Rocky Mountain Spotted Fever

Most ticks don’t carry the bacteria, so there’s little risk of getting the disease even if bitten, but knowing what symptoms to look for can be a big help in getting quick treatment if you are infected - Mukesh Patel MD

Rocky Mountain Spotted Fever
Rocky Mountain Spotted Fever

image by: Navajo Nation CHR/Outreach Program

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Major Misnomer: 8 things you need to know about Rocky Mountain spotted fever

1. You don’t have to be in the Rocky Mountains to catch RMSF. There are four types of ticks in the U.S. that can transmit this bacteria to you: the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), brown dog tick (Rhipicephalus sanguineus), and the Cayenne tick (Amblyomma cajennense). Cases of RMSF have been reported all over the U.S., and there have also been some in Canada. In 2008, all but 8 states reported cases of RMSF to the CDC.

2. Rocky Mountain spotted fever can be a deadly disease if not treated promptly. The national fatality rate is about 3%, but this rate is much higher in certain states…

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 Major Misnomer: 8 things you need to know about Rocky Mountain spotted fever

One of the better reviews of RMSF.

American Lyme Disease Foundation

Rocky Mountain spotted fever (RMSF) is the most serious tick-borne disease in the United States and is caused by Rickettsia rickettsii, a type of bacteria known as rickettsia. These bacteria are transmitted to humans by the bite of certain hard ticks. The two most important species of ticks that can transmit R. rickettsii in the United States are Dermacentor variabilis (the American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick).

Lyme and Tick-borne Diseases Research Center

Rocky Mountain spotted fever (RMSF) is one of about a dozen spotted fever illnesses found in the Americas, Europe, Asia and Australia. All are caused by bacteria belonging to the genus Rickettsia, a group of pleomorphic (shape-changing), non-motile microbes that replicate only inside of eukaryotic host cells.

The Tick That Bit Me

Infection with Rickettsia rickettsii bacteria transmitted through a tick bite. Humans can also become infected by squashing ticks with their bare hands. Types of ticks that spread RMSF include: the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), brown dog tick (Rhipicephalus sanguineus), and the Cayenne tick (Amblyomma cajennense). “Rocky Mountain” is a misnomer, as many cases have also been reported in the eastern United States.

Tick Encounter

Rocky Mountain Wood ticks are found predominantly in shrublands, lightly wooded areas, open grasslands, and along trails, mainly at lower elevations. All life stages of this tick can transmit Colorado tick fever virus (CTFV) to humans, and Rocky Mountain spotted fever (RMSF) rickettsia (Rickettsia rickettsii) to humans, cats, and dogs.


Rocky Mountain spotted fever can be a severe or even fatal illness if not treated in the first few days of symptoms. Doxycycline is the first line treatment for adults and children of all ages, and is most effective if started before the fifth day of symptoms. The initial diagnosis is made based on clinical signs and symptoms, and medical history, and can later be confirmed by using specialized laboratory tests. RMSF and other tickborne diseases can be prevented.


Although RMSF is most common in the southeastern part of the United States (Virginia, Georgia, and the Carolinas), it occurs in other states as well. It's relatively rare (about 250 to 2,000 cases per year in the United States), but can be a serious disease if not treated properly.


Although it was first identified in the Rocky Mountains, Rocky Mountain spotted fever is most commonly found in the southeastern part of the United States. It also occurs in parts of Canada, Mexico, Central America and South America. Early signs and symptoms of Rocky Mountain spotted fever include severe headache and high fever. A few days later, a rash usually appears on the wrists and ankles. Rocky Mountain spotted fever responds well to prompt treatment with antibiotics.


RMSF is a potentially serious tick-borne disease that can cause fatalities, and it is the most common cause of fatal tick-borne diseases in the United States.

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