Resource competition drives natural and rebound dynamics of snails and schistosomes

资源竞争驱动钉螺和血吸虫的自然和反弹动态

• 批准号: 10343763
• 负责人: David James Civitello
• 金额: $ 34.24万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-16 至 2025-02-28
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10343763
• 关键词: Address; Agriculture; Behavior Therapy; Benign; Biological; Chemicals; Communicable Diseases; Disease; Ecosystem; Exposure to; Food; Fresh Water; Goals; Habitats; Health; Human; Individual; Infection; Link; Measures; Metabolic; Methods; Modeling; Modernization; Morbidity - disease rate; Parasites; Persons; Pharmaceutical Preparations; Physiological; Plants; Platyhelminths; Poison; Population; Production; Proxy; Reproduction; Research; Resources; Risk; Schistosoma; Schistosomiasis; Seasons; Shapes; Site; Skin; Snails; Source; Statistical Models; Testing; Water; Work; Zoonoses; control trial; density; design; disability-adjusted life years; exposed human population; food resource; global health; improved; infection risk; interest; laboratory experiment; mathematical model; novel; programs; reproductive; theories; transmission process; uptake; vector-borne

RESOURCE COMPETITION DRIVES NATURAL AND REBOUND DYNAMICS OF SNAILS AND SCHISTOSOMES Project summary More than 250 million people are infected with schistosomes, flatworms in the genus Schistosoma, and 20 million humans suffer from severe morbidity due to schistosomiasis. Humans become infected after exposure to larval parasites (cercariae) that are produced by infected snails in freshwater habitats. Therefore, the production of cercariae by snail populations represents an important component of the human risk of exposure, infection, and disease. Schistosomiasis control incorporates many programs, including drug administration, behavioral intervention and snail control. Snail control programs reduce snail density by applying toxic chemical molluscicides or lethal predators. However, snails themselves do not directly infect humans. Instead, snails release free living cercariae that directly cause human infections following skin contact. This mismatch between the target of control (snails) and the proximate cause of human infections (cercariae) complicates schistosome control because the production of cercariae per snail is sensitive to ecological conditions, such as snail density. The vast majority of models and control trials examining the natural dynamics and control of schistosomes assume that snails are all equally infectious, leading to the assumption that snail density directly correlates with cercariae density, and therefore potential for human exposure. However, infected snails can produce >50-fold more cercariae when food is abundant, competitors are scarce, and physical conditions are otherwise benign. Thus, counter to conventional wisdom, cercarial densities, and human exposure potential, could be greatest when the density of snails is lower and growing. Therefore, studying the dynamic link between snail and cercarial density is critical to designing optimal snail control strategies, because these dynamics determine the timing and magnitude of human risk. This research will combine field and laboratory experiments to test novel hypotheses for the dynamics of cercariae in natural settings that arise from theory we developed to explicitly incorporate energy uptake and use by snails and schistosomes in dynamic scenarios. Specifically, we will test predictions that: (1) there are brief, intense peaks of cercarial density early in the season, when individual snails are large and highly reproductive, (2) the presence of other food sources, such as decaying plants can sustain cercarial production over longer periods, and (3) reducing, but not eliminating, snails from water bodies could backfire, causing little reduction or even an increase in cercariae, by relaxing competition for food. Ultimately, this work can improve the prediction and control of a parasite causing major global health burden.

资源竞争驱动蜗牛的自然和反弹动力 和血吸虫 项目概要 超过2.5亿人感染血吸虫、扁虫属 血吸虫病，有 2000 万人因血吸虫病而罹患严重疾病。 人类在接触由以下物质产生的幼虫寄生虫（尾蚴）后会受到感染 淡水栖息地受感染的蜗牛。因此，蜗牛种群产生尾蚴 是人类接触、感染和疾病风险的重要组成部分。 血吸虫病控制包括许多项目，包括药物管理、 行为干预和蜗牛控制。蜗牛控制程序可降低蜗牛密度 使用有毒化学杀软体动物剂或致命的捕食者。然而，蜗牛本身并不 直接感染人类。相反，蜗牛会释放游离的尾蚴，直接导致人类死亡 皮肤接触后感染。控制目标（蜗牛）与实际目标之间的不匹配 人类感染（尾蚴）的直接原因使血吸虫控制变得复杂，因为 每只蜗牛尾蚴的产生对生态条件（例如蜗牛密度）很敏感。 绝大多数模型和控制试验检查自然动力学和 血吸虫控制假设所有蜗牛都具有同等传染性，从而得出以下假设 蜗牛密度与尾蚴密度直接相关，因此对人类的潜在影响 接触。然而，当食物被感染时，受感染的蜗牛会产生超过 50 倍的尾蚴。 资源丰富，竞争对手稀少，身体状况良好。因此，计数器 根据传统观点，尾蚴密度和人类接触潜力可能是最大的 当蜗牛的密度较低且生长时。因此，研究二者之间的动态联系 蜗牛和尾蚴密度对于设计最佳蜗牛控制策略至关重要，因为这些 动态决定人类风险的时间和程度。 这项研究将结合现场和实验室实验来测试新的假设 尾蚴在自然环境中的动态，是由我们开发的理论明确提出的 将蜗牛和血吸虫在动态场景中的能量吸收和使用结合起来。 具体来说，我们将测试以下预测：(1) 尾蚴密度存在短暂而强烈的峰值 在季节初期，当个体蜗牛很大并且繁殖力很强时，（2）存在 其他食物来源，例如腐烂的植物，可以更长时间地维持尾蚴的产生 (3) 减少但不是消除水体中的蜗牛可能会适得其反，导致 通过放松对食物的竞争，尾蚴几乎没有减少甚至增加。最终，这 这项工作可以改善对造成全球重大健康负担的寄生虫的预测和控制。