Lauren Smith, a veterinarian at Patan Zoo, is examining a Florida puma cub whose mother suffers from a recently discovered neurological disease, feline leukoplasm (FLM). The researchers examined and found that the cub and her siblings were healthy, but the lioness did not recover from the disease.
Photograph by CARLTON WARD JR.
Written by: DOUGLAS MAIN
Florida mountain lions once spread throughout the southeastern United States, but were nearly extinct due to widespread hunting. By the 1970s, fewer than 30 Florida cougars remained. Although the number of this endangered cat has increased significantly over the past few decades, reaching a total of about 200, its future is still difficult to say optimistic.
That's why scientists are worried about a newly discovered neurological disorder that causes Floridian mountain lions and short-tailed cats to have weakness in their limbs and, in severe cases, partial paralysis. Diseased animals often have difficulty walking, which can lead to starvation and death. The disease is known as feline leukoplasmide (FLM) and three Florida mountain lions have been diagnosed. However, florida may have had at least 19 Florida mountain lions and 18 short-tailed cats diagnosed with the disease since the spring of 2017.
A male Florida mountain lion cub struggles to get up after losing control of its hind legs — a sign of FLM.
Darrell Land, head of the mountain lion team at the Florida Fish and Wildlife Conservation Commission (FWC), said it's unclear what causes the disease.
"There is no conclusive evidence at this time. This is a bit troubling because you might think that if there had been a simple answer, we would have found out long ago. ”
Scientists' most certain guess is that a neurotoxin is responsible for the disease. Pathogens (such as viruses) are also possible, but less likely. The disease can also be caused by a combination of factors, such as nutrient deficiencies and neurotoxins. Because at least two cats have been found to have the disease, it means that it is not a congenital lesion passed from parents to offspring.
After an MRI scan at the University of Florida Veterinary Hospital, technician Des Muir put a sleeping Florida mountain lion cub back on a trolley to reunite it with her brother. The MRI scan mainly scanned the spinal cord and brain of Florida mountain lions, and it was clear that the neurological symptoms of FLM were obvious.
Mark Cunningham, the FWC's wildlife veterinarian, said the researchers suspect the disease, characterized by damaged nerve cells, appeared early in the life of the Florida mountain lion and generally does not worsen or improve. In some areas, the disease affects a significant percentage of Florida mountain lion pups.
Cunningham said the FWC has made studying the disease a top priority. He said a range of organizations, research institutions and ordinary citizens, including photographers who set camera traps, were working together to find out what caused the disease.
Florida mountain lions face multiple threats, including vehicle collisions, deadly fights over limited territory, and economic exploitation. If the new disease "remains at the same level, there's a good chance we'll see The Florida mountain lion population affected," Cunningham said.
"This is truly an unprecedented event in wildlife, at least in felines," he added.
Worrying findings
In early 2018, in the spiral swamp area north of Naples, an ancient cypress forest, photographers Ralph Arwood and Brian Hampton captured a video of a Florida puma mother who had just given birth to three cubs. By mid-May, though, something was clearly not quite right. Two of the male cubs have difficulty walking and are visibly weak on their hind legs. Arwood notified the FWC.
A few months later, photographer and National Geographic explorer Carlton Ward, Jr. encountered a Florida puma mother as she walked toward a camera trap she had set nearby. He was excited at that moment until he saw one of its cubs, dragging its legs on the ground, while the lioness was waiting for it. "It's really heartbreaking to see this scene," he said. "It's the saddest, most helpless thing I've ever seen."
In southwest Florida, the female Florida mountain lion was fitted with a tracking collar. The tracking camera later captured it with two cubs, but the cubs developed more severe FLM symptoms. Because the florida mountain lions are in a worrying condition, conservationists capture them and take them away from the wild. The two cubs survived and now live in a permanent habitat in the White Oak Reserve. Lionesses developed irreparable FLM-related injuries, and staff euthanized them and studied their brain and spine tissue to determine the cause of the disease.
Cunningham said one of the cubs never appeared again and was presumed dead, while the other, wearing a GPS collar, fell off a few months later, whose fate is unknown. Since then, several Florida mountain lions and short-tailed cats suspected of having FLM have emerged in the spiral swamp area.
Cunningham added that through a retrospective analysis of the video captured by the camera trap, the researchers found suspected FLM cases in the Babcock Ranch Sanctuary in April 2017, or the earliest known case. The symptoms of suspected diseased animals photographed by camera traps are difficulty walking, and there is no other known cause that can be explained. An official diagnosis is difficult because testing of the spinal cord of recently deceased animals is required to be determined.
Of the three officially confirmed Florida mountain lion cases, one was a lioness who gave birth to two cubs near Imocali in the summer of 2019. In the video captured by the camera, her hind legs were so weak that in the end all three cougars were captured by state wildlife officials because they were likely to be unable to survive. Researchers at the Tampa Zoo examined the two cubs, and the lioness was taken to the University of Florida College of Veterinary Medicine.
The lioness underwent various tests, including magnetic resonance imaging, neurological examinations, and blood tests, but none could explain her condition. By this time, it could barely walk, and the veterinary team made a difficult decision to euthanize it. "It's really sad. I went out of my way to help it," said Jim Wellehan, a veterinarian at the University of Florida who witnessed what happened to her.
Fortunately, the two cubs survived, and now the two healthy adult mountain lions live in a large paddock in the White Oak Preserve in northeast Florida.
Disappearing axons
The autopsy of a Florida mountain lion with FLM showed serious damage to its spinal cord: What was originally an axon or nerve fiber was filled with small holes, said Nicole Nemeth, a veterinary pathologist with the Southeastern Wildlife Disease Collaborative Research Team, one of the researchers who helped analyze samples of the diseased animals.
A toxic substance may have killed the axon, said Ian Duncan, a neuroscientist at the University of Wisconsin who worked with the FWC. He is an expert in the study of myelin sheath diseases, the fatty layer that protects the nerve fibers of the central nervous system in mammals. At first it seemed that FLM might be involved in the degeneration of the myelin sheath, but the researchers' analysis of the spinal cord of the diseased and dead Florida mountain lion showed that this was not the case.
So far, researchers have screened several Florida mountain lion corpses for a large number of toxic substances, including rodenticide, pesticide, herbicide and heavy metals, but no definitive results have been established.
Duncan and others suspect that the virus is unlikely to be the culprit because there is no clear evidence of inflammation, which is an inevitable consequence of infection, he said. Neurotoxins produced by naturally growing algae or certain microbes in their habitat are another possible culprit, and researchers are setting out to investigate.
In general, felines — such as domestic cats, cheetahs and jaguars — seem to be more susceptible to neurological disorders than other mammals, Nemeth said.
Another threat
Dave Onorato, chief mountain lion biologist at the FWC, said: "FLM is a bit like an unknown at the moment. We don't want to overemphasize its dangers, but it could really affect the Florida Mountain Lion's recovery process. ”
Onorato said the disease has the potential to disrupt an already uncertain recovery process for Florida mountain lions, so it's important to relocate them to new territories to fend off the growing threat.
Veterinarian Lara Cusack and biologist Mark Lotz took blood samples from a Florida mountain lion cub in the Spiral Swamp Sanctuary, and video taken by the tracking camera showed the cougar showed signs of having FLM. The cub undergoes a thorough examination by a veterinarian before being released back into the wild.
Florida mountain lions must expand their range northward, and this is only possible if wildlife corridors are protected. In 2016, researchers found a female Florida mountain lion north of the Klusahach River, a major waterway near Fort Myers, for the first time in 43 years, an important milestone for them.
While many researchers are optimistic about the future of the Florida mountain lion, there are also some who are very worried. Deborah Jansen, a mountain lion biologist at the National Park Service, said: "The future of Florida mountain lions is full of uncertainties and they face very big dilemmas, especially this neurological disease. ”
(Translator: Stray Dog)