The tick response to Rickettsial dissemination during typical and atypical Rickettsial infection

Ticks are the only disease vectors for spotted fever group (SFG) Rickettsia which are obligate intracellular bacteria belonging to the genus Rickettsia. In nature, ticks maintain the infection of SFG Rickettsia via vertical and horizontal transmission. However, the prevalence of rickettsial transmission is limited to certain species of ticks, and this limitation is known as a specific tick/Rickettsia relationship. Due to the continuous increase of tick-borne rickettsial disease cases in the United States, which contrasts with very low prevalence of Rickettsia in tick vectors, the study of vector competence of tick to Rickettsia is needed in order to understand the ecology and epidemiology of tick-borne rickettsioses. Here we characterized the role of Dermacentor variabilis á-catenin during rickettsial infection in tick ovaries suggesting a role in rickettsial infection in tick ovaries. We demonstrated that the typical nonpathogenic (R. montanensis) and typical pathogenic (R. rickettsii) Rickettsia persistently infect Dermacentor variabilis compared to atypical Rickettsia (R. amblyommii), and only R. montanensis is able to disseminate to tick ovaries. D. variabilis glutathione S-transferase1 (DvGST1) has been identified as a tick immune-like molecule that specifically responds to atypical rickettsial challenge in tick midguts suggesting a role in controlling atypical rickettsial infection in tick midguts. DvGST1 is highly upregulated in tick midguts during bloodmeal acquisition. The function of GST is known to be involved with detoxification and oxidative stress reduction, and acaricide resistance in ticks. Silencing of DvGST1 gene demonstrates significant reduction of mRNA and enzyme activity of DvGST1 in tick midguts; however, further characterization of DvGST1 is needed due to the off-target effect of negative control dsRNA. Continued study on the tick/Rickettsia interaction influencing tick vector competence for Rickettsia will lead to a better understanding of ecology and epidemiology of tick-borne rickettsioses.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Veterinary Pathology and Pathobiology

Grantor

Veterinary Medical Sciences - Pathobiological Sciences

Year dc:date.available

2011

Author dc:creator

• Sunyakumthorn, Piyanate

• capillary feeding technique
• Kunitz protease inhibitor
• lysozyme
• defensin
• interference phenomenon
• rickettsial internalization
• tick immunity
• RNA interfence

Statement dc:rights

• unrestricted
• Release the entire work immediately for access worldwide.

Identifier

etd-04192011-205428
https://repository.lsu.edu/gradschool_dissertations/848

OAI identifier oai:identifier

oai:repository.lsu.edu:gradschool_dissertations-1847