Why Do Great Apes Have Heart Disease?

Chantek the orangutan was well-known for his ability to use sign language with his keepers at Zoo Atlanta. Although he was shy about communicating with strangers, he would frequently sign with his caregivers. When the popular primate died in early August at 39 years old, he was one of the oldest living male orangutans in North America.

Although his cause of death is not yet known, Chantek was being treated aggressively for heart disease. Cardiac issues are a common problem for great apes — western lowland gorillas, orangutans, chimpanzees and bonobos — that are kept in captivity. Researchers from across the country are working together at the Great Ape Heart Project, based at Zoo Atlanta, to create a database to collect, analyze and share cardiac data, while working to find treatments for the disease.

Chantek contributed vital data to the program, says veterinarian Hayley Murphy, director of the project and the zoo's vice president of animal divisions.

"Every time an ape dies, it's really heartbreaking for all of us, and Chantek was definitely a unique individual and had a worldwide following," Murphy tells MNN. With his death, she says, people are learning more about cardiac disease in great apes and the project that is working to find out more about it.

"We're getting the news out there that modern-day zoos are all about taking the very best care of their animals ... We need to take the best care of these animals from an animal health and a conservation aspect."

Gathering data

Until recently, most apes were examined for diagnostic testing under general anesthesia, but it's not as safe or as accurate for apes with heart disease as testing when the animal is awake, says Murphy.

When asked if it was possible to do heart tests when apes were awake, keepers took up the challenge. They started using positive reinforcement like treats and juice to teach the animals to sit for voluntary blood pressure readings, cardiac ultrasounds and blood draws to help monitor their health. Chantek participated in the world's first voluntary echocardiogram (EKG) ever performed with an awake orangutan, which was used to help diagnose his heart condition.

Learning about cardiac disease

Researchers began to note in the late '70s and early '80s that there were great apes in institutions that had died due to heart disease, but it wasn't for many more years that extensive population-based heart surveys were performed, says Murphy. And that's when researchers started to see that cardiovascular disease was a leading cause of death, specifically for adult apes in captivity.

Up until that point, infectious disease and nutrition were the main causes of death.

"Part of the reason it shifted was that apes were living longer and we solved those other (infectious disease and nutrition) issues," Murphy says.

As it became apparent that there was a problem with the ape cardiovascular system, what was originally a grassroots effort, the Great Ape Heart Project was formally created in 2010 with its first grant from the Institute of Museum and Library Services.

A network of volunteer experts including human and veterinary cardiologists, pathologists, geneticists, nutritionists, epidemiologists and animal behaviorists from various parts of the country now work together to analyze and discuss data.

Most of the information comes from apes in the U.S., although as word of the project spread, data is also trickling in from other parts of the world, according to Murphy.

It comes from animals in zoos, sanctuaries and research facilities. "Anybody who cares for great apes, we want their information," she says. Right now, more than 80 institutions have sent more than 1,000 data points.

Why study captive apes?

Researchers at the Great Ape Heart Project are specifically studying heart disease in captive apes because that's the data that is available to them and that's the population they want to keep healthy. There isn't significant information about why the animals die in the wild.

"We don't know why we're seeing (heart disease) in zoo populations and we don't know why they're dying in the wild because wild apes aren't usually necropsied," Murphy says. "We don't know the state of their heart and we don't do diagnostics on them. We have seen some heart disease in wild living apes but not to the extent that we see in our populations."

It could be due to the fact that apes in captivity live longer than those in the wild.

"I do think it's a probability of longer-living apes in zoological populations, but we don't have the science to back that up," she says.

The ultimate goal

Although it would be ideal to be able to stop all heart disease in great apes, there's a certain amount that is inevitable because — as in humans — it's a factor of aging, Murphy says.

"I want to stop the heart disease that's related to things that are in our control," she says. "The other goal is to provide the best clinical care we can. We have these apes in our care and it's our ultimate responsibility to take the best care of them, mentally and physically, that we can. Truly, it's very powerful to have all the knowledge in one place and we're trying to stop heart disease the best that we can."