Different paths – the same virulence: Experimental study on avian single and co-infections with Plasmodium relictum and P. elongatum
Description
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.
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For experimental study we used two avian malaria parasites, Plasmodium (Haemamoeba) relictum (lineage pSGS1, GenBank accession no. JX993045) isolated from a naturally infected Common crossbill (Loxia curvirostra) and Plasmodium (Huffia) elongatum (lineage pERIRUB01, GenBank accession no. KT282462) isolated from naturally infected European robin (Erithacus rubecula). Birds were caught at the Biological Station “Rybachy” of the Zoological Institute of the Russian Academy of Science. Infections were multiplied and cryopreserved in liquid nitrogen. The experimental work was carried out from September to October 2015 at the Nature Research Centre, Vilnius, Lithuania. Experimental animals (domestic canary, Serinus canaria domestica) were purchased commercially and maintained in separate cages in a vector-free room under controlled conditions (11/13 h light/dark photoperiod, 21 ± 1 C). All birds were provided ad libitum food and water. Birds were randomly allocated to four treatment groups, 6 birds in each group: 1) birds receiving single P. relictum infections (PR group), 2) birds receiving single P. elongatum infections (PE), 3) birds receiving simultaneously mixed P. relictum and P. elongatum infections (MI), and 4) birds receiving uninfected blood (control).