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Rocky Mountain Spotted Fever (RMSF)


Within our practice we have confirmed two cases of RMSF in Shiawassee County within the last year.


RMSF is a disease caused by the bacteria Rickettsia rickettskii and transmitted by ticks, which causes damage and inflammation within blood vessels.


Don’t be fooled by the name – although it was first discovered in the Rocky Mountains, RMSF is present in many other places, among them the Pacific Northwest, Southeastern states, and even Michigan, although it is less common here.


RMSF is spread via tick bites. The American Dog Tick, the most common tick in Michigan, can act as a vector for RMSF.


The tick must feed for 5–20 hours to pass the disease, which is a shorter period than many other tick-borne diseases. Many animal species can carry the bacteria, but only dogs and people become ill. The incubation period until clinic signs develop is 2 days to 2 weeks. People get RMSF only directly from ticks, not from dogs who have been infected.


In dogs the symptoms can include fever, swollen face and/or limbs, lethargy, muscle and/or joint pain, vomiting, diarrhea and decreased appetite. In people the disease can be quite serious and even fatal; symptoms include headache, muscle pain, swollen limbs, and rash.


Lab testing is required to diagnose Rocky Mountain Spotted Fever. The treatment is a long course of doxycycline. If diagnosed and treated early the prognosis is excellent.


Preventing tick bites is the best way to avoid getting RMSF and other tick-borne diseases. Use effective tick control that kills attached ticks in less than 10 hours. Call the clinic for more information on tick control products.


You can become infected from tick saliva. Wear disposable gloves when removing a tick from your pet and either flush the tick down a toilet or put it in a plastic bag.  If you want help identifying a tick, we are happy to help you with that or you can submit a picture to

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