Once limited to the western United States, the disease has now appeared in Quebec and Ontario — with climate change driving its spread.

In recent days, parts of Quebec and Ontario have reported the return of a bacterial disease transmitted to humans mainly through tick bites, often carried by ticks that live on dogs.

What is Rocky Mountain Spotted Fever?

Rocky Mountain Spotted Fever (RMSF) is a serious infection caused by the bacterium Rickettsia rickettsii. People can get it from the bite of infected ticks, including the American dog tick, the Rocky Mountain wood tick, and, in some areas, the brown dog tick. In Canada, the brown dog tick is mostly found indoors, where dogs live and does not survive well in the wild.

After a tick bite, the bacteria enter the bloodstream and damage the lining of blood vessels. This causes inflammation and leaking, which can harm important organs.

Symptoms and Diagnosis

Symptoms usually appear three to twelve days after a tick bite and include high fever, severe headache, muscle pain, nausea, and fatigue. A characteristic rash often appears two to five days after the fever begins, starting on the wrists and ankles before spreading to the trunk, and sometimes the palms and soles.

About ten percent of people with RMSF never get a rash, and less than half have one in the first three days. This means the rash is not always a good sign for early diagnosis. Tiny spots of bleeding under the skin, called petechiae, can appear later and show that the disease is severe. Children under ten are more likely to get seriously ill.

It can be hard to diagnose RMSF early because the symptoms look like those of common illnesses such as the flu. Blood tests and biopsies can confirm RMSF, but they often do not work well in the early stages. Doctors usually start treatment based on symptoms and whether you might have been exposed to ticks.

Treatment and Complications

Doctors recommend doxycycline for everyone, including children and pregnant women. Treatment should start right away and last at least five to seven days, and continue for three days after the fever goes away. Most people feel better within one or two days. If there is no improvement, doctors will look for other causes.

If not treated, up to 20 to 30 percent of people with RMSF may die. With quick treatment, the risk drops to less than one percent. But if treatment is delayed, the risk can rise to 40 to 50 percent. Severe cases can cause lasting nerve damage, problems with organs, or even gangrene that may require amputation.

Recent Spread in Canada

Until recently, RMSF was rare in Canada, with only a handful of cases—between zero and three annually—reported in British Columbia. In August 2025, the first locally acquired case in Quebec’s Eastern Townships was confirmed; the patient recovered after doxycycline treatment.

In July 2025, several dogs in Long Point, Ontario, were diagnosed with RMSF, one of them fatally. These cases suggest that infected ticks are spreading in eastern Canada.

Climate Change and Tick Expansion

Warmer weather and longer summers are helping ticks live and spread in more places. More rodents and deer also mean more ticks. Because of climate change, ticks are now found in new areas of Canada.

Key Health Notes

• RMSF is not spread directly from person to person.

• Dogs can carry infected ticks into homes.

• Prevention focuses on avoiding tick bites:

• 8Use repellents with DEET or icaridin.

• Wear clothing treated with permethrin.

• Choose long, light-colored clothing outdoors.

• Check your body and clothes after being in wooded or grassy areas.

• Remove ticks quickly with tweezers.

• There is currently no commercial human vaccine for RMSF, though experimental vaccines were tested in the 1920s.

Historical Background

RMSF was first described in Montana in the late 19th century and was called “black fever” because of its bloody rash and high fatality. In 1906, microbiologist Howard Ricketts identified the bacterium that causes the disease, which now bears his name. In the 1920s, scientists attempted to produce serums and vaccines, but the real breakthrough came in the 1940s with the introduction of tetracycline antibiotics, which sharply reduced mortality.

Rocky Mountain Spotted Fever is still rare, but it is a serious disease. Its recent cases in Quebec and Ontario show that climate change is helping ticks and their diseases spread to new places. It is important to recognize symptoms early and start treatment with doxycycline quickly. Raising public awareness and keeping a close watch on tick populations can help stop RMSF from becoming a bigger health problem in Canada.

Frequently Asked Questions

Personal risk – How likely am I or my family to encounter infected ticks in my area?

Right now, Rocky Mountain Spotted Fever is still rare in Canada. Most cases have happened in the United States, especially in the south-central and southeastern areas. In Canada, there have only been a few cases in British Columbia and, more recently, some in Quebec and Ontario. This means the risk is low, but not zero, especially if you spend time outdoors in grassy, brushy, or wooded places where ticks live. The risk is higher during the warmer months, from spring to fall.

Tick removal – What is the safest and most effective way to remove a tick if I find one?

The safest way to remove a tick is with fine-tipped tweezers. Hold the tick close to the skin and pull straight up with steady pressure. This helps keep the mouthparts from breaking off in the skin. After you remove the tick, wash the bite area and your hands with soap and water or use an alcohol-based sanitizer. Do not use petroleum jelly, matches, or chemicals, as these are ineffective and may raise the risk of infection.

Symptoms – What should I do if I develop symptoms after a tick bite, and how quickly should I seek medical help?

If you get a fever, a bad headache, muscle pain, nausea, or a rash within a few days to two weeks after a tick bite, see a doctor right away. Do not wait for a rash, since some people never get one. Early treatment is very important. Antibiotics like doxycycline work best when started quickly, and waiting too long can make the illness much more serious or even deadly.

Pets – How can I protect my pets from ticks and prevent them from bringing ticks indoors?

Pets, especially dogs, can carry ticks indoors. Protect them by:

• Using veterinarian-recommended tick prevention products (topical treatments, oral medications, or tick collars).
• Checking your pet’s fur and skin regularly, especially after being outdoors.
• Keeping grass and shrubs trimmed in yards to reduce tick habitats.
• Washing pet bedding frequently.
• Consult your veterinarian for the best prevention strategy for your region and your pet’s health.