FLEA- AND LOUSE-BORNE TYPHUS GROUP RICKETTSIOSES

Etiology and Epidemiology

• Humans become infected when Rickettsia-laden flea feces are scratched into pruritic bite lesions; less often, the flea bite itself transmits the organisms or aerosolized rickettsiae from flea feces are inhaled.
• In the United States, endemic typhus occurs mainly in southern Texas and southern California; globally, it occurs in warm (often coastal) areas throughout the tropics and subtropics.
• Flea bites often are not recalled by pts, but exposure to animals such as cats, opossums, raccoons, skunks, and rats is reported by ∼40%.
• Risk factors for severe disease include older age, underlying disease, and treatment with a sulfonamide drug.

Clinical Manifestations

• Rash is apparent at presentation (usually ∼4 days after symptom onset) in 13% of pts; 2 days later, half of the remaining pts develop a maculopapular rash that involves the trunk more than the extremities, is seldom petechial, and rarely involves the face, palms, or soles.
• Pulmonary disease is common, causing a hacking, nonproductive cough in 35% of pts. Almost one-fourth of pts who undergo CXR have pulmonary densities due to interstitial pneumonia, pulmonary edema, and pleural effusions.
• Laboratory abnormalities include anemia, leukopenia early in the course, leukocytosis late in the course, thrombocytopenia, hyponatremia, hypoalbuminemia, mildly increased hepatic aminotransferase levels, and prerenal azotemia.
• Complications may include respiratory failure, hematemesis, cerebral hemorrhage, and hemolysis.
• The duration of untreated disease averages 12 days (range, 9–18 days).

Diagnosis

Treatment: Endemic Murine Typhus (Flea-Borne)