It started with a seabird - white wings coated in black oil.
Almost 25 years ago, Dr. Sherri Cox took a vacation from her corporate job to volunteer during a devastating oil spill in Galicia, Spain, where more than 60,000 tonnes of heavy fuel oil contaminated thousands of kilometres of coastline.
Among the 300,000 seabirds estimated to have died in the spill, Cox spotted a northern gannet just offshore, trembling and unreachable.
"You should only see gannets come to the shoreline if they're nesting or sick," Cox explains. Knowing the bird would die like this, she says, was a major turning point in her life.
"How can I go back to the corporate world when so many wild animals need our help?"
She didn't. Instead, she studied at the Ontario Veterinary College at the University of Guelph and dedicated her life to wildlife medicine and rehabilitation. Today, Cox is a U of G professor and the volunteer medical director of the National Wildlife Centre (NWC), an animal rehabilitation facility she co-founded in 2014.
Her patients are bears, birds, geese, foxes, deer, turtles and any injured wildlife, especially those endangered and threatened by human activity.
Before it opened its new facility in Caledon, Ont, the centre was run primarily through a mobile hospital and a volunteer network - and still managed to treat more than 5,000 native wild animals and more than 200 species.
"We see sick animals often before they have made it onto the radar of wildlife biologists or those interested in disease surveillance," Cox says. "The public may bring in a sick animal, and it's our job to find out what is going on."
In 2022, that early access changed the course of avian influenza research in North America.
That spring, young foxes arrived at the centre showing tremors and signs of neurological distress. They didn't fit the profile for rabies, and Cox had a hunch.
First researchers to detect avian flu in North American mammals
Avian flu - specifically highly pathogenic avian influenza (HPAI) - was sweeping through wild birds at the time, and Cox decided to submit samples to test the sick foxes. The blood work she sent to the Canadian Wildlife Health Cooperative, and subsequently to the Canadian Food Inspection Agency, came back positive.
"We were the first to diagnose HPAI in mammals in North America for this particular strain affecting birds in 2021/2022," she says - proof that rehabilitation centres could be powerful early-warning systems.
More findings were unexpected. The virus seemed to be affecting the brain more in mammals. A nasal swab may not detect the virus, she told those in her network. Neurological disease can look like rabies or distemper in mammals, but it is transmitted differently. Some foxes died; others developed antibodies and fully recovered.
"That was a key moment," she says, "when we realized this wasn't a death sentence in all mammals. Some animals could survive and build immunity."
But the implications still concerned her. It turned out the foxes were eating dead and infected birds. Were other species at risk? Could it spread from mammal to mammal?
In the following weeks, she helped alert other rehabilitators across Canada: If you see fox kits with neurological symptoms, you may want to test them for avian flu. And be careful.
"Wildlife rehabilitators play such an important role in avian influenza, because if we don't take in the animals, someone else - the public - will," she says. "If the public takes in sick and dying geese and puts them beside their chickens, for example, then that is a huge problem."
The living research of wildlife rehabilitation
Cox began co-authoring papers on more unusual spillover cases in mammals, contributing key pieces to a growing body of global evidence: HPAI is adapting, mutating and occasionally crossing the boundaries between species.
She describes the fox case as just one example of her "living" research: unusual stories walk in the door and demand answers.
Alongside avian flu, she has published studies on black bears exposed to bromethalin, a neurotoxicant with no antidote, and widespread lead poisoning in Ontario's trumpeter swans. Her team is also developing faster methods to detect lead in the field using portable x-rays, with hopes of protecting both wildlife and the people who consume wild game.
Through it all, Cox oversees and trains a growing network of veterinary interns stationed across Canada in partnership with wildlife rehabilitation facilities in Nova Scotia, Manitoba and Alberta. More than a researcher, she is a capacity builder for the world's threats to animals.
And now she is a leader in the growing field known as wildlife rehabilitation science. She examines what knowledge can be gained from the clinical work performed in rehab centres. Publishing studies, she notes, is as much about alerting others to new and strange developments as it is about testing hypotheses and questions.
"We like to publish unusual or non-reported cases, like avian flu found in red foxes, striped skunks and mink," she says. "My work helps us share information on new diseases, on trends, treatments and diagnostics."
A mission, she hopes, that will inspire the next generation.
As the director of U of G's Master of Wildlife Biology, Cox leads the first program in the world to offer a specialization in wildlife rehabilitation.
And she is always looking for new students, especially as habitat loss and urban sprawl increase the frequency of animal injuries and disease transmission. With climate change, too, the need for trained professionals is that much clearer.
"We need more support," she says. "More funding, more training, more students. Because as wildlife rehabilitators and wildlife veterinarians working in the field, we truly are the first line of defence."
As questions remain for her avian flu research - whether surviving mammals can pass immunity, how climate change will shape the movement of the disease - Cox holds that line of defence strong.
"And who knows what will walk through our doors tomorrow?"
The National Wildlife Centre is open seven days a week to respond to sick, injured and orphaned wild animals. Its hotline can be reached at (416) 577-4372.
