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Ticks and Tularemia: Do We Know What We Don't Know?
Briana Zellner1, Jason F Huntley1
1Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States.
Frontiers in Cellular and Infection Microbiology
|May 30, 2019
Summary
Ticks are the primary U.S. reservoir and transmitter of Francisella tularensis (F. tularensis), the bacterium causing tularemia. This review examines the known, unknown, and debated roles of various tick species in F. tularensis transmission and environmental persistence.
Area of Science:
- Microbiology and Infectious Diseases
- Vector-borne Diseases
- Public Health
Background:
- Francisella tularensis (F. tularensis) causes tularemia, a zoonotic disease with high morbidity and mortality across numerous mammalian species, including humans.
- F. tularensis is a severe public health threat, classified as a NIH Category A Priority Pathogen and CDC Tier 1 Select Agent due to its low infectious dose, diverse infection routes, and potential for rapid, lethal disease.
- In the U.S., most tularemia cases are tick-mediated, with ticks serving as the principal environmental reservoir for F. tularensis.
Purpose of the Study:
- To review current knowledge regarding the roles of different tick species as environmental reservoirs for F. tularensis.
- To summarize the known and debated aspects of various tick species acting as transmission vectors for diverse F. tularensis genotypes/strains.
- To identify knowledge gaps and areas of scientific debate concerning tick-mediated tularemia.
Main Methods:
- Literature review of existing studies on Francisella tularensis and tick vectors.
- Analysis of reported tick species involved in harboring and transmitting F. tularensis.
- Synthesis of information on different F. tularensis genotypes/strains and their association with specific tick vectors.
Main Results:
- The American dog tick (Dermacentor variabilis) is identified as a primary tick vector for F. tularensis in the U.S.
- Other tick species, including the lone star tick (Amblyomma americanum), are also confirmed to harbor F. tularensis.
- Evidence suggests varying roles for different tick species in the ecology and transmission of F. tularensis.
Conclusions:
- Ticks are critical components of the F. tularensis life cycle and transmission dynamics in the United States.
- Further research is needed to fully elucidate the specific contributions of various tick species and F. tularensis strains to tularemia epidemiology.
- Understanding tick-host-pathogen interactions is crucial for public health strategies aimed at preventing and controlling tularemia.