Karvonen A, Paukku S, Valtonen E T, Hudson P J
Department of Biological and Environmental Science, P.O. Box 35, 40014, University of Jyväskylä, Finland.
Parasitology. 2003 Sep;127(Pt 3):217-24. doi: 10.1017/s0031182003003561.
The transmission dynamics of the cercariae of Diplostomum spathaceum were investigated under laboratory conditions using cercariae collected from naturally infected Lymnaea stagnalis. Cercariae were kept in a constant temperature of 20 degrees C and the survival and infectivity to naïve young rainbow trout recorded at 3-h intervals until few cercariae were alive. Mortality initially remained constant but increased rapidly after 20 h. While a model of constant mortality fitted the survival data, an age-dependent model provided a better fit and implied that cercariae tended to carry similar quantities of resources and once these were exhausted the cercariae died. Cercarial infectivity also showed an age-dependent pattern although infectivity tended (P = 0.09) to increase with age over the first 6 h of life and then fall. The per capita transmission rate of cercariae was investigated by experimentally infecting rainbow trout under standardized conditions, first with an increasing cercarial density and second, by keeping density constant but increasing numbers of cercariae. The per capita transmission rate was frequency dependent and averaged 0.341/h (+/- 0.036).
在实验室条件下，使用从自然感染的椎实螺（Lymnaea stagnalis）收集的尾蚴，对剑带双穴吸虫（Diplostomum spathaceum）尾蚴的传播动力学进行了研究。尾蚴保持在20摄氏度的恒定温度下，每隔3小时记录其对未感染的幼虹鳟的存活率和感染力，直至几乎没有尾蚴存活。死亡率最初保持恒定，但在20小时后迅速增加。虽然恒定死亡率模型符合存活数据，但年龄依赖性模型拟合得更好，这意味着尾蚴倾向于携带相似数量的资源，一旦这些资源耗尽，尾蚴就会死亡。尾蚴的感染力也呈现出年龄依赖性模式，尽管在生命的最初6小时内，感染力倾向于（P = 0.09）随年龄增加，然后下降。通过在标准化条件下对虹鳟进行实验感染来研究尾蚴的人均传播率，首先增加尾蚴密度，其次保持密度恒定但增加尾蚴数量。人均传播率与频率相关，平均为0.341/小时（±0.036）。
