SEEN - SE European Bird Migration Network
Parasitemia of avian malaria in naturally and experimentally infected hosts of a migratory songbird

Pavel Zehtindjiev1, Mihaela Ilieva1 & Staffan Bensch 2

1 Kalimok Station – Institute of Zoology, Bulgarian Academy of Sciences, Bulgaria
2 Department of Ecology, Lund University, Ecology Building, Sweden

Very little is known about the progress of infection of avian malaria parasites in wild birds. We monitored changes of parasitemia of specific mitochondrial lineages of Plasmodium parasites in captive Great Reed Warblers Acrocephalus arundinaceus during the autumn and winter of 2005, involving both naturally infected adults and experimentally infected juveniles. The first aim of the study was to follow the development of parasitemia of naturally infected Great Reed Warblers throughout the winter when they normally are at their African winter quarter where the transmission of the malaria parasites takes place. We did not find predicted increase of the parasitemia relative to initial levels during the period November–January when the sub-Saharan wintering areas are still rather wet and vectors should be abundant and transmission conditions are optimal. The second aim was to investigate the development of infections in juvenile birds during their first encounter with malaria parasites and we did this by transferring infected blood from donors to uninfected juveniles. We predicted that the naïve birds, experimentally infected with the Plasmodium lineages GRW2 and GRW4 should develop higher parasitemia than seen in the adult donor birds as primary infections are expected to make the birds more sick than at the chronic stages of the infections. To find out whether the infections affected the performance of the birds, we monitored several indicators of physiological condition (subcutaneous fat level, body mass and temperature) with the prediction that experimentally infected birds should do less well than uninfected control birds. Strong variations in the impact of mixed and single infections were found.

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