Patient 1 was a previously healthy, 51-year-old woman. During July 2004, she visited family residing in rural Ohio and participated in a variety of outdoor activities. Although she saw many wild animals, including deer, she did not report tick attachment or insect bites. Within 24 hours of her return home to North Carolina, a nonpuritic, slightly raised, circular red lesion, approximately the size of a quarter, was noted on the medial aspect of her thigh. Within 3 days, the lesion expanded to the size of a hand. Two weeks later, she exhibited a dry cough, fatigue, muscle pain in the upper body, severe chills, and extreme pain in both feet.
During the next 2 years, these symptoms persisted, along with exertional chest pains, a previously undiagnosed ausculted II to III/VI holosystolic murmur, headaches, difficulty speaking, difficulty sleeping, weakness involving the arms, joint pain, and facial tremors. No abnormalities were shown on an electrocardiogram. An echocardiogram identified mildly thickened aortic and mitral valve leaflets, mild aortic insufficiency, and mild mitral regurgitation.
After the acute illness, the woman reported cycles of illness every 3 to 4 weeks. Results of numerous complete blood counts were normal, with the exception of persistently low neutrophil counts of 2,000–2,500 neutrophils/μL. All serum biochemical parameters remained within normal reference ranges during the 2-year illness. Borrelia burgdorferi C6 peptide and immunoglobulin (Ig) M and IgG antibodies to Babesia microti were not detected. Results of PCRs specific for Anaplasma phagocytophilum, B. microti, and B. burgdorferi were negative. Oral antimicrobial drugs resulted in transient improvement; however, symptoms returned within days after the use of these drugs was stopped. Blood culture resulted in the detection of Candidatus B. melophagi and isolation of B. henselae. Her serum was not reactive with B. henselae or B. vinsonii subsp. berkhoffii antigens.
Treatment with rifampin and azithromycin, started in January 2006, resulted in some overall improvement in symptoms. Cefuroxime was added in February, and the combination resulted in substantial improvement, after which the drugs were selectively withdrawn. For 15 years before the onset of illness, this person had worked as an animal shelter manager in West Virginia and as a veterinary office manager in Virginia. Animal contact was minimal, but she had been bitten by fleas and mosquitoes. Travel history was limited to the eastern and central United States.
Patient 2 was a 65-year-old woman whose condition had been diagnosed as pericarditis of undetermined etiology in September 2004. Six months later, because of residual fatigue and muscle weakness in the arms and legs, mostly on her right side, a blood sample was cultured in Bartonella alpha proteobacteria growth medium (BAPGM).
The woman lived on a farm in southern California with her husband and managed a large animal sanctuary that also housed ≈100 cats and ≈100 dogs. She had resided in southern California for 50 years but occasionally traveled to the southeastern United States and other countries. She was directly involved in daily care of animals and had exposure to pet cattle and sheep, wolf hybrids, lamas, emus, pigs, horses, and numerous pet bird species. Bites and scratches were a daily occurrence, and exposure to cattle and sheep occurred at least weekly. In addition, the woman reported daily exposure to biting flies, occasional exposure to ticks and mosquitoes, and infrequent exposure to fleas or lice. Sheep keds had never been observed on sheep by the attending veterinarian. Blood culture resulted in isolation of Candidatus B. melophagi. Serum was reactive at a titer of 64 to B. henselae, B. vinsonii subsp. berkhoffii, and B. quintana antigens.
We used BAPGM and other published blood culture methods to test blood samples from both women (2
). Candidatus B
DNA was amplified directly from blood of patient 2, and from the respective BAPGM enrichment cultures and 14-day subculture colonies from both patients. Sequence analysis of respective colony isolates showed B
(internal transcribed spacer [ITS] sequence identical to Houston 1 strain, data not shown) and Candidatus B
from patient 1 and Candidatus B
(isolate 05-HO-1) from patient 2. Both isolates were composed of extremely small gram-negative bacilli consistent with Bartonella
spp. Sequence analyses for both isolates are summarized in the . Unfortunately, attempts to separate B
and Candidatus B
colonies from the sample of patient 1 by serial passage were unsuccessful. Bartonella
sp. DNA was not amplified from an uninoculated BAPGM control culture or from sheep blood used as a supplement. Flagella, as visualized in the Candidatus B
strain K-2C isolated from sheep blood (), were not visualized in the human 05-HO-2 strain by transmission electron microscopy.
Sequence similarities for 16S–23S ITS and 3 genes from 2 patient isolates and available GenBank sequences*
Figure Transmission electron micrographs of Candidatus Bartonella melophagi–like isolate 05-HO-1 from a human (A) (image provided by the North Carolina State University–College of Veterinary Medicine Electron Microscopy Facility, Raleigh, NC, (more ...)