Rocky Mountain spotted fever natural history

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Overview

If left untreated patients with Rocky Mountain spotted fever will undergo three developmental stages of infection. The early stages of infection begin within 2-14 days of inoculation by an infected tick and present themselves as a fever, nausea, vomiting, and a severe headache. Late stage progression of symptoms will result in a maculopapular rash, abdominal and joint pain. Further progression of the disease, if left untreated, will result in the following complications; gangrene, pulmonary complications, ARDS, cerebral edema as well as other long term complications. Ultimately, if Rocky Mountain spotted fever progresses entirely untreated, it will conclude in the patient's death. With a fatality rate as high as 87%, without antibiotic intervention. [1] [2]

Natural history

Rocky Mountain spotted fever patients will progress from early symptoms to late symptoms and possible chronic conditions, as well as death, if left untreated. The infection begins with inoculation of the disease from an infected tick. Once inoculated, the organism Rickettsia rickettsii will incubate for 2- 14 days. As the incubation period concludes early onset symptoms will begin, these symptoms are listed below.

Early onset symptoms

Treatment is most effective if an antibiotic therapy is administered at this point. As the disease progresses, treatment loses effectiveness, thus it is of utmost importance to diagnose and begin treatment early on. Most individuals who begin treatment will usually clear the infection.

After the first three days of early onset symptoms, other symptoms will progress. These symptoms are described as late stage symptoms and will include the characteristic rash that is commonly associated with Rocky Mountain spotted fever. Not all patients will have the same clinical presentation of the disease. Particularly, the rash is present within the majority of infected patients, yet 10-15% of patients may never develop the characteristic spotted rash. If the infection progresses in severity, patients will be hospitalized at this point. Late stage symptoms may be observed below.

Late stage

With proper treatment and antibiotic therapy, most patients will have cleared the infection. However, if left untreated or improperly diagnosed, Rocky Mountain spotted fever will progress further and may involve chronic complications or severe tissue damage as well as death. Complications and chronic conditions associated with untreated development of Rocky Mountain spotted fever are found below.

Untreated or improperly diagnosed

Complications

Possible complications include:

Long term complications
  • Paralysis of lower extremities
  • Impaired bladder function
  • Impaired bowel function
  • Gangrene and amputation
  • Hearing impairment
  • Movement and speech disorders[3]
  • These complications are most frequent in persons recovering from severe, life-threatening disease, often following lengthy hospitalizations. [5]

Prognosis

  • The prognosis is usually good for patients suffering from a Rocky Mountain spotted fever infection.
  • Factors that might contribute to a poor prognosis are infections within children 0-9, especially 5-9, and adults over 60 years of age. With a higher rate of fatality within these groups.
  • Other host factors associated with severe or fatal Rocky Mountain spotted fever include advanced age, male sex, African-American race, chronic alcohol abuse, and

glucose-6-phosphate dehydrogenase (G6PD) deficiency.

  • It should be noted that although the prognosis is usually good, RMSF is a severe illness and many infected patients will be hospitalized.
  • The mortality rate is approximately 20% if untreated and 5% if treated properly. [2]
  • Infection with R. rickettsii may provide long lasting immunity against re-infection.
  • Previous infection 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. [6]

References

  1. 1.0 1.1 1.2 Mills, Jackie. Rocky Mountain Spotted Fever. Austin CC. Derived: Masters, E. J., G. S. Olson, S. J. Weiner, and C. D. Paddock. 2003. Rocky Mountain spotted fever: a clinician’s dilemma. Archive of Internal Medicine 163:769–774. http://archinte.ama-assn.org/cgi/content/full/163/7/769 Accessed January 11, 2016
  2. 2.0 2.1 Dantas-Torres, Filipe. Lancet Infect Disease 2007;7:724-32. Department of Immunology, Center of Research Aggeu Magalhaes, Oswaldo Cruz Foundation. Recife Pernambuco, Brazil. Volume 7, November 2007. Accessed on January 11, 2016
  3. 3.0 3.1 Rocky Mountain Spotted Fever general information. American Lyme Disease Foundation (2016). Accessed on January 11, 2016
  4. Rocky Mountain Spotted Fever Symptoms. Centers for Disease Control and Prevention (2015). http://www.cdc.gov/rmsf/symptoms/index.html Accessed on December 30, 2015
  5. Rocky Mountain Spotted Fever Symptoms. Centers for Disease Control and Prevention (2015). http://www.cdc.gov/rmsf/symptoms/index.html Accessed on December 30, 2015
  6. Rocky Moutnain Spotted Fever. Department of Health. Idaho Health District 4. http://www.cdhd.idaho.gov/CD/public/factsheets/rockymtnspottedfever.htm Accessed on January 11, 2016