Brucella canis in dogs: An underrecognized zoonotic pathogen requiring a one health response.

Brucella canis is a facultative intracellular, Gram-negative coccobacillus and an underrecognized zoonotic pathogen maintained primarily in domestic dogs. Unlike smooth Brucella species, B. canis expresses a naturally rough lipopolysaccharide (LPS) phenotype, characterized by absence or marked truncation of the O-polysaccharide chain. This antigenic profile reduces the performances of routine smooth-antigen serological assay and contribute to underdiagnosis in veterinary and human medicine. A recent global meta-analysis including 175,675 canine samples estimated pooled canine prevalence of 7.96%, with substantial geographic heterogeneity and markedly higher values in high-density breeding, kennel, and shelter settings. In dogs, infection results in reproductive failure, persistent bacteremia, and a high proportion of asymptomatic carriers capable of intermittent shedding. Human infection remains infrequently reported but is likely underestimated; a recent scoping review (68 cases) found that 80% of infections with known exposure were associated with direct dog contact. Clinical presentation in humans is nonspecific, and diagnostic limitations further obscure detection. This review critically evaluates current knowledge on microbiology, epidemiology, clinical manifestations, and diagnostic challenges of B. canis, with emphasis on limitations of existing diagnostic tools, variability in epidemiological data, and gaps in validation of emerging methods. We highlight the need for standardized diagnostic algorithms, improved antigen specificity, and integrated surveillance systems. A coordinated One Health framework is proposed to improve detection, reduce transmission, and strengthen cross-sectoral response.