Slater Noa, Mitchell Rebecca Mans, Whitlock Robert H, Fyock Terry, Pradhan Abani Kumar, Knupfer Elena, Schukken Ynte Hein, Louzoun Yoram
Gonda Brain Research Center, Bar-Ilan University, Ramat Gan, Israel.
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY, USA.
Vet Res. 2016 Feb 29;47:38. doi: 10.1186/s13567-016-0323-3.
Super-shedders are infectious individuals that contribute a disproportionate amount of infectious pathogen load to the environment. A super-shedder host may produce up to 10,000 times more pathogens than other infectious hosts. Super-shedders have been reported for multiple human and animal diseases. If their contribution to infection dynamics was linear to the pathogen load, they would dominate infection dynamics. We here focus on quantifying the effect of super-shedders on the spread of infection in natural environments to test if such an effect actually occurs in Mycobacterium avium subspecies paratuberculosis (MAP). We study a case where the infection dynamics and the bacterial load shed by each host at every point in time are known. Using a maximum likelihood approach, we estimate the parameters of a model with multiple transmission routes, including direct contact, indirect contact and a background infection risk. We use longitudinal data from persistent infections (MAP), where infectious individuals have a wide distribution of infectious loads, ranging upward of three orders of magnitude. We show based on these parameters that the effect of super-shedders for MAP is limited and that the effect of the individual bacterial load is limited and the relationship between bacterial load and the infectiousness is highly concave. A 1000-fold increase in the bacterial contribution is equivalent to up to a 2-3 fold increase in infectiousness.
超级排菌者是指那些向环境中释放大量感染性病原体的个体。超级排菌宿主产生的病原体可能比其他感染性宿主多1万倍。多种人类和动物疾病都报告发现了超级排菌者。如果它们对感染动态的影响与病原体负荷呈线性关系，那么它们将主导感染动态。我们在此着重于量化超级排菌者对自然环境中感染传播的影响，以检验这种影响是否真的发生在副结核分枝杆菌（MAP）中。我们研究了一个已知每个宿主在每个时间点的感染动态和细菌负荷的案例。使用最大似然法，我们估计了一个具有多种传播途径的模型的参数，包括直接接触、间接接触和背景感染风险。我们使用来自持续性感染（MAP）的纵向数据，其中感染个体的感染负荷分布范围很广，相差三个数量级以上。基于这些参数，我们表明超级排菌者对MAP的影响是有限的，个体细菌负荷的影响也是有限的，并且细菌负荷与传染性之间的关系是高度凹形的。细菌贡献增加1000倍相当于传染性最多增加2至3倍。
