Rodent-Associated Bartonella Febrile Illness, Southwestern United States

Jonathan Iralu; Ying Bai; Larry Crook; Bruce Tempest; Gary Simpson; Taylor McKenzie; Frederick Koster


Emerging Infectious Diseases. 2006;12(7):1081-1086. 

In This Article


Serum samples from 114 patients with acute febrile illness, including 14 with both acute- and convalescent-phase serum samples, were tested at a dilution of 1:32 by IFA with a panel of 9 Bartonella antigens. All positive samples were retested at a dilution of 1:32 and at doubling dilutions to 1:4,096. In 12 of 13 cases with titers ≤512 to any rodent-associated antigen, the titer to the N. albigula–associated Bartonella antigens (NA-AB antigens) were the highest measured. Therefore, only the titers to NA-AB antigens are shown in Table 1 . IFA titers to NA-AB ≥128 were observed more often in undifferentiated febrile illness (group A, 24 of 76) than in the 3 groups with specific diagnoses (groups B–D, 4 of 38) (χ2 = 4.98, p = 0.026, using Yates' correction). Among 24 patients in group A with titers ≥128, a total of 11 had convalescent-phase titers ≥512. Clinical information was sufficient to analyze for 9 of these 11 patients: 5 patients with both acute- and convalescent-phase titers ( Table 2 ) and 4 patients with only a convalescent-phase titer ( Table 3 ). Nine patients in group A with both acute- and convalescent-phase serum samples showed no increase in titer or a titer >64.

Of 24 patients with pneumonic disease (groups B and C), only 1 had a titer of 128 to NA-AB antigens. Of 14 patients with other diagnosed febrile illnesses (group D) not listed in Table 2 and Table 3 , three had high titers to NA-AB antigens ( Table 1 ). A 35-year-old man with aortic valve endocarditis and cultures of blood and valve positive for S. aureus had an NA-AB titer of 1,024 on admission and the following day. A 30-year-old man with fever, myalgias, headache, thrombocytopenia, and leukopenia with admission serum positive by PCR for Borrelia hermsii (tickborne relapsing fever) had an acute-phase (day 1) titer of 256 and a convalescent-phase (day 24) titer of 1,024 to NA-AB antigens. A 23-year-old woman with fever and acute hepatic injury had positive convalescent-phase (day 28) IgM phase I (512) and IgG phase II (1,024) titers for Coxiella burnetii antigens and an NA-AB antigen titer of 256 in a convalescent-phase serum sample.

Five of the 14 patients with acute- and convalescent-phase serum samples in group A showed a ≥4-fold increase in titer to NA-AB antigens and convalescent-phase titers >512 on days 14, 7, 7, 12, and 42, respectively, after admission ( Table 2 ). Each of the 5 who seroconverted had a clinical syndrome characterized by fever (temperature >39ºC), chills, pronounced myalgias in the back and thighs, nausea, and headache. Two who seroconverted had a sore throat and 2 had diarrhea, but none had other upper or lower respiratory symptoms, abnormal chest radiograph results, lymphadenopathy, hepatosplenomegaly, bleeding, rash, altered consciousness, or abnormal neurologic findings. Thrombocytopenia and leukopenia were common ( Table 2 and Table 3 ), but no patients had evidence of coagulopathy, or cardiac, pulmonary, renal, or neurologic disease.

Four other patients in group A had a single titer >512 to NA-AB antigens on days 21, 7, 20, and 23, respectively, after admission ( Table 3 ). This group had elevated levels of serum transaminase, bilirubin, and alkaline phosphatase, which is indicative of active hepatitis. These 4 patients were treated with doxycycline, and all recovered without sequelae. Of the 9 patients listed in Table 2 and Table 3 , one had a diagnosis of chronic alcoholism (patient 6, Table 3 ). All 9 were negative for hepatitis A, B, and C; Q fever; Rocky Mountain spotted fever; murine typhus; leptospirosis; granulocytic or monocytic ehrlichiosis; plague; and tularemia; they also had negative titers for HIV, hantavirus, and antinuclear antibody. Patients 6, 8, and 9 were tested for antibody to hepatitis E at the Hepatitis Branch of CDC in Atlanta, Georgia, and were negative (M. Favorov, pers. comm.). Patients 1, 4, and 6 had 6-, 3-, and 3-fold lower titers, respectively, to the known Bartonella pathogen antigens compared with the titer to NA-AB antigens ( Table 2 and Table 3 ).


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