Humans aren’t the only ones susceptible to diseases caused by viruses, bacteria, and fungus. For example, whitetail deer have been falling prey to diseases like CWD and EHD for years.
By Dr. Dave Samuel
As I write this (March 27), we are in the middle of the Coronavirus pandemic that is sweeping the world. I know you’re weary from hearing and reading about this virus, and I am, too. However, this virus stimulated me to dig out a copy of a book I read several years ago and had saved on my computer. The title is, “Why Bother About Wildlife Diseases,” written by Dr. Milton Friend and published in 2014.
Google that title and read this brilliant book. It’s online, and it covers the importance of zoonoses, which are infectious diseases transmissible from animals to humans, and vice versa (Coronavirus is a zoonosis). Dr. Friend notes that there are 870 species of infectious organisms that you can get from wildlife. As an aside, with this many infectious organisms out there, if you don’t wear plastic gloves when gutting your deer or other species you hunt, you are flirting with serious diseases, some of which can kill you.
The book has numerous examples of past zoonoses, and it describes how these zoonoses are resurging and emerging at rates never seen before. As I skimmed through this book, a quote that relates to Coronavirus caught my eye. Dr. Friend includes a quote from a 2012 book titled, “Spillover: Animal Infections and the Next Human Pandemic,” by David Quammen. The quote is eerily predictive, and remember, this was in 2012. The “Next Big One” (highly virulent pandemic that sweeps across the world) “is not only possible but probable…it will almost certainly be a zoonotic disease…that emerges from wildlife and will most likely be a virus.” Indeed, the Coronavirus did emerge from wildlife, and it obviously is a virus.
Dr. Friend notes that these growing number of infectious agents have an adaptive advantage over us, and they are crossing over what we used to believe were species barriers and getting to us, and to other wildlife. He also notes that 75 percent of emerging zoonoses around the world came from wildlife. As you know, the Coronavirus reportedly came from bats in China.
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It turns out that in the past 20 years or so, wildlife has taken some major hits from not only viruses, but bacteria, fungus, and of course, prions.
A prime example is West Nile virus, which was first found around New York City in 1999, and is now found worldwide in 294 bird species and 25 mammal species. It has killed hundreds of thousands of birds, of which hawks, owls, and crows are especially vulnerable. Of particular interest to hunters is the fact that West Nile virus is playing a role in the downward trend of ruffed grouse populations.
Chytridiomycosis is an amphibian fungal disease that is devastating to hundreds of species of amphibians, especially frogs and salamanders. It was first discovered in dead frogs in Queensland, Australia, in 1993, and attacks the skin of amphibians, leading to death. Since being found, the chytrid fungus has caused 500 amphibian species to decline severely, or go extinct, in over 35 countries around the world. The disease is transferred by direct contact, or the frog can get it from infected water. If an infected frog doesn’t die immediately, it may move to other waters, thus spreading fungal spores. This means that many or all amphibians in this newly infected water will die from the disease. You can treat individual frogs with chemicals that kill the fungus, but in the wild, there is no practical way to eliminate this disease. Releasing captive amphibians is one way to spread this disease. One way you can help prevent the spread is by disinfecting boots when moving from one water source to another when you are fishing.
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Then there is Chronic Wasting Disease (not caused by a virus but rather a prion). Enough has been written about this disease. Suffice it to say that the infective prions can remain viable in the soil for decades. Pending revolutionary research, eradication of CWD is probably impossible.
Whirling disease is caused by a bacteria that infects the cartilage tissue of the head and spine of trout and salmon. Rainbow trout are the most susceptible, forcing some states to stock the more resistant brown trout in some streams and rivers. There is circumstantial evidence that some trout can develop resistance, but this disease has had disastrous effects on the trout fisheries in some Western rivers and is an ongoing problem. My brother in Alberta tells me that the famous trout fishing Bow River that flows through Calgary is now infected with this bacterial disease.
Although not a wildlife species (except for foxes, coyotes, and wolves), dogs are very important to us. Canine parvovirus is a very contagious disease spread by direct contact with an infected dog or an infected object such as feces. When your dog contacts feces from an infected dog, it will get the disease. Symptoms include severe diarrhea, blood in stools, and vomiting. If left untreated, your puppy can die in two days. For adult dogs, the disease is 90-percent fatal. Fortunately, there is a vaccine, something we all wish we’d find for Coronavirus.
Rabies is a viral disease of mammals that is usually transmitted via a bite from a rabid animal, with raccoons, skunks, bats, and foxes being the most common carriers. When a person is bit by a rabid animal, symptoms (fever, headache, weakness) may not appear for a month, but once they appear, death occurs within a few days. If people get the vaccine within a few days of the bite, they usually survive. I recently read a paper that discussed the fact that 20,000 people die every year in India from rabies. I never imagined rabies was that serious anywhere. The worst part of that story is that most are children bitten by stray dogs.
Duck plague is caused by a herpes virus, and was first found in America in 1967 on Long Island, New York. It most frequently affects captive waterfowl, and there have only been two major outbreaks in the wild. Again, it is transmitted from bird to bird, or via contact with infected feces. Another viral disease that has made a lot of news since a major outbreak in 2007, followed by several other outbreaks since, is epizootic hemorrhagic disease (EHD) in deer.
Bats are very important components of our ecosystem, and the white-nose syndrome caused by a fungus was first found in a cave in upstate New York in 2006. By 2012, the estimated kill was 6.7 million bats nationwide, but that number has been far exceeded since that time. In many winter hibernating caves, it has killed 90 percent of the bats. By any measure, this fungus has devastated our bats. There is some promising research, but as of now there is no cure.
Coronavirus has changed our lives, but as you see, diseases caused by a virus, a bacteria, or a fungus, have seriously impacted our wildlife. There is much speculation as to why we’re seeing a resurgence in these serious wildlife diseases. Climate change, more urban interaction of wild and domestic animals, more use of chemicals in food production, and more water and ocean pollution, have all been discussed as possible reasons. We really are in this together, and relative to humans and wildlife, we need to clean up our act.
