Department of Ecology and Evolution, University of Lausanne, Lausanne, 1015, Switzerland.
Biogéosciences, UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 boulevard Gabriel, 21000, Dijon, France.
Parasit Vectors. 2022 Jun 2;15(1):187. doi: 10.1186/s13071-022-05292-w.
Changes in host phenotype following parasite infection are often considered as host manipulation when they seem advantageous for the parasite. However, putative cases of host manipulation by parasites are rarely tested in field-realistic conditions. Infection-induced phenotypic change cannot be conclusively considered as host manipulation if no evidence shows that this trait is adaptive for the parasite in the wild. Plasmodium sp., the parasites causing malaria in vertebrates, are hypothesized to "manipulate" their host by making their odour more attractive to mosquitoes, their vector and final host. While this is fairly well supported by studies on mice and humans, studies focusing on avian malaria give contradictory results.
In the present study, genotyped birds at different stages (uninfected, acute and chronic) of Plasmodium relictum infection were exposed, in a large outdoor aviary, to their natural vector, the mosquito Culex pipiens.
After genotyping the blood meals of more than 650 mosquitoes, we found that mosquitoes did not bite infected birds more than they bit them before infection, nor more than they bit uninfected hosts.
Our study highlights the importance of testing ecological behaviours under natural conditions and suggests that different processes might be at play in mammals and birds regarding potential manipulation of attractiveness by malaria parasites.
当宿主表型的变化似乎对寄生虫有利时，通常被认为是寄生虫对宿主的操纵。然而，在野外实际条件下，很少有寄生虫对宿主进行操纵的案例得到检验。如果没有证据表明这种性状在野外对寄生虫具有适应性，那么感染引起的表型变化不能被明确地认为是宿主操纵。疟原虫属寄生虫会导致脊椎动物疟疾，它们被假设通过使宿主的气味对蚊子（其传播媒介和最终宿主）更有吸引力来“操纵”宿主。虽然这在针对老鼠和人类的研究中得到了很好的支持，但针对禽疟的研究却得出了相互矛盾的结果。
在本研究中，处于不同阶段（未感染、急性和慢性）感染疟原虫 relicta 的基因型鸟类在一个大型户外鸟舍中暴露于其自然传播媒介——库蚊 Culex pipiens 下。
在对超过 650 只蚊子的血餐进行基因分型后，我们发现蚊子叮咬感染鸟类的次数并不比感染前多，也不比叮咬未感染宿主的次数多。
我们的研究强调了在自然条件下检验生态行为的重要性，并表明哺乳动物和鸟类中，关于寄生虫对吸引力的潜在操纵，可能涉及不同的过程。
