In 2016, four lion cubs at South Africa’s Sabi Sands, a private game reserve bordering Kruger National Park, mysteriously fell ill. The cubs became sluggish, experts say, withering away into weak, depressed husks. Slowly, they lost the ability to move their back legs and had to drag themselves on their front limbs in order to get around.
The disability quickly morphed into a full-on paralysis of the hind quarters, pinning the young cubs to the ground and making it impossible for them to move.
Two of the lion cubs the vets looked at died, and two did not. It was later revealed that two grown lionesses showed similarly lethargic symptoms around the same time, and it's possible other lions in the area also appeared sick.
Veterinarians were stumped by the animals’ condition. How could the cubs be playful one day but paralyzed the next with no obvious explanation? After further study, they found that the lions may have been stricken with something called white muscle disease.
Normally only seen in livestock like sheep, cattle, and goats, the condition is caused by a muscle-gripping mineral deficiency that can lead to paralysis and heart failure, which was the cubs’ ultimate cause of death. (Related: “Mysterious Giraffe Disease Has Scientists Baffled”)
“It’s quite an interesting way that the disease was showing,” says veterinarian Joel Alves, who studied the sick cubs. “I have never seen anything like that in my country before.”
Two years later, questions still remain. For starters, it’s difficult to pinpoint if the cubs actually had white muscle disease, since this may be the first recorded case observed in lions. How did the lions contract it, if this condition is normally only seen in domesticated livestock? And if the disease ever showed up again in Sabi Sands, how should it be treated, if at all? Footage and details recently brought to National Geographic might help to answer some of these questions.
A Curious Cub Case
After two of the ill cubs died, veterinarian Zoe Glyphis performed necropsies on the corpses and extracted tissue samples to send to a pathology lab. Researchers at the lab examined the specimens under a microscope and found evidence of what they thought could be white muscle disease.
White muscle disease gets its name from white marks it leaves on the muscles of infected animals, which are streaked with dead cells and calcification. It’s typically seen in livestock animals that don’t have enough vitamin E and selenium in their systems due to a poor diet. As natural antioxidants, these minerals prevent cell death that can lead to the disease, as well as the paralysis and heart failure associated with it.
Since younger animals have higher metabolisms that oxidize faster, offspring are often affected by white muscle disease more readily than their parents. Although two lionesses in the area fell ill with the condition, they both survived, as did two out of the four cubs, according to Jamie Paterson, a safari guide for the broadcast company WildEarth. Paterson saw the condition break out amongst the lions, and adds that the affected cubs were not all from the same litter.
“These buffalo, however, were emaciated from a prolonged drought,” James Hendry, another WildEarth safari guide, writes to National Geographic in an email. “The logical conclusion is that buffalo were unable to eat sufficient, good-quality forage to provide them with vitamin E and selenium and that this deficiency was then passed on to the lions feeding off their meat.”
Record drought paired with population growth have sparked an urban water crisis in Cape Town, and authorities warn that the city will face “Day Zero”—when Cape Town must shut off its taps because of dangerously low reservoir levels—by mid-July. The Lowveld already has nutrient-poor soil, and deficient plants can make for poor sustenance for animals, which can push these deficiencies up the food chain from grass-grazing species like buffalo to apex predators like lions. (Related: “From Not Enough to Too Much, the World’s Water Crisis Explained”)
The vets can’t say if white muscle disease is the sole reason for the lions’ condition, since this is a small case that’s never been seen in this species before. But, it’s likely. Rabies, canine distemper virus, and bacterial infections were ruled out during testing. Alves says the animals’ lethargic condition could be the result of a viral infection, but without fresh tissue samples, this theory can’t be confirmed.
“No one can really say what is and isn’t possible. It’s a very poorly described disease process,” Alves says. “We don’t have a 100 percent diagnosis to confirm it.”
One thing’s for certain, Alves says: “If the drought conditions continue in the country, we know that lions in times of nutritional stress predominantly prey on buffalo.”
With continued environmental stress in South Africa, it’s possible this mysterious ailment could crop up again in the future.
In a free-roaming area like Sabi Sands, conservationists and park staff want to keep the land as natural and human-free as possible. Some might say the goal is to mimic how the land would have been thousands of years ago before humans, but today, the private property is fenced off.
“Anything that’s natural, the lines become very blurred,” Alves says. “The general consensus is that you do not interfere, hard as that may be.”
Managing something like white muscle disease is difficult. If this condition shows up on the reserve in other lions after consuming buffalo meat, the cats could be injected with vitamin E and selenium and monitored to see if similar symptoms develop. But, Alves says, that scenario would mess with nature because injecting a manmade antidote is not a natural way to cure the disease. But if the fences weren’t there to begin with, he adds, then perhaps there would be no white muscle disease at all. (“Watch: Can Drones Help Save Wildlife Around the World?”)
“You can’t really say that maybe these buffalo wouldn’t have moved to an area where there’s better grazing,” Alves says. In that case, the buffalo would have been healthy. (Related: “How Humans Are Shaping Our Own Evolution”)
“The fact that things are fenced,” Alves says, “means that they have to be managed.”