Honors College Theses

Publication Date

4-29-2021

Major

Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dr. Marina E. Eremeeva

Abstract

Rickettsia are obligate intracellular tick-borne bacteria that cause acute undifferentiated febrile illness accompanied by headache, malaise, myalgias, and disseminated endothelial infection. Immune responses to Rickettsia and pathogenesis of rickettsioses are not fully understood. Current work with Rickettsia is limited to vertebrate models that are strictly regulated and have low throughput. Since the innate immune system of vertebrates retains striking similarities with the immune response in insects, invertebrates are being used to study host responses to various pathogens. The purpose of this study was to evaluate if larvae of the greater wax moth Galleria mellonella (GML) can be used as an in vivo invertebrate model to study Rickettsia infection. GML were infected with 104 to 107 plaque-forming units (PFU) of Rickettsia philipii 364D, or R. rickettsii Sheila Smith and kept at 34°C for 120 hours. Controls were injected with heat-inactivated Rickettsia, K36 buffer, or not injected. Infected and control GML were examined daily for phenotypic and behavioral changes. Hemolymph was collected daily from 5 GML per group for microscopy and DNA extraction. SYBR-Green-PCR assay was used to estimate Rickettsia DNA copy numbers in the hemolymph of infected GML. Rickettsia rickettsii caused a dose-dependent lethal infection in GML. Larvae infected with less-virulent R. philipii survived but exhibited dose-dependent morphological and phenotypical changes. Rickettsia were detected in the hemolymph and hemocytes of infected GML by PCR and microscopy, respectively, at each point of infection. In conclusion, GML are susceptible to Rickettsia and should be explored further as an alternative model of infection.

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Available for download on Saturday, April 25, 2026

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