Cardiac Checkups for Gorillas
Humans aren’t the only primates that can develop heart disease. The Zoo goes to great lengths to monitor the heart health of the gorillas.
BY Karyl Carmignani
PHOTOGRAPHY BY KEN BOHN
Graceful despite his hefty 345 pounds, he soundlessly crosses the room to meet his keeper at the mesh. She holds a bucket of his prized daily fruit allotment in one hand and a reusable bottle filled with his favorite low-calorie juice in the other. Mandazzi, a handsome western lowland gorilla, makes an excited grumbling sound and sits before her, pressing his chest into the mesh and turning his head to the right.
He raises his massive arms to grasp the specially made handles secured to the wall for this training. “This behavior took a long time to establish,” said Nerissa Foland, primary gorilla keeper at the Zoo. “It takes a lot of trust and patience on both sides of the barrier to get this far.” She is referring to training the Zoo’s four adult male gorillas to voluntarily undergo heart scans while fully awake, so staff can monitor the mighty apes’ heart health. Mandazzi and Ekuba’s ultrasounds are strictly preventative; Paul Donn and Maka have been diagnosed with heart disease and take medication for it, which is tucked in banana-flavored baby food.
It’s a Guy Thing
Cardiovascular disease is the most common cause of death for great apes in zoos. Of the known heart-related gorilla fatalities, 70 percent were males, most in their 20s or 30s. The exact cause is still unknown, though possibilities abound: genetic defect, dietary issues, too much or too little exercise, stress, a bacterial or viral infection, or simply a by-product of living longer in zoos. Gorilla hearts are quite similar to human hearts—a 350-pound gorilla’s heart next to that of a Sumo wrestler would be nearly identical—but they exhibit different kinds of heart disease.
Humans tend to get fatty plaque buildup (from “bad” cholesterol) inside arteries, which clogs heart function. In gorillas, heart disease is typically a gradual thickening of muscle walls (called fibrosing cardiomyopathy), which blocks electrical impulses and weakens the heart’s ability to pump blood. Still, heart medication for gorillas is the same as for humans—beta blockers and ACE inhibitors—and dosage is adjusted to the animal’s size.
The gorillas are also trained to place an arm into a metal sleeve and hold for a blood pressure reading. However, we do not yet have the gorilla-strong Tough Cuff to collect the data. If you would like to help us provide great ape heart health with this tool, you can donate to sandiegozoo.org/wishlist.
Observation Is Key
“We want to preventatively manage the disease,” said Nerissa. Despite a low-starch, low-sodium diet and maintaining a healthy weight, some gorillas develop heart disease. Once diagnosed, the apes are closely observed for telltale signs like coughing, shortness of breath, sleeping sitting up, and swollen hands. “We take photos of their hands to compare them over time, as sometimes it’s difficult to tell if their thick fingers are actually swollen,” she explained. Keepers also observe the apes closely to collect resting respiration rates.
The program was kick-started during the care of regal silverback Memba. “We were able to get in-depth images of his heart while he was under anesthesia for other routine preventative medical exams, and we followed up with training and ultimately ultrasound images while he was awake.” Training him to go along with the heart monitoring procedures provided “diagnostic evidence of his ailment and helped us provide the best end-of-life care for him.” After Memba died in 2015, Nerissa vowed to help his sons avoid a similar fate, and the training program continued in earnest.
Oh, That’s Chilly!
Persuading a gorilla to participate can be a time-consuming proposition, but Nerissa was confident that the positive reinforcement—and her longtime relationship with the animals—would overcome any trepidation the apes might have. The gorillas are trained in about 25 husbandry behaviors (nail filing, teeth brushing, and wound irrigation, among others), which help keepers maintain their health without anesthesia. Included in the trained behaviors is presenting the chest and allowing keepers to place a probe. However, once the veterinarian was on board, part of the process involved applying gel to the area being touched by the probe. For a gorilla, this could be unsettling.
“I tried warming it up first and even put it inside a plastic bag, so it wouldn’t get on their skin,” she said. Eventually, they accepted the strange sensation as part of the session. It was important to get the apes’ complete cooperation to collect the most accurate data. “They had to present and hold, and position, and even learn hand signals to move a few inches, so we could get the best images of the heart.” The training sessions were so positive for the great apes that they seem to look forward to it now!
What’s Up, Doc?
The gorillas were calm and confident with the behaviors, and Nerissa was ready for a veterinarian to join in. But would this “stranger” cause the animals to not cooperate? She needed a long-term commitment from a vet, so they could monitor the gorillas over time and share heart data with the Gorilla Cardiac Database started by Zoo Atlanta.
Fortunately, Associate Veterinarian Ben Nevitt, D.V.M was committed to the cause—and a very patient man. “In the beginning, the gorillas would only hold the position for about 10 seconds,” said Dr. Ben, “but now they remain still for several minutes at a time. This allows us to find the ‘landing marks’ on their hearts.” For instance, age plays a role in where to place the probe. “For large, young males like Mandazzi, the heart is a bit higher in the chest than in older males like Paul Donn.”
Participating in Their Care
Clear ultrasound images allow doctors to assess how the therapy is working. “If we see fluid around the heart, we can increase their dosage,” said Dr. Ben. He explained that when an ape is under anesthesia for routine preventative medical exams, they can get a deeper reading; a full heart scan takes 30 to 40 minutes. While awake, the gorillas won’t hold still for that long, so the shorter weekly ultrasounds are critical to the animals’ heart health.
“The gorillas play a big part in their own health care,” said Ben. “It is gratifying to work with such smart animals that want to figure things out and interact with us.” Perhaps the gorillas are just happy to have a good heart-to-heart with their dedicated humans.