PhD, University of Cincinnati, 2015, Medicine: Toxicology (Environmental Health)

Cryptosporidiosis is an environmentally-associated human diarrheal disease caused by the etiological agent, Cryptosporidium. This parasitic pathogen is an intestinal protozoan that is abundant in the environment as highly resistant oocysts and can cause life-threatening consequences in immunosuppressed individuals. Of the various species found in the environment, one of the human-infective species is Cryptosporidium parvum. Parasite development and propagation occurs within a unique intracellular but extracytoplasmic parasitophorous vacuole at the apical surface of intestinal epithelial cells. Very little is known regarding the pathogenesis of C. parvum and what host factors are involved in infection. In order to assess differences in host susceptibilities, we compared several different host cell types using an in vitro model. Specifically, we introduced a new small intestinal epithelial cell type, FHs 74 Int, which supported better infection of C. parvum. Moreover, this cell type sustained the development and growth of the parasite over 48 hours. The molecular mechanisms of Cryptosporidium pathogenesis and the factors that cause variation in infection are poorly understood. Two different intestinal epithelial cells, HCT-8 and FHs 74 Int, had drastically different levels of infections, with the first supporting much less infection than the second. Using the FHs 74 Int model, we studied the expression patterns of several host factors before and after infection to C. parvum. One protein of interest was the tyrosine phosphatase Src homology-2 domain-containing phosphatase 2 (SHP-2). SHP-2, encoded by the human PTPN11 gene, is a ubiquitously expressed protein tyrosine phosphatase that acts on paxillin. In this study, we found that SHP-2 co-localizes at the apical end of the C. parvum infection site. Moreover, inhibition of SHP-2 abrogated complete infection and decreased phosphorylated levels of another protein-of-interest, paxillin. Paxillin is moderat (open full item for complete abstract)

Committee: Jagjit Yadav Ph.D. (Committee Chair); Susan Kasper Ph.D. (Committee Member); Susan Waltz Ph.D. (Committee Member); Ying Xia Ph.D. (Committee Member) Subjects: Environmental Health

MS, University of Cincinnati, 2005, Arts and Sciences : Geology

This study addresses concerns of surface water contamination entering a valley-train aquifer used by the Springfield Water Treatment Plant in Clark County, Ohio. Ground water is derived partly from infiltration of surface water through the riverbed of the adjacent Mad River. Of particular concern is biological pathogen Cryptosporidium parvum that is resistant to conventional treatment. Transient, finite-difference ground water flow modeling and particle tracking are conducted, based on a geologically similar model near Dayton, Ohio. Site-specific parameters used for modeling are derived from previous investigations, pump tests, and gain-loss studies conducted at the SWTP. Modeling is conducted for a flooding event when the aquifer is most sensitive to surface infiltration. Minimum travel times from Mad River to the production wells were estimated at around a day, but do not account for river bank filtration. The results provide a basis for additional study on the sensitivity of infiltration of surface contaminants.

Committee: Dr. David Nash (Advisor) Subjects: Geology; Hydrology

Doctor of Philosophy, The Ohio State University, 2005, Veterinary Preventive Medicine

Cryptosporidiosis, an infection caused by several genotypically and phenotypically diverse Cryptosporidium species, is a serious enteric disease of animals and humans worldwide. The current understanding of cryptosporidiosis, transmission, diagnosis, treatment and prevention measures for this disease is discussed. Contaminated water represents the major source of Cryptosporidium infections for humans. Manure from cattle can be a major source of Cryptosporidium oocysts. Oocysts transport to surface water can occur through direct fecal contamination, surface transport from land-applied manure or leaching through the soil to groundwater. Identification of Cryptosporidium species and genotypes facilitates determining the origin of the oocysts and to recognize sources of infection in outbreak situations and the risk factors associated with transmission. Very few studies have applied isolation methods to field samples because of difficulties with detection of oocysts in environmental samples. The objective of this study was to develop an easy method that can be applied to field samples to rapidly detect the presence of Cryptosporidium oocysts and identify their species. A molecular detection system that included an oocyst recovery method combined with spin column DNA extraction, followed by PCR-hybridization for detection and a Real-Time PCR-melting curve analysis for species assignment. Due to its versatility and capability of rapid high-throughput analysis of multiple targets, an oligonucleotide microarray was also designed to identify Cryptosporidium parasites and discriminate between species. The detection assay was then used to assess Cryptosporidium contamination in swine and poultry samples and to study the transport of Cryptosporidium oocysts through disturbed (tilled) and non-disturbed (no-till) soil during simulated rainfall. The results of the study demonstrated the potential of the assay for the detection of the parasite in environmental samples. In vitro cult (open full item for complete abstract)

Committee: Srinand Sreevatsan (Advisor) Subjects:

Doctor of Philosophy, Miami University, 2007, Zoology

Freshwater ecosystems are especially susceptible to climatic change, including anthropogenic-induced changes, as they are directly influenced by the atmosphere and terrestrial ecosystems. A major environmental factor that potentially affects every element of an ecosystem, directly or indirectly, is ultraviolet radiation (UVR). UVR has been shown to negatively affect the DNA of aquatic organisms by the same mechanism, formation of photoproducts (cyclobutane pyrimidine dimers; CPDs), as in humans. First, the induction of CPDs by solar UVR was quantified in four aquatic and terrestrial temperate ecosystems. Data show significant variation in CPD formation not only between aquatic and terrestrial ecosystems but also within a single ecosystem and between seasons. Second, there is little quantitative data on UV-induced DNA damage and the effectiveness of DNA repair mechanisms on the damage induced in freshwater invertebrates in the literature. The rate of photoproduct induction (CPDs) and DNA repair (photoenzymatic and nucleotide excision repair) in Daphniafollowing UVR exposures in artificial as well as two natural temperate lake systems was tested. The effect of temperature on the DNA repair rates, and ultimately the organisms' survival, was tested under controlled laboratory conditions following artificial UVB exposure. The results of these studies suggest a significant interaction of UVR and temperature on individual survival and ultimately population dynamics in freshwater systems. Lastly, freshwater human pathogens have negative effects ranging from gastrointestinal distress in otherwise healthy individuals to death in the immunocompromised and elderly. The control of infectious pathogens in water treatment is imperative. The abiotic and biotic environmental stressors of human pathogens are not well understood. Herein, solar radiation and artificial UVB are shown to significantly decrease the infectivity of Cryptosporidium parvum in vitro. The generalist filter feed (open full item for complete abstract)

Committee: Craig Williamson (Advisor) Subjects: