Transcript Rocky Mountain Spotted Fever

Rocky Mountain
Spotted Fever
Rocky Mountain Spotted Fever:
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First recognized in 1896 in the Snake River Valley of
Idaho and was originally called "black measles" because
of the characteristic rash.
Howard T. Ricketts established the identity
of the infectious organism that causes this
disease, Rickettsia rickettsii.
He and others described the
epidemiologic features of the disease,
including the role of tick vectors.
Sadly, Dr. Ricketts died of typhus (another
rickettsial disease) in Mexico in 1910.
Epidemiology:
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A bit of a misnomer, this disease has been
identified in almost all of the continental US,
with perhaps the exception of Maine and
Vermont
Most cases reported in south Atlantic, southeastern
and south central states
 54% of cases were from NC, TN, OK, SC and Ark
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Transmission:
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Vector=tick
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Wood tick, dog tick and Lone Star tick
Both dog and Lone Star ticks are found in NC
 Wood tick is primarily in western US, and Rocky
Mountain area
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DOG TICK: Transmits
RMSF, but probably not
Lyme
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LONE-STAR TICK:
Transmits RMSF, and
human monocytic
ehrlichiosis
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Two-thirds of RMSF cases occur in children
younger than 15 years
Males are infected more commonly (1.7-2.2:1)
Caucasians are more common than AfricanAmericans
Peak months of infection are April-October
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R. rickettsii organisms are released through
saliva during a feeding
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Usually 12-24 hrs of attachment is required
Incubation period is 2-14 days
Once organisms enter the body, they multiply
within endothelial cell linings of small blood
vessels
Signs and Symptoms:
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EARLY:
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LATE:
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Fever, nausea, vomiting, severe headache, anorexia and
malaise
Rash, joint pain and diarrhea
Classic triad=fever, rash and headache
Rash: appears between day 2 to 5 of illness
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Blanching, erythematous macules arouond ankles feet, later
wrists and hands; palms and soles often involved
Petechiae on day 6
10-15% of infected patients are without rash
Important points:
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Only 40-60% of those infected have a history
of tick bite
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RMSF may be clinically indisginguishable from
Human Monocytic ehrlichiosis
Laboratory tests:
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Hyponatremia (20%)
Thrombocytopenia (33%)
Anemia, increased LFTs or BUN (25%)
CSF: monocytic pleocytosis, increased protein
Diagnosis:
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Largely clinical
Suspect if classic triad
 Acute and convalescent titers (> 3 wks apart)
 Immunofluorescence assay
 PCR
 Isolation of R rickettsii from clinical specimen
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Treatment:
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Should be started immediately
Doxycycline, usually 7-10 days
100 mg PO BID for adults
 4 mg/kg/day div BID for children
 Discontinue 72 hrs after defervescence
 Teeth staining if < 9 years old; probably requires 5-6
courses before staining appears
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Prevention:
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Protective clothing
Repellants
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Avoid DEET if under 12 months
Full body examinations
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To remove attached ticks, use the following procedure:
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1. Use fine-tipped tweezers or shield your fingers with a tissue, paper towel, or
rubber gloves (Figure 17). When possible, persons should avoid removing ticks
with bare hands.
2. Grasp the tick as close to the skin surface as possible and pull upward with
steady, even pressure (Figure 18). Do not twist or jerk the tick; this may cause the
mouthparts to break off and remain in the skin. (If this happens, remove mouthparts
with tweezers. Consult your health care provider if infection occurs.)
3. Do not squeeze, crush, or puncture the body of the tick because its fluids
(saliva, body fluids, gut contents) may contain infectious organisms.
4. After removing the tick, thoroughly disinfect the bite site and wash your hands
with soap and water.
5. Save the tick for identification in case you become ill. This may help your
doctor make an accurate diagnosis. Place the tick in a plastic bag and put it in your
freezer. Write the date of the bite on a piece of paper with a pencil and place it in
the bag.
Resources:
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Center for Disease Control and Prevention.
Rocky Mountain spotted fever. Available at:
http://www.cdc.gov/ncidod/dvrd/rmsf
Pickering, L. Red Book; 26th edition. pp. 532534.
Razzaq, S. Rocky Mountain Spotted Fever: A
Physician’s Challenge. Pediatrics in Review. Vol.
26, No. 4 April 2005. pp. 125-129.