"Fatal disease that causes animals to become listless and unafraid of people is linked to brain tumor and previously unknown virus" by Ellen Huet from "San Francisco Chronicle"
As someone who cares for about 100 raccoons a year, Melanie Piazza knows that a listless, placid raccoon is not a healthy one.
"A lot of the calls were, 'There's a raccoon sitting on my porch and he hasn't moved all day, and I open the door and he doesn't move,' and that's not normal," said Piazza, the director of animal care at WildCare, a wildlife refuge in San Rafael and one of several Bay Area care centers baffled in recent years by a rise in strange raccoon behavior.
The centers would occasionally collect raccoons like this and try to rehabilitate them, but their condition would only worsen and the animals would eventually die. Their symptoms were unlike those of any disease the center's staff had seen before.
"After some time in care, a lot of them would lose control of the back end of their body," Piazza said. "They would be walking and their hips would fall to the side. Head-trauma-type injuries can cause that, but it doesn't develop over time. And their eyes had a very different appearance. They seemed to be, for lack of a scientific term, bugging out of their heads."
The mystery affliction stumped wildlife refuge centers, which are on the front lines of dealing with wild animals in the Bay Area. But after veterinary scientists at UC Davis spent two years collecting raccoons from Sonoma, Marin and Contra Costa county wildlife centers, they found an answer: Each of the diseased raccoons had a brain tumor as well as a previously unknown virus.
Tumors are already rare in raccoons, and the emergence of a new virus that is highly correlated with the brain tumors is a startling find that makes perfect sense to Piazza and WildCare's staff, who had noticed the disease for years but often had to classify it as distemper, a different virus, because they didn't know what it was.
Staffers, frustrated with a seemingly unknown disease but unable to afford an exploratory necropsy, eventually found a donation to pay for the procedure. That raccoon was the first sent to UC Davis' veterinary pathology lab, and WildCare later provided numerous raccoons to the lab for inclusion in the study.
"It was incredibly validating, I have to say," said Piazza. "From 15 to 20 years of experience, we knew something was wrong but didn't have the scientific backup."
The findings, published in the January issue of the journal Emerging Infectious Diseases, analyzed 10 diseased raccoons collected between March 2010 and May 2012, mostly from the Bay Area with one from southern Oregon. The raccoons studied had all shown similar symptoms while alive and, after necropsies, similar tumors in their brains.
They also all tested positive for a specific virus in the polyoma family, called RacPyV, or raccoon polyomavirus. Other polyomaviruses affect humans and other mammals, and one particular virus is known to cause a rare kind of skin cancer in humans. That connection between the virus family and cancer tipped researchers off to testing the raccoon brains for RacPyV, said Patty Pesavento, an associate professor of veterinary pathology at UC Davis who worked on the project.
Scientists aren't sure whether other animals can carry or are affected by RacPyV, but don't think it's likely it can affect humans.
"Polyoma viruses are thought to be fairly species specific," Pesavento said. "But that being said, raccoons share their life, their water lines, our yards, garbage, everything. They're exposed intimately with opossums, cats, dogs, squirrels, rats and humans. We're looking at all those animals."
Pesavento's next question is: Does this virus cause the tumors? She's hoping to spread the word to local residents and refuge centers so that they know when they see a raccoon that might have a neurological disease - like if, for example, humans spot a raccoon during the day.
"Most of (the diseased raccoons) are very quiet, actually, not aggressive," Pesavento said. "They kind of walk in circles quietly, they're not scared of you."
Anyone who spots a raccoon with similar behavior should call their local wildlife rehab or animal control center.
But Pesavento and Piazza hope also to answer eventually the bigger question: Is there an environmental cause to the disease outbreak?
"Raccoons are a good sentinel species to what's going on in our back yard," Piazza said. "If they're getting cancers and living in our water sources and trash and back yards, then it's something to pay attention to."