Dissertations, Theses, and Capstone Projects

Date of Degree

2-2015

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Susan L. Perkins

Subject Categories

Evolution | Parasitology | Zoology

Keywords

Bat, disease origins, Natural History Museums, Species delimitation, Toll-like receptor 2, Trypanosoma cruzi

Abstract

Trypanosoma cruzi is a genetically diverse parasite that causes Chagas disease, one of the most important zoonoses in the Americas. This generalist parasite of mammals belongs to a clade mostly comprised of bat parasites, the T. cruzi clade. The origins (i.e., biogeographic history and evolution of hosts associations) of this parasite are far from being understood, and the main areas that need further study are: species limits within T. cruzi sensu lato, further studies on the diversity of T. cruzi clade members and their hosts, and research on adaptations of the hosts to trypanosome infections. In this dissertation I explore these research areas in five core chapters (Ch.2 to Ch.6), and these are the main results per chapter: ch.2) Proposed the recognition of Tcbat as a major diagnostic typing unit of T. cruzi. Ch.3) Found high genetic diversity in the bat exclusive lineage T. c. marinkellei than in the other subdivisions of T. cruzi. Also, reported Tcbat and T. c. marinkellei for Ecuador. Ch.4) Determined that the number of putative species in the T. cruzi clade is underestimated, and more strikingly, that the bat Artibeus jamaicensis is the vertebrate host with the highest number of trypanosomes (5 species) detected in a single locality. Ch.5) Results indicate that T. cruzi sensu lato is actually comprised of three species - the generalist T. cruzi, and two parasites of bats, Trypanosoma marinkellei and Trypanosoma sp. nov.; that there is a previously undetected high diversity of T. cruzi relatives associated with bats, and use of bats as hosts has evolved several times and in three different clades of parasites. Ch.6) Tested the hypothesis that immune genes in bats evolve under stronger positive selection than in other mammals because of the high diversity of pathogens associated with bats--including trypanosomes of the T. cruzi clade. I used the gene TLR2, as a candidate gene. These results help to understanding better the diversity of the T. cruzi clade, and the importance of bats on the origins of T. cruzi sensu strict and Chagas disease.

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