Rocky Mountain spotted fever

Rocky Mountain spotted fever is caused by the bacterium Rickettsia rickettsii and transmitted by infected ticks, most commonly by the American dog tick (Dermacentor variabilis). Signs and symptoms include fever, headache, nausea, muscle pain and rash. Rocky Mountain spotted fever is currently not a Disease of Public Health Significance as human cases have been rare in Ontario with less than five human cases since 1979. The best prevention is to avoid tick bites by using insect repellent, wearing proper clothing, removing tick habitats from around the home, conducting regular tick checks and removing ticks as soon as possible after bites.

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Communicable Disease Control

Communicable.DiseaseControl@oahpp.ca

Published 22 Oct 2025