Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item Climate Change and Vibrio species: Investigation of Environmental Parameters Associated with Occurrence and Transmission(2023) Brumfield, Kyle David; Colwell, Rita R.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Climate change, associated with shifts in the geographical range of biological species, has become increasingly important in emergence and re-emergence of disease. Vibrio spp., native to aquatic ecosystems, are commonly associated with aquatic invertebrates, notably crustaceans and zooplankton. Some species of the genus Vibrio cause infection in humans, of which Vibrio cholerae, the etiological agent of pandemic cholera, is the most documented. Pathogenic non-cholera Vibrio spp., namely Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis and also septicemia and extra-intestinal infections. They are responsible for a large number of public health emergencies in developed countries, including the United States. As sea temperatures rise and salinity profiles are altered, a pattern of poleward spreading of non-cholera Vibrio spp. has been observed globally, demonstrating significant geographic expansion of these bacterial populations, corroborated by an associated increase in the number of reported vibriosis cases. Since Vibrio spp., including pathogenic vibrios, play an important role in the degradation of polymeric substances, such as chitin, and in biogeochemical processes, they cannot be eradicated. Hence, routine monitoring and an early warning system are needed for public health preparedness. Since the 1960’s, ongoing research has focused on environmental factors linked with occurrence and distribution of clinically relevant Vibrio spp. and their role in disease transmission. We have reported that lack of, or damage to, water, sanitation, and hygiene (WASH) infrastructure, coupled with elevated air temperatures, and followed by above average rainfall promotes exposure of a population to contaminated water, hence increases the risk of an outbreak of cholera. Global predictive intelligence models applicable to diseases caused by non-cholera Vibrio spp. are in development. The research reported here describes results of intensive sampling to detect and characterize Vibrio spp. in the Chesapeake Bay, Maryland, and the Florida Gulf Coast, the latter an area significantly impacted by Hurricane Ian, September 2022, with a spike in confirmed vibriosis cases and deaths during weeks following the storm. Results of this study provide confirmation of environmental predictors for Vibrio spp. and document long-term increase and extended seasonality of Vibrio populations in the Chesapeake Bay. Using satellite remote sensing data, we demonstrate the impact of extreme heat, precipitation, and other key environmental and geophysical factors (e.g., temperature, salinity, and chlorophyll) on prevalence of pathogenic Vibrio spp. in aquatic systems. This study lays the groundwork for a predictive intelligence system for Vibrio spp. and other pathogens under varying climatic scenarios.Item DEVELOPMENT, VALIDATION, AND APPLICATION OF A QUANTITATIVE POLYMERASE CHAIN REACTION ASSAY TO ASSESS HEMATODINIUM PEREZI PREVALENCE IN ENVIRONMENTAL SAMPLES(2012) Hanif, Ammar; Schott, Eric J; Jagus, Rosemary; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dinoflagellate parasites in the Hematodinium genus have emerged as important pathogens of economically important crustaceans worldwide, causing significant economic losses to fisheries and aquaculture. An understanding of the routes of infection in blue crab (Callinectes sapidus) populations would be facilitated by an improved knowledge of environmental reservoirs. A previously used PCR assay, based on small subunit rRNA sequences, lacked the specificity needed for Hematodinium perezi detection of environmental samples. Therefore a quantitative PCR assay based on the internal transcribed spacer 2 (ITS2) region of H. perezi rRNA genes was developed, validated, and applied to examine temporal and spatial incidences of environmental reservoirs in Delmarva coastal bays. H. perezi was detected in sediment and water in several Delmarva coastal bays, as well as the host, C. sapidus. Results suggest the existence of localized sediment reservoirs in areas where hydrological and geophysical features allow for the formation of cell deposits.