Raccoon Rabies in Ontario
Rabies virus occurs in a variety of strains, each associated with a preferred mammalian host. Ontario was the site, for many years, of an ongoing epizootic of arctic fox strain rabies virus, which was gradually eliminated through a program of aerial and ground baiting with oral rabies vaccine. The last case of fox strain rabies detected in southern Ontario was in 2012. Bat strain rabies is an ongoing concern in the province.
Ontario has also long been at risk for the incursion of raccoon strain rabies, which is widespread in the northeastern United States, with cases occurring in northern and western New York state along the border with Ontario. Animals in Ontario have been protected through a combination of oral vaccination of rabies vector species and by the natural barriers formed by the Niagara and St. Lawrence Rivers. The barrier in eastern Ontario was breached in 1999 with cases occurring in several locations on the Ontario side of the river. The Ontario Ministry of Natural Resources and Forestry responded with an intensive program of point infection control and vaccination, resulting in the elimination of raccoon strain rabies by 2005.
Although the vaccine barriers have continued to be maintained, a raccoon infected with the raccoon strain of rabies was detected in early December in Hamilton following an altercation with two dogs. The Ontario Ministry of Natural Resources and Forestry has responded to this event with a program of increased surveillance and aerial and ground baiting with oral vaccine. Testing of wildlife (e.g., raccoons, skunks) found acting in an unusual manner or found dead has since resulted in the detection of several more cases of rabies. The disease has now been found in areas to the south and west of the original case.
Unfortunately, there are no natural barriers to the spread of the disease, and it has moved into a part of the province in which there is a high density of raccoons living in close proximity to a large population of humans and domestic animals. Although agricultural and natural areas abound, a substantial proportion of the area has been urbanized, and raccoons are found throughout the region. The establishment of raccoon rabies in this area would create substantial challenges from the point of view of wildlife, domestic animal and human health.
A concurrent epidemic of Canine Distemper Virus (CDV) in raccoons and skunks complicates the situation. CDV also causes significant neurological disease in affected animals. When both diseases are present in a geographic area, it is not possible to tell from observation of the affected animal which disease is likely to be responsible for the clinical signs observed.
In the face of this outbreak, it is important for pet owners to ensure that their pets are up to date with vaccinations for rabies, and in the case of dogs, for CDV as well. Any wild animal, particularly the common rabies vector species (e.g., raccoon, skunk, fox) that is acting strangely should be treated as a potential source of rabies and contact should be avoided.
Reports of wildlife acting strangely or found dead in this area should be reported to the provincial rabies hotline (1-888-574-6656). Wildlife found dead outside of this area can be reported to the CWHC (1-866-673-4781). Instances of contact between domestic animals and suspicious wildlife should be reported to your local veterinarian. Veterinarians seeking assistance with risk assessments, testing or post-exposure management of domestic animals should contact OMAFRA via the Agricultural Information Contact Centre (1-877-424-1300). Incidents of contact between suspicious wildlife and people should be reported to the local public health unit.
By Drs. Claire Jardine & Doug Campbell – CWHC Ontario/Nunavut