Brookfield Zoo received confirmation this week that Malena, an 11-year-old Amur tiger, tested positive for COVID-19. (CZS/Brookfield Zoo)

The Chicago Zoological Society announced Oct. 1 that one of the big cats in its collection has tested positive for COVID-19, the first animal at Brookfield Zoo known to have contracted the disease.

Malena, an 11-year-old Amur tiger, began showing symptoms of an upper respiratory illness, “including lethargy, coughing and sneezing,” late last week, according to a press release issued by the zoo.

Those symptoms were in line with those exhibited by big cats infected at other zoos, so Brookfield Zoo submitted samples to the University of Illinois Veterinary Diagnostic Laboratory and to the U.S. Department of Agriculture’s National Veterinary Services Laboratories, which is responsible for monitoring and reporting COVID-19 cases in animals.

An unspecified number of other cat species at Brookfield Zoo also have displayed similar symptoms, and the zoo’s veterinary staff has submitted additional tests to the lab. Those test results are expected back next week, but all of the animals are recovering, the press release stated.

Dr. Mike Adkesson, vice president of clinical medicine for the Chicago Zoological Society, said Malena’s prospects for recovery were good, given the experience of big cats who’d contracted COVID-19 at other zoos.

“Malena is an older tiger and therefore at an elevated risk,” Adkesson said in the press release. “However, she’s in good health and her symptoms have been relatively minor. We are optimistic she will make a full recovery.”

In September, Brookfield Zoo veterinary staff had begun the systematic inoculation of some 300 animals in the collection, including Malena, who had received a first dose of the Zoetis COVID-19 vaccine on Sept. 16.

“Having had one dose of the animal vaccine, it’s reasonable to expect that Malena’s immune system was partially primed to combat the virus, and therefore the severity of her illness has been decreased,” said Adkesson.

Malena’s bout with COVID-19 comes nine months after undergoing surgery twice in January to address a degenerative hip condition. On Jan. 27, surgeons spent six hours implanting an artificial hip, but it dislodged within a day. Malena spent two more hours in surgery on Jan. 30 to remove the implant and undergo another procedure.

Brookfield Zoo has closed its Clouded Leopard Rain Forest and Desert’s Edge exhibits until further notice as a precaution, though the big cats still can roam freely in their outdoor habitats.