Medical News

Meerkats Keep Dropping Dead From Heart Failure

At the start of the spring of 2015, Jeffrey, a three-year-old meerkat, was happily eating, tussling with his brothers, and surveying zoo patrons from his usual perch, his forepaws gathered and his black-tipped snout aloft. But one day in April, his caretakers discovered him in his enclosure, so weak that he could barely lift his head. By the time he was brought to Eric Baitchman, the head vet at Massachusetts’s Stone Zoo, Jeffrey was losing consciousness. Baitchman nudged a tube down his patient’s straw-size throat to help him breathe; an ultrasound revealed a heart in failure.

Eight days later, despite a strict regimen of meds, Jeffrey was dead. And within the next three years, both of Jeffrey’s brothers—two of the zoo’s remaining three meerkats—would die in similar ways.

All three brothers were diagnosed with dilated cardiomyopathy, or DCM, a serious condition in which the muscles of the heart weaken and expand, compromising the organ’s ability to pump blood. Before Jeffrey, Baitchman had never seen the disease in a meerkat, and he wondered if the family at Stone Zoo had simply been a fluke. If it wasn’t, he thought, perhaps the disease had genetic roots. Finding them might be key to saving future generations of meerkats—or maybe even people with similarly faulty hearts.

Baitchman, who is on the leadership team of Zoo New England, reached out to other zoos with families of meerkats—and quickly began to hear a chorus of “Yes, us too.” Michael Garner, a pathologist who examined Jeffrey’s heart, confirmed the same pattern: For years, vets from around the country had been sending him misshapen meerkat hearts, normally the diameter of a walnut but many now ballooned out to the size of a large apricot. According to an analysis Garner did in 2017, about a quarter of meerkat deaths in an American-zoo pathology database were linked to some sort of cardiac disease, among which DCM looked to be an especially common cause.

Everything Baitchman has since learned about how this disease manifests in meerkats points to his original hunch: “It almost had to be hereditary,” he told me. In partnership with a team of genomics experts, he has spent the past several years collecting dozens of tissue samples from zoo meerkats across the U.S. for genetic analysis. The team is still in the process of analyzing the 86 genomes they’ve amassed, and haven’t yet pinpointed genes clearly linked to DCM. But one of Baitchman’s collaborators, Alexander Bick, a geneticist at Vanderbilt, told me that he is hopeful that one will show up, because the condition is so easily passed on. If just one meerkat parent has it, about half of their kids seem to get it, too.

[Read: Something mysterious is killing captive gorillas]

Bick is interested in meerkat hearts in part because DCM is one of the most common cardiomyopathies in humans, too, and a leading reason for heart transplants. The condition can be managed with medications and implants, but eventually, many people’s hearts still fail. And although genetics is thought to play a role in the majority of human DCM cases, only about a third of them have a mutation with a known connection to the disease, Bick told me. As families have shrunk in recent decades, common genetic mistakes have been harder to trace using the traditional method of mapping a disease’s presence in sprawling family trees; certain populations of wild meerkats, inbred for generations, seem to have almost the opposite issue. The meerkat population spread across American zoos also appears to be made up of all, roughly, half-cousins, based on scientists’ best estimates—“essentially all part of one enormous family tree,” Bick told me.

In recent years, plumbing the genomes of other animals has proved remarkably useful for human medicine. Dog genomes have helped researchers better understand human airway diseases, pain disorders, cancers, birth defects, and sleep disorders; studies in rhesus macaques yielded insights into the genes that influence alcohol consumption and endometriosis. The next big treatment for the lethal neurological disease Tay-Sachs could come from genetic research into cats.

There’s no guarantee that meerkat genetics will reveal anything about ours. The genomes of certain breeds of dogs, which develop DCM as well, have been thoroughly scoured for clues about the disease. But the genes that underlie DCM in canines have shown almost no overlap with those in people, Katie Nadolny, a veterinary cardiologist who has been studying DCM in meerkats, told me.

And meerkats are much less well understood than dogs are. Researchers don’t have a strong sense of what healthy meerkat hearts look like in the wild, Rachel Johnston, a genomics expert at the Broad Institute and Zoo New England, who has been collaborating with Baitchman, told me. They’re also unsure how common DCM might be in nature, where many meerkats live in more diverse populations, eat more varied diets, and more often die from infectious disease, or predation, or simply because they’re “famously homicidal,” Jenny Tung, a researcher at the Max Planck Institute for Evolutionary Anthropology who is studying the genetics of wild meerkats, told me. Asking how different a captive population might be is a natural next step. Those questions might not yield benefits for humans, or even meerkats outside of zoos. But whatever answers researchers find could save meerkats like Jeffrey, before their hearts quietly fail.