Pandemics and comparisons in the wild
Pennsylvania Game Commission officials, in cooperation with experts, have recently put together a Chronic Wasting Disease management plan for our state’s deer. Although CWD transmission takes place much more slowly than Covid-19 transmission, and the incubation period is much slower (18 to 24 months) the number of CWD positives has doubled in the state since last year.
Of course, the presence of CWD doesn’t disrupt the lives of deer, where the term social distancing has no meaning. Deer are very social animals who typically move about in small groups. They interact with each other within these groups, and with other deer as they travel.
CWD is contagious from deer to deer and also from the environment to deer. Although biologists and PGC officials can do nothing to eliminate deer to deer transmission they can take steps to reduce the environment to deer transmission.
In other words, no feeding of deer should happen. Feeding deer causes them to group in one place and makes it much more likely that disease transmission occurs. It’s not just CWD; there are lots of diseases and parasites deer can get – lice, mites, hemorrhagic disease, lung worm, rabies, dermatophilosis, brucellosis and more.
“What is a wildlife biologist’s first response to any of these diseases? Social distancing!” said Jeannine Fleegle, Wildlife Biologist, PGC Deer and Elk Section. “Before the COVID-19 pandemic, I didn’t have a term for it, but I sure do now.”
“Many diseases, if not all, are exacerbated and perpetuated by the congregation of animals.”
Fleegle explained a related term, R naught. R naught is a measure of how contagious a disease is. If that value is less than 1 (i.e. 1 infected deer infects less than 1 other deer), the infection cannot be sustained in the population and it disappears.
If it equals 1, the disease hangs around but doesn’t get out of control. If it is greater than 1, one infection causes multiple new infections and an outbreak or epidemic is possible. The way to reduce the R naught value is to enact social distancing.
“Keeping an infected deer away from healthy deer will prevent transmission, lower the R naught value, and hopefully the infection will peter out or stabilize,” Fleegle said, adding that deer aren’t good at social distancing.
“You never see a deer alone and they rarely follow the 6-feet-apart rule! This makes things much worse,” she said. “How do wildlife managers mandate social distancing in a social animal?”
“While deer still can go out to obtain essential items, you must close your facility,” she said. “That’s right – stop feeding deer.”
“Sharing corn-filled plates and licking the same mineral lollipop are sure to keep any nasty bug going,” Fleegle said. “And I can guarantee that no deer covers its cough or sneeze at a corn pile.”
Fleegle said that of course, the current public health crisis rightly overshadows any wildlife disease issue. However, she pointed out that more than 40% of emerging human parasites and pathogens originate in wildlife.