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，是最严重的腹泻疾病，并在整个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具有重要预测作用的因素，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，利用卫星监测叶绿素a浓度，可以估计浮游动物的数量。鉴于我们迄今取得的成功，我们将在查塔克和Mathbaria这两个地理位置相距很远的地点开展流行病学和生态监测，我们在这两个地点记录了可预测的季节性霍乱暴发：一个在春季，另一个在秋季。使用改进的检测方法，我们将枚举环境样本中霍乱弧菌的多种形态和生命阶段，包括可存活但不可培养的形式（VBNC）。将对临床和环境分离株与地理信息系统监测之间的遗传关联进行表征，以建立难以在基因组水平上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认识到的因素，以及其他研究者发现的，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的能力增强，以及浮游生物群落动态。利用从我们以前的研究中确定的环境变量，并纳入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爆发，从而允许早期动员预防和治疗措施。最近出现的廉价口服霍乱疫苗使这一目标更加重要。

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.