Presumptive identification of smooth Brucella strain antibodies in canines
Helms, Alyssa B.
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Brucellosis is a zoonotic disease caused by a Gram-negative coccobacillus. There are four Brucella strains of zoonotic importance in our domestic species, subdivided by their culture phenotypes: Brucella abortus (B. abortus, B. melitensis, B. suis (smooth strains) and B. canis (rough strain). Dogs can serve as hosts for all four of the zoonotic strains; however, routine serologic testing in dogs has been limited to the identification of antibodies to B. canis. The aim of our study was to identify a serologic test that can be utilized to identify smooth Brucella strain antibodies in canines. We hypothesize that the Brucella abortus Fluorescence Polarization Assay would be successful in identifying antibodies to smooth Brucella strain in canines. Ninety-five dogs, including forty-five hog hunting dogs were screened for circulating antibodies to any of the four zoonotic strains of the bacteria utilizing a combination of Canine Brucella Slide Agglutination Test (CBSA), Brucella canis Agar Gel Immunodiffusion II test (AGID), Brucella abortus Card Agglutination Test (BCA), and the Brucella abortus Fluorescence Polarization Assay (FPA). Test interpretation results yielded a 0% (0/95) smooth Brucella strain seropositivity rate, with 2% (2/95) of dogs yielding inconclusive rough Brucella strain serology results (0-2% rough strain seropositivity rate). Additionally, a retrospective portion of the study was performed to identify sera containing circulating antibodies to any of the smooth strains of Brucella by testing previously banked canine serum samples stored at Cornell's Veterinary Diagnostic Laboratory from 2018-2019 via Brucella abortus FPA. Of the 769 serum samples tested, 13/769 (1.7%) yielded an inconclusive result, 725/769 (94.2%) were negative, 30/769 (4%) yielded a positive FPA test result, and 1/769 (0.1%) had to be excluded due to insufficient sample remaining to perform the diagnostic test. Of the 30 FPA positive canine serum samples, 97% (29/30) also tested positive on the CBSA test. Additionally, there was a statistically significant (p <0.0001) likelihood of altered (spayed/neutered) and mixed breed dogs to be FPA positive when compared to intact, purebred dogs.
General Audience Abstract
Brucellosis is a bacterial disease that can cause severe reproductive, orthopedic and general illness in both dogs and humans. There are four different species of Brucella that can be transmitted between animals and people: Brucella canis, abortus, suis, and melitensis. Although Brucella canis is the species that is widely recognized and breeding dogs are routinely tested for this strain, we have vastly under recognized the ability for dogs to contract and transmit the other three (smooth) Brucella species. Of added concern is the fact that the test currently used to screen dogs for brucellosis only identifies Brucella canis infection. Thus, veterinarians may be missing cases where dogs are infected with other Brucella species. This study revealed promising evidence in identification of smooth Brucella strain antibodies in canines, particularly altered and mixed breed canines, via the Brucella abortus Fluorescent Polarization Assay. The contributions of this study are threefold. First, to heighten awareness that both smooth and rough strains of brucellosis infection in dogs are infectious diseases of zoonotic concern. Second, it demonstrates that smooth Brucella strain infection along with the traditional strategy of selectively screening dogs breeding dogs may be underestimating the prevalence of brucellosis among the canine population in the United States thus, supporting the need for broadened screening recommendations. Third, it reveals the need for a commercially-available, validated test for the smooth strains of brucellosis in dogs and offers direction for future research efforts to likely focus on the validation of the Brucella abortus Fluorescent Polarization Assay.
- Masters Theses