In the Literature
Guarino C, Franklin-Guild R, Goodrich E, Conklin R, Frye E, Pinn-Woodcock T. Antibody response over time correlated with treatment outcome in 30 dogs naturally infected with Brucella canis (2017-2022). Am J Vet Res. 2025;84(4):ajvr.23.01.0014. doi:10.2460/ajvr.23.01.0014
The Research …
Initial diagnosis of Brucella canis infection is often made using a serologic assay (eg, indirect fluorescent antibody test, ELISA, rapid slide agglutination test [RSAT]). These assays require confirmation with an agar gel immunodiffusion assay (AGID II) and are usually run in parallel with an RSAT using 2-mercaptoethanol (2ME).
This study describes the clinical presentation and outcomes of dogs treated for B canis and the usefulness of the quantitative serologic canine Brucella multiplex (CBM) assay in concomitantly monitoring clinical response to treatment. The CBM assay is a novel screening test that uses synthetic reagents to test for 2 Brucella spp–specific antigens (ie, BP26, PO1).
Dogs (n = 30) included in the study were serologically positive for B canis, positive on 2ME-RSAT/AGID II, and positive on follow-up. The most common signs included back or hip pain (19/30) and lameness or limb weakness (19/30). The most common reason for initiating B canis testing was radiographic diagnosis of discospondylitis (27/30). Treatment regimens varied, with 96.7% of dogs receiving some form of polytherapy. Doxycycline in combination with another drug was used in 90% of cases.
No conclusions were reached regarding the most effective treatment regimen; however, use of doxycycline as monotherapy was not recommended. Sixty to 185 days after treatment initiation, a significant difference in the decrease of PO1 antibody values measured by CBM assay was seen in dogs with resolution of clinical signs compared with dogs without resolution.
… The Takeaways
Key pearls to put into practice:
B canis is found worldwide. Although the true seroprevalence of B canis in dogs in North America is not well known, studies from animal shelters indicate it is between 0% to 9%.1
Young dogs presented with recurring lameness or back or hip pain should be screened for B canis. When B canis is clinically suspected, a negative result on a single test should prompt additional diagnostic testing. Many states require that B canis–positive dogs be reported.
There is no agreed upon standard treatment protocol, and treatment cannot guarantee clearance.1 B canis can hide from the immune system inside cells, making treatment failure common and bacteremia intermittent.1,2 Signs may abate with treatment, but recrudescence and shedding may occur. Owners of B canis–positive dogs should be made aware of the zoonotic risk, expense and demands of treatment, and potential for recrudescence.
As B canis is essentially a lifelong zoonotic infection, euthanasia is an option; however, CBM assay along with changes in clinical signs may aid in monitoring treatment response. The CBM assay may also help in recognizing recrudescence before clinical signs return. When using the CBM assay to guide treatment, a 40% decline in PO1 antibody values 2 to 6 months posttreatment likely indicates a positive response.
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