Author:
Roger M.Barkin
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 and ersoni (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
Signs and Symptoms
History
- Tick bite reported within 14 d of rash in 60% of patients
- Incubation varies 2-14 d with median 7 d
- Exposure to ticks, often in rural environment
Physical Exam
- Rash:
- Initial rash (3-5 d)
- Macular, red, and flat
- Blanches under pressure
- 1-4 mm diameter
- In hours to days:
- Becomes darker, papular, dusky, and palpable
- In 2-3 d:
- 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 of patients
- 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 illness more common in those who are advanced in age, male sex, African American, chronic alcohol abusers, or have glucose-6-phosphate dehydrogenase deficiency
Essential Workup
Clinical diagnosis supplemented by confirmatory lab findings such as hyponatremia, anemia, and thrombocytopenia
Diagnostic Tests & Interpretation
Lab
- Serology:
- Diagnose by single titer >1:64 or 4-fold increase. Antibody may not be detected in the first few days of symptoms
- Methods:
- Immunofluorescent antibody (sensitivity of 95%)
- Complement fixation
- Indirect hemagglutination test
- Indirect immunofluorescence assay is reference stand ard
- CBC:
- Normal WBC count
- Thrombocytopenia
- Anemia
- Electrolytes, BUN/creatinine, glucose:
- 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 (PCR) 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 and streptococcal sepsis
- 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
Prehospital
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
- Clinicians removing the tick should wear gloves, using fine forceps to grasp as close to the point of attachment. Pull outward with gentle traction, avoiding twisting or squeezing. Clean and disinfect the wound after removal
Pediatric Considerations |
- 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
|
Pregnancy Prophylaxis |
| Most experts recommend the use of doxycycline in pregnant women despite the inherent risks. There are significant complications of chloramphenicol in this population |
Medication
First Line
- Doxycycline: 100 mg (peds: 2.2 mg/kg for <45 kg) PO/IV b.i.d for 5-7 d. Patient should generally be treated 3 d beyond becoming afebrile
- In critically ill adult patients, consider 200 mg q12h for 72 hr, often given via the IV route
Second Line
- Acetaminophen: 500 mg (peds: 10-15 mg/kg/dose) PO q4h; do not exceed 5 doses/24 hr or 4 g/24 hr
- Chloramphenicol: 75 mg/kg/24 hr PO or IV q6h for 5-7 d and 48 hr after defervescence. Significant complications exist
- Solu-Medrol: 125 mg (peds: 1-2 mg/kg) IV
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
Follow-up Recommendations
Reflective of ongoing complications
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