Variation in host susceptibility to different pathogens: an experimental and phylogenetic study of Drosophila-viruses

Author(s)

Camila Souza Beraldo

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2018-08-30

Examining board members

Rodrigo Cogni; Louis Bernard Klaczko; Tiago Bosisio Quental; Katherine Elizabeth Roberts

• Advisor: Rodrigo Cogni

Abstract

Host shifts -- where a pathogen jumps from one host species to another -- have been described as one of the main factors leading to emerging infectious diseases (EID). The harm that a pathogen causes to a host (virulence) varies following a host shift. Differences in susceptibilities among host species means that pathogens may be more likely to switch between certain groups of hosts. Factors that determine the variation in host susceptibility are still unknown, but one possible predictor is the host evolutionary history. Here, we examine how phylogenetically related hosts vary in susceptibility when dealing with infections of two viruses differing in pathogenicity. We infected 39 species of Drosophilidae with Drosophila A virus (DAV), a virus initially described as avirulent, and we measured host mortality (virulence) and virus replication (viral load). Then, we compared our results to previously collected data from the virulent Drosophila C virus (DCV) and we analysed the data of both viruses together. We found large variation in DAV virulence and viral load, with benign infections in some cases and high mortality in others. There was phylogenetic correlation in viral load, with species presenting similar viral load clustering together in the phylogeny. However, we did not find correlation for virulence, indicating that DAV virulence was not predictable based on viral load. Also, we did not find correlation between DAV and DCV results, indicating that variation in host susceptibility is not predictable by other pathogens infections. It is possible that hosts and parasites ecology or genetic traits may be also influencing susceptibility variation. These results suggest that although some traits are predicted by phylogeny, to determine the factors driving host susceptibility variation to different pathogens following host shifts is a very complex task (AU)

• FAPESP's process: 16/09934-4 - Influence of host's evolutionary history on parasite and host fitness: a case study of drosophilids and Drosophila a virus
• Grantee: Camila Souza Beraldo
• Support Opportunities: Scholarships in Brazil - Master