By Stan Deresinski, MD, FACP, FIDSA, FESCMID

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: Disseminated cat scratch disease may present as a fever of unknown origin.

SOURCE: Landes M, Maor Y, Mercer D, et al. Cat scratch disease presenting as fever of unknown origin is a unique clinical syndrome. Clin Infect Dis 2019 Nov 23. pii: ciz1137.

Landes and colleagues analyzed data obtained from a national surveillance of cat scratch disease (CSD) in Israel from 2004-2017 to characterize cases presenting with fever lasting > 14 days without a cause identified. Of the approximately 2,800 patients with CSD, 126 (4.1%) were reported to have had fever of unknown origin, but only 66 patients, 89% of whom were immunocompetent, were included in this study after various exclusions. The patients ranged in age from 3 to 88 years (median 35.5 years); 83% reported contact with felines. The median duration of fever was four weeks. In 48%, the fever occurred daily, while in 52% it had a relapsing pattern. Loss of > 5% of body weight occurred in 37.5% of the patients.

The diagnosis was confirmed by serology in 65/66 patients, and Bartonella henselae DNA was detected in seven patients in tissue. Investigation found involvement of one or more organ systems in 39 (59%) patients: 23 with hepatic and/or splenic lesions, 12 with ocular disease, four with multifocal osteomyelitis, and three with pneumonitis. One patient each had pericarditis, pleuritis, meningitis, and sensorineural hearing loss.

Antibiotics with possible activity against B. henselae, mostly azithromycin and doxycycline, were administered to 46 (70%) patients for two days to 3.5 months. The mean duration of fever was four weeks whether antibiotics were taken or not. Nonetheless, symptoms eventually resolved in 56 of the 59 patients with follow-up; the other three had ocular involvement with visual residua.


In classic CSD, characterized by regional lymphadenitis that is self-limited, fever may occur in up to 30% of patients, but it lasts a mean of only six days. The patients in the series described here lacked classic findings of CSD and had fever that lasted at least 14 days. This syndrome has been described before, but it has been characterized more often as disseminated or simply named by the focal sites of infection identified, such as osteomyelitis. Such focal sites were identified in 59% of the patients reported by Landes et al. One site of infection not included in this case series is heart valves; the diagnosis of Bartonella endocarditis often is quite difficult.

A finding of note in this series is the fact that the prolonged fever had a relapsing pattern in approximately one-half of patients. The authors pointed out that relapsing fever was characteristic of “trench fever,” which is caused by Bartonella quintana, a louse-borne infection seen in modern times in people who are homeless in the United States and Europe. Of course, relapsing fever also may be caused by Borrelia (e.g., Borrelia hermsii in the western United States, Borrelia persica in Israel) and also may be caused by lymphoma, among other things.


  1. Edouard S, Nabet C, Lepidi H, et al. Bartonella, a common cause of endocarditis: A report on 106 cases and review. J Clin Microbiol 2015;53:824-829.