The Great Ape Heart Project and How It Could Help Humans With Heart Conditions
Most people know that heart disease kills an astounding number of humans each year. But did you know that it’s also the No. 1 killer of orangutans, gorillas and other apes living in captivity?
Enter the Great Ape Heart Project, a revolutionary undertaking led by Dr. Hayley Murphy, DVM, director of veterinary services at Zoo Atlanta, to get to the bottom of why cardiovascular disease affects many great apes.
Vetstreet sat down with Dr. Murphy to discuss the important initiative, which could someday even help humans with faulty tickers.
Q. Why is heart disease so crucial to study in these species?
A. Dr. Murphy: "Heart disease is important because, in captivity, it’s a major cause of mortality. All of these species are endangered or critically endangered, and when we’re managing them in captivity, it’s our responsibility as caretakers and veterinarians to protect their health and welfare. We’re investigating why it happens, if it’s something that we can prevent and how we can treat it."
Q. Do we know if heart disease is something that we see in captivity because these animals live longer?
A. "That’s a really great question. When we started looking at gorillas over 10 years ago, we made some assumptions that it was a geriatric issue, but that turns out not to be the case. It’s not necessarily an age-related disease in captivity because we do see it occur in younger animals as well.
"The other question we get asked is whether it occurs in the wild, and we don’t really have great answers yet. We know from looking at animals who have died in the wild that it does occur, but in very small numbers — only two to three animals have ever been documented to have it in the wild. But we don’t know whether that’s because we haven’t found a lot of dead gorillas with bodies in good enough shape to get an answer. In the wild, there may be a lot more who die that we never find, so percentage-wise, we can’t say very much. It’s still a big mystery, and we’re struggling to answer that question."
Q. When you say that younger animals are affected, how young are we talking?
A. "In gorillas, we have seen changes in their hearts as young as 13 to 15 years of age; a male gorilla can live upwards of 40 to 50 years, so that’s pretty young. Between 13 and 23 — mid-puberty to young adulthood — we see a lot of affected animals. And it’s usually males."
Q. So does this mean that it affects the whole species, not just individuals?
A. "Right. And it certainly caused a lot of alarm when we started seeing this in younger animals. It’s kind of a double whammy — not only does it affect your existing population, but if you’re taking out genetically valuable animals at the height of their reproductive age, that’s a double hit for the population."
Q. When did you launch the Great Ape Heart Project?
A. "A little over 10 years ago, I started the Gorilla Cardiac Project with a human cardiologist, Dr. Ilana Kutinsky. We can’t say a heart is diseased or abnormal until we know what normal is for an animal of that size and age. We were using humans as a reference — looking at a gorilla heart and comparing it to a human heart — but we weren’t sure that was accurate. So the first thing that we had to do was get enough gorillas studied to come up with reference ranges for what was normal and abnormal. That was a big first step — it sounds so basic, but it really had never been done."
Q. Did you find that gorilla hearts were different from human hearts?
A. "There wasn’t a huge difference, but there was enough of a difference that we don’t use human reference ranges anymore. Their hearts are generally a little bit bigger than you would expect — by bigger, I mean thicker walls — and their heart pumps a lot harder normally. Their function is more like athlete hearts, so you can’t use a couch-potato human heart as a standard because gorilla hearts function normally at a much higher performance rate."
Q. What about other great ape species?
A. "There are a lot of published reports for laboratory chimpanzees, but that’s not so much true for the zoo population, and we don’t want to make assumptions. So, right now, we’re looking at the zoo population to see if they have the same heart disease prevalence that we see in research colonies. Dr. Vickie Clyde at the Milwaukee County Zoo is the champion of bonobo heart disease, and she has just submitted a paper for publication on their reference ranges. Orangutans, unfortunately, are a bit further behind, but I think they’re going to be where they need to be a lot quicker because we know what needs to be done. So it’s really exciting that we’re on the precipice of looking at all four of the great apes at one time."
Q. Speaking of orangutans, you had a milestone in February, when your zoo was the first facility to perform an awake echocardiogram on an orangutan.
A. "We’re very proud of that. It’s a species that no one was sure we could do it on because of their body shape, but we have gotten images, and we’re really excited about that."
Q. It must be a lot of work to train the animals to cooperate. Why do it this way?
A. "We’ve been looking at these hearts for a long time with general anesthesia. Some of the general anesthetics that we use depress blood pressure and affect cardiac function. We started to wonder what the heart looked like in an awake animal. My goal was to see the cardiac function without the effect of anesthesia and monitor response to treatment without having to do repeated anesthetic events, especially since risks from anesthesia go up in older guys with really bad hearts.
"When I started in this business, no one thought that could be done. Now we can do awake echocardiograms, measure blood pressure and get blood samples from orangutans — all without anesthesia. The keepers spend a large amount of time training the animals, and we use volunteer echo sonographers who do this on humans every day. The animals love it because they get a lot of attention and treats. I’m the lucky one who gets to come in for the fun stuff at the end."
Q. Can the results from this project tell us something about human health?
A. "Human heart disease is certainly a big risk factor for mortality. In humans, we mostly see coronary artery disease, so we expected to see that in gorillas, especially because we knew that their serum cholesterol levels are high. But we don’t see that in gorillas. Instead, we tend to see fibrosis in the heart muscle, kind of like scar tissue forming, and that’s a lot different. You do see that in humans, but it’s not common.
"So our questions are: Why is it different? If gorillas have such high cholesterol levels, why aren’t they getting coronary artery disease? And is it the same in all apes? The last one is a big question. And we’re just starting to look at orangutans more closely to get to the answer. We even see a couple variations of it in gorillas, so we don’t know if it’s one syndrome that progresses or if we’re dealing with two different syndromes.
"The bottom line is that we can learn a lot from each other. I think we’re going to learn a lot from the research that’s done with human cardiac disease that will apply to apes, and vice versa. What we learn from apes will help humans in the future."