INFECTIOUS DISEASEEhrlichiosis
■ Obligate intracellular Gram-negative coccobacillus of the Ehrlichiasp.
■ Transmitted by IxodesorAmblyommaticks (reservoir =deer, mice, other
mammals)
■ Geographic and temporal distribution similar to Lyme disease
SYMPTOMS/EXAM
■ Incubation period: 1–21 days (median =7 days)
■ Initially flulike symptoms
■ 10% develop a RMSF-like rash.
DIFFERENTIAL
Rickettsial diseases (eg, RMSF), bacterial meningitis
DIAGNOSIS
■ Leukopenia, thrombocytopenia, transaminitis (~75%)
■ Mulberrylike clusters (morulae) of the tiny bacteria form inside leukocytes
(seen on peripheral blood smear).
■ IgG antibody titers confirm diagnosis.
TREATMENT
Doxycycline, tetracycline, or chloramphenicol
COMPLICATIONS
■ ARDS, renal failure, DIC, cardiomegaly, encephalitis
■ Neurologic sequelae, death (~2%)
Babesiosis
■ Malarialike protozoan parasites of the genus Babesiainfect red blood cells,
leading to hemolytic anemia
■ Vector: Ixodesticks (same as Lyme disease)
■ Reservoir: Deer, mice
■ Scattered areas in the United States (especially Northeast) during summer
months
SYMPTOMS/EXAM
■ Incubation: 1–4 weeks
■ Flulike illness with:
■ High spiking fevers
■ Dark urine (from hemolytic anemia)
■ No rash
■ More severe if splenectomy
DIFFERENTIAL
Malaria, Lyme disease
DIAGNOSIS
■ Thick and thin Giemsa-stained smears
■ Budding tetrad in “Maltese cross” formation
If suspected, both RMSF and
ehrlichiosis must be treated
immediately (based on clinical
suspicion), since the illnesses
can be rapidly fatal.