Rocky Mountain spotted fever

Notifiable disease. Can be fatal if not treated early.

Doxycycline is the drug of choice for treatment in patients of all ages and is almost always curative, especially if given in the first 5 days of illness. As the risk of death rises if appropriate therapy is not started before the fifth day of illness, doxycycline should be prescribed for suspected disease before confirmatory diagnostic test results are available.

Signs and symptoms may be difficult to distinguish from those of common viral illnesses, leading to delayed diagnosis. Diagnosis should be considered in any person with a compatible clinical presentation and recent outdoor exposure.

A characteristic eschar or scab at the site of the tick bite is absent, in contrast to infections due to other tick-borne spotted fever group rickettsiae. A history of tick bite may not be elicited in up to nearly half of cases.

Rocky Mountain spotted fever (RMSF) is a systemic vasculitis caused by infection with Rickettsia rickettsii, a tick-borne, gram-negative, intracellular bacterium.[1]Biggs HM, Behravesh CB, Bradley KK, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever and other spotted fever group rickettsioses, ehrlichioses, and anaplasmosis - United States. MMWR Recomm Rep. 2016;65:1-44. http://www.cdc.gov/mmwr/volumes/65/rr/rr6502a1.htm http://www.ncbi.nlm.nih.gov/pubmed/27172113?tool=bestpractice.com Rickettsia rickettsii is one of the spotted fever group (SFG) rickettsiae and is closely related to the other group members by genetic and antigenic characteristics. It is the most frequently reported SFG rickettsial infection in North America and the most common fatal tick-borne infection in the US.[2]Drexler NA, Dahlgren FS, Heitman KN, et al. National surveillance of spotted fever group rickettsioses in the United States, 2008-2012. Am J Trop Med Hyg. 2016;94:26-34. http://www.ncbi.nlm.nih.gov/pubmed/26324732?tool=bestpractice.com [3]Openshaw JJ, Swerdlow DL, Krebs JW, et al. Rocky mountain spotted fever in the United States, 2000-2007: interpreting contemporary increases in incidence. Am J Trop Med Hyg. 2010;83:174-182. http://www.ajtmh.org/content/83/1/174.long http://www.ncbi.nlm.nih.gov/pubmed/20595498?tool=bestpractice.com Detailed content on other rickettsial infections is covered by our separate Rickettsial Diseases topic.