Laboratory tests confirm deadly rabbit disease in Canada

There is an ongoing outbreak of rabbit hemorrhagic disease in British Columbia.

Starting in March, dead rabbits were discovered in Nanaimo and surrounding areas on Vancouver Island and the Delta region of the Lower Mainland.

This deadly disease is caused by a tiny virus known as a calicivirus. It is very infectious and can spread rapidly through rabbit populations, causing death in most infected individuals.

While the outbreak in rabbits may have minimal effects on trade and agriculture, the fact it has arrived in Canada is concerning. Our country excludes imports from some countries to protect against a number of important diseases. It isn’t known exactly where the virus came from, although other countries including the United States have reported the presence of this disease in rabbits.

The outbreak appears to be limited to European/domestic rabbits that run feral in many B.C. areas. Pet rabbits are also susceptible. The risk to native wild rabbits and hares like jackrabbits appears to be low because there are no known cases in these related species. Humans cannot contract the disease. Other animals including dogs, cats and birds are also not susceptible.

Scientists characterized the first known outbreak of rabbit hemorrhagic disease in China in 1984, which killed an estimated 140 million rabbits. From there, the virus spread to South Korea and Europe, where it remains endemic. Outbreaks have occurred in Mexico. In 2011, a case was reported in a pet rabbit from Manitoba. Despite a rigorous investigation, the source of the Manitoba case is unknown.

In Australia and New Zealand, where feral rabbits are a major agricultural pest, the virus was purposely introduced to control populations.

It appears the outbreaks are occurring in countries that have a large number of feral European rabbits. The large number of feral rabbits in B.C. fits with this characteristic.

Rabbit hemorrhagic disease often manifests as sudden death. If observed early in the course of the disease, infected rabbits may have fever, lack of appetite, mental dullness and difficulty breathing. There is often hemorrhaging from the nose. The virus attacks blood vessels causing bleeding in a number of tissues. It also targets the liver, leading to death of infected liver cells. This can result in liver failure and jaundice.

Rabbits show signs of illness and die within two to four days after infection. Infected rabbits shed the virus in their feces and other secretions. Rabbits become infected by direct contact with infected rabbits or through contaminated materials such as bedding, clothing, water and equipment. Blood feeding insects can also transmit the virus. The virus is extremely hardy and can survive for months in dead rabbit carcasses.

There is no specific treatment for the disease beyond supportive care. Rabbitries and pet owners can limit their risk by practising good biosecurity. This includes limiting visitors with recent contact with rabbits, hygiene, disinfection and monitoring. Rabbits should be housed indoors or in double-fenced areas to avoid contact with feral rabbits.

B.C. has imported vaccines to deal with the outbreak. Pet owners and those who raise rabbits for meat or fur will have access to the vaccine through their veterinarians.

Wild rabbits will likely continue to be affected because it is impractical to vaccinate wild populations and the stress involved in capturing the wild animals may actually cause them to be more susceptible to disease.

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