Predicting the success of biological control for snail vectors of human schistosomiaisis

项目摘要 血吸虫是一种寄生蠕虫，专性地在人类宿主和蜗牛载体之间循环。传输 不同蜗牛种群之间的动态差异很大，导致人类接触风险的差异。200多 目前有1000万人感染了病毒，使其成为第二大最有害的病毒。 疟疾之后的热带病。目前还没有预防感染的疫苗，以及治疗感染者的药物 患者受到新出现的耐药性和治疗后立即再次感染的可能性的限制。 因此，用于预防人类感染的一种工具是对蜗牛种群的生物控制。一 生物控制的一种方法是引入非媒介蜗牛，它们在食物竞争中胜过媒介 资源这一战略在一些地区行之有效，在另一些地区则失败了。原则上，非媒介蜗牛 应该通过转移搜索寄生虫， 适当的媒介（“诱饵效应”）和减少媒介蜗牛的数量。我们假设 媒介蜗牛和非媒介蜗牛的身体大小可能是一个重要但被忽视的特征， 蜗牛生物防治的成果。该提案旨在通过将实验和 复杂的传动动力学数学模型。这个项目的结果可以帮助解释 目前用非媒介蜗牛进行生物控制的缺点，提出了可能 改善疾病控制，并建立一个框架，以评估未来蜗牛引入如何影响人类 暴露于病毒。我们将重点关注曼氏血吸虫和埃及血吸虫这两种 这些寄生虫共同导致大多数人类感染，这些感染只感染了 属和泡螺属。我们将使用Melanoides作为非媒介竞争对手蜗牛 因为它以前曾被有意地引入一些流行地区，结果好坏参半。 在具体目标1中，我们将使用一种新的寄生虫荧光标记生物测定法来确定 影响对S. mansoni和S.并建立数学模型， 预测非病媒和病媒体大小对多物种间寄生虫传播的影响 社区.在具体目标2中，我们将使用实验性的传染病来测试这些预测， 蜗牛群落的物种组成各不相同。这项工作将使我们能够确定生态背景 其中控制蜗牛可以帮助预防人类血吸虫病。此外，我们的数据将使我们能够 严格测试非媒介蜗牛如何影响寄生虫动态，以指导公共卫生 风险地区的干预措施和管理战略。了解蜗牛的生态是 在全世界范围内对抗这种毁灭性的疾病。

Project Summary Schistosomes are parasitic worms that obligately cycle between human hosts and snail vectors. Transmission dynamics vary greatly among populations of snails, causing variability in human risk of exposure. Over 200 million people are currently infected with schistosomes, making it the second most detrimental Neglected Tropical Disease following malaria. There is no vaccine to prevent infection, and drug treatment of infected patients is limited by emerging drug resistance and the immediate potential for re-infection following treatment. Therefore, one tool used to prevent infections in humans is biological control of snail populations. One approach to biological control is the introduction of non-vector snails that outcompete vectors for food resources. This strategy has been effective in some regions and failed in others. In principle, non-vector snails should decrease transmission potential of schistosomes to people by diverting searching parasites away from appropriate vectors (a “decoy effect”) and by decreasing the abundance of vector snails. We hypothesize that the body size of vector and non-vector snails may be an important yet overlooked trait that explains variable outcomes in snail biological control. This proposal aims to address these gaps by combining experiments and mathematical models of schistosome transmission dynamics. The results of this project could help explain the current shortcomings of biological control with non-vector snails, suggest conditions or strategies that may improve disease control, and build a framework to evaluate how future snail introductions could affect human exposure to schistosomes. We will focus on Schistosoma mansoni and Schistosoma haematobium, the two species of schistosome that together cause the majority of human infections, which only infect snails in the genera Biomphalaria and Bulinus, respectively. We will use Melanoides as a non-vector competitor snail because it has previously been intentionally introduced to schistosome endemic regions with mixed outcomes. In Specific Aim 1, we will use a novel parasite fluorescent-labeling bioassay to determine the vector traits that influence exposure and susceptibility to S. mansoni and S. haematobium and build a mathematical model to predict the impact of non-vector and vector body size upon schistosome transmission in multi-species communities. In Specific Aim 2, we will test these predictions using experimental schistosome epidemics in snail communities that vary in species composition. This work will allow us to determine the ecological context in which snail control can aid in human schistosomiasis prevention. Furthermore, our data will allow us to rigorously test how non-vector snails influence schistosome dynamics in order to guide public health interventions and management strategies in at-risk regions. Understanding snail ecology is a key step in combatting this devastating disease worldwide.