Data from: Host nutrition alters the variance in parasite transmission potential

The environmental conditions experienced by hosts are known to affect their mean parasite transmission potential. How different conditions may affect the variance of transmission potential has received less attention but is an important question for disease management, especially if specific ecological contexts are more likely to foster a few extremely infectious hosts. Using the obligate-killing bacterium Pasteuria ramosa and its crustacean host Daphnia magna, we analysed how host nutrition affected the variance of individual parasite loads, and therefore transmission potential. Under low food, individual parasite loads showed similar mean and variance, following a Poisson distribution. In contrast, among well-nourished hosts, parasite loads were right-skewed and over dispersed, following a negative binomial distribution. Abundant food may therefore yield individuals causing potentially more transmission than the population average. Measuring both the mean and variance of individual parasite loads in controlled experimental infections may offer a useful way of revealing risk factors for potential highly infectious hosts.

宿主所处的环境条件已被证实会影响其寄生虫的平均传播潜能。然而，不同环境条件如何影响传播潜能的方差，相关研究却相对匮乏，但该问题对于疾病防控至关重要——尤其当特定生态环境更易催生少数传染性极强的宿主时。本研究以专性致死细菌腊氏芽孢杆菌（Pasteuria ramosa）及其甲壳类宿主大型溞（Daphnia magna）为实验模型，分析了宿主营养状况对个体寄生虫载量方差的影响，进而明确其对传播潜能的作用。在食物匮乏条件下，个体寄生虫载量的均值与方差近似相等，符合泊松（Poisson）分布。与之相反，营养充足的宿主体内的寄生虫载量呈现右偏分布且过度离散，符合负二项（negative binomial）分布。由此可见，充足的食物供给可能会催生传播潜能高于种群平均水平的宿主个体。在可控实验感染条件下，同时测定个体寄生虫载量的均值与方差，或可为识别潜在高传染性宿主的风险因子提供有效路径。