Using the basic reproduction number to assess the effects of climate change in the risk of Chagas disease transmission in Colombia

The dynamics of vector-borne diseases has often been linked to climate change. However the commonly complex dynamics of vector-borne diseases make it very difficult to predict risk based on vector or host distributions. The basic reproduction number (R-0) integrates all factors that determine whether a pathogen can establish or not. To obtain R-0 for complex vector-borne diseases one can use the next-generation matrix (NGM) approach. We used the NGM to compute R-0 for Chagas disease in Colombia incorporating the effect of temperature in some of the transmission routes of Trypanosoma cruzi. We used R-0 to generate a risk map of present conditions and a forecast risk map at 20 years from now based on mean annual temperature (data obtained from Worldclim). In addition we used the model to compute elasticity and sensitivity indexes on all model parameters and routes of transmission. We present this work as an approach to indicate which transmission pathways are more critical for disease transmission but acknowledge the fact that results and projections strongly depend on better knowledge of entomological parameters and transmission routes. We concluded that the highest contribution to R-0 comes from transmission of the parasites from humans to vectors, which is a surprising result. In addition, parameters related to contacts between human and vectors and the efficiency of parasite transmission between them also show a prominent effect onR(0). (C) 2013 Elsevier B.V. All rights reserved.