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Salem Health: Infectious Diseases & Conditions, 2nd Edition

Rocky Mountain Spotted fever

by Michelle Badash

Category: Diseases and conditions

Anatomy or system affected: Blood, cardiovascular system

Definition

Rocky Mountain spotted fever (RMSF) is a severe disease that is potentially fatal. The disease, which is spread by ticks, was first recognized in the Rocky Mountains area of the United States. RMSF is now found in most U.S. states.

Causes

RMSF is caused by the bacterium Rickettsia rickettsii, which is carried by the American dog tick and the Rocky Mountain wood tick. When an infected tick bites a human, the disease is passed through the person’s skin into the bloodstream. The bacteria multiply inside cells of the inner lining of small arteries, causing inflammation. The inflammation is known as vasculitis.

A male Dermacentor tick, a vector for Rocky Mountain spotted fever. Image courtesy of the CDC via the Public Health Image Library.

Infect2e_p0935_1.jpg

Risk Factors

Factors that increase the chance of getting RMSF include exposure to tick-infested areas, contact with pets that roam in tick-infested areas, being outdoors often during the months of April to September, and residing in or visiting states where RMSF occurs most commonly. These states include, but are not limited to, Arkansas, Georgia, Kentucky, North Carolina, South Carolina, Oklahoma, Tennessee, and Virginia. At higher risk are men, children, and young adults.

Symptoms

The first symptom of RMSF is a sudden high fever that often occurs within one to fourteen days of a tick bite. Other symptoms may include nausea, vomiting, muscle pain, a lack of appetite, and a severe headache. Later signs may include a rash, abdominal pain, joint pain, diarrhea, a cough, irritability, insomnia, lethargy, confusion, delirium (or, in severe cases, coma), and an enlarged liver, spleen, and lymph nodes. In severe cases, symptoms include low blood pressure and shock.

Screening and Diagnosis

A doctor will ask about symptoms and medical history and will perform a physical exam. RMSF can be difficult to diagnose because it resembles other diseases. Three indicators that the doctor will look for are a fever, a rash (which may not be present early), and a history of a tick bite (which is not always known by the patient). Blood tests may be done to confirm the diagnosis. Treatment is often started based on a best guess. Doctors sometimes fail to consider RMSF as a diagnosis when adults or children present with only a high fever. One should be sure the doctor knows if the patient has been outdoors.

Treatment and Therapy

RMSF is treated with antibiotics, and it is important to start this treatment early. The most commonly used antibiotics in treating RMSF are doxycycline and tetracycline.

Prevention and Outcomes

The best way to prevent RMSF is to limit one’s exposure to ticks. Persons who live in areas that are prone to ticks should take the following precautions: wear light-colored clothing; tuck pants into socks; apply insect repellents containing NN-diethyl metatoluamide, or DEET, to exposed skin; and apply permethrin to clothing. For young children, DEET should be avoided or used sparingly. After returning from outdoor areas, one should carefully check for ticks and should also check pets for ticks.

Further Reading

1 

Bratton, R. L., and G. R. Corey. “Tick-Borne Disease.” American Family Physician 71 (2005): 2323.

2 

Chen, Luke F., and Daniel J. Sexton. “What’s New in Rocky Mountain Spotted Fever?” Infectious Disease Clinics of North America 22 (2008): 415-432.

3 

EBSCO Publishing. DynaMed: Rocky Mountain Spotted Fever. Available through http://www.ebscohost.com/dynamed.

4 

Goddard, Jerome. Physician’s Guide to Arthropods of Medical Importance. 4th ed. Boca Raton, Fla.: CRC Press, 2003.

5 

Schlossberg, David, ed. Infections of Leisure. 4th ed. Washington, D.C.: ASM Press, 2009.

6 

Vanderhoof-Forschner, Karen. Everything You Need to Know About Lyme Disease and Other Tick-Borne Disorders. 2d ed. Hoboken, N.J.: John Wiley & Sons, 2003.

7 

Walker, David H. “Rickettsia rickettsii and Other Spotted Fever Groups.” In Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John F. Bennett, and Raphael Dolin. 7th ed. Philadelphia: Churchill Livingstone/Elsevier, 2009.

Web Sites of Interest

Centers for Disease Control and Prevention

http://www.cdc.gov/ticks

Public Health Agency of Canada

http://www.phac-aspc.gc.ca

See also: Anaplasmosis; Arthropod-borne illness and disease; Behçet’s syndrome; Bubonic plague; Cat scratch fever; Colorado tick fever; Ehrlichiosis; Encephalitis; Fever; Giardiasis; Hemorrhagic fever viral infections; Inflammation; Lyme disease; Mediterranean spotted fever; Plague; Rickettsia; Ticks and infectious disease; Tularemia; Vectors and vector control; Zoonotic diseases.

Citation Types

Type
Format
MLA 9th
Badash, Michelle. "Rocky Mountain Spotted Fever." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0500.
APA 7th
Badash, M. (2020). Rocky Mountain Spotted fever. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Badash, Michelle. "Rocky Mountain Spotted Fever." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed December 14, 2025. online.salempress.com.