Robust gorillas mysteriously dying in zoos

Problem was, no one had defined how a normal gorilla heart operated.

But as ultrasound information was entered into a database and compared to necropsy reports on deceased gorillas, clues began to appear. “We started noticing that some gorilla hearts were grossly abnormal from others,” Kutinsky says. “The abnormal ones were mildly enlarged, very thick, and weren’t pumping as much blood.”

The findings raised more questions: Were the heart abnormalities the result of genetic differences? The gorilla’s sex? Did climate play a role? How big a factor was diet? Were the gorillas getting enough exercise in their enclosures? Or too much? Was heart disease being caused by bacterial or viral infections?

Some even asked: Were gorillas developing heart disease because of the way they were reared or socially grouped at the zoos?

As the scope of the mystery widened, the number of cases of apes developing heart problems steadily climbed.

One was Babec, a 24-year-old lowland gorilla at the Birmingham Zoo in Alabama. Male gorillas in zoos have lived to age 54, and median life expectancy is 30; so when Babec started coughing, eating less and clutching at his chest in early 2003, the staff veterinarians examined him, and identified his nemesis: cardiomyopathy.

Human medication didn't help
Although the gorilla was given medications for heart disease in humans, his condition kept deteriorating. He lost 80 pounds (20 percent of his body weight), was accumulating fluid in his abdomen. And by the summer of 2004, his heart pumped just 10 percent of the blood his body needed.

With Babec in the final stage of heart failure, the zoo risked a procedure never before attempted on a gorilla: the implantation in Babec’s chest of an advanced pacemaker that corrects the heart’s electrical circuitry and restores its ability to contract properly.

Today, Babec’s prognosis is excellent. He’s dropped the excess water weight, his heart and other organs work more efficiently, and his heart and pacemaker are continuously monitored.
Neal Kay, a cardiologist at the University of Alabama at Birmingham’s Heart and Vascular Center who volunteered to perform the operation, later remarked that the only reason Babec still greets visitors to the Birmingham Zoo is that “we got to him in time.”

Such intervention could save individuals like Babec — but still largely unaddressed were questions of why gorillas develop heart disease in the first place, and how to halt the disease’s progression.

Mehgan Murphy / Smithsonian Institution via AP Smithsonian's National Zoo veterinarian Suzan Murray, left, and animal keeper Rebecca Malinsky train Kwame, a 7-year-old male western lowland gorilla, to give voluntary blood samples. As positive reinforcement, gorillas are fed grapes to keep their arms in a sleeve specially designed to give veterinarians access to the veins in their forearms.

That’s why in November 2006 — three months after Mopie and Kuja died at the National Zoo — ape experts, human cardiologists, and zoo epidemiologists, pathologists and managers from around the country gathered at the Brookfield Zoo in Chicago to establish what they called the “Gorilla Health Project.”

Their first task: To build a National Gorilla Cardiac Database. With it, veterinarians could track rates of heart disease and death and try to learn why scar tissue was replacing cardiac muscle in apes.

To Kristen Lukas, chair of the Gorilla Species Survival Plan for the Association of Zoos and Aquariums, the project marks “a sea change” in how zoos will care not only for gorillas, but a host of other endangered species in captivity.

This level of networking between veterinary and human medical experts from universities, hospitals and animals rights groups “just never happened before,” she says.

Meehan, the Chicago veterinarian who has worked with gorillas since 1979, expects the initiative to bring animal care forward a quantum leap from, say, the 1960s, when gorillas were originally brought to North American zoos and staff struggled just to keep the captive population alive.

Gathering new data will present challenges, of course. One is the need for echocardiograms of apes. To do the test, a gorilla must be anesthetized, “which carries a certain amount of risk,” says cardiologist David Liang of Stanford University, a consultant to the Gorilla Foundation in California.

Prime suspect: Diet
Another option, some experts say, might be to perform biopsies on affected gorillas to obtain tiny samples of heart muscle. This, too, would require anesthesia.

Many primatologists and veterinarians consider diet a prime suspect of heart disease in captive animals. And exploring that may require extensive study of the mortality of western lowland gorillas in the wild, they say — which, for many reasons, is tricky.

Gorillas in the wild tend to die younger, meaning not as many live long enough for age-related disorders to show up. Moreover, male silverbacks — the king of gorilla society — often hide symptoms of illness because they fear they may be challenged by younger males.

Still, research in the wild has paid off before. Not long ago, for example, it was learned that lowland gorillas, which are primarily herbivores, wade into swampy lake areas and eat vegetation growing underwater.

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“There was no way of knowing that sort of thing was happening until somebody went out there to Africa and noticed what the gorillas were doing,” says primatologist Joseph Erwin of the Foundation for Comparative and Conservation Biology in Needmore, Pa.

Ellen Dierenfeld, a gorilla nutritionist at the St. Louis Zoo, says that a member of the ginger family, Aframomum melegueta, is a staple food of western lowland gorillas in their native environments.

Some scientists say Aframomum is a powerful antibacterial, antiviral, antifungal and anti-inflammatory “natural drug,” which may serve as a preventive medicine for the gorillas. But this and other native African plants are often not part of zoo gorillas’ daily diets.

The Gorilla Health Project’s diet and other data should be gathered by early 2009, analyzed and shared later that year, says Pam Dennis, a veterinarian in charge of analyzing the information.

“The important thing is that we’re now working to prevent the diseases in the first place,” says Dennis, an epidemiologist with the Cleveland Metroparks Zoo and Ohio State University.

“We started out trying to figure out human health by studying animals. Now we’re turning to our findings in humans to figure out how to treat animals,” she says with a chuckle. “It’s come full circle, which is sort of a beautiful thing.”

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