Epidemiology and pathology of avian malaria in penguins undergoing rehabilitation in Brazil

Abstract

Seabird rehabilitation is a valuable strategy to mitigate the impacts of oil pollution and other anthropogenic factors, and can significantly contribute to the conservation of penguins. However, infectious diseases such as avian malaria (Plasmodium spp.) can hamper the success of rehabilitation efforts. We combined morphological and molecular diagnostic methods to investigate the epidemiology and pathology of Plasmodium in Magellanic penguins (Spheniscus magellanicus) at rehabilitation centers along 2500 km of the coastline of Brazil. True prevalence of malarial parasites was estimated between 6.6% and 13.5%. We identified five species, three of which had not been described infecting penguins (P. cathemerium, P. nucleophilum, P. unalis); an additional five distinct Plasmodium lineages were also distinguished, and albeit unidentified these clearly correspond to species that also have not yet been reported in penguins. Our results indicate that the diversity of plasmodia that may infect these birds is greater than previously recognised. Considering the well-defined seasonality observed in this study, it is clear that rehabilitation centers could benefit by narrowing their preventative efforts on penguins maintained or admitted during the Austral spring-summer, particularly by preventing mosquitoes from coming into contact with penguins.

Figure 1

Geographic distribution of the sampling effort, detection and lineages of Plasmodium spp. Pie charts represent sampling effort (size) and percentage of positive results (red fraction). Blue areas represent the wintering (light blue) and breeding (darker blue) distribution of Magellanic penguins [9].

Figure 2

Monthly distribution of Plasmodium infections in Magellanic penguins at rehabilitation facilities in Brazil. Line represents the incidence of Plasmodium infections (number of cases first recorded at each month; right vertical axis). Bars represent the susceptible population (number of penguins that spent one or more days at the rehabilitation facilities in a given month; left vertical axis). Data is combined for all facilities and years.

Figure 3

Phylogenetic tree of the Plasmodium spp. lineages identified in penguins. (red) Magellanic penguins undergoing rehabilitation along the coast of Brazil (this study), (blue) published penguin-infecting lineages, (black) reference lineages. Branch lengths are drawn proportionally to the extent of changes (scale bar is shown).

Figure 4

Histological findings associated with avian malaria in Magellanic penguins. (a) exoerythrocytic meronts in endothelial cells (arrowheads) within a liver arteriole (R0040, P. tejerai); (b) parasitized erythrocyte (arrowhead) within a cerebral blood vessel (CRAM2127, P. nucleophilum); (c) diffuse granulocytic interstitial pneumonia, congestion and edema (IF584, P. tejerai); (d) diffuse necrotizing splenitis with an exoerythrocytic meront within an endothelial cell of a central arteriole (arrowhead) (R0290, P. cathemerium); (e) multifocal perivascular mononuclear hepatitis, congestion and hemosiderosis (R0093, Plasmodium sp lineage E). Hematoxilin-Eosin. Scale bars = 15 μm.