JOHANNESBURG — Lions at a South African zoo that caught the coronavirus from their companions were sick for more than three weeks and continued to test positive for up to seven weeks, according to a new study that raised concerns about the virus’ spread among wildlife.
It’s not clear how much virus the lions carried or whether they were actively contagious for the entire time they tested positive. But prolonged periods of infection in big cats would increase the risk that an outbreak in the wild would spread more widely and infect other species, researchers said. That could eventually make the virus endemic among wild animals and, in the worst case, give rise to new variants that can jump back to humans.
The study at the University of Pretoria is likely the first of its kind in Africa. According to Professor Marietjie Venter, the lead researcher on the study, researchers began monitoring captive wild animals in zoos and nature reserves after a tiger at the Bronx Zoo became ill with the coronavirus in April 2020.
The research team tracked two cougars who contracted the coronavirus at a private zoo in July 2020, during South Africa’s first wave of pandemic. The cougars, which are not native to South Africa, started showing symptoms including loss of appetite, diarrhea, runny noses and persistent cough. Both cats made a full recovery after 23 days.
About a year later, three lions in the same zoo started showing similar symptoms. One of the lions, an older female, contracted pneumonia. The lion’s boss and an engineer at the zoo also tested positive for the virus.
This time, researchers were able to sequence the samples and found that the lions and their handler were infected with the same Delta variant. The disease the lions developed, especially in the older female, showed that animals, like humans, could develop severe symptoms from Delta, which triggered the deadliest wave of pandemic in South Africa.
The lions recovered after 25 days, but had positive PCR tests for more than three additional weeks. PCR tests amplify the genetic material of the virus and can therefore detect even very small amounts. The data suggested that the amount of virus the lions were carrying had decreased over those weeks, and it was not clear exactly how long they had been contagious.
In a captive environment, the animals were quarantined, but in larger parks across South Africa, where lions are a common public attraction, controlling an outbreak could be “very, very difficult,” the study said. especially if it went unnoticed. . These lions are often fed by humans rather than hunting for themselves, increasing their exposure.
“If you don’t know it’s Covid, there’s a risk that it could then spread to other animals and possibly back to humans,” said Dr. Venter, a professor of medical virology, who collaborated with a wildlife veterinarian for this study. The animals had been infected long enough “that the virus can actually undergo mutations,” she said, “but there’s a higher risk that if you’re in a wildlife sanctuary and it spreads in the wild, then it could become endemic.”
The coronavirus causing the global pandemic likely originated in bats and eventually jumped onto humans, in what are known as ‘overflow’ infections.
Scientists warn that “spillover” infections from humans infecting animals — as has happened to minks, deer and domestic cats — can devastate entire ecosystems in the wild. Infections released into the wild could also increase the virus’ potential to spread uncontrollably and mutate in animals, possibly into variants that are dangerous to humans.
A well-studied phenomenon concerns infections among large populations of mink in captivity. At a mink farm in Denmark, the virus mutated into a new strain during the human-mink transition, leading to the massive slaughter of the animals in that country and Europe to prevent it from spreading back to humans.
In contrast, the South African study involved small outbreaks, but Dr. Venter noted that the spread in mink shows the potential danger of larger outbreaks in wildlife.