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Differentiating Dengue from Rickettsia

Event Spotted Fever Group Typhus Group Ehrlichia/Anaplasma Rickettsia Rickettsia Rocky Mountain spotted Murine typhus Ehrlichiosis fever (RMSF) Rickettsia typhi Ehrlichia spp. Disease and Rickettsia rickettsii Agent African Tick Bite Fever Epidemic typhus Anaplasmosis (ATBF) Rickettsia prowazekii Anaplasma phagocytophilum Rickettsia africae

Tick bite • Murine–fleas Tick bite Transmission • Epidemic- human body lice

2–21 days 10–14 days 2–14 days Incubation

• Maculopapular rash in • Maculopapular rash in • Organism in white blood 80% of RMSF cases 20%–60% of murine cells and often causes Differentiating • Eschars are common in and epidemic typhus leukopenia Features ATBF; may also have cases • Maculopapular rash in maculopapular rash • Cough and stupor about 30% of ehrlichiosis more common with cases; rash is rare in epidemic typhus anaplasmosis • ARDS, DIC, multisystem • Both diseases can be • Mental status changes, organ failure, and digital severe and fatal with neurological impairment, necrosis with RMSF, Case respiratory distress, and organ failure fatality of 20%–80% and organ failure especially in among untreated cases. • Case fatality rates in immunocompromised Complications • Rare complications of untreated epidemic patients peripheral neuropathy typhus cases can be • Ehrlichiosis is more likely and myocarditis in ATBF as high as 30%, while to be fatal than cases; ATBF is usually usually < 5% with anaplasmosis, but case self-limited murine typhus fatality rates < 5% for both Paired serum indirect Paired serum IFA for IgG PCR in acute whole blood immunofluorescence assay Diagnosis ¹ (IFA) for IgG

Skin biopsy of rash Skin biopsy of rash Paired serum IFA for IgG

Treatment (for Doxycycline Doxycycline Doxycycline adults and children of all ages)

Centers for Disease Control and Prevention 1 National Center for Emerging and Zoonotic Infectious Diseases