Epidemiology and Ecology of Vibrio cholerae in Bangladesh

描述（由研究者提供）：霍乱，由霍乱弧菌血清群O1和O139引起，是最严重的肠道疾病，在发展中国家继续造成显著的发病率和死亡率。目前，全世界约有52个国家报告了这一情况。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对霍乱暴发的发生有显著预测作用的因素，包括水温、pH值和地表水的电导率，沿着地表沃茨中浮游生物和产霍乱毒素细菌的浓度。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。通过跟踪浮游植物的食物来源，利用卫星监测叶绿素a浓度，可以估计浮游动物的数量。 由于我们迄今取得的成功，我们将在查塔克和马瑟巴里亚这两个地理位置相距甚远的地点进行流行病学和生态监测，我们在那里记录了可预测的季节性霍乱爆发：一次在春季，另一次在秋季。使用改进的检测方法，我们将在环境样本中列举多种形态和生命阶段的霍乱弧菌，包括活的但不可培养的形式（VBNC）。将进行临床和环境分离株之间的遗传关联的表征和GIS监测，以建立在基因组水平上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，我们将调查我们以前的研究中认识到的因素，以及其他研究人员确定的因素，但尚未包括在我们的预测模型中，即微生物群落动态，增加能力的V. cholesterol附着到几丁质表面，浮游生物群落动态。利用从我们以前的研究中确定的环境变量，并结合证明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，目的是使其有助于预测霍乱疫情，从而及早采取预防和治疗措施。最近廉价的口服霍乱疫苗使这一目标更加重要。 公共卫生相关性：该项目旨在找出霍乱在流行病中发生的原因。我们假定，海洋环境中的因素在引发流行病方面发挥重要作用。这项研究正在孟加拉国农村进行，利用最近开发的技术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.