The epidemic process of the parasite Ichthyophonus hoferi in cultured rainbow trout Oncorhynchus mykiss was quantitatively estimated by both the cohabitation experiment and two standard models (the Kermarck-McKendrick model and the Reed-Frost model). For analysis of the parasite transmission by cohabitation, fish in two replicate tanks were exposed to 1, 5, or 10 infected fish, and daily mortality was counted for 102 d. Despite simple experiments for artificial exposure to the pathogen, the daily estimate of dead fish in the Kermarck-McKendrick model did not fit the observed number of dead fish in the experiment. In contrast, when the longest possible incubation period (generation time) was assumed to be 51 d in the Reed-Frost model, the estimated number of dead fish in discrete generations was close to the observed number of dead fish. If the time unit was 51 d, the estimated mortalities in the generation-based Kermarck-McKendrick model were significantly correlated with observed mortalities. These results suggest that the deterministic aspects of the epidemic process of the parasite can be quantitatively demonstrated on a 51-d timescale or longer, whereas transmission on a daily timescale is uncertain.

中文翻译：

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养殖虹鳟鱼寄生虫的传播及流行模式比较

通过同居实验和两种标准模型（Kermarck-McKendrick 模型和 Reed-Frost 模型）对养殖虹鳟 Oncorhynchus mykiss 中寄生虫 Ichthyophonus hoferi 的流行过程进行了定量估计。为了分析共栖寄生虫传播，将两个重复池中的鱼暴露于 1、5 或 10 条受感染的鱼，并计算 102 天的每日死亡率。尽管对病原体的人工暴露进行了简单的实验，但 Kermarck-McKendrick 模型中每天对死鱼的估计与实验中观察到的死鱼数量不符。相比之下，当 Reed-Frost 模型中最长可能的潜伏期（世代时间）假设为 51 天时，离散世代中估计的死鱼数量接近观察到的死鱼数量。如果时间单位为 51 d，则基于代的 Kermarck-McKendrick 模型中的估计死亡率与观察到的死亡率显着相关。这些结果表明，寄生虫流行过程的确定性方面可以在 51 天或更长时间的时间尺度上进行定量证明，而在每日时间尺度上的传播是不确定的。