Questions and Answers
- What is Rocky Mountain spotted fever?
- How do people get Rocky Mountain spotted fever?
- What are the symptoms of Rocky Mountain spotted fever?
- In the United States, where do most cases of Rocky Mountain spotted fever occur?
- How is Rocky Mountain spotted fever diagnosed?
- How is Rocky Mountain spotted fever treated?
- Can a person get Rocky Mountain spotted fever more than once?
- How can Rocky Mountain spotted fever be prevented?
- What is the best way to remove a tick?
- Do folklore remedies work?
What is Rocky Mountain spotted fever?
Rocky Mountain spotted fever (RMSF) is the most severe tick-borne rickettsial illness in the United States. This disease is caused by infection with the bacterial organism Rickettsia rickettsii.
The organism that causes Rocky Mountain spotted fever is transmitted by the bite of an infected tick. The American dog tick (Dermacentor variabilis) and Rocky Mountain wood tick (Dermacentor andersoni) are the primary athropods (vectors) which transmit Rocky Mountain spotted fever bacteria in the United States. The brown dog tick Rhipicephalus sanguineus has also been implicated as a vector as well as the tick Amblyomma cajennense in countries south of the United States.
Patients infected with R. rickettsii usually visit a physician in their first week of illness, following an incubation period of about 5-10 days after a tick bite. The early clinical presentation of Rocky Mountain spotted fever is often nonspecific and may resemble many other infectious and non-infectious diseases.
Initial symptoms of Rocky Mountain spotted fever may include:
- muscle pain
- lack of appetite
- severe headache
Later signs and symptoms of Rocky Mountain spotted fever include:
- abdominal pain
- joint pain
Three important components of the clinical presentation are fever, rash, and a previous tick bite, although one or more of these components may not be present when the patient is first seen for medical care. Rocky Mountain spotted fever can be a severe illness, and the majority of patients are hospitalized.
Rocky Mountain spotted fever is a seasonal disease and occurs throughout the United States during the months of April through September. Over half of the cases occur in the south-Atlantic region of the United States (Delaware, Maryland, Washington D.C., Virginia, West Virginia, North Carolina, South Carolina, Georgia, and Florida). The highest incidence rates have been found in North Carolina and Oklahoma. Although this disease was first discovered and recognized in the Rocky Mountain area, relatively few cases are reported from that area today.
A diagnosis of Rocky Mountain spotted fever is based on a combination of clinical signs and symptoms and specialized confirmatory laboratory tests. Other common laboratory findings suggestive of Rocky Mountain spotted fever include thrombocytopenia (decreased platelets), hyponatremia (low blood sodium), and elevated liver enzyme levels.
Rocky Mountain spotted fever is best treated by using a tetracycline antibiotic, usually doxycycline. This medication should be given in doses of 100 mg every 12 hours for adults or 4 mg/kg body weight per day in two divided doses for children under 45 kg (100 lbs). Patients are treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Standard duration of treatment is 5 to 10 days. Because laboratory confirmation is generally not available during acute illness, treatment is initiated based on clinical and epidemiological information.
Infection with R. rickettsii is thought to provide long lasting immunity against re-infection. However, prior illness with Rocky Mountain spotted fever should not deter persons from practicing good tick-preventive measures or visiting a physician if signs and symptoms consistent with Rocky Mountain spotted fever occur, especially following a tick bite, as other diseases may also be transmitted by ticks.
See the Tickborne Rickettsial Diseases prevention page for tips on preventing Rocky Mountain spotted fever.
See the Tickborne Rickettsial Diseases tick removal page for instructions on removing ticks.
No. Folklore remedies, such as the use of petroleum jelly or hot matches, do little to encourage a tick to detach from skin. In fact, they may make matters worse by irritating the tick and stimulating it to release additional saliva or regurgitate gut contents, increasing the chances of transmitting the pathogen. These methods of tick removal should be avoided. See the Tickborne Rickettsial Diseases tick removal page for instructions on the proper way to remove a tick.
- Page last reviewed: April 1, 2008
- Page last updated: April 1, 2008
- Content source: Division of Viral and Rickettsial Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases