Canine distemper virus: an ongoing concern for wildlife in Ontario.

Canine distemper virus (CDV) is highly contagious and can cause a severe, often fatal, disease that affects many different body systems including the immune, respiratory, and neurological systems. The virus is found worldwide, and despite the virus name, it poses a risk to a wide range of wildlife species as well as our furry companions – the domestic dog. Fortunately, CDV is not known to infect people. In Ontario, we don’t see many distemper cases in dogs thanks to widely available vaccines and a community of dedicated pet owners and veterinarians. However, CDV has been around in Ontario for at least 60 years impacting some of our local wildlife species.

The first species that comes to mind might be the raccoon – maybe you have even seen one acting strangely, unsteady on its feet or with discharge from the eyes or nose? What you may not know is that some of our other less commonly encountered species can also be affected by CDV, including skunks, foxes, coyotes, badgers, fishers, and mink. Over the years, CDV has become the most common infectious cause of death for many of the wildlife species examined through local disease surveillance activities and unfortunately, it is likely that this virus is here to stay.

As we have been reminded by COVID-19, viruses are in the business of evolving and changing over time – CDV is no different. Multiple CDV strains have been reported from dogs and wildlife around the world including variants that appear to be regionally specific and some that are found across boundaries and large geographic areas. In fact, part of my research involves investigating the genetic make-up of the CDV strains that are present here in Ontario. We are still learning about the practical impacts of genetic variation in this virus. For example, are certain CDV strains more virulent (i.e., severe), transmissible, or likely to infect one species over another? Will CDV vaccines used in domestic dogs eventually need to be updated to remain protective against an evolving virus? There are many questions left to answer. In the meantime, we can take a proactive approach to mitigate the possible risks associated with introducing and/or moving CDV strains into new areas or species.

Generally speaking, close contact with an infected animal or their discharge is how the virus spreads to a susceptible host. We also know that the virus can be spread between different species (including from dogs to wildlife and vice versa). Wild animals naturally travel within their home range which is one way that the virus can move around within an area. This natural movement is probably not a realistic or desired target for the control of CDV. Human-facilitated animal mixing and movement on the other hand, whether it be wildlife or domestic dogs, is an important mechanism for the movement of CDV strains across large geographic distances and into new species. Therefore, responsible and sound decision-making surrounding animal translocation is crucial. The CWHC recently released a report which summarizes best practices for mitigating disease risks associated with the translocation of wildlife in a rehabilitation context (http://www.cwhc-rcsf.ca/reports.php#tech-reports).

Unfortunately, there are no specific medications available for treating canine distemper that have been proven safe and effective for use in domestic or wild animals. CDV prevention remains our best and primary control strategy.

So, what does all of this mean and what can we do?

1. To keep your pets safe – Vaccination remains the best control strategy, so it is important to keep up to date with routine vaccines as recommended by your veterinarian. Keep dogs on a leash and supervised while outdoors and, if you are considering adopting a dog, do a bit of research to ensure you are selecting a reputable source.
2. To keep our wildlife safe – We have many amazing wildlife species in Ontario that are facing mounting risks from disease, loss of habitat and other human activities. We can all play a part in helping to protect our wildlife by viewing from a distance, refraining from feeding wild animals, and learning about and supporting efforts that promote wildlife health in your area.
3. To keep yourself safe – An important point to remember is that rabies virus is also present in Ontario. Rabies can infect the same species and cause symptoms that look identical to CDV. However, in addition to affecting wild and domestic mammals, rabies virus poses a serious risk for humans. Do not approach wild animals and if you see a dead wild animal or an animal behaving strangely, please make a report to your local CWHC regional centre. If you think you may have been exposed to rabies you should contact your doctor or local public health unit. Animal owners should report any potential exposure of their animals to their veterinarian.

Submitted by:

Jolene Giacinti