Transmission of Yersinia pestis by Fleas: Molecular Mechanisms

National Institute Of Allergy And Infectious Diseases

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Abstract

Plague is a zoonosis that is present in wild rodent populations worldwide and is transmitted primarily by fleas. Yersinia pestis, the plague bacillus, is unique among the enteric group of gram-negative bacteria in having adopted an arthropod-borne route of transmission. Y. pestis has evolved in such a way as to be transmitted during the brief encounter between a feeding flea and a host. A transmissible infection primarily depends on the ability of Y. pestis to grow in the flea as a biofilm that is embedded in a complex extracellular matrix. Bacteria in the biofilm phenotype are deposited into the dermis together with flea saliva, elements which cannot be satisfactorily mimicked by needle- injection of Y. pestis from laboratory cultures. This project focuses on the interactions of Y. pestis with its flea vector that lead to transmission. One goal is to identify and determine the function of Y. pestis genes that mediate flea-borne transmission and the initial encounter with the host innate immune system at the infection site in the skin. A second goal is to characterize the flea response to infection, including the flea immune response and how Y. pestis resists it. Detailed understanding of the bacterial-flea interaction may lead to novel strategies to interrupt the transmission cycle. We have also established systems to compare the relative importance of the two modes of transmission and the relative vector competence of different flea species. Our studies of the vector competence and vectorial capacity of fleas and lice will be essential to more realistic mathematical modeling of the epidemiology of plague transmission and the conditions that lead to plague epizootics. We worked to complete several ongoing studies prior to shutdown of the laboratory in April 2023 (the PI retired on April 30, 2023).