Parasite diversity in an endemic region for avian malaria and identification of a parasite causing penguin mortality

Understanding the population structure of Plasmodium parasites is essential for malaria intervention. A survey of parasites in vectors and host infections was conducted in an area of intense mortality due to malaria in a captive penguin (Spheniscus demersus) colony, using a novel method for identification of Plasmodium species by amplification of ribosomal sequences in DNA or RNA. Three phylogenetically distinct groups of avian Plasmodium were detected in mosquitoes (Culex) collected at the study site (Baltimore Zoo, Baltimore, MD) during a period of high transmission. One of the three clades of Plasmodium was found to be prevalent in penguins monitored through the malaria transmission season and consistent with morphological identification as Plasmodium relictum. This parasite sequence was directly associated with the death of a penguin. Thus, a complete transmission cycle is defined at this site. Phylogenetic comparison of ribosomal sequences to an authenticated reference strain of Plasmodium relictum indicates that this is not the parasite causing death in the penguins, suggesting that different parasites may be morphologically indistinguishable.