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OTTAWA – Lyme disease is so prevalent in parts of Canada that many public health units now badume that if you get stung by a tick, you have to be treated for Lyme disease.
In Ottawa, where more than two-thirds of the ticks tested in some neighborhoods carry the bacteria that causes Lyme disease, the public health department does not care to test it at all.
Dr. Vera Etches, the unit's lead physician, said that in 2016 and 2017, more than one-fifth of the black-legged ticks tested in Ottawa had become positive for Lyme disease again.
"It's a threshold," she says. "Once you know that more than 20% of the ticks in your area carry the Lyme disease bacteria, we do not need to make sure of it, which is what we call now. a "risk area". "
This means that if a tick is found on a person and that it has remained there for more than 24 hours, the patient should receive antibiotics to prevent Lyme infection even without any tick tests. It takes 24 hours before bacteria in the tick's gut move to the salivary glands and are transferred to a person.
After three days, the preventive treatment no longer works, patients have to wait for the symptoms or enough time for the antibodies to develop and appear during the test. It may take more than a month before symptoms appear. They are generally similar to the effects of the flu, including fever and body aches, as well as, usually but not always, a rash. It usually takes about as long to antibodies to the immune system during a lab test.
If it is not treated, Lyme disease can cause serious diseases such as meningitis, but Etches does not hesitate to specify that, as it is caused by a bacterium, it can be treated with drugs.
"It's good news, in fact, that there are effective antibiotics for treating Lyme disease," she said.
Most public health units in Canada used to test ticks submitted by the public and conduct their own surveillance by actively searching for tick populations and testing them. Some, including those in Ottawa, have decided that now that Lyme disease is endemic, they should move on to public education, prevention, and treatment.
Lyme disease was named in honor of the city of Lyme, Connecticut, where the first case was diagnosed in 1975. It is caused by a bacterium exchanged between blacklegged ticks, migratory birds and small mammals such as mice and chipmunks. Ticks bite birds and small mammals infected with the bacteria and infect and then spread the disease when they bite their next victims.
Ten years ago, most cases diagnosed in Canada involved people bitten by ticks during a trip to the United States. But climate change has brought southern Canada to milder winters, which means ticks that migrate to Canada from the backs of migratory birds are now surviving in greater numbers in the winter, spreading faster the bacteria that cause Lyme disease.
Canada began monitoring cases of Lyme disease in 2009, while 144 cases were confirmed or considered probable. It is estimated that only 79 of these cases were contracted in Canada.
In 2017, more than 1,400 cases were confirmed or probable across the country, including more than two – thirds in Ontario and most of them would have been contracted locally.
National statistics for 2018 are not yet available, but in Ontario, their numbers have dropped significantly, from 967 in 2017 to 612 in 2018. Etches explained that it was because 2018 was hotter and drier than 2017 and that ticks thrived in cool and wet weather.
A 2014 study by the National Collaborating Center for Infectious Diseases at the University of Manitoba suggested that ticks carrying Lyme disease expanded their territory by about 46 km a year, an expectation confirmed by mapping of health units
In 2017 and 2018, Point Pelee National Park, near Windsor, Ontario, was considered a risk area, but the rest of Windsor-Esbad County, in the extreme south of Ontario, was considered a risk area. Ontario, was not. In 2019, almost the entire county was added to the list of risk areas.
By 2017, all of Nova Scotia was at risk of contracting Lyme disease.
In New Brunswick, six of the 15 counties were at risk in 2018.
There are also areas at risk for Lyme disease in southern Manitoba, northwestern Ontario, British Columbia and Quebec. Some cases of Lyme have been found in the other four provinces, but their numbers are very low and have generally been contracted elsewhere.
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