Epidemiologic evaluation of the risk factors associated with exposure and seroreactivity to Bartonella vinsonii in dogs

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.

Serum samples from 1,920 sick dogs.

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.

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.

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.