By Day 5, the patient was clinically improved and deemed safe for discharge on empiric treatment with ciprofloxacin 750 mg twice daily and doxycycline 100 mg twice daily to complete a 14-day course of antibiotic therapy for bubonic plague. The bubo culture subsequently grew Y pestis, confirming the diagnosis. The patient made a full recovery and was greatly improved when seen in the outpatient setting by the treating infectious disease physician. Outpatient ultrasound repeated 3 weeks after discharge showed borderline lymphadenopathy, no greater than 1 cm.
DISCUSSION
Between 2000 and 2009, there were 57 cases of Y pestis in the United States; in early 2015, 11 cases were found in 6 Western states.1 The plague presents in the bubonic form 80% to 95% of the time, and it has never been reported in Michigan (where we treated this patient); however, there was a laboratory case in Illinois. Although rats were traditionally the host for Y pestis, the prairie dog, Cynomys gunnisoni, is a host in the United States.2 Rodents are the most important hosts, but more than 200 mammalian species, including domestic pets, have had reported infections. Transmission is primarily via flea bites, but Y pestis also may be transmitted via respiratory secretion, inhalation, or direct handling of contaminated animal tissues. Due to the risk of respiratory spread, the Centers for Disease Control and Prevention must be notified of a diagnosis.3,4
Y pestis travels from the site of the flea bite to regional lymph nodes, where it reproduces, and the resultant inflammatory reaction creates buboes. The bacteria then circulate in the blood to other organs, although Y pestis bacteria are primarily removed by the liver and spleen. Patients often develop symptoms such as headache, fevers, chills, and gastrointestinal distress. Diagnosis is reached by bubo culture or rapid testing for the F1 antigen. Early intervention with antibiotics is crucial as untreated bubonic plague has a mortality rate of 50% to 90%.3,4
The differential diagnosis for unilateral inguinal lymphadenopathy with associated constitutional symptoms was broad, in this case, and included pelvic inflammatory disease, bubonic plague, iliopsoas abscess, lymphogranuloma venereum, bartonellosis, infectious mononucleosis, and tick-borne diseases, such as ehrlichiosis, tularemia, Lyme disease, Rocky Mountain spotted fever, and Colorado tick fever.
Treatment. Food and Drug Administration–approved treatments include streptomycin (gentamicin 5 mg/kg/day IM or IV for 14 days is more widely utilized), doxycycline 200 mg PO once daily for 10 to 14 days, and fluoroquinolones (ciprofloxacin 500-750 mg every 12 hours for 10-14 days). Trimethoprim-sulfamethoxazole may be used as an alternative, but limitations include potentially incomplete or slowed responses.
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