Poulin R
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Parasitology. 2006 Jan;132(Pt 1):143-51. doi: 10.1017/S0031182005008693.
Global warming can affect the world's biota and the functioning of ecosystems in many indirect ways. Recent evidence indicates that climate change can alter the geographical distribution of parasitic diseases, with potentially drastic consequences for their hosts. It is also possible that warmer conditions could promote the transmission of parasites and raise their local abundance. Here I have compiled experimental data on the effect of temperature on the emergence of infective stages (cercariae) of trematode parasites from their snail intermediate hosts. Temperature-mediated changes in cercarial output varied widely among trematode species, from small reductions to 200-fold increases in response to a 10 degrees C rise in temperature, with a geometric mean suggesting an almost 8-fold increase. Overall, the observed temperature-mediated increases in cercarial output are much more substantial than those expected from basic physiological processes, for which 2- to 3-fold increases are normally seen. Some of the most extreme increases in cercarial output may be artefacts of the methods used in the original studies; however, exclusion of these extreme values has little impact on the preceding conclusion. Across both species values and phylogenetically independent contrasts, neither the magnitude of the initial cercarial output nor the shell size of the snail host correlated with the relative increase in cercarial production mediated by rising temperature. In contrast, the latitude from which the snail-trematode association originated correlated negatively with temperature-mediated increases in cercarial production: within the 20 degrees to 55 degrees latitude range, trematodes from lower latitudes showed more pronounced temperature-driven increases in cercarial output than those from higher latitudes. These results suggest that the small increases in air and water temperature forecast by many climate models will not only influence the geographical distribution of some diseases, but may also promote the proliferation of their infective stages in many ecosystems.
全球变暖会以多种间接方式影响全球生物群和生态系统的功能。最近的证据表明，气候变化会改变寄生虫病的地理分布，对其宿主可能产生巨大影响。气温升高也有可能促进寄生虫的传播并增加其在当地的数量。在此，我汇总了关于温度对吸虫寄生虫感染阶段（尾蚴）从其蜗牛中间宿主中逸出的影响的实验数据。温度介导的尾蚴产出变化在吸虫物种间差异很大，温度每升高10摄氏度，尾蚴产出量从略有减少到增加200倍不等，几何平均数表明几乎增加了8倍。总体而言，观察到的温度介导的尾蚴产出增加比基本生理过程预期的要大得多，基本生理过程通常可见2至3倍的增加。一些尾蚴产出量的最极端增加可能是原始研究中所用方法导致的假象；然而，排除这些极端值对先前的结论影响不大。在物种值和系统发育独立对比中，初始尾蚴产出量的大小和蜗牛宿主的壳大小均与温度升高介导的尾蚴产量相对增加无关。相反，蜗牛 - 吸虫组合起源的纬度与温度介导的尾蚴产量增加呈负相关：在20度至55度纬度范围内，来自低纬度的吸虫比来自高纬度的吸虫表现出更明显的温度驱动的尾蚴产出增加。这些结果表明，许多气候模型预测的空气和水温的小幅升高不仅会影响某些疾病的地理分布，还可能促进其感染阶段在许多生态系统中的增殖。
