Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001
Performing Department
Animal Health Research Center
Non Technical Summary
The collection of endosymbiotic organisms that reside within a host organisms can include viruses, fungi and bacteria, and are known as microbiome. The microbiome has come under increasing scrutiny as a force influencing pathogen acquisition and transmission. We will analyze the microbiome of the Dermacentor andersoni tick focusing our initial efforts on the bacterial endosymbionts. In this project we will catalog the repertoire of endosymbionts and demonstrate that we can manipulate the composition of the microbiome. Future work plans to use the manipulated ticks to show that we can affect transmission of pathogens through manipulation of the microbiome.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Pathogen transmission results when the minimal infectious dose requirement is met - a variable dependent on the intrinsic infectiousness of the pathogen and immune status of the host. For pathogens transmitted by arthropods, which compose 30% of recently emergent infectious diseases, there is the additional complexity of vector capacity defined as, C =ma2VPn/-logeP, where C = vectorial capacity, the number of infective bites received daily by a single host; m = density of vectors in relation to density of hosts; a = proportion of vectors feeding on a host divided by the length of gonotrophic cycle in days; v = vector competence; p = daily survival of vectors; n = extrinsic incubation period. Each of these components can be affected by the microbiome of the vector. To date most studies of vector capacity have considered the effects of Wolbachia on vector lifespan, reproductive success, and, more recently, on development of infectivity of a second, unrelated microbe. Similarly, microbiome effects on transmission efficiency have been identified, illustrated by the interference of transmission of the highly pathogenic Rickettsia rickettsii by Dermacentor andersoni ticks when the ticks have been previously colonized with the non-pathogenic Rickettsia peacockii. Although these studies provide compelling evidence of the effects of microbial symbionts or normal flora on vector capacity, they do not address the effects of the broader microbiome on transmission of vector-borne infectious diseases. As contemporary studies of the human gut have revealed, the microbiome is complex and both spatially and temporally dynamic-all of which affect gut physiology and pathophysiology. How the microbiome of the arthropod vector shapes pathogen transmission represents a significant gap in knowledge in the ecology of infectious diseases-understanding of which will have broad impact on control of transmission of vector-borne animal, human, and plant pathogens. The goal of this proposal is to understand the effect of the microbiome on transmission. We propose to use the cattle pathogen, Anaplasma marginale and its tick vector, D. andersoni, as this system allows us to work with a natural transmission model using relevant vector and host species and provides directly applicable data for an economically important veterinary disease (anaplasmosis) as well as being a model for rickettsial pathogens in general. To test the hypothesis that the tick microbiome is a determinant of the efficiency of vectorial capacity, we propose three Specific Aims: 1) Determine if there are significant differences in the microbiome among tick populations with differing A. marginale transmission phenotypes; 2) Demonstrate an altered microbiome population structure in the tick after antibiotic treatment. 3) Test whether changes in the tick microbiome induced by antibiotic treatment alters the vectorial capacity for A. marginale. The request for funding is to generate preliminary data on the D. andersoni microbiome and our ability to stably affect the composition of the microbiome. Expected outputs will be the generation of large data sets of 16S sequence data from treated and untreated ticks.
Project Methods
To test the hypothesis that the tick microbiome is a primary determinant of the efficiency of vectorial capacity, we will examine the endosymbiont community from field collected ticks over the course of the study to determine the dynamics of the microbiome over time. In parallel we will use three tick populations with differing susceptibilities to pathogen and document the community structure before and after treatment with antibiotics and determine if alterations in the community structure correlate with an altered transmission phenotype. We will restore the microbiome to the original levels and determine if this restores the original transmission phenotype. We will use PCR amplification of bacterial 16S rDNA genes from tick genomic DNA, sequencing and bioinformatic characrterization of the data using programs such as CLC genomics workbench and the RDP classifier.