Zoos Aim to Ward Off a Penguin Killer

Ben Stansall/Agence France-Presse — Getty Images

Penguins at the London Zoo. Last year, six penguins died of malaria at the zoo.

By DONALD G. McNEIL Jr.

Published: October 6, 2013

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 100 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.

London is also where the first case of penguin malaria was diagnosed almost a century ago; it was found in a King penguin in 1926.

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 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,” Dr. 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.”

Not all penguins hail from the frigid South Pole. Some nest on beaches where the daytime temperatures can reach 110 degrees. But all come from places so arid as to be considered deserts, so they do not face mosquitoes at home.

“We get maybe one mosquito a year at Punta Tombo,” said P. Dee Boersma, a University of Washington biologist who for 30 years has studied Magellanic penguins on a hot, dry stretch of Argentine coast.

She has found antibodies to malaria in some birds, she said, and assumes that they were bitten during their winter migration to coastal Brazil but survived.

“They go north for Mardi Gras,” she said.

Different zoos take different protective measures.

The Maryland Zoo, Dr. Wack said, believes in letting its birds build a natural immunity — something humans can also do, if they survive repeated childhood bouts of malaria.

All newly arrived penguins “go on the bleed list,” she said. Their blood is drawn once a week, and if parasites are found, they are given malaria drugs. Since it takes about 13 days for symptoms to develop, most do not get sick. After two summers, they normally have enough antibodies to let them survive an infection.

New York City zoos use the same methods most other zoos do.

The King, Gentoo and Chinstrap penguins at the Central Park Zoo in Manhattan are safe because they are exhibited in a giant walk-in refrigerator; trespassing mosquitoes don’t last long.

Magellanics at the Bronx Zoo live in an outdoor habitat modeled on Punta Tombo, and the African black-footed penguins at the aquarium on Coney Island live in an exhibit vaguely resembling their home, the beaches around Cape Town, South Africa.

The Bronx Zoo conducts a fierce but natural war on mosquitoes, Dr. Sheppard said. Its ponds are stocked with larvae-eating fathead minnows. Standing water is drained, or where it collects, it is dosed with Bacillus thuringiensis, an insect-killing bacterium.

At the London Zoo, birds are given lavender for nesting material, and their pens are sprayed with lavender oil, which is thought to repel mosquitoes.

And at most zoos other than Maryland’s, the birds get a daily dose of primaquine or chloroquine, the same medicines that were the first choice for humans suffering from malaria from about 1950 to about 2000, during which time human-infecting parasites in many countries developed resistance. The medicines still work on bird-infecting parasites.

As it turns out, it is easier to get penguins to take their medicine than it is to get children to.

“You stick the pill in a fish and train the birds to come up and take it,” Dr. Sheppard said. “The keepers can tell which one is which by looking at their spots. That’s critical, because every one has to get a daily dose. You can’t let the bully bird get all the treats.”

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