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Bartonella are fastidious, hemotropic, gram-negative bacteria that have been identified in a variety of domestic and wild mammals. There are currently more than 20 known species or subspecies of Bartonella, several of which are recognized as emerging human and canine pathogens.1 Comparable clinical manifestations such as endocarditis, peliosis hepatis, granulomatous hepatitis, lymphadenitis, and epistaxis have been observed in humans and domestic dogs infected with Bartonella spp.2 Bartonella are usually vector-borne, although for many recently identified species the vector involved in transmission has not been identified.1 Bartonella vinsonii subsp. berkhoffii was first isolated from a dog with endocarditis in 19933 and was subsequently implicated in a human case of endocarditis.4 Domestic dogs, like humans, appear to mainly be accidental hosts for several Bartonella species.1 Because of the close association of dogs with humans, dogs may serve as good sentinels for human exposure to Bartonella. The purpose of the present survey was to assess for the first time exposure to B. vinsonii subsp. berkhoffii, as measured by serum antibodies, in domestic dogs from two areas of Morocco.
Serum samples from 147 dogs from the Moroccan capital of Rabat and the city of Khenifra were available for testing. Rabat is on the Atlantic coast of this northwest African country and has a moderate, Mediterranean climate. Khenifra is located approximately 300 km southeast of Rabat and has a semi-arid climate. Blood samples were collected from dogs in Rabat between May 2002 and July 2003. The samples from Rabat included 24 owned dogs seen at the Institut Agronomique et Vétérinaire Hassan II (Rabat, Morocco) for various medical conditions and 22 stray dogs from the dog pound. In April 2004, 101 samples were collected from dogs in Khenifra as part of a study on echinococcosis. Dogs in Khenifra were mostly rural dogs that were allowed to freely roam. Unfortunately, information on signalment and relevant medical information for these 147 dogs were not available. Serum samples were tested in our laboratory for antibodies against B. vinsonii subsp. berkhoffii using an indirect immunofluorescent antibody assay, as previously described.5 Serum samples were initially screened at dilutions of 1:32 and 1:64. The intensity of bacillus-specific fluorescence was scored subjectively from 1 to 4, with a score 
2 at a dilution of 1:64 reported as a positive result. Samples positive at a dilution of 1:64 were titrated in serial two-fold dilutions to the end point. The same two readers performed a double-blind reading of each slide. Negative and positive serum control samples were included on each slide. The Fisher’s exact test was used to evaluate differences in seroprevalence among owned and stray dogs from Rabat, and a chi-square test was used to test for a difference in antibody prevalence between stray dogs in Rabat and dogs in Khenifra. Statistical tests were performed using Epi-Info version 6 (Centers for Disease Control and Prevention, Atlanta, GA).
Overall, 56 (38%) of the 147 dogs tested were seropositive for antibodies against B. vinsonii subsp. berkhoffii. Among the 24 owned dogs from Rabat, only 1 (4%) dog was seropositive, whereas 8 (36%) of 22 stray dogs from Rabat were seroreactive. The difference between exposure to B. vinsonii subsp. berkhoffii in owned dogs from Rabat compared with stray dogs was statistically significant (P = 0.009). Of the 101 dogs tested from Khenifra, 47 (47%) had antibodies against B. vinsonii subsp. berkhoffii. There was no difference between antibody prevalence in stray dogs from Rabat compared with dogs from Khenifra (P = 0.53). Reciprocal titers among the 56 seropositive dogs ranged from 64 to 8,192, with high titers (512) observed in 26 (46%) of these dogs (Table 1
).
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This is the first report on prevalence of antibodies to B. vinsonii subsp. berkhoffii in dogs in north Africa. The findings reported here indicate exposure of domestic dogs in Morocco to B. vinsonii subsp. berkhoffii or a closely related species of Bartonella. Previous studies have implicated ticks as potential vectors of B. vinsonii subsp. berkhoffii,12,13 but since information on exposure to ectoparasites was not collected as part of this study, it is not possible to draw any conclusions about the vector involved in transmission. The study focused on seroreactivity to B. vinsonii subsp. berkhoffii exclusively due to limited amounts of serum and because B. vinsonii subsp. berkhoffii is the zoonotic Bartonella species most commonly associated with domestic dogs. Further studies are needed to definitively identify the infecting species of Bartonella and to assess human exposure to Bartonella in Morocco.
Received August 10, 2005. Accepted for publication September 9, 2005.
Acknowledgments: We thank Younesse Elouasbi, Adil Bourhila, and Reda Mezzoug (Institut Agronomique et Vétérinaire Hassan II) for their help in collecting the dog blood samples.
* Address correspondence to Bruno B. Chomel, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616. E-mail: bbchomel{at}ucdavis.edu 
Authors’ addresses: Jennifer B. Henn, Rickie W. Kasten, and Bruno B. Chomel, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, E-mails: jebrady{at}ucdavis.edu, rwkasten{at}ucdavis.edu, and bbchomel{at}ucdavis.edu. Brian A. VanHorn and Malika Kachani, College of Veterinary Medicine, Western University of Health Sciences, 309 East Second Street, Pomona, CA 91766-1854, E-mails: bvanhorn{at}westernu.edu and mkachani{at}westernu.edu.
Reprint requests: Bruno B. Chomel, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, Telephone: 530-752-8112, Fax: 530-752-2377, E-mail: bbchomel{at}ucdavis.edu.
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