0071643192.pdf

INFECTIOUS DISEASE

Give a single dose of

doxycycline for the prophylaxis

of high-risk tick bites.

The classic triad of tick

exposure, fever, and rash is

only initially present in a

minority of RSMF cases.

WOUNDPROPHYLAXIS

■ Prophylaxis

■ Ixodestick bite (other ticks do not infect)

■ Only if tick attached >48 hours

■ Single 200-mg dose doxycycline <72 hours after bite

A 17-year-old male presents with fever and flulike symptoms a few days

after a hiking trip in North Carolina. He has recently developed a macu-

lopapular rash, which started on his wrists/ankles and progressed to involve

his palms/soles and trunk. What treatment should be initiated?

Doxycycline, tetracycline, or chloramphenicol.

Rocky Mountain Spotted Fever

■ Obligate intracellular coccobacillusRickettsia rickettsii

■ Carried by Dermacentorsp. ticks (on deer, horses, cats, dogs)

■ Peak transmission between April and September (95%)

■ Majority of cases in south Atlantic states(eg, North Carolina, South

Carolina), not the Rockies!

■ Two-thirds of cases in children

SYMPTOMS/EXAM

■ Incubation period: 2–14 days

■ Sudden onset of flulike, AGE-like, or meningitislike symptoms (headache =

prominent feature).

■ Classic triad (present in only ~18% initially)

■ History of tick exposure (~65%)

■ Fever (~75%)

■ Rash (~50%)

■ Maculopapular→petechial/purpuric.

■ Starts on wrists/ankles

■ Spreads centripetally (extremities →trunk)

■ Classically involves palmsandsoles

DIFFERENTIAL

Viral illnesses (eg, enterovirus, mononucleosis, measles, rubella), meningo-

coccal infection, gonococcemia, leptospirosis, typhus

DIAGNOSIS

■ Treat empirically if suspected on clinical grounds

■ CXR abnormalities in 25% (eg, interstitial infiltrate)

■ Serology (positive 6–10 days after onset) or rash biopsy

TREATMENT

■ Doxycycline, tetracycline, or chloramphenicol

■ Untreated=25% mortality

COMPLICATIONS

■ Interstitial pneumonitis leading to ARDS

■ Myocarditis, CHF, DIC, shock

■ Seizures, encephalomyelitis, coma