Joint Epidemiological Investigation Results of the Canine Brucellosis Outbreak at a Breeding Facility Associated with a Human Brucellosis Case, 2025.

OBJECTIVES: Canine brucellosis, caused by Brucella canis, is a zoonosis transmitted through contact with infected dogs or infectious reproductive materials. Following a report of human B. canis infection in Paju-si, Gyeonggi-do, in April 2025, canine brucellosis was identified at a dog breeding facility operated by the patient's spouse. A joint investigation was conducted to assess potential transmission and prevent further spread. METHODS: Interviews assessed symptoms, facility visits, and dog contact; blood culture results were reviewed. Of 99 dogs at the facility, 85 aged ≥6 months underwent serologic and culture testing. Fifty-eight puppies distributed during the previous 6 months were traced, and 34 final owners were monitored for 24 weeks after their last exposure. RESULTS: The patient intermittently visited the facility and had contact with dogs. Her asymptomatic spouse had a negative blood culture on April 29, 2025. Of 85 dogs tested, 11 (12.9%) were positive (n=10) or suspected positive (n=1), representing at least 11.1% of all 99 dogs; B. canis was isolated from four dogs. Among 34 distributed dogs with identified final owners, all 14 tested were negative; the remaining 20 dogs, aged <6 months, had no clinical signs and untested. No owner reported symptoms suggestive of brucellosis during follow-up. CONCLUSIONS: Transmission to the patient was likely from infected dogs or infectious materials. Detection of infected dogs in all breeding units highlights the limitations in early recognition. Testing newly introduced and breeding dogs, prompt diagnosis after reproductive abnormalities, and stronger information sharing between human and animal health sectors are needed.