Zoos all around the world love penguins. They’re cute, they don’t require much space, they never eat zookeepers. And children adore watching them, especially at feeding time.
But as carefree as they might look, torpedoing through the water or rocketing into the air like a Poseidon missile, zoo penguins are stalked by an unrelenting killer: malaria.
“It’s probably the top cause of mortality for penguins exposed outdoors,” said Dr. Allison N. Wack, a veterinarian at the Maryland Zoo in Baltimore, which is building a new exhibit that will double its flock to a hundred birds. If left untreated, the disease would probably kill at least half the birds it infected, though outbreaks vary widely in intensity.
The avian version is not a threat to humans because mosquitoes carrying malaria and the parasites are species-specific; mosquitoes that bite birds or reptiles tend not to bite mammals, said Dr. Paul P. Calle, chief veterinarian for the Wildlife Conservation Society, which runs New York City’s zoos. And avian malaria is caused by strains of the Plasmodium parasite that do not infect humans.
But for penguins in captivity, the threat is so great that many zoos dose their birds in summer with pills for malaria, said Dr. Richard Feachem, director of global health at the University of California, San Francisco. Last year, six Humboldt penguins in the London Zoo died of malaria.
Since then, there have been many outbreaks of avian malaria, including at zoos in Baltimore, South Korea, Vienna and Washington, D.C.
The last major American one was at the Blank Park Zoo in Des Moines, Iowa, during the hot, wet summer of 1986. From May to September of that year, 38 of the 46 Magellanic penguins the zoo had just imported from Chile succumbed.
They died despite the efforts of the National Animal Disease Center in nearby Ames, Iowa. Veterinarians made the correct diagnosis from symptoms even though parasites were not found in blood samples until late in the outbreak. The birds died despite being put on a two-drug prophylactic cocktail of the sort that a tourist to Africa might take.
While human malaria is a scourge of the tropics, killing an estimated 660,000 people a year, it has largely been chased out of the world’s temperate regions. But animal and bird variants of the disease are widespread.
“Whether you are a pigeon or a mouse or a lizard or an elephant, you have your own malaria,” Feachem said.
Avian malaria is endemic everywhere except in the cold polar regions and on some Pacific islands where the right mosquitoes have never established themselves. (However, it is a new and growing threat in Hawaii, where it is devastating the honeycreeper population.)
Through long exposure, most bird species have built up a natural resistance. “But penguins have a problem,” said Christine Sheppard, a former chief of ornithology at the Bronx Zoo, “because they come from habitats without mosquitoes.”