Keesing F, Holt R D, Ostfeld R S
Department of Biology, Bard College, PO Box 5000, Annandale, NY 12504, USA.
Ecol Lett. 2006 Apr;9(4):485-98. doi: 10.1111/j.1461-0248.2006.00885.x.
The transmission of infectious diseases is an inherently ecological process involving interactions among at least two, and often many, species. Not surprisingly, then, the species diversity of ecological communities can potentially affect the prevalence of infectious diseases. Although a number of studies have now identified effects of diversity on disease prevalence, the mechanisms underlying these effects remain unclear in many cases. Starting with simple epidemiological models, we describe a suite of mechanisms through which diversity could increase or decrease disease risk, and illustrate the potential applicability of these mechanisms for both vector-borne and non-vector-borne diseases, and for both specialist and generalist pathogens. We review examples of how these mechanisms may operate in specific disease systems. Because the effects of diversity on multi-host disease systems have been the subject of much recent research and controversy, we describe several recent efforts to delineate under what general conditions host diversity should increase or decrease disease prevalence, and illustrate these with examples. Both models and literature reviews suggest that high host diversity is more likely to decrease than increase disease risk. Reduced disease risk with increasing host diversity is especially likely when pathogen transmission is frequency-dependent, and when pathogen transmission is greater within species than between species, particularly when the most competent hosts are also relatively abundant and widespread. We conclude by identifying focal areas for future research, including (1) describing patterns of change in disease risk with changing diversity; (2) identifying the mechanisms responsible for observed changes in risk; (3) clarifying additional mechanisms in a wider range of epidemiological models; and (4) experimentally manipulating disease systems to assess the impact of proposed mechanisms.
传染病的传播本质上是一个生态过程，涉及至少两个物种，通常是多个物种之间的相互作用。因此，生态群落的物种多样性可能会影响传染病的流行率也就不足为奇了。尽管现在有许多研究已经确定了多样性对疾病流行率的影响，但在许多情况下，这些影响背后的机制仍不清楚。从简单的流行病学模型入手，我们描述了一系列多样性可能增加或降低疾病风险的机制，并说明了这些机制对媒介传播和非媒介传播疾病以及对专性和兼性病原体的潜在适用性。我们回顾了这些机制在特定疾病系统中可能如何运作的例子。由于多样性对多宿主疾病系统的影响一直是近期许多研究和争议的主题，我们描述了最近的几项努力，以阐明在何种一般条件下宿主多样性会增加或降低疾病流行率，并举例说明。模型和文献综述都表明，高宿主多样性更有可能降低而不是增加疾病风险。当病原体传播依赖于频率，且病原体在物种内的传播大于物种间的传播时，尤其是当最易感宿主也相对丰富和广泛分布时，随着宿主多样性增加疾病风险降低的可能性尤其大。我们最后确定了未来研究的重点领域，包括：（1）描述随着多样性变化疾病风险的变化模式；（2）确定导致观察到的风险变化的机制；（3）在更广泛的流行病学模型中阐明其他机制；（4）通过实验操纵疾病系统来评估所提出机制的影响。
