Rocky Mountain Spotted Fever, Emergency Medicine

Basics

Description

Rickettsial invasion of small blood vessels: ‚

Causes direct vascular damage
Superimposed additional vascular damage/vasculitis due to immunologic phenomena

Etiology

Acute infection by Rickettsia rickettsii via tick vector:
- Dermacentor andersoni (wood tick) in the western states
- Dermacentor variabilis (dog tick) in the eastern states
Reported in all states; 1/2 of cases occur in 5 states (NC, SC, TN, OK, AR), as well as parts of Central America and South America
More common April " “September, but can occur any month
More common in males and in individuals 40 " “64 yr of age

Diagnosis

Signs and Symptoms

History

Tick bite reported within 14 days of rash in 60% of patients
Incubation varies 2 " “14 days with median 7 days
Exposure to ticks, often in rural environment

Physical Exam

Rash:
- Initial rash (3 " “5 days)
  - Macular, red, and flat
  - Blanches under pressure
  - 1 " “4 mm diameter
- In hours to days:
  - Becomes darker, papular, dusky, and palpable
- In 2 " “3 days:
  - Petechial or purpuric
  - Positive Rumpel " “Leede test
  - May coalesce or ulcerate
- In severe disease, necrosis of dependent peripheral parts may occur.
- Location:
  - Begins in flexor surfaces of wrist and ankles, rapidly spreading to palms and soles
  - Spreads centripetally involving extremities; may involve trunk and face
  - 15% with centrifugal spread to palms and soles
  - 10% of patients do not have rash
  - Often not identified when patient initially presents for care
Pulmonary:
- Nonproductive cough
- Chest pain
- Dyspnea
- Rales
GI:
- Often associated with fatal Rocky Mountain spotted fever
- Secondary to vasculitis
- Nausea/vomiting
- Abdominal pain/distention
- Ileus
- Hepatosplenomegaly
Neurologic:
- Focal or generalized neurologic manifestation in 2/3
- Meningismus
- Severe, unremitting headache
- Encephalitis
Other:
- Generalized edema
- Dehydration
- Malaise
- Myalgia
- Retinal hemorrhage and conjunctivitis
Complications:
- Disseminated intravascular coagulation (DIC)
- Noncardiogenic pulmonary edema
- Acute renal failure
- Severe or fatal in advanced age, male sex, African American, chronic alcohol abuse, glucose-6-phosphate dehydrogenase deficiency

Essential Workup

Clinical diagnosis supplemented by confirmatory lab findings such as hyponatremia, anemia, and thrombocytopenia ‚

Diagnosis Tests & Interpretation

Lab

Serology:
- Diagnose by single titer >1:64 or 4-fold increase. Antibody may not be detected in the 1st few days of symptoms
- Methods:
  - Immunofluorescent antibody (sensitivity of 95%)
  - Complement fixation
  - Indirect hemagglutination test
  - Indirect immunofluorescence assay is reference standard.
CBC:
- Normal WBC count
- Thrombocytopenia
- Anemia
Electrolytes, BUN/creatinine, glucose:
- Hyponatremia <130 mEq/L
Liver profile:
- Elevated aspartate aminotransferase
- Lactate dehydrogenase
Arterial blood gas for:
- Hypoxia
- Respiratory alkalosis
Coagulation profile if DIC suspected
Microbiology:
- Immunohistologic antibody stain of skin biopsy
- Isolation of R. rickettsii (time-consuming/expensive)
- Polymerase chain reaction assay
CSF:
- Pleocytosis and increased protein

Imaging

Chest radiograph for pulmonary edema, pneumonia
Echocardiography:
- Decreased left ventricular contractility

Diagnostic Procedures/Surgery
Skin biopsy may be confirmatory if immunohistologic antibody studies available. ‚

Differential Diagnosis

Other tick-borne diseases:
- Ehrlichiosis: Older adults
- Relapsing fever
- Lyme disease: Erythema chronicum migrans
- Tularemia
- Babesiosis
- Colorado tick fever
Infectious diseases:
- Meningococcemia " ”late winter, early spring; maculopapular or petechial rash
- Measles " ”late winter, early spring; severe prodrome
- Rubella " ”palms and soles spared
- Varicella " ”does not have rash in extremities
- Viral exanthem
- Infectious mononucleosis " ”palms and soles spared
- Disseminated gonococcal infection " ”pustular lesions
- Typhus " ”rash starts at trunk with centrifugal spread
- Secondary syphilis
- Scarlet fever
- Kawasaki disease " ”red, cracked lips
- Toxic shock syndrome
- Gastroenteritis
- Staphylococcal sepsis
Inflammatory causes:
- Allergic vasculitis
- Thrombotic thrombocytopenic purpura
- Collagen vascular disease
- Juvenile rheumatoid arthritis
Heat illness

Treatment

Pre-Hospital

Stabilize as appropriate ‚

Initial Stabilization/Therapy

ABC management
0.9% NS IV fluid bolus for dehydration
Oxygen for hypoxia

Ed Treatment/Procedures

Correct fluid and electrolyte deficits.
Initiate antibiotic therapy immediately based on clinical and epidemiologic findings. Should not be delayed until lab confirmation is obtained:
- Doxycycline " ”drug of choice
- Chloramphenicol in pregnant and allergic patients
- Sulfonamides make infection worse.
Administer acetaminophen for fever.
Consider high-dose steroids for severe cases complicated by extensive vasculitis, encephalitis, or cerebral edema (controversial).
Better outcome in children if treatment begins before day 5 of illness
Treat complications:
- DIC
- Adult respiratory distress syndrome
- CHF
Medication

Highest incidence in 5 " “9 yr olds
2/3 of cases occur in children <15 yr.
Doxycycline is used in children due to potential for fatal cases, the relatively low risk of significant dental discoloration with a short course, and adverse effects of chloramphenicol

Use chloramphenicol in pregnant patients. ‚

Medication

First Line
Doxycycline: 100 mg (peds: 2 mg/kg for <45 kg) PO or IV BID for 5 " “7 days. Patient should generally be treated 2 " “3 days beyond becoming afebrile. ‚
Second Line

Acetaminophen: 500 mg (peds: 10 " “15 mg/kg/dose) PO q4h; do not exceed 5 doses/24 h or 4 g/24 h
Chloramphenicol: 75 mg/kg/24 h PO or IV q6h for 5 " “7 days and 48 hr after defervescence
Solu-Medrol: 125 mg (peds: 1 " “2 mg/kg) IV

Follow-Up

Disposition

Admission Criteria
Moderate to severe symptoms ‚
Discharge Criteria

Mild, early disease with early treatment
Notify family because of clustering and potential exposures.

Issues for Referral
Reflective of defined complications ‚

Followup Recommendations

Reflective of ongoing complications ‚

Pearls and Pitfalls

Early treatment based on the clinical presentation and epidemiology is indicated. ‚

Additional Reading

Buckingham ‚ SC, Marshall ‚ GS, Schutze ‚ GE, et al. Clinical and laboratory features, hospital course, and outcome of Rocky Mountain spotted fever in children. J Pediatr. 2007;150:180 " “184.
Centers for Disease Control and Prevention. Tickborne rickettsial diseases. Rocky Mountain spotted fever. Available at http://www.cdc.gov/ticks/diseases/rocky_mountain_spotted_fever./ Updated April 30, 2012.
Chapman ‚ AS, Bakken ‚ JS, Folk ‚ SM, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichiosis and anaplasmosis " “United States: A practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep. 2006;55(RR-4):1 " “27.
Chen ‚ LF, Sexton ‚ DJ. Whats new in Rocky Mountain spotted fever? Infect Dis Clin North Am. 2008;22:415 " “432.
Masters ‚ EJ, Olson ‚ GS, Weiner ‚ SJ, et al. Rocky Mountain spotted fever: A clinician's dilemma. Arch Intern Med. 2003;163:769 " “774.

Codes

ICD9

082.0 Spotted fevers ‚

ICD10

A77.0 Spotted fever due to Rickettsia rickettsii ‚

SNOMED

186772009 Rocky Mountain spotted fever (disorder)
240616003 Eastern Rocky Mountain spotted fever
240615004 Western Rocky Mountain spotted fever

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