Coutinho F A, Griffin M, Thomas J D
Parasitology. 1981 Feb;82(1):111-20. doi: 10.1017/s0031182000041901.
This paper describes a modification of the model for the transmission of schistosomiasis proposed by Macdonald (1965), which allows the snail host-locating efficiency of the miracidium to be taken into account. The modified model allows for a choice of miracidia efficiency. If it is assumed that the miracidia are inefficient hunters than the resulting model is very sensitive to perturbations; relatively small changes in small numbers not only cause appreciable changes in the percentage of snails infected but resulted in attainment of the threshold (the point at which schistosomiasis ceases to be endemic). If, however, the miracidia are efficient snail hunters then the model is much less sensitive to perturbations; here the percentage of snails infected is much less affected by changing snail numbers, and the threshold is much more difficult to reach by reducing snail numbers. It is argued that, on the whole, the empirical data give more support to the latter model, although there are some circumstances under which the former model might apply. However, even with these modifications it is considered that the Macdonald model does not provide a satisfactory explantation of field observations.
本文描述了对麦克唐纳（1965年）提出的血吸虫病传播模型的一种修正，该修正考虑了毛蚴寻找螺蛳宿主的效率。修正后的模型允许选择毛蚴效率。如果假设毛蚴寻找螺蛳的效率较低，那么所得模型对干扰非常敏感；少量的相对小变化不仅会导致感染螺蛳百分比出现明显变化，还会导致达到阈值（即血吸虫病不再呈地方性流行的点）。然而，如果毛蚴是高效的螺蛳猎手，那么模型对干扰的敏感性要低得多；此时感染螺蛳的百分比受螺蛳数量变化的影响要小得多，而且通过减少螺蛳数量更难达到阈值。有人认为，总体而言，经验数据更支持后一种模型，尽管在某些情况下前一种模型可能适用。然而，即使有这些修正，人们认为麦克唐纳模型仍不能令人满意地解释实地观察结果。
