Different paths – the same virulence: Experimental study on avian single and co-infections with Plasmodium relictum and P. elongatum

In the present experimental study we analysed the development of two avian malarial parasites Plasmodium elongatum (genetic lineage pERIRUB01) and Plasmodium relictum (genetic lineage pSGS1) and their impact on host fitness 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 specializes on 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.