Disease dynamics, ecology, and biology of Coccidioides spp. in Arizona

Steinken Kollath, Daniel (2022) Disease dynamics, ecology, and biology of Coccidioides spp. in Arizona. Doctoral thesis, Northern Arizona University.

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Abstract

The disease Valley fever (coccidioidomycosis, San Joaquin Valley Fever) is caused by two species of soil dwelling fungal pathogens within the genus Coccidioides (C. posadasii and C. immitis). Infection is established when a susceptible mammal inhales environmental arthroconidia shed from the saprobic lifecycle of the fungus. Although the lone route of infection comes from the environment, abiotic and biotic factors that influence the distribution and dispersal of the organism in the environment are poorly understood. My dissertation research is focused on using microbiological, molecular, and epidemiological tools to investigate the disease dynamics, basic biology, and ecology of these important fungal pathogens. In Chapter 1, I provide background information, a review of the literature, and highlight gaps in knowledge that are important to fully understanding these fungi. In Chapter 2 I employ sophisticated statistical models on epidemiological data from Arizona to gain insights into the seasonality of Valley fever. This study looked at specifically how climatic variables can predict outbreaks. This type of analysis can be used to improve public health surveillance of the disease and understand basic biology of the fungi in natural soil habitat. In brief, I found that temperature and water availability are crucial for the soil microbes of the hot and arid Sonoran Desert ecosystem. In Chapter 3, I experimentally examine how these factors influence the growth of the fungus and the discharge of infectious arthroconidia in soil and employ mechanistic growth models in order to predict the growth and shed pattern. Importantly, this is the first study to quantify this biological process and will aid the development of future disease models. Soil is an extremely complex habitat, with many biological interactions that can influence the distribution of populations of certain microbes. In Chapter 4 I examine the relationships of commonly occurring soil bacteria and fungi with Coccidioides spp. I use molecular tools to identify bacteria and fungi that are interacting with Coccidioides spp. at multiple sites in soil and examine whether these microbes have an antagonistic, synergistic, or neutral relationship with the pathogen. I then apply analytical chemistry techniques to characterize the secreted metabolites of the microbes with antagonistic properties. The goal of Chapter 4 is to identify microbes and/or metabolites that suppress the growth of Coccidioides spp. in hyper-endemic areas of Valley fever. Microbes with synergistic properties can also be used as indicator species for the presence of Coccidioides spp. in the soil. The knowledge gained from my dissertation helps to understand this deadly pathogen in the laboratory and in the field and improve disease modeling to prevent fatal infections of humans and domestic animals.

Item Type:	Thesis (Doctoral)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Coccidioides; Ecology; modeling; Valley fever; Arizona; Fungal pathogens; Vectors
Subjects:	R Medicine > RC Internal medicine
MeSH Subjects:	C Diseases > C02 Virus Diseases
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	07 Jun 2023 16:41
Last Modified:	07 Jun 2023 16:41
URI:	https://openknowledge.nau.edu/id/eprint/5975

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