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Signs and Symptoms

  • Rocky Mountain spotted fever, (RMSF) is the most severe rickettsiosis in the United States.

  • RMSF is a rapidly progressive disease and without early administration of doxycycline can be fatal within days.
  • Signs and symptoms of RMSF begin 3-12 days after the bite of an infected tick. However, because tick bites are not painful, many people do not remember being bitten.
  • Illness generally begins with sudden onset of fever and headache and most people visit a healthcare provider during the first few days of symptoms.

Early illness (days 1-4)

  • Fever
  • Headache
  • Gastrointestinal symptoms (nausea, vomiting, anorexia)
  • Abdominal pain (may mimic appendicitis or other causes of acute abdominal pain)
  • Myalgia
  • Rash (typically occurs 2-4 days after the onset of fever)
  • Edema around the eyes and on the back of hands

Late illness (day 5 or later)

  • Altered mental status, coma, cerebral edema
  • Respiratory compromise (pulmonary edema, acute respiratory distress syndrome)
  • Necrosis, often requiring amputation
  • Multiorgan system damage (CNS, renal failure)

Risk factors for severe illness

  • Delayed treatment
  • Children < 10 years
  • Persons with glucose-6-phosphate dehydrogenase (G6PD) deficiency

Rash

Early Stage of Rocky Mountain Spotted Fever

Figure 1: Example of an early-stage rash in an RMSF patient.

  • While most (90%) people with RMSF have some type of rash during the course of illness, less than 50% of patients have a rash during the first 3 days of illness, when most people first seek medical care. For this reason, clinicians should consider RMSF if other signs and symptoms support a diagnosis, even if a rash is not present.

Early Rash

  • A classic case of RMSF involves a rash that appears 2-4 days after the onset of fever as small, flat, pink, macules on the wrists, forearms, and ankles and spreads to include the trunk and sometimes the palms of hands and soles of feet.
  • Rash can be highly variable and people who fail to develop a rash, or develop an atypical rash, are at increased risk of being misdiagnosed.

Late Rash

  • The petechial rash of RMSF does not typically appear until day 5-6 of illness.
  • NOTE: Petechiae are a sign of severe disease. Every attempt should be made to treat before petechiae develop.

Infection in Children

  • Children represent less than 6% of spotted fever cases, but 22% of spotted fever fatalities.
  • Children with RMSF frequently report experiencing nausea, vomiting, loss of appetite, and rash, but are less likely to report a headache than adults.
  • Other frequently observed signs and symptoms in children with RMSF include abdominal pain, altered mental status, and edema involving the dorsum of the hands or around the eyes.
  • Children < 10 years are five times more likely than adults to die from RMSF.
  • Early treatment with doxycycline saves lives.
  • Doxycycline is the treatment of choice for adults and children of all ages.

RMSF the most severe spotted fever rickettsiosis in the United States. Similar, but less severe diseases caused by closely related bacteria can be easily confused with RMSF. Other spotted fevers in the United States include:

  • Rickettsia parkeri rickettsiosis, caused by parkeri
  • Pacific Coast tick fever, caused by Rickettsia 364D
  • Rickettsialpox, caused by Rickettsia akari

These diseases share many signs and symptoms, including fever, headache, and rash, but are typically less severe than RMSF. Patients with these spotted fevers can also show signs of an eschar (dark necrotic scab at the site of the arthropod bite). Eschars are not common in cases of RMSF.

Later Stage of Rocky Mountain Spotted Fever

Figure 2: Example of a later-stage rash in an RMSF patient.

Bloodwork

Healthcare providers should also look at routine blood tests, such as a complete blood cell count and a chemistry panel when making the diagnosis.

  • General laboratory findings can include thrombocytopenia, hyponatremia, or elevated levels of hepatic transaminases although these tests may not appear abnormal in early stages of illness.

Long-term Effects of RMSF

  • R. rickettsii infects the endothelial cells that line the blood vessels causing vasculitis. As infection continues, bleeding or clotting in the brain or other vital organs may occur.
  • Patients who had severe RMSF requiring prolonged hospitalization may have long-term health problems caused by disease:
    • Neurological deficits
    • Damage to internal organs
    • Vascular damage requiring amputation:
      • Loss of fluid from damaged vessels can result in loss of circulation to the extremities, fingers, toes or even limbs. Irreversible injury by ischemic damage may result in amputation of damaged tissue or digits.

Those who do not have this kind of vascular damage in the initial stages of the disease typically experience a full recovery.

  • No evidence of chronic disease: There is no evidence that rickettsii causes persistent or chronic disease.

For more in-depth information about signs and symptoms of RMSF, see: Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States: A Practical Guide for Health Care and Public Health Professionals (2016) [PDF – 48 pages]

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