Epidemiology and Ecology of Vibrio cholerae in Bangladesh

描述(由调查者提供)：霍乱由O1和O139群霍乱弧菌引起，是最严重的腹泻疾病，在整个发展中国家继续造成严重的发病率和死亡率。目前，全世界约有52个国家报告了这种疾病。在我们的第一项研究中，我们在孟加拉国的四个农村地区进行了每两周一次的临床和环境监测。对我们积累的临床和环境数据的分析确定了显著预测霍乱暴发发生的因素，包括水温、pH值和地表水的电导率，以及地表水中浮游生物和产生霍乱毒素的细菌的浓度。一个重要的发现是，浮游动物，即桡足类，是霍乱弧菌的有效宿主。通过追踪浮游植物的食物来源，使用卫星监测的叶绿素a浓度，有可能估计浮游动物的数量。随着我们迄今取得的成功，我们将在查塔克和马特巴里亚这两个相距甚远的地理地点进行流行病学和生态监测，我们记录了可预见的季节性霍乱疫情：一次在春季，另一次在秋季。使用改进的化验方法，我们将列举环境样品中霍乱弧菌的多种形态和生活阶段，包括活的但不能培养的霍乱弧菌(VBNC)。将对临床分离株和环境分离株之间的遗传联系进行表征，并进行地理信息系统监测，以确定在基因组一级难以记录的关键流行病学关系。为了阐明霍乱暴发的局部变异性，我们将调查从我们之前的研究中识别的因素，以及其他研究人员识别的、但尚未包括在我们的预测模型中的因素，即微生物群落动态、附着在几丁质表面的霍乱弧菌能力增强以及浮游生物群落动态。利用我们先前研究确定的环境变量，并纳入与霍乱病例相关的新变量，我们将改进我们的霍乱传播模型，使其适用于预测霍乱暴发，从而及早动员预防和治疗措施。最近廉价的口服霍乱疫苗的出现使这一目标更加重要。 与公共卫生相关：该项目是为了找出霍乱在流行中发生的原因。我们推测，海洋环境中的因素在引发流行病的发生中发挥着重要作用。这项研究是在孟加拉国农村地区进行的，使用最近开发的技术来进一步确定这些因素。

DESCRIPTION (provided by investigator): Cholera, caused by Vibrio cholerae serogroups O1 and O139, is the most severe of diarrheal diseases and continues to cause significant morbidity and mortality throughout the developing world. Presently, it is reported in approximately 52 countries worldwide. During our first study, we carried out biweekly clinical and environmental surveillance in four rural areas of Bangladesh. Analysis of our accumulated clinical and environmental data identified factors that are significantly predictive for occurrence of cholera outbreaks, including water temperature, pH, and conductivity of surface water, along with concentrations of plankton and cholera toxin- producing bacteria in surface waters. A significant finding was that zooplankton, namely copepods, serve as an effective host for V. cholerae. By tracking their phytoplankton food source, using satellite monitoring of chlorophyll a concentration, it is possible to estimate zooplankton populations. With our successes to date, we will conduct epidemiological and ecological surveillance in Chattak and Mathbaria, two widely separated geographical sites, where we have documented predictable seasonal cholera outbreaks: one in the spring and the other in the fall. Using improved assays, we will enumerate multiple morphologies and life stages of V. cholerae in environmental samples, including the viable but nonculturable form (VBNC). Characterization of genetic associations between clinical and environmental isolates and GIS surveillance will be conducted to establish key epidemiological relationships that have been difficult to document at the genomic level. To elucidate local variability in cholera outbreaks, we will investigate factors recognized from our previous study, as well as those identified by other investigators, but not yet included in our predictive model, namely microbial community dynamics, increased competence of V. cholerae attached to chitinous surfaces, and plankton community dynamics. Using environmental variables identified from our previous studies and incorporating the new variables that prove to be correlated with cholera cases, we will refine our model of cholera transmission with the intent to render it useful for predicting cholera outbreaks, thereby allowing early mobilization of preventative and treatment measures. The very recent availability of inexpensive oral cholera vaccines makes this objective even more relevant. PUBLIC HEALTH RELEVANCE: This project is being done to find reasons why the disease cholera occurs in epidemics. We postulate that factors in the marine environment play important roles in triggering the onset of epidemics. The study is being done in rural Bangladesh, using recently developed technology to further define these factors.