Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 26, Number 12—December 2020
Research Letter

Brucella canis in Commercial Dog Breeding Kennels, Ontario, Canada

Article Metrics
citations of this article
EID Journal Metrics on Scopus
J. Scott WeeseComments to Author , Kathleen Hrinivich, and Maureen E.C. Anderson
Author affiliations: University of Guelph, Guelph, Ontario, Canada (J.S. Weese); Animal Hospital of Cambridge, Cambridge, Ontario (K. Hrinivich); Ministry of Agriculture, Food and Rural Affairs, Guelph (M.E.C. Anderson)

Cite This Article


We evaluated the prevalence of Brucella canis seropositivity in a convenience sample of dogs from commercial breeding kennels in Ontario, Canada. Overall, 127/1,080 (11.8%) dogs from 23/63 (37%) kennels were seropositive. The prevalence of positive dogs within kennels with >1 positive dog ranged from 3.9% to 100% (median 33%).

Brucella canis is a dog-adapted Brucella species that most commonly causes reproductive disease and diskospondylitis in dogs and can be carried long-term and subclinically. Zoonotic infections are uncommonly reported (14), but may be underdiagnosed (3,5).

In Canada, Brucella canis has been found predominantly in imported dogs. However, it was identified in 2 adult female dogs from a commercial breeding kennel in Ontario, Canada, in March 2019. We conducted an investigation of prevalence and distribution of B. canis in the broader commercial dog breeding population.

We collected serum samples from a convenience sample of dogs at commercial breeding kennels in southern Ontario, Canada. We used rapid slide agglutination test (RSAT) and followed up with positive results using 2-mercaptoethanol RSAT (2ME-RSAT). We performed PCR on whole (EDTA treated) blood from a subset of B. canis−seropositive dogs.

We identified positive RSAT and 2ME-RSAT tests in 127/1,080 (11.8%) clinically normal dogs from 23/63 (37%) kennels during March 15−December 18, 2019 (1–61 dogs/kennel, median 7). We considered reactive an additional 82 (7.6%) dogs that were positive by RSAT but negative by 2ME-RSAT; 63 (77%) of those were from kennels from which positive dogs were identified. The prevalence of positive dogs within kennels that had >1 positive dog ranged from 3.9% to 100% (median 33%). Whole blood samples from 20 dogs tested by PCR were all negative. We retested 130 dogs 4–6 weeks after the initial test (Table).

The seropositive rate contrasts with a 1980 study that reported 0.3% seroprevalence in dogs from southwestern Ontario (6). Studies in other regions have reported seroprevalence rates of 0%–4.6%; higher rates (e.g., 20%–83%) were reported in some breeding kennels (1,79). A structured approach to enrollment was not possible because enrollment was based on kennel operators’ willingness to participate. Various population enrollment biases might be present in the prevalence estimate. These results should be taken as an indication of widespread presence of B. canis bacteria in this population, with high rates in some kennels and the potential for introduction of infected puppies into households.

Because B. canis infection is a notifiable disease in Ontario, we obtained data from 2013–2018 from the Ontario Ministry of Agriculture Food and Rural Affairs. Provincially, there were no positive test results for B. canis in dogs in 2013, 2015 and 2017, and 1–3 cases in each of 2014, 2016, and 2018. Because prior surveillance was limited, it is unclear whether this is a new problem or one that was previously overlooked. However, these 0–3 diagnoses/year and anecdotal data about recent reproductive disease in some affected kennels make it unlikely that B. canis infection was present but undiagnosed. The origin of the infection could not be properly investigated, but it was suspected to have originated from breeding dogs imported from eastern Europe in 2018.

Without a standard approach for clinical or surveillance testing for B. canis bacteria, we used the sensitive RSAT followed by the more specific 2ME-RSAT, which is considered a confirmatory test (10). Cases with RSAT-positive but 2ME-RSAT−negative results were common; most were subsequently negative. A possible cause was transient cross-reaction with Bordetella bronchiseptica vaccination or another pathogen; we could not investigate specifically because information about B. bronchiseptica vaccination or infection in these dogs was not available. The potential for false-positive results should be considered, particularly because infected dogs are often euthanized in accordance with regulatory requirements.

Limited PCR testing was performed because of negative results in the first 20 samples; negative results were presumed due to the intermittent nature of B. canis bacteremia in clinically normal animals. Although PCR or culture can provide a definitive diagnosis, sensitivity can be low for screening; it is higher when testing reproductive or fetal fluids or tissues from abortions or stillbirths for B. canis.

Limited clinical data were available. Some affected kennels reported substantial reproductive challenges presumably associated with brucellosis (e.g., small litter sizes, abortions, stillbirths, low conception rates) whereas no problems were reported in others. Whether this reflects lack of recognition of problems, subclinical infection, or early infection that had not yet resulted in overt reproductive disease is unclear.

Underdiagnosis of B. canis as a cause of nonspecific disease (e.g., undulating fever, fatigue, headache, malaise, chills, weight loss, hepatomegaly, splenomegaly, lymphadenopathy) and human brucellosis is a concern; physicians are more likely to perform serologic tests that target smooth Brucella species (B. abortus, B. suis, and B. melitensis). Physicians should consider the potential presence of B. canis in patients with disease suggestive of brucellosis, especially those with animal contact, and realize the limitations of serologic testing.

Brucella canis should be considered endemic to commercial dog kennels in Ontario, with potential human health risks. B. canis screening of breeding dogs is recommended (10), and testing of puppies from parents of unknown Brucella status is reasonable.

Dr. Weese is a veterinary internist at the University of Guelph, Guelph, Ontario, Canada. His primary research interests are infectious diseases and infection control, and he has a particular interest in emerging diseases, zoonotic diseases, and antimicrobial stewardship.



We thank Tim Pasma for providing B. canis reports from previous years in Ontario.

This study was supported by the Ontario Animal Health Network.



  1. Johnson  CA, Carter  TD, Dunn  JR, Baer  SR, Schalow  MM, Bellay  YM, et al. Investigation and characterization of Brucella canis infections in pet-quality dogs and associated human exposures during a 2007–2016 outbreak in Michigan. J Am Vet Med Assoc. 2018;253:15.
  2. Lucero  NE, Corazza  R, Almuzara  MN, Reynes  E, Escobar  GI, Boeri  E, et al. Human Brucella canis outbreak linked to infection in dogs. Epidemiol Infect. 2010;138:2805. DOIPubMedGoogle Scholar
  3. Lucero  NE, Escobar  GI, Ayala  SM, Jacob  N. Diagnosis of human brucellosis caused by Brucella canis. J Med Microbiol. 2005;54:45761. DOIPubMedGoogle Scholar
  4. Dentinger  CM, Jacob  K, Lee  LV, Mendez  HA, Chotikanatis  K, McDonough  PL, et al. Human Brucella canis infection and subsequent laboratory exposures associated with a puppy, New York City, 2012. Zoonoses Public Health. 2015;62:40714. DOIPubMedGoogle Scholar
  5. Hensel  ME, Negron  M, Arenas-Gamboa  AM. Brucellosis in dogs and public health risk. Emerg Infect Dis. 2018;24:14016. DOIPubMedGoogle Scholar
  6. Bosu  WTK, Prescott  JF. A serological survey of dogs for Brucella canis in southwestern Ontario. Can Vet J. 1980;21:198200.PubMedGoogle Scholar
  7. Brower  A, Okwumabua  O, Massengill  C, Muenks  Q, Vanderloo  P, Duster  M, et al. Investigation of the spread of Brucella canis via the U.S. interstate dog trade. Int J Infect Dis. 2007;11:4548. DOIPubMedGoogle Scholar
  8. Dahlbom  M, Johnsson  M, Myllys  V, Taponen  J, Andersson  M. Seroprevalence of canine herpesvirus-1 and Brucella canis in Finnish breeding kennels with and without reproductive problems. Reprod Domest Anim. 2009;44:12831. DOIPubMedGoogle Scholar
  9. Higgins  R, Hoquet  F, Bourque  R, Gosselin  Y. A serological survey for Brucella canis in dogs in the Province of Quebec. Can Vet J. 1979;20:3157.PubMedGoogle Scholar
  10. Bramlage  DJ, Fortney  W, Kesler  RM, Mabray  CJ, Mason  JW, Reinhold  H, et al. Best practices for Brucella canis prevention and control in dog breeding facilities. US Department of Agriculture. 2015 [cited 2020 Oct 21].




Cite This Article

DOI: 10.3201/eid2612.201144

Original Publication Date: November 10, 2020

Table of Contents – Volume 26, Number 12—December 2020

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.



Please use the form below to submit correspondence to the authors or contact them at the following address:

J. Scott Weese, Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G2W1 Canada

Send To

10000 character(s) remaining.


Page created: October 08, 2020
Page updated: November 19, 2020
Page reviewed: November 19, 2020
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.