Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
Parasitology. 2012 Jun;139(7):847-63. doi: 10.1017/S0031182012000200. Epub 2012 Feb 16.
The twin concepts of zooprophylaxis and the dilution effect originated with vector-borne diseases (malaria), were driven forward by studies on Lyme borreliosis and have now developed into the mantra "biodiversity protects against disease". The basic idea is that by diluting the assemblage of transmission-competent hosts with non-competent hosts, the probability of vectors feeding on transmission-competent hosts is reduced and so the abundance of infected vectors is lowered. The same principle has recently been applied to other infectious disease systems--tick-borne, insect-borne, indirectly transmitted via intermediate hosts, directly transmitted. It is claimed that the presence of extra species of various sorts, acting through a variety of distinct mechanisms, causes the prevalence of infectious agents to decrease. Examination of the theoretical and empirical evidence for this hypothesis reveals that it applies only in certain circumstances even amongst tick-borne diseases, and even less often if considering the correct metric--abundance rather than prevalence of infected vectors. Whether dilution or amplification occurs depends more on specific community composition than on biodiversity per se. We warn against raising a straw man, an untenable argument easily dismantled and dismissed. The intrinsic value of protecting biodiversity and ecosystem function outweighs this questionable utilitarian justification.
人畜共患病预防和稀释效应这两个概念起源于媒介传播疾病（疟疾），后来在莱姆病研究的推动下得以发展，并形成了“生物多样性可预防疾病”这一口号。其基本思想是，通过将有传播能力的宿主与无传播能力的宿主混合，降低了媒介生物吸食有传播能力宿主的概率，从而降低了感染媒介的丰度。最近，这一原理已被应用于其他传染病系统——蜱传疾病、昆虫传播疾病、通过中间宿主间接传播的疾病、直接传播的疾病。有人声称，各种不同类型的额外物种通过多种不同的机制作用，导致传染病原体的流行率降低。对这一假设的理论和经验证据的审查表明，即使在蜱传疾病中，它也仅在某些情况下适用，而如果考虑到正确的衡量标准——感染媒介的丰度而不是流行率，那么它适用的情况就更少。发生稀释还是放大取决于特定的群落组成，而不是生物多样性本身。我们警告不要提出一个站不住脚的论点，这个论点很容易被推翻。保护生物多样性和生态系统功能的内在价值超过了这一有争议的功利主义理由。
