October 23, 2024
Zoonotic diseases in Canada
Be informed, be aware and stay safe
BY J LYNN FRASER
In urban Canada we tend to forget that ordinary animals, birds and the landscape itself can be harmful if certain conditions occur. One such harm is found in zoonotic diseases. Zoonosis is “any disease or infection that is naturally transmissible from vertebrate animals to humans” (WHO, 2020).
Several zoonotic diseases that cause illness in landscapers and horticulturalists are present in Canada.
Bird flu / avian influenza A / H5N1
Bird flu can spread between birds, as well as between birds and mammals — including humans. Wild aquatic birds can carry bird flu and pass it on to domestic birds like chickens, ducks and turkeys. As of August 2024, five Canadian provinces had reported incidences of bird flu, with no human infections. In the U.S., as of April 2024, there have been 13 reports of human infections.
Measures to prevent bird flu include avoiding sick birds that have symptoms such as coughing and sneezing as well as lacking energy or movement. Also avoid animals lacking energy and showing neurological signs. Human infections are rare and symptoms may be mild, such as coughing and shortness of breath. It is important to be aware of the presence of backyard poultry and pets that may have been exposed to infected birds. A severe infection can include pneumonia and fevers — even death. Washing hands with soap and water, and avoiding touching one’s nose, eyes and mouth is critical. Wearing a good fitting N95 respirator or mask is advised.
Lyme disease and babesiosis
Lyme disease is found in every province. Infected blacklegged (deer) ticks transmit the disease through their bite after latching on for 24 hours, then transmitting the bacteria, which carries Lyme disease, to people and pets. If Lyme disease has been transmitted a rash will appear within three to 30 days in a bull’s eye pattern. Along with the rash, Infection Prevention and Control Canada (IPAC) says fever, chills, fatigue, body aches and a headache may occur. In the weeks that follow, joint pain, nausea and vomiting, diffuse rash and neurological problems, as well as heart problems, eye inflammation, liver inflammation (hepatitis) and severe fatigue may develop.
Staying out of areas known to have ticks in the spring and fall is a preventative measure. Ticks are often found in moist, shaded environments — especially leafy wooded areas and overgrown grassy habitats.
Babesiosis is also transmitted by blacklegged ticks in Canada, as is Anaplasma phagocytophilum and Powassan virus. According to Public Health Ontario, symptoms of a Babesiosis infection include fever, chills, sweats, headache, body aches, loss of appetite, nausea and fatigue. Infection may also produce hemolytic anemia, with symptoms including fatigue, jaundice, dark urine, thrombocytopenia and renal failure.
Mosquito-borne diseases (MBDS)
Some diseases need “reservoir hosts” to be passed on to humans, says the Canadian Centre for Occupational Health and Safety (CCOHS). West Nile virus and Eastern equine encephalitis (EEE), seen recently in Massachusetts, are found in wild birds. Deer spread Jamestown Canyon virus. Squirrels, chipmunks, hares, rabbits and rodents spread Snowshoe hare virus. St. Louis encephalitis is found in wild birds, domestic fowl and bats.
People infected by MBDs do not always show symptoms. However, symptoms may appear after several days to two weeks and may include fever, fatigue, headache, nausea, vomiting and rashes. The CCOHS also states that those with serious manifestations of MBDs will “develop inflammation of the brain, spinal cord or the membranes that protect the brain and spinal cord (conditions called encephalitis, myelitis and meningitis).”
Dr. Isaac Bogoch, associate professor at the University of Toronto’s Department of Medicine and an infectious diseases specialist and general internist at the Toronto General Hospital, advises landscapers and horticulturalists to be aware that “fresh and free standing water, of which Canada has a lot of, are insect breeding grounds.” Awareness of grass, weeds, wooded and shaded areas is also wise. Caution should be shown when outdoors between May and September, especially at dusk or dawn, and when around animals that could carry MBDs.
Dr. Lynora Saxinger, professor in the University of Alberta’s Division of Infectious Diseases, advises using a repellent like Icaridin (Picaridin) or DEET to help against tick- and mosquitoborne diseases. She suggests wearing light coloured clothing, which makes it easier to spot ticks, and covering the ankle area on pants by tucking them into socks. “There is also pre-treated travel clothing available,” says Saxinger. Other measures include performing daily full body checks and remembering to shower or bathe within two hours of being in forested or long grass areas.
In general, being aware of the environment in which you work is important. Contact with an infected animal may be direct, such as through animal saliva, blood, urine or feces, or indirect, through exposure to contaminated surfaces or objects, including animal habitats, contaminated air or receiving a scratch from an infected animal. It also includes consuming food or water contaminated by animals.
Rabies
A bite from a rabid animal to a human is rare in Canada, but the consequences are fatal. In Canada, bats, skunks, raccoons and foxes are most likely to transmit rabies. According to the Government of Canada, 26 people have died in the country due to rabies since 1924. In September 2024, an Ontario resident was confirmed to have been bitten by a bat and now has rabies. A friendly animal may be an infected one. To prevent being bitten, be aware of animals showing excessive salivation, abnormal behaviour, weakness and clumsiness.
The future
Climate change is making Canada more hospitable to ticks and mosquitoes, enabling them to extend their range. As a result, Canadians are exposed to tick- and mosquito-borne diseases that were not a concern in the past, such as St. Louis encephalitis, Rift Valley fever, Japanese encephalitis, and La Crosse, Dengue and Chikungunya viruses.
Dr. Bogoch comments that due to climate change, some diseases found in Central and South America and in the southern U.S. are now travelling northward. Dr. Saxinger notes that southern Canada will experience these changes and local public health notices are a good way to stay informed.