京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20752号 / 理博第4328号 / 新制||理||1622(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 石田 厚, 教授 工藤 洋, 教授 田村 実 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Background: An estimated 1.27 million people per year are experiencing acute gastrointestinal illness (AGI) due to private water sources, which are federally unregulated drinking water sources in the US (Murphy et al., 2017). Previous studies have found a relationship between drinking water source (domestic well or publicly supplied water) and waterborne disease. Although some work has been done to characterize the quality of water in karstic terrain, and karst is considered to be a risk factor for pathogenic contamination of domestic wells, little work has been done to assess the relationship between karst and incidence of enteric disease. There is also little known about the socio-demographic factors of populations in the US using domestic wells. Although studies have also shown an association between rain, antecedent rain, and waterborne illness, the relationship is not well defined. Objective: The dissertation uses spatiotemporal and epidemiologic methods to characterize domestic well users in Pennsylvania, determine the relationship between use of domestic wells and cases of illness, and investigate an interactive effect between rain and drought on county level occurrence of reporting of illness. This work includes illness due to Salmonella, Campylobacter, Giardia, and Cryptosporidium as reported to the PA department of health. The population of interest is the estimated 12.8 million people who lived in PA from 2010-2019, of which an estimated 3.5 million used a domestic well. Aim 1: Determine whether populations of Pennsylvania that rely on domestic wells are more socially vulnerable than those with access to public water supply or wastewater treatment. Hypothesis: Census tracts that are generally more socially vulnerable are also more likely to lack access to public water supply. Aim 2: Determine presence of spatial clusters of reportable enteric diseases (Salmonella, Campylobacter, Giardia, or Cryptosporidium) between 2010 and 2019 in PA, and whether those clusters are associated with drinking water source (whether a domestic well or publicly supplied water). Hypothesis 1: Enteric disease in PA for the 2014 - 2018 time period cluster in time and space. Hypothesis 2: The incidence risk ratio of reported enteric disease will be positively associated with the proportion of households utilizing domestic wells. Aim 3: Determine the effects of rain and drought on weekly counts of reportable enteric illness (Salmonella, Campylobacter, Giardia, or Cryptosporidium) in PA, 2010-2019. Hypothesis 1: County level weekly enteric illness incidence rates are positively associated with total rain (cm) in prior week(s). Hypothesis 2: The incidence rate of reportable enteric illness by county is associated with an interaction between total rain (cm) in the prior week by county and drought conditions as measured by the Palmer Drought Severity Index in the same week the rain is measured preceding disease onset. Methods: Using county and zip code tabulation area incidence data on enteric illnesses made available from the Pennsylvania Department of Health for the years 2010 to 2019, this thesis investigated the potential relationships between rain, drought conditions, use of private wells, and the occurrence of karstic terrain and illness. The social characteristics of those who do not have access to public water supply were also explored. This was done in three parts, all utilizing ecologic study designs. Aim 1: We assessed how social vulnerability measures co-occur with domestic well use and also how those patterns change over space using a profile regression method. Aim 2: We examined the spatial patterns, by Zip Code Tabulation Area using a Poisson Spatial only SaTScan analysis with 5% of the state population without Philadelphia allowing for hierarchical clusters, and temporal patterns, using the R software trending package to develop a season adjusted negative binomial model to assess outbreaks, of weekly reported enteric illnesses. The weekly county incidence rates for each illness were also assessed by percentage of a county that did not have access to public water supply and presence of karst using a zero-inflated negative binomial model with random intercept for county. Philadelphia was excluded because they did not share their data. To assess the second hypothesis, that the incidence risk ratio of reported enteric disease is positively associated with the proportion of households utilizing domestic wells, a zero-inflated negative binomial model with a random intercept for county was utilized to determine if there was an association. This same model was expanded as assessment of an association between illness rates and percentage of a county underlain by karst. Aim 3: We assessed multiple time lags using a zero-inflated negative binomial model with random intercept for county to determine if there was an relationship between county level weekly rainfall (cm) and drought, as measured by the Palmer Drought Severity Index, on the weekly incidence rates of these four reportable enteric illnesses. Philadelphia was excluded, because they did not share their data. If both the amount of rain and the level of drought were found to be related to the number of cases of illnesses, an interaction was assessed for that lag time.Results: Aim 1: Measures of social vulnerability have 15 distinct profiles or clusters in the state of PA. These clusters occur spatially heterogeneously across the state. Five distinct population-profiles are more likely to rely on a domestic well. Two of these profiles are also more likely to experience social vulnerability when measured at the census tract level. In general, census tracts with higher proportions of homeowners, lower proportions of those without a high school diploma, lower median per capita income, and higher proportions of children under the age of 5 and 17 are more likely to rely on an unregulated drinking water source than populations with greater proportions of their population having a high school diploma, higher median per capita income and lower proportions of their population consisting of people under the age of 5 and 17. Aim 2: All four pathogens, which were assessed, have spatial heterogeneity in the state of Pennsylvania. All pathogens had higher incidence rates in the summer and lowest rates in the winter. However, most outbreaks occurred in the wintertime. A positive association was found between quartile of area of a county not served by public water supply and incidence rates of campylobacteriosis [IRR = 1.35 (95%CI 1.21, 1.51 p < 0.001)], cryptosporidiosis [IRR = 1.33 (95%CI 1.07, 1.66, p < 0.05)], and giardiasis [IRR = 1.25 (95%CI 1.11, 1.42, p < 0.01)]. An association was also observed between the quartile of area of a underlain by karst and incidence rates of campylobacteriosis [IRR = 1.21 (95%CI 1.08, 1.35, p <0.01)] and cryptosporidiosis [IRR = 1.36 (95%CI 1.09, 1.69, p < 0.01)]. Aim 3: There was at least one lag time (weeks between weekly measure of rain and specimen collection) where the amount of rain was positively associated with counts of campylobacteriosis, salmonellosis, and giardiasis. We also evaluated potential associations between enteric disease and rain as well as previous drought conditions (wetness or lack thereof) with various time-lags for 66 counties of PA for a 10-year time, Philadelphia is not included in this analysis because their data was not shared. In the case of Salmonella, there were four different lag times with an increase in incidence (weeks 4, 5, 11 and 12) and Giardia had two different lag times that showed an increase in incidence (weeks 12, and 14 ). At week 11 for cases due to Campylobacter, there was also an assessed interaction, while both rain and drought, as measured by the weekly Palmer Drought Index (PDI) had a positive relationship with risk, the relationship changed direction and was protective [IRR = 0.9997 (95%CI 0.9997, 0.9999, p < 0.01)]. Conclusions: The key findings are: 1. There are distinct profiles of domestic well users that differ by measures of social vulnerability. Two types of census tracts in PA are likely to have a high number of domestic wells and experience high social vulnerability traits. 2. Enteric illnesses due to Salmonella, Campylobacter, Giardia and Cryptosporidium, have patterns of clustering spatially across the state, and have a strong relationship with season. 3. There is a positive association between the area of a county not served by public water supply and incidence rates of campylobacteriosis, cryptosporidiosis, and giardiasis. 4. There is a positive association between the area of a county underlain by karst and incidence rates of campylobacteriosis and cryptosporidiosis. 5. That rain and drought (wetness) conditions weeks to several weeks prior, affect the incidence rate ratio of cases of Giardia, Cryptosporidium, Campylobacter, and Salmonella in Pennsylvania. The relationship between rain and drought conditions and illness varies by organism type which could be attributed to incubation period, reporting time, transport time in the environment and exposure sources (drinking water, food, recreation). There was evidence of an interactive effect between rain and drought conditions for cases of campylobacteriosis, with an 11-week lag time. / Epidemiology

With the increasing scarcity of water resources, soil moisture stress is the single most threat to global soybean production causing extensive yield losses. The objectives of this study were to investigate soil moisture stress effects on all aspects of soybean growth and development processes and to develop functional algorithms that could be used for field management decisions and in soybean crop modeling. To fulfill these objectives, six experiments were conducted; one in vitro osmotic stress study on seed germination, four studies by imposing five soil moisture treatments, 100, 80, 60, 40, and 20% of daily evapotranspiration of the control at different growth stages using sunlit plant growth chambers, and one transgenerational study on seed germination at different osmotic levels and offspring growth at three irrigation treatments (100, 66, and 33% based on field capacity) for plants grown at different soil moisture levels. Two cultivars from maturity group V, Asgrow AG5332 and Progeny P5333RY, with different growth habits were used in all these studies. Midday leaf water potential, plant height, mainstem nodes, gas-exchange traits, canopy reflectance, and several yield components including pod weight, seed yield, and seed quality were measured. Soil moisture stress decreased biomass, net photosynthesis, yield, individual seed weight, maximum seed germination, protein, fatty acids, sucrose, N, and P and increased oil, stachyose, Fe, Mg, Zn, Cu, and B contents. Overall, Asgrow AG5332 was more tolerant to drought stress than Progeny P5333RY. Soil moisture stress induced changes in seed quality that were correlated with seed germination and seedling vigor in the F1 generation. These data can be used to build a model-based decision support system capable of predicting yield under field conditions.

The Mississippi River Valley Alluvial Aquifer (MRVAA) aquifer is the principal water source for Mid-South irrigators, but the current rate of withdrawal from the aquifer is not sustainable. Means to increase the sustainability of the MRVAA is to improve corn’s water use efficiency (WUE) while, concurrently, maintaining or improving profitability. The objectives of this experiment were to determine the effects of sensor-based irrigation threshold, planting date, and hybrid on corn grain yield, WUE, and net returns above seed and irrigation cost. Season long irrigation thresholds of -50 kPa full irrigation (FI) and -125 kPa limited irrigation (LI) were used, utilizing furrow irrigation. In conclusion, utilizing a delayed irrigation trigger of -125 kPa decreases grain yield and, ultimately, net returns in years with less naturally occurring rainfall, but increases WUE. Shifting the planting date earlier and using full-season (FS) hybrids, increases grain yield, WUE, and net returns.

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This thesis explores the impact of drought on communal violence, posing the research question: How does drought influence the occurrence of communal violence? Considering empirical evidence and theoretical postulations from previous research, economic grievances are introduced as a crucial factor in the causal pathway between drought and communal violence. Thus, two hypotheses are put forward to address the research question: incidences of communal violence will increase following droughts (H1), and an increase in economic grievances is associated with an increase in communal violence incidence in instances following drought (H2). The study employs a quantitative analysis utilizing climate, conflict, socioeconomic, and geographic information systems (GIS) data, employing generalizedlinear mixed models (GLMMs) in R to test the hypotheses for Kenya from 1997 to 2012. The findings indicate the inability to reject the null hypothesis for H1, suggesting no significant increase in communal violence following drought. The null hypothesis for H2 is generally not rejected, except for in one model, suggesting an association between economic grievances and communal violence 12 months following drought. While this thesis contributes to understanding the link between drought, economic grievances, and communal violence, further research is needed to explore alternative research designs, geographical contexts, and time periods.