CANMORE – A fatal disease detected in Canmore’s feral rabbit population will likely cause mass die-offs.
Earlier this week, test results confirmed Rabbit Hemorrhagic Disease (RHD) – a highly contagious and fatal viral disease of rabbits that hit Calgary hard earlier this fall – in a rabbit carcass that was found on Bow Valley Trail on Dec. 1.
“I think what we can expect is that it will spread into the rabbit population in that area and likely cause a considerable mortality event,” said veterinary pathologist Jennifer Davies, director of the diagnostic services unit and associate professor at the University of Calgary’s faculty of veterinary medicine.
“As we have seen in other locations in North America, this is likely a disease that has now been introduced into a native population, which probably doesn’t have any immunity to this disease, and this particular viral disease in rabbits and hares is highly contagious and highly fatal.”
RHD is specific to lagomorphs – rabbit and hare species. After being exposed to the virus, rabbits usually become sick within one to five days. Death is common after a short period of illness, although rabbits may also die suddenly without any signs.
While Canmore feral rabbits are considered an invasive species and are trapped by the Town of Canmore, the concerns centre more on the risk of this strain of the disease known as RHDV2 on native hares such as snowshoe hares or residents’ pet bunnies.
Town of Canmore officials say they are particularly concerned the fatal disease could spread to the native hare population and are asking residents to report any hare carcasses they may come across to [email protected].
“We do not take the spread of this disease lightly,” said Caitlin Van Gaal, environmental and sustainability supervisor for the Town of Canmore.
“We are particularly concerned about the wild hare population and so we have been talking with Alberta Environment about that.”
Davies said three rabbit carcasses from Canmore were received for testing at the University of Calgary, but one was too badly scavenged by ravens to be valuable for post-mortem examination.
“One of the animals had compatible growth lesions and microscopic lesions of Rabbit Hemorrhagic Disease,” she said, noting tissue samples were sent to the Animal Health Centre in Abbotsford, B.C., for PCR testing.
“We got positive results back from that animal on Monday so that does confirm the presence of Rabbit Hemorrhagic Disease.”
A third rabbit carcass was sent to the university on Dec. 8.
“It also had compatible lesions both with the naked eye and under the microscope of Rabbit Hemorrhagic Disease and we do have testing still pending on that one,” Davies said.
In mid-November, Canmore residents began to notice rabbits when dropping dead in various residential neighbourhoods without explanation.
One long-term resident, Andrew Duff, alerted the Town of Canmore about a dead rabbit in his yard on Nov. 17. He had seen several dead rabbits in his neighbourhood by Riverside Park.
“I guess I am not surprised. That is really the only explanation that made sense,” said Duff on learning that the disease has been confirmed in Canmore.
“I hope it hasn't affected any domestic rabbits or other similar species.”
Davies said time will tell how the virus behaves in Canmore, noting the disease is new to this part of the world.
“Those rabbits that survive, though, may develop some natural immunity to the disease and the population may spring back,” she said.
The virus is highly persistent in the environment and may not be eliminated.
“At this point, it’s a very hardy virus, very good at surviving in very cold temperatures and high heats as well,” Davies said.
RHD has been sporadically popping up in various locations in North America in the last few years. It was initially found in Canada on British Columbia’s Vancouver Island and the Gulf Islands in 2018, wiping out a considerable number of rabbits.
The virus has been confirmed in a few places in Alberta, including the Taber area in spring 2021, a small outbreak in Edmonton in fall 2021 and then a larger outbreak in the feral domestic rabbit population in Calgary this fall.
This newer strain, RHDV2, is different from the previous one, which only infected European rabbits, from which household and feral rabbit populations are derived. The previous strain did not pose a threat to wild lagomorph species in North America.
However, that changed in 2020 when the RHDV2 strain spread into the wildlife lagomorph population in the southwest United States and northern part of Mexico, resulting in mass die-off of jackrabbit and cottontail populations.
If people do see dead native hare species in the Canmore area, they are asked to contact the Town of Canmore, the wildlife disease unit with the province or the Canadian Wildlife Health Cooperative node at the University of Calgary faculty of veterinary medicine.
“We are keeping a close eye on the native lagomorph species,” Davies said.
During the outbreak of the disease in Calgary in the fall, Davies said two animals submitted for testing as mountain cottontails were confirmed to have RHD.
“We are confirming that through genetic testing, just to make sure that they haven’t been confused with feral domestic rabbits,” she said.
The disease does not infect humans, but it is spread between rabbits through direct contact with infected saliva, runny nose and eyes, urine, manure, blood and infected fur or carcasses. It can also be spread by infected objects.
Van Gaal said the RHD poses no risk to human health.
“If people do find rabbit carcasses on their property, we recommend bagging and putting them in the bear-proof waste bins, and then we also recommend wearing gloves when doing so,” she said.
The disease, however, is a threat to pet rabbits.
“I think anyone who owns rabbits right now should be operating under heightened vigilance that this disease is circulating in the area,” Davies said.
There are several steps that owners of pet bunnies are advised to take, including reaching out to their vet and looking into the vaccine that is available to protect pet rabbits against this disease.
“There also is a need for heightened bio-security, because this is not the time for rabbits to be outside and potentially in contact with other wild rabbits,” Davies said.
“It’s maybe the time to limit visitors into your house that are interacting with the rabbit. The virus is quite hardy and can hitch a ride on things like food or clothing or hands, so changing shoes and clothing, washing hands with warm, soapy water before interacting with pet rabbits.”
Meanwhile, the Town of Canmore’s feral rabbit trapping program undertaken by an independent contractor is ongoing.
Feral rabbits, given their ability to draw large carnivores into town in search of a meal and are a non-native species in Canmore, were raised as a serious concern by the Bow Valley human-wildlife coexistence taskforce in 2018.
According to the municipality, $587,000 has been spent on the removal of 2,130 feral rabbits, at a cost of $275 per rabbit, since the program began in 2012.
“The intent is to still carry forward with that program,” Van Gaal said.
“There are still reports of rabbits in the community, as recently as yesterday, and we would like to continue the program moving forward as much as possible.”
