Restriction of Francisella novicida Genetic Diversity during Infection of the Vector Midgut

PLoS Pathogens

Susan M. Noh¹  Guy H. Palmer¹  Massaro W. Ueti²  David W. Crowder³  Kathryn E. Reif³ 

[1] Animal Disease Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Pullman, Washington, United States of America;Department of Entomology, Washington State University, Pullman, Washington, United States of America;Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, and Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, United States of America

关键词: Pathogens;    Ticks;    Species diversity;    Blood;    Vector-borne diseases;    Nymphs;    Host-pathogen interactions;    Population genetics;   

DOI  :  10.1371/journal.ppat.1004499

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

The genetic diversity of pathogens, and interactions between genotypes, can strongly influence pathogen phenotypes such as transmissibility and virulence. For vector-borne pathogens, both mammalian hosts and arthropod vectors may limit pathogen genotypic diversity (number of unique genotypes circulating in an area) by preventing infection or transmission of particular genotypes. Mammalian hosts often act as “ecological filters” for pathogen diversity, where novel variants are frequently eliminated because of stochastic events or fitness costs. However, whether vectors can serve a similar role in limiting pathogen diversity is less clear. Here we show using Francisella novicida and a natural tick vector of Francisella spp. (Dermacentor andersoni), that the tick vector acted as a stronger ecological filter for pathogen diversity compared to the mammalian host. When both mice and ticks were exposed to mixtures of F. novicida genotypes, significantly fewer genotypes co-colonized ticks compared to mice. In both ticks and mice, increased genotypic diversity negatively affected the recovery of available genotypes. Competition among genotypes contributed to the reduction of diversity during infection of the tick midgut, as genotypes not recovered from tick midguts during mixed genotype infections were recovered from tick midguts during individual genotype infection. Mediated by stochastic and selective forces, pathogen genotype diversity was markedly reduced in the tick. We incorporated our experimental results into a model to demonstrate how vector population dynamics, especially vector-to-host ratio, strongly affected pathogen genotypic diversity in a population over time. Understanding pathogen genotypic population dynamics will aid in identification of the variables that most strongly affect pathogen transmission and disease ecology.

【 授权许可】

CC BY