Nature Research Centre, Akademijos 2, LT-08412 Vilnius, Lithuania.
Nature Research Centre, Akademijos 2, LT-08412 Vilnius, Lithuania.
Int J Parasitol. 2018 Dec;48(14):1089-1096. doi: 10.1016/j.ijpara.2018.08.003. Epub 2018 Oct 24.
Co-infections are prevalent worldwide, however, we are still struggling to understand interactions between different parasites and their impacts on host fitness. In the present experimental study we analysed the infection dynamics of two avian malarial parasites Plasmodium elongatum (genetic lineage pERIRUB01) and Plasmodium relictum (genetic lineage pSGS1) and their impacts on host health during single and co-infections. We reveal that P. elongatum intensity of parasitemia is enhanced by the presence of P. relictum during co-infection, while the parasitemia of P. relictum stays the same. This illustrates how development of a parasite (P. elongatum) which infects both mature and young (polychromatic) red blood cells (RBCs) is facilitated during co-infection with a parasite which specialises in adult RBCs only (P. relictum). The virulence of co-infections was similar to that of the more virulent parasite (P. elongatum). However, the profile of infection and the mechanisms that caused mortality were different. Birds infected with P. elongatum only start to die due to non-regenerative anaemia, when intensity of parasitemia is light and the number of polychromatic RBCs decrease dramatically. Meanwhile, co-infected birds start to die when the mean intensity of parasitemia reaches 10% and the number of polychromatic RBCs increases abnormally, reflecting regenerative anaemia. Our findings reveal that typically measured parameters of virulence (e.g., mortality rate, level of hematocrit) can be the same during single and co-infections, but the mechanisms responsible for the observed virulence can be different. This information serves a better understanding of the processes underpinning the interactions of co-infected parasite species.
合并感染在全球范围内普遍存在，但我们仍在努力了解不同寄生虫之间的相互作用及其对宿主适应性的影响。在本实验研究中，我们分析了两种禽疟原虫 Plasmodium elongatum（遗传谱系 pERIRUB01）和 Plasmodium relictum（遗传谱系 pSGS1）的感染动态及其在单一和合并感染期间对宿主健康的影响。我们揭示，在合并感染中，P. relictum 的存在增强了 P. elongatum 的寄生虫血症强度，而 P. relictum 的寄生虫血症保持不变。这说明了感染一种寄生虫（P. elongatum）的发展情况，这种寄生虫感染成熟和年轻（多染）红细胞（RBC），而感染一种寄生虫（P. relictum）只专门感染成年 RBC ，在合并感染中会得到促进。合并感染的毒力与更毒力的寄生虫（P. elongatum）相似。然而，感染的模式和导致死亡的机制是不同的。仅感染 P. elongatum 的鸟类由于非再生性贫血而开始死亡，此时寄生虫血症强度较轻，多染性 RBC 数量急剧减少。同时，合并感染的鸟类开始死亡，当平均寄生虫血症强度达到 10%，多染性 RBC 数量异常增加时，反映再生性贫血。我们的研究结果表明，单一和合并感染期间通常测量的毒力参数（例如死亡率、血细胞比容水平）可能相同，但导致观察到的毒力的机制可能不同。这些信息有助于更好地了解合并感染寄生虫物种相互作用的潜在过程。
