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

项目摘要 血吸虫是寄生的蠕虫，必须在人类宿主和蜗牛媒介之间循环。传输 钉螺种群之间的动态差异很大，导致人类接触风险的变异性。超过200人 目前有100万人感染了血吸虫，使其成为第二个最有害的被忽视的疾病 继疟疾之后的热带病。没有预防感染的疫苗，也没有治疗感染的药物 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个工具是对蜗牛种群进行生物控制。一 生物防治的方法是引入非媒介蜗牛，它们在食物方面比媒介蜗牛更具竞争力 资源。这一战略在一些地区有效，在另一些地区失败。原则上，非媒介蜗牛 应该通过转移搜索寄生虫来减少血吸虫对人的传播潜力 适当的媒介(“诱饵效应”)和减少媒介蜗牛的丰度。我们假设 媒介和非媒介蜗牛的身体大小可能是解释变量的一个重要但被忽视的特征 钉螺生物控制的成果。这项提案旨在通过将实验和 血吸虫传播动力学的数学模型。这个项目的结果可以帮助解释 目前非媒介钉螺生物防治的不足之处表明，条件或战略可能 改善疾病控制，并建立一个框架来评估未来引入蜗牛对人类的影响 接触到血吸虫。我们将重点关注曼氏血吸虫和血吸虫这两个 血吸虫的一种，它们共同引起大多数人类感染，这些感染只感染世界上的蜗牛 Biomphalaria属和Bulinus属。我们将使用黑粉菌作为非媒介竞争对手蜗牛 因为它以前曾被故意引入血吸虫病流行区，结果好坏参半。 在特定目标1中，我们将使用一种新的寄生虫荧光标记生物测定来确定 影响曼氏葡萄球菌和血瘤沙门氏菌的暴露和敏感性并建立数学模型 预测非媒介和媒介个体大小对多物种血吸虫传播的影响 社区。在具体目标2中，我们将使用实验性的血吸虫病流行来检验这些预测。 种类组成各不相同的蜗牛群落。这项工作将使我们能够确定生态环境 其中灭螺可以帮助人类预防血吸虫病。此外，我们的数据将使我们能够 严格检测非媒介钉螺对血吸虫动态的影响，以指导公共卫生 高危地区的干预和管理战略。了解蜗牛生态是 在全世界抗击这种毁灭性的疾病。

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.