Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA.
Am Nat. 2012 Mar;179(3):E70-96. doi: 10.1086/664488. Epub 2012 Jan 27.
Classical epidemic theory focuses on directly transmitted pathogens, but many pathogens are instead transmitted when hosts encounter infectious particles. Theory has shown that for such diseases pathogen persistence time in the environment can strongly affect disease dynamics, but estimates of persistence time, and consequently tests of the theory, are extremely rare. We consider the consequences of persistence time for the dynamics of the gypsy moth baculovirus, a pathogen transmitted when larvae consume foliage contaminated with particles released from infectious cadavers. Using field-transmission experiments, we are able to estimate persistence time under natural conditions, and inserting our estimates into a standard epidemic model suggests that epidemics are often terminated by a combination of pupation and burnout rather than by burnout alone, as predicted by theory. Extending our models to allow for multiple generations, and including environmental transmission over the winter, suggests that the virus may survive over the long term even in the absence of complex persistence mechanisms, such as environmental reservoirs or covert infections. Our work suggests that estimates of persistence times can lead to a deeper understanding of environmentally transmitted pathogens and illustrates the usefulness of experiments that are closely tied to mathematical models.
经典传染病理论主要关注直接传播的病原体，但许多病原体是在宿主接触传染性颗粒时传播的。理论表明，对于此类疾病，病原体在环境中的持续时间会强烈影响疾病动态，但持续时间的估计值，以及对该理论的相应检验，极为罕见。我们考虑了持续时间对舞毒蛾杆状病毒动态的影响，该病原体通过幼虫食用被传染性尸体释放的颗粒污染的叶子传播。通过野外传播实验，我们能够在自然条件下估计持续时间，将我们的估计值插入标准传染病模型中表明，传染病通常是由蛹化和衰竭的组合而不是仅由衰竭来终止的，这与理论预测的相反。将我们的模型扩展到允许多个世代，并包括冬季的环境传播，表明即使没有复杂的持续存在机制，例如环境储库或隐性感染，病毒也可能长期存活。我们的工作表明，对持续时间的估计可以更深入地了解环境传播的病原体，并说明了与数学模型紧密结合的实验的有效性。
