Rabies

What is Rabies?

Rabies is a disease that affects the nervous system of mammals. The virus that causes rabies is usually passed from one animal to the next through the bite or scratch of an infected animal. In Canada and the United States, foxes, raccoons, skunks and bats are the main transmitters of the disease. Pets and domestic animals can also be infected with rabies and there is a chance that they may pass the disease on to humans. Therefore, while rabies is not a resource itself, it is included in the ministry's state of the resources reports because it is a stressor on wildlife, pets and domestic animals and is a public health concern.

Figure 1. Microscopic view of the rabies strain.

This report provides the general public with information about the state of rabies in Ontario and the province's Wildlife Rabies Control Program. Through education, the public can play a role in controlling rabies in wildlife, and take direct measures to ensure that their own health and the health of their pets and domestic animals are protected.

What are the different types of rabies in Ontario?

There are three types (strains) of rabies in Ontario:

• fox strain,
• raccoon strain, and
• bat strain.

All three strains can kill humans and other animals. While each strain can infect any mammal, fox (or Arctic) strain is carried mainly by fox and skunks; raccoon (or mid-Atlantic) strain is carried mainly by raccoons; and bat strain is carried mainly by bats.

What are the symptoms of rabies?

An animal normally develops symptoms of rabies within three to four weeks; however, it can take from two weeks to over a year. Once an animal exhibits the symptoms of rabies the disease is almost always fatal.

Infected animals may show the following symptoms:
- lose their fear of humans
- become paralyzed in their hind limbs
- drool
- show extreme aggression towards other animals or objects
- isolate themselves
- have a drooping head, sagging jaw, abnormal facial expressions and vocalizations
- gnaw and bite their own limbs

Where did rabies come from?

Fox Strain (Arctic Strain)
Fox strain rabies was the first strain to be diagnosed in Ontario. Its existence was initially confirmed in 1954 near James Bay in northern Ontario, and then it spread southwards throughout the rest of Ontario. By December 1955, fox strain had reached southern Ontario. Between 1958 and 1990 there was an average of 1,500 confirmed cases in the province each year, primarily in the south.

Raccoon Strain (Mid-Atlantic Strain)
Raccoon rabies was originally reported in Florida in the late 1940s. By 1977, as a result of relocated, infected raccoons, it began spreading northwards through the Atlantic Coast states. In 1999, raccoon rabies crossed the St. Lawrence River from New York and entered southeastern Ontario.

Bat Strain
Bat strain rabies was first diagnosed in Ontario in 1961. Despite large numbers of bats in southern Ontario, rabid bat cases are infrequent. Researchers estimate that less than two per cent of bats actually carry the rabies virus.

How does Ontario control rabies?

• The Ministry of Natural Resources Rabies Research and Development Unit, working in partnership with other provincial and federal ministries, universities, and private industries, has been a lead agency in rabies research and control. This research aims to develop effective and economical methods to vaccinate wild animals against rabies, improve rabies monitoring programs, and increase our understanding of both the rabies virus and the role of wildlife in spreading the disease.
• This research has also led to the development of Ontario's Wildlife Rabies Control Program, which began in the mid 1980s.
• Rabies is controlled in Ontario's wildlife through one of two methods – vaccination or, in emergency situations, by the selective euthanization of wild animals.

Vaccination
There are two ways that vaccinations are administered to wild animals in Ontario – through baits, which are eaten, or by manual injections. There is currently no vaccination method for bats because they are insect eaters and will not eat the vaccine baits used for other wild animals. International research is currently under way to develop a method for vaccinating bats.

Baits
Vaccine-filled baits are used to vaccinate wild animals over a large area. Baits are distributed throughout the area by airplanes (Figure 2a) or on the ground. When a target animal eats or bites into the vaccine-bait (Figure 2b), the vaccine is absorbed in the mouth and they become immunized against the rabies virus.

While oral vaccines for immunizing raccoon and fox have been used since 1989, there has not been a similar vaccine to immunize skunks until recently. The Ontario Ministry of Natural Resources and partners have developed a new oral vaccine for skunks and, in 2006, began distributing this vaccine in southern Ontario.

Since 1989, approximately 18,500,000 rabies vaccine baits have been distributed in Ontario.

Figure 2(a). Rabies vaccine baits are dropped from aircraft over large areas. Figure 2(b). The most common vaccine-bait system used in Ontario. The vaccine is embedded in the bait (in the centre) and is then distributed by airplanes or on the ground throughout an area.

Manual Injections
When the area that needs to be vaccinated is smaller (typically less than 1,000 square km), vaccinations may be manually injected. Animals are trapped, injected with the rabies vaccine and then released on site (Figure 3). This method is called Trap-Vaccinate-Release (TVR).

Figure 3. The Trap-Vaccinate-Release method is another strategy used to help control the spread of rabies in Ontario.

Euthanization
Ontario has a large raccoon population, especially in urban areas. There are approximately 1.1 million raccoons in southern Ontario alone, which makes it likely that people, pets, livestock and other wildlife may come into contact with raccoons.

To protect public and animal health, aggressive strategies are used to restrict the spread of raccoon strain rabies in Ontario. In emergency situations, these strategies sometimes involve euthanasia of raccoons and skunks within a localized area.

When a case of raccoon strain rabies occurs in an area that has not been recently treated, raccoons and skunks within five km of the case may be euthanized. This occurs in order to quickly restrict the disease from spreading to other animals. Animals outside the five-km radius are vaccinated either through the TVR or bait methods.

This report is also available as a PDF.

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