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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » LAPRU » Research » Publications at this Location » Publication #334395

Research Project: Cattle Fever Tick Control and Eradication

Location: Livestock Arthropod Pests Research

Title: Imaging of Borrelia turicatae producing the green fluorescent protein reveals persistent colonization of the Ornithodoros turicata midgut and salivary glands from nymphal acquisition through transmission

Author
item Wilder, Hannah - Baylor College Of Medicine
item Krishnavajhala, Aparna - Baylor College Of Medicine
item Boyle, William - Mississippi State University
item Damania, Ashish - Baylor College Of Medicine
item Thornton, Justin - Mississippi State University
item Perez De Leon, Adalberto - Beto
item Teel, Pete - Texas A&M Agrilife
item Lopez, Job - Baylor College Of Medicine

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2016
Publication Date: 3/1/2017
Citation: Wilder, H.K., Krishnavajhala, A., Boyle, W.K., Damania, A., Thornton, J.A., Perez De Leon, A.A., Teel, P.D., Lopez, J.E. 2017. Imaging of Borrelia turicatae producing the green fluorescent protein reveals persistent colonization of the Ornithodoros turicata midgut and salivary glands from nymphal acquisition through transmission. Applied and Environmental Microbiology. 83(5):2503-2516.

Interpretive Summary: Some species of soft ticks transmit spiral-shaped bacteria, also known as spirochetes, that cause Relapsing fever (RF) in humans. However, gaps in our knowledge exist regarding the infection process of soft ticks with spirochetes, which is also important for disease transmission to humans and other animals through the bite of infected ticks. Thus, the RF spirochete scientifically known as Borrelia turicatae (B. turicatae) was transformed to express the green fluorescent protein (gfp) biomarker to study tick colonization and transmission of RF spirochetes. The ability of B. turicatae-gfp to infect the soft tick, Ornithodoros turicata, and mice, and its transmission by soft ticks to mice was evaluated. B. turicatae-gfp remained viable for at least 18 months in the starved immature stage of the soft tick. Spirochete populations persistently colonized the tick midgut and salivary glands. Use of B. turicatae-gfp allowed us to document that after tick feeding, the salivary glands remained populated with spirochetes. The RF spirochete expressing the gfp biomarker generated through this study is an important tool that can be used to study further the mechanisms of tick colonization and transmission, which is important to understand epidemiological aspects of soft tick-borne RF affecting humans and other animals.

Technical Abstract: Relapsing fever (RF) spirochetes colonize and are transmitted to mammals primarily by Ornithodoros ticks, and little is known regarding the pathogen’s life cycle in the vector. To further understand vector colonization and transmission of RF spirochetes, Borrelia turicatae expressing a green fluorescent protein (GFP) reporter (B. turicatae-gfp) was generated. The transformants were evaluated during the tick-mammalian infectious cycle, from the third nymphal instar to adult stage. B. turicatae-gfp remained viable for at least 18 months in starved fourth stage nymphal ticks, and the studies indicated that spirochete populations persistently colonized the tick midgut and salivary glands. Our generation of B. turicatae-gfp also revealed that after tick feeding the salivary glands remained populated with spirochetes. The B. turicatae-gfp generated in this study is an important tool to further understand and define the mechanisms of vector colonization and transmission. Importance: In order to interrupt the infectious cycle of tick-borne relapsing fever spirochetes, it is important to enhance our understanding of vector colonization and transmission. Toward this, we generated for the first time a strain of Borrelia turicatae that constitutively produced the green fluorescent protein, and we evaluated fluorescing spirochetes during the entire infectious cycle. We determined that the midgut and salivary glands of Ornithodoros turicata ticks maintain the pathogens throughout the vector’s life cycle and remain colonized with the spirochetes for at least 18 months. We also determined that the tick’s salivary glands were not depleted after a transmission blood feeding. These findings set the frame work to further understand the mechanisms of midgut and salivary gland colonization.