Dobson A P
Department of Biology, Princeton University, New Jersey 08544.
Q Rev Biol. 1988 Jun;63(2):139-65. doi: 10.1086/415837.
The ability of parasites to change the behavior of infected hosts has been documented and reviewed by a number of different authors (Holmes and Bethel, 1972; Moore, 1984a). This review attempts to quantify the population dynamic consequences of this behavior by developing simple mathematical models for the most frequently recorded of such parasite life cycles. Although changes in the behavior of infected hosts do occur for pathogens with direct life cycles, they are most commonly recorded in the intermediate hosts of parasites with complex life cycles. All the changes in host behavior serve to increase rates of transmission of the parasites between hosts. In the simplest case the changes in behavior increase rates of contact between infected and susceptible conspecific hosts, whereas in the more complex cases fairly sophisticated manipulations of the host's behavioral repertory are achieved. Three topics are dealt with in some detail: (1) the behavior of the insect vectors of such diseases as malaria and trypanosomiasis; (2) the intermediate hosts of helminths whose behavior is affected in such a way as to make them more susceptible to predation by the definitive host in the life cycle; and (3) the behavior and fecundity of molluscs infected with asexually reproducing parasitic flatworms. In each case an expression is derived for R0, the basic reproductive rate of the parasite when first introduced into the population. This is used to determine the threshold numbers of definitive and intermediate hosts needed to maintain a population of the pathogen. In all cases, parasite-induced changes in host behavior tend to increase R0 and reduce the threshold number of hosts required to sustain the infection. The population dynamics of the interaction between parasites and their hosts are then explored using phase plane analyses. This suggests that both the parasite and intermediate host populations may show oscillatory patterns of abundance. When the density of the latter is low, parasite-induced changes in host behavior increase this tendency to oscillate. When intermediate host population densities are high, parasite population density is determined principally by interactions between the parasites and their definitive hosts, and changes in the behavior of intermediate hosts are less important in determining parasite density. Analysis of these models also suggests that both asexual reproduction of the parasite within a host and parasite-induced reduction in host fecundity may be stabilizing mechanisms when they occur in the intermediate hosts of parasite species with indirect life cycles.(ABSTRACT TRUNCATED AT 400 WORDS)
寄生虫改变受感染宿主行为的能力已被许多不同的作者记录和综述过（霍姆斯和贝塞尔，1972年；摩尔，1984a）。本综述试图通过为这类寄生虫生命周期中最常记录的情况建立简单的数学模型，来量化这种行为对种群动态的影响。虽然具有直接生命周期的病原体确实会导致受感染宿主行为的改变，但这种情况最常记录在具有复杂生命周期的寄生虫的中间宿主中。宿主行为的所有变化都有助于提高寄生虫在宿主之间的传播率。在最简单的情况下，行为变化会增加受感染和易感同种宿主之间的接触率，而在更复杂的情况下，则会对宿主的行为模式进行相当复杂的操控。本文详细探讨了三个主题：（1）疟疾和锥虫病等疾病的昆虫传播媒介的行为；（2）蠕虫的中间宿主，其行为受到影响，从而使其在生命周期中更容易被终宿主捕食；（3）感染无性繁殖寄生扁虫的软体动物的行为和繁殖力。在每种情况下，都推导出了R0的表达式，即寄生虫首次引入种群时的基本繁殖率。这用于确定维持病原体种群所需的终宿主和中间宿主的阈值数量。在所有情况下，寄生虫引起的宿主行为变化往往会增加R0，并减少维持感染所需的宿主阈值数量。然后使用相平面分析来探索寄生虫与其宿主之间相互作用的种群动态。这表明寄生虫和中间宿主种群可能都呈现出丰度的振荡模式。当后者的密度较低时，寄生虫引起的宿主行为变化会增加这种振荡趋势。当中间宿主种群密度较高时，寄生虫种群密度主要由寄生虫与其终宿主之间的相互作用决定，中间宿主行为的变化对确定寄生虫密度的重要性较小。对这些模型的分析还表明，当寄生虫在具有间接生命周期的寄生虫物种的中间宿主中进行无性繁殖以及寄生虫引起宿主繁殖力下降时，它们可能都是稳定机制。（摘要截选至400字）
