Morphological comparisons of the Plasmodium (Novyella) species reported from North American birds, with comments on a species from the barred owl Strix varia Barton

Abstract

The application of detailed morphological comparisons to the identification of avian malaria parasites in their natural hosts was tested by the study of a Plasmodium (Novyella) species in a barred owl Strix varia from southern Georgia. The parasite was characterised by the presence of fan-shaped schizonts that produced only four merozoites and elongate, slender gametocytes that were pigmented conspicuously. The schizonts were larger than those of P. hexamerium, P. vaughani and P. rouxi, and gametocytes were longer, although of comparable width to those of the other Novyella species which occur in North American birds. Schizonts and gametocytes caused significant hypertrophy of host erythrocyte nuclei, but did not enlarge the host cell. Although the morphological comparison suggests that the Novyella parasite of the barred owl probably deserves taxonomic distinction, formal description should await the study of experimental infections or the acquisition of additional natural infections.