By Cheryl Lyn Dybas
Special to The Washington Post
Monday, August 21, 2006
BIRMINGHAM, Ala. -- Gorilla gorilla gorilla .
The scientific name of the endangered western lowland gorilla echoes like a cry for help.
Adult western lowland gorillas in captivity are dying of an unexplained heart condition called fibrosing cardiomyopathy, which turns healthy heart muscle into fibrous bands unable to pump blood. The condition is similar to a human form of heart disease.
No one has kept track of exactly how many captive gorillas have succumbed, but veterinarians Tom Meehan of the Brookfield Zoo in Chicago and Linda Lowenstine of the University of California at Davis calculated that 41 percent of deaths of captive gorillas -- and 70 percent of deaths of the males older than 30 -- are the result of heart disease, primarily fibrosing cardiomyopathy.
The toll includes Mopie, National Zoo, July 3; Kuja, National Zoo, July 1; Pogo, San Francisco Zoo, May 24; Tumai, Memphis Zoo, May 18; Akbar, Toledo Zoo, Dec. 6, 2005; Sam, Knoxville Zoo, Nov. 17, 2000; Michael, the Gorilla Foundation in California, April 19, 2000.
Babec, a western lowland gorilla at Alabama's Birmingham Zoo, is a rare exception, having been successfully treated surgically for the condition.
Nearly two years ago, cardiologist Neal Kay, working with the zoo's chief veterinarian, Marie Rush, implanted an advanced pacemaker in Babec's chest. The procedure, called cardiac resynchronization therapy or CRT, corrected the breakdown in the heart's electrical circuitry that comes with fibrosing cardiomyopathy, and restored the organ's ability to contract properly.
On a steamy summer morning earlier this month, the 26-year-old gorilla, whose prognosis is now excellent, looked the picture of health as he pointed to his chest while a visitor looked on.
"Babec is a bright light at the end of an otherwise dark tunnel," said Kay, who treats his human patients at the University of Alabama at Birmingham's Heart and Vascular Center. "We got to him in time."
Medical technology may save the day for individual gorillas, but the answer to why captive gorillas are falling ill remains as tangled as vines in the gorillas' native West African swamps. Veterinarians and medical specialists are also treating ailing gorillas with heart drugs but "have few clues about why gorillas are succumbing to the disease," said cardiologist Ben Byrd of the Vanderbilt University Heart Institute in Nashville, who has advised veterinarians at the National Zoo.
"The thing that has us stumped," said Lowenstine of UC at Davis, "is that it doesn't appear to be related to coronary artery disease or cholesterol levels."
Meehan thinks that "it might be a bacterial or viral infection of the heart. It could be a response to stress, in which harmful substances called catecholamines are released, or something in gorillas' diet in captivity that wild gorillas either eat or don't eat."
As far as anyone knows, the condition is not found in the wild. "However, few studies have been done of wild gorillas' health," said primatologist Dan Wharton of the Bronx Zoo/Wildlife Conservation Society, "so it's hard to compare."
Veterinarian Tom Clarkson of North Carolina's Wake Forest University, who studies gorillas and other primates, suspects a virus: "Viral infection is one of the main causes of cardiomyopathy, but if that's it, what's the virus, and how is it being transmitted?"
Gorillas are also prone to periodontal disease, which is linked to heart problems in humans; bacteria from gum infections can cause inflammation elsewhere in the body, including the heart.
Protecting captive western lowland gorillas is all the more important because they are endangered in the wild and at risk of being driven to extinction by the year 2050 because of hunting, habitat destruction and infectious diseases such as Ebola.
"The captive population of 375 gorillas soon might be all there is," said veterinarian Hayley Murphy of Zoo New England in Boston. She and cardiologist Ilana Kutinsky, of the Michigan Heart Group in Troy, recently started the National Gorilla Cardiac Database to track the cases in hopes of discovering why so many gorillas are stricken.
"One of the biggest challenges," said cardiologist David Liang of Stanford University, a consultant to the Gorilla Foundation in California, "is that you need to do an echocardiogram to see how well the heart is functioning. A gorilla has to be anesthetized for that, which carries a certain amount of risk." Some zoos are training gorillas to cooperate with simple medical procedures such as blood pressure checks and blood tests without anesthesia, but echocardiograms must be done when gorillas are asleep.
Byrd and Kay think it might be possible to use blood tests for B-type natriuretic peptide (BNP) or homocysteine to check gorillas' heart function without anesthetizing the animals, but it will take further research to confirm that.
Another step, Byrd thinks, might be to perform biopsies on affected gorillas to obtain tiny samples of heart muscle, although this, too, would require anesthesia.
Some scientists are searching the African bush for a solution. Primatologists believe that a key is studying what western lowland gorillas die from in the wild.
"Without knowing that," said Joe Erwin of the Foundation for Comparative and Conservation Biology in Needmore, Pa., "the cardiac problem in captive gorillas is even harder to get a handle on."
Wild gorillas' diet is made up almost exclusively of fiber-laden plants -- roots, shoots and leaves -- and some experts consider diet a chief suspect in the captive animals' disease.
Ellen Dierenfeld, a gorilla nutritionist at the St. Louis Zoo, has found that a member of the ginger family, Aframomum melegueta, also known as "grains of paradise," "is a staple food of western lowland gorillas in their natural habitat."
"Aframomum is a potent antibacterial, antiviral, antifungal and anti-inflammatory 'natural drug,' " said primatologist Michael Huffman, of Japan's Kyoto University. "The plants may be as much a source of preventive medicine for gorillas as they are of food."
Zoos try to give gorillas foods as close to their natural diet as possible, Dierenfeld said, "but aframomum and other native African plants are not part of captive gorillas' daily diets."
Until a way is found to prevent the disease, the best hope for gorillas in zoos may be the procedure that Kay, the Birmingham cardiologist, used to save Babec.
On July 1, his team was called from Birmingham to the National Zoo to operate on Kuja, a 23-year-old gorilla whose cardiomyopathy had rapidly progressed to emergency status. "A June echocardiogram of Kuja's heart showed almost no pumping ability," Kay said.
By the time Kay got to Washington, however, it was too late. Kuja's heart -- the heart of a "silverback," the adult male king of gorilla society -- had died.
"By the time we arrived, Kuja's blood pressure was just about gone," Kay said. "We gave it everything we had, but we couldn't save him."