Ebert Dieter
Institut für Zoologie, Universität Basel, Rheinsprung 9, CH-4051 Basel, Switzerland.
Evolution. 1998 Dec;52(6):1869-1871. doi: 10.1111/j.1558-5646.1998.tb02267.x.
Two experimental studies, Ebert (1994) and Ebert and Mangin (1997), described a genetic correlation between parasite virulence and the number of transmission stages found in the hosts. It was concluded that this correlation is evidence that within-host growth rate of the parasite is positively correlated with virulence. Hochberg (1998) has criticized this interpretation, arguing that differential infectivity and density-dependent parasite growth could confound the results. Here I point out that density dependence is unlikely to have confounded the results, but, at least for Ebert (1994), differential infectivity is likely to have been a confounding factor. However, Ebert and Mangin (1997) measured infectivity and showed that strains with higher infectivity had lower virulence, which is contrary to Hochberg's hypothesis. In summary, I conclude that differential infectivity played a role in the assessment of the correlation between parasite reproduction and virulence, but that differential within-host growth remains the most likely explanation for the correlation observed in Ebert and Mangin (1997).
两项实验研究，埃伯特（1994年）以及埃伯特和曼金（1997年），描述了寄生虫毒力与在宿主中发现的传播阶段数量之间的遗传相关性。得出的结论是，这种相关性证明寄生虫在宿主体内的生长速率与毒力呈正相关。霍赫贝格（1998年）批评了这一解释，认为不同的感染力和密度依赖性寄生虫生长可能会混淆结果。在此我指出，密度依赖性不太可能混淆结果，但至少对于埃伯特（1994年）的研究而言，不同的感染力很可能是一个混淆因素。然而，埃伯特和曼金（1997年）测量了感染力，并表明感染力较高的菌株毒力较低，这与霍赫贝格的假设相反。总之，我得出结论，不同的感染力在评估寄生虫繁殖与毒力之间的相关性中起到了作用，但宿主内生长差异仍是埃伯特和曼金（1997年）所观察到的相关性的最可能解释。
