, damps fluctuations in minimum and maximum RH and delays these RH fluctua tions when compared to an external reference. We discuss possible effects o f environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones. (C) 1999 Published by Elsevier Science B.V. All rights reserved.