Objectives: To determine seroprevalence to Bartonella vinsonii subsp berkhoffii in a population of sick dogs from North Carolina and Virginia and to evaluate potential risk factors associated with increased likelihood of exposure to the organism.
Sample population: Serum samples from 1,920 sick dogs.
Procedure: An indirect fluorescent antibody assay was performed on each sample, and the end-point antibody titer was recorded. A case (seropositive) was defined as a dog with reciprocal titer > or = 64, and a control (seronegative) was defined as a dog with reciprocal titer < 16 that was referred within 0 to 3 days of referral of a corresponding case. From this population, 207 dogs (69 cases and 138 controls) were included in a case-control seroepidemiologic study.
Results: 3.6% (69/1,920) of the dogs were seropositive to B vinsonii subsp berkhoffii. Results of the case-control study indicated that seropositive dogs were more likely to live in rural environments, frequently on a farm, were free to roam the neighborhood, and were considered to be predominantly outdoor dogs. Moreover, seropositive dogs were 14 times more likely to have a history of heavy tick exposure. After analysis of the case-control study, a more detailed examination of banked sera from dogs with known tick exposure was performed. High correlation was found between sero-reactivity to B vinsonii and seroreactivity to E canis or B canis (36.0 and 57.1%, respectively). Sera derived from dogs experimentally infected with E canis or R rickettsii did not cross react with B vinsonii antigen.
Conclusions and clinical relevance: Several potential risk factors are associated with canine exposure to B vinsonii. Rhipicephalus sanguineus, the tick vector for E canis and B canis, may be involved in B vinsonii transmission among dogs.