Plasmodium infection in African penguins (Sphenicus demersus)

Abstract

Avian malaria, caused by Plasmodium spp. infection, is the most important cause of mortality of captive penguins in open-air colonies in the United States. Additionally, avian malaria poses an obstacle to successful rehabiliation of penguins in several wild populations. Infected Culex spp. mosquitoes transmit the disease and a single malarial sporozoite is sufficient to initiate infection. Avian malaria occurs worldwide due to extensive bird migration patterns and wide geographic host ranges. Birds that evolved in the absence of mosquitoes, such as African black-footed penguins (Sphenicus demersus) serve as aberrant hosts, with resultant high morbidity and mortality rates after exposure. While Plasmodium relictum and P. elongatum appear to be the Plasmodium spp. implicated in malarial infections in captive black-footed penguins in North American, P. juxtanucleare has been associated with mortality in free-ranging African penguins. Penguins commonly die without displaying clinical signs or parasitemia. Typical antemortem clinical signs of malaria infection include anorexia, depression, vomiting, dyspnea, seizing, and sudden death. Premonitory signs of infection are often subtle and frequently are lacking altogether. Classic pathological lesions have been described for avian malarial infections in black-footed penguins and include splenomegaly, edematous lungs, subcutaneous edema, and hydropericardium. An ELISA for detecting anti-Plasmodium spp. has been developed to assist in the diagnosis of avian malaria and an anticircumsporozoite DNA vaccine has been refined for experimental use in captive African penguins in North America. Plasmodium juxtacunleare-associated mortality in rehabilitated free-ranging black-footed penguins verus infection in non-rehabilitated wild penguins has also been examined. The objective of this paper is to present a comprehensive report on various aspects of Plasmodium spp. infections in captive African black-footed penguins in North America. A special section at the end of the report is devoted to a discussion of avian malaria in free-ranging black-footed penguins