Investigation and characterization of Brucella canis infections in pet-quality dogs and associated human exposures during a 2007-2016 outbreak in Michigan

Abstract

OBJECTIVE To estimate Brucella canis seropositivity rates for purebred dogs being bred by noncommercial breeders, describe epidemiological findings in infected commercial dog-production facilities, and characterize B canis infection in pet dogs and the risk to human health. DESIGN Retrospective descriptive study. SAMPLE 2,799 canine specimens submitted to the Michigan State University Veterinary Diagnostic Laboratory for B canis testing and records of B canis reports provided to the Michigan Department of Agriculture and Rural Development from 2007 through 2016. PROCEDURES Results of B canis laboratory tests and epidemiological findings for reported cases of B canis were reviewed and summarized. Federal and state public health officials were interviewed regarding human B canis infection. State veterinarians were interviewed regarding canine brucellosis reporting and control procedures. RESULTS Estimated B canis seropositivity was 0.4% among purebred Michigan dogs owned by noncommercial breeders. Infection was confirmed in dogs from 17 commercial dog-production facilities, 3 shelters, and 1 rescue agency. Estimated infection prevalence in production facilities ranged from 2 of 22 (9%) to 5 of 6 (83%). Transfer of infected dogs involved 22 Michigan counties and 11 states. Seven of 20 privately owned infected dogs had diskospondylitis; I also had uveitis. Fifty-three veterinary hospital or diagnostic laboratory personnel had inadvertent exposure to the pathogen. Brucella canis was isolated from 1 commercial production facility owner. CONCLUSIONS AND CLINICAL RELEVANCE B canis was uncommon in purebred dogs being bred by noncommercial breeders but endemic in Michigan commercial facilities producing dogs destined to become household pets. Infected pet dogs caused human B canis exposure, and several pet dogs had debilitating disease not associated with the reproductive system.

Figure I—

Distribution of Michigan dogs by county during a Brucella canis outbreak from January I, 12007, through December 31, 2016. Numbers for entities in each category were assigned chronologically as dogs potentially infected with B canis were identified; in some instances, specific information such as the location of a home or facility to which a dog had been moved or sold could not be recalled or was not provided, and numbers could not be assigned. B = Noncommercial dog breeder. C = Individually owned dogs (case numbers). P = Commercial dog-production facility. R = Rescue agency (a and b represent 2 different dogs that were placed in foster care homes by the group). S = Shelter.

Figure 2—

Flow diagrams showing intrastate and interstate movement of dogs to and from Michigan facilities where B canis infection was confirmed, and interstate movement of infected individual dogs. One-way and 2-way movements are indicated by single- and double-headed arrows, respectively. *Brucella canis infection in the owner of a Wisconsin commercial production facility from which infected dogs moved to S3 in Michigan. †Influenza-like symptoms in 3 veterinary hospital staff members who worked with the dog. ‡Infected dogs with diskospondylitis. §Needle stick incurred by a veterinary technician during blood sample collection. ‖Infected dog with diskospondylitis and uveitis. See Figure I for remainder of key.