Studying the distribution of parasitic helminth body size across a population of definitive hosts can advance our understanding of parasite population biology. Body size is typically correlated with egg production. Consequently, inequalities in body size have been frequently measured to infer variation in reproductive success (VRS). Body size is also related to parasite age (time since entering the definitive host) and potentially provides valuable information on the mode of acquisition and establishment of immature (larval) parasites within the host: whether parasites tend to establish singly or in aggregates. The mode of acquisition of soil-transmitted helminths has been a theoretical consideration in the parasitological literature but has eluded data-driven investigation. In this paper, we analyse individual Ascaris lumbricoides weight data collected from a cohort of human hosts before and after re-infection following curative treatment, and explore its distribution within and among individuals in the population. Lorenz curves and Gini coefficients indicate that levels of weight inequality (a proxy for VRS) in A.lumbricoides are lower than other published estimates from animal-helminth systems. We explore levels of intra-host weight aggregation using statistical models to estimate the intraclass correlation coefficient (ICC) while adjusting for covariates using a flexible fractional polynomial transformation approach capable of handling non-linear functional relationships. The estimated ICCs indicate that weights are aggregated within hosts both at equilibrium and after re-infection, suggesting that parasites may establish within the host in clumps. The implications of a clumped infection process are discussed in terms of ascariasis transmission dynamics, control and anthelmintic resistance.

中文翻译：

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滴流或聚集感染过程？对人类寄生蛔虫体重聚集的分析，蛔虫。

研究寄生蠕虫身体大小在终宿主种群中的分布可以增进我们对寄生虫种群生物学的理解。体型通常与产蛋量相关。因此，经常测量体型的不平等以推断繁殖成功率 (VRS) 的变化。体型还与寄生虫年龄（进入最终宿主后的时间）有关，并可能提供有关宿主内未成熟（幼虫）寄生虫的获取和建立模式的宝贵信息：寄生虫倾向于单独建立还是聚集建立。获得土壤传播的蠕虫的模式一直是寄生虫学文献中的理论考虑因素，但没有进行数据驱动的调查。在本文中，我们分析了在治愈性治疗后再次感染之前和之后从一组人类宿主中收集的个体蛔虫体重数据，并探索其在人群中的个体内部和个体之间的分布。洛伦兹曲线和基尼系数表明 A.lumbricoides 的体重不平等水平（VRS 的代表）低于其他已发表的动物蠕虫系统估计值。我们使用统计模型探索主机内权重聚合的水平，以估计类内相关系数 (ICC)，同时使用能够处理非线性函数关系的灵活分数多项式变换方法调整协变量。估计的 ICC 表明，在平衡和再感染后，权重在宿主内聚合，表明寄生虫可能在宿主体内成群结队。从蛔虫病传播动态、控制和抗蠕虫药性方面讨论了聚集感染过程的影响。