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Rocky Mountain Spotted Fever, Emergency Medicine

Basics

Description

- Rash: - Initial rash (3 " “5 days) - Macular, red, and flat - Blanches under pressure - 1 " “4 mm diameter

- 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

- Neurologic: - Focal or generalized neurologic manifestation in 2/3 - Meningismus - Severe, unremitting headache - Encephalitis

- 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.

- Electrolytes, BUN/creatinine, glucose: - Liver profile: - Elevated aspartate aminotransferase - Lactate dehydrogenase

- 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

- 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.

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 statesDermacentor 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 flatBlanches under pressure1 " “4 mm diameterIn hours to days:Becomes darker, papular, dusky, and palpableIn 2 " “3 days:Petechial or purpuricPositive Rumpel " “Leede testMay coalesce or ulcerateIn severe disease, necrosis of dependent peripheral parts may occur.Location:Begins in flexor surfaces of wrist and ankles, rapidly spreading to palms and solesSpreads centripetally involving extremities; may involve trunk and face15% with centrifugal spread to palms and soles10% of patients do not have rashOften not identified when patient initially presents for care
  • Pulmonary:Nonproductive coughChest painDyspneaRales
  • GI:Often associated with fatal Rocky Mountain spotted feverSecondary to vasculitisNausea/vomitingAbdominal pain/distentionIleusHepatosplenomegaly
  • Neurologic:Focal or generalized neurologic manifestation in 2/3MeningismusSevere, unremitting headacheEncephalitis
  • Other:Generalized edemaDehydrationMalaiseMyalgiaRetinal hemorrhage and conjunctivitis
  • Complications:Disseminated intravascular coagulation (DIC)Noncardiogenic pulmonary edemaAcute renal failureSevere 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 symptomsMethods:Immunofluorescent antibody (sensitivity of 95%)Complement fixationIndirect hemagglutination testIndirect immunofluorescence assay is reference standard.
  • CBC:Normal WBC countThrombocytopeniaAnemia
  • Electrolytes, BUN/creatinine, glucose:
  • Liver profile:Elevated aspartate aminotransferaseLactate dehydrogenase
  • Arterial blood gas for:HypoxiaRespiratory alkalosis
  • Coagulation profile if DIC suspected
  • Microbiology:Immunohistologic antibody stain of skin biopsyIsolation 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 adultsRelapsing feverLyme disease: Erythema chronicum migransTularemiaBabesiosisColorado tick fever
  • Infectious diseases:Meningococcemia " ”late winter, early spring; maculopapular or petechial rashMeasles " ”late winter, early spring; severe prodromeRubella " ”palms and soles sparedVaricella " ”does not have rash in extremitiesViral exanthemInfectious mononucleosis " ”palms and soles sparedDisseminated gonococcal infection " ”pustular lesionsTyphus " ”rash starts at trunk with centrifugal spreadSecondary syphilisScarlet feverKawasaki disease " ”red, cracked lipsToxic shock syndromeGastroenteritisStaphylococcal sepsis
  • Inflammatory causes:Allergic vasculitisThrombotic thrombocytopenic purpuraCollagen vascular diseaseJuvenile 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 choiceChloramphenicol in pregnant and allergic patientsSulfonamides 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:DICAdult respiratory distress syndromeCHF
  • 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