Immigration and establishment of urban Trypanosoma cruzi populations

Abstract

Changing environmental conditions, including those caused by human activities, reshape biological communities through both loss of native species and establishment of non-native species in the altered habitats. Dynamic interactions with the abiotic environment impact both immigration and initial establishment of non-native species into these altered habitats. The repeated emergence of disease systems in urban areas worldwide highlights the importance of understanding how dynamic migratory processes affect the current and future distribution and abundance of pathogens in urban environments. In this study, we examine the pattern of invasion of Trypanosoma cruzi--the causative agent of human Chagas disease--in the city of Arequipa, Peru. Phylogenetic analyses of 136 T. cruzi isolates from Arequipa and other South American locations suggest that only one T. cruzi immigrant established a population in Arequipa as all T. cruzi isolated from vectors in Arequipa form a recent monophyletic group within the broader South American phylogeny. We discuss several hypotheses that may explain the limited number of established T. cruzi lineages despite multiple introductions of the parasite.\n\nAuthor SummaryHuman-associated pests and pathogens, who benefit from the abundance of humans and human-associated hosts or vectors, commonly invade environments altered by human activities. As the number and size of human-disturbed environments increase, so does the importance of identifying ecological and environmental factors that affect the probability that disease systems immigrate to, subsequently establish populations in, urban environments. We examined the number and timing of immigration and establishment events of Trypanosoma cruzi, the causative agent of Chagas disease, in a currently endemic area. Phylogenetic analyses of 136 T. cruzi isolates suggests that the current population descended from a single, recent immigration event. We discuss historical and ecological hypotheses that can explain the limited T. cruzi diversity in this region.