Fellous Simon, Koella Jacob C
Division of Biology, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, United Kingdom.
Am Nat. 2009 Jun;173(6):E177-84. doi: 10.1086/598490.
The ecological and epidemiological processes underlying the success of parasites competing within individual hosts are not yet clear. We investigated one idea: that increasing one parasite's infectious dose might decrease the success of its competitor. We reared uninfected larvae of the mosquito Aedes aegypti and exposed them to two concentrations of the microsporidium Vavraia culicis and of the protozoan Ascogregarina culicis. The rate at which Vavraia produced its infectious spores depended on its dose and that of its competitor: when the dose of Vavraia was high, only the higher dose of Ascogregarina slowed the production of spores, but when the dose was low, either dose of Ascogregarina did. Ascogregarina was least likely to produce oocysts when its competitor's dose was high and the mosquito was reared with little food. This was due to the mosquito's preadult mortality induced by Vavraia. Our results show that increasing the dose of a parasite can increase its deleterious effects on a coinfecting parasite. Since dose increases with a parasite's prevalence, such dose effects could lead to an epidemiological feedback that ultimately eliminates one of the parasites.
寄生物在单个宿主体内竞争成功背后的生态和流行病学过程尚不清楚。我们研究了一种观点：增加一种寄生物的感染剂量可能会降低其竞争者的成功率。我们饲养未感染的埃及伊蚊幼虫，并将它们暴露于两种浓度的微孢子虫库蚊瓦氏孢子虫和原生动物库蚊阿氏聚孢虫中。库蚊瓦氏孢子虫产生感染性孢子的速率取决于其自身剂量及其竞争者的剂量：当库蚊瓦氏孢子虫的剂量较高时，只有较高剂量的库蚊阿氏聚孢虫会减缓孢子的产生，但当剂量较低时，任何一种剂量的库蚊阿氏聚孢虫都会如此。当竞争者的剂量较高且蚊子在食物匮乏的情况下饲养时，库蚊阿氏聚孢虫产生卵囊的可能性最小。这是由于库蚊瓦氏孢子虫引起的蚊子成虫前期死亡率所致。我们的结果表明，增加一种寄生物的剂量会增加其对共感染寄生物的有害影响。由于剂量会随着寄生物的流行率增加，这种剂量效应可能会导致一种流行病学反馈，最终消除其中一种寄生物。
