Brucella canis in Montana

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• • • Guidance Documents
    • Disease Summary
    • Reportable Disease Information
    • Epidemiological Information
    • Guidance for Testing/Surveillance of Animals in Shelter/Rescue Channels
    • Guidance for Testing/Surveillance of Dogs in Breeding Kennels
    • Brucella canis Testing Options
    • Laboratory Criteria for Diagnosis and Case Definitions
    • Management Recommendations
    • Human Health Risk
    • Additional Resources

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    GUIDANCE DOCUMENTS

    Guidance for Testing and Test Interpretation Flow Chart (PDF)
    Guidance for owners of B. canis positive dog (PDF)
    Prevention and Control Recommendations (PDF)

     

    DISEASE SUMMARY

    Brucella canis (B. canis), the bacteria that causes canine brucellosis, is one of several zoonotic Brucella species. The domestic dog is the only significant host of B. canis and dogs rarely become infected with other Brucella spp (i.e. Brucella abortus in cattle or wildlife). The disease is endemic in areas with large populations of stray, intact dogs.

    This disease is mainly transmitted through reproduction and by nose/mouth contact with vaginal discharge or birthing fluids from an infected female. However, semen, urine, feces, blood, saliva, and nasal secretions can also contain the bacteria and are potential risks for transmission to people and other dogs. Furthermore, puppies can become infected from their mother during pregnancy.

    Clinical signs in intact animals include abortion, infertility, and genital abnormalities (esp. orchitis, inflammation of the testicles). However, recent cases have involved spayed/neutered dogs who may present with more general signs such as lethargy, lymph node enlargement and lameness/back pain due to discospondylitis. Additionally, many dogs with B. canis infection show no clinical symptoms. Unfortunately, the infection may go unnoticed for years, especially in animals infected at birth.

    For additional disease information on B. canis please click here.

     

    REPORTABLE DISEASE INFORMATION

    B. canis is a zoonotic reportable disease in Montana per Administrative Rule 32.3.104. The department has quarantine authority; however, cases involving single animals or cases isolated to a private residence are not routinely quarantined. Owners of B. canis positive dogs should be given information regarding the risks of this disease and the recommended management: Guidance for Owners of B. canis Positive Dog can be found here.

    Failure to comply to management recommendations and to disclose B. canis diagnosis will lead to a continued increase in positive cases, devasting disease in dogs, and potentially cases in humans.

     

    EPIDEMIOLOGICAL INFORMATION

    DOL has been tracking an increase in the number of overall testing and of reported B. canis positive cases, with several cases epidemiologically related based upon where animals originated. Areas with large populations of sexually intact animals, including reservations, are at a higher risk for B. canis infection. As a result, animal shelters/rescue organizations and individuals living in or around these areas are at a higher risk for homing infected animals.

    We are beginning to see a broader distribution of cases throughout the state. Shelter/rescue groups have contributed greatly to MT surveillance and perform a significant amount of MT testing.

     

    Fig. 1: Graph showing number of overall B. canis tests vs Number of positive results from screening tests performed at MVDL.  Last updated 2/1/2023. 

     

    

    Fig. 2: Number of positive B. canis tests by county from 7/1/2021-6/30/2022.

     

    

    Fig. 3: Number of positive B. canis tests by county from 7/1/2022-1/31/2023. Last updated 2/1/2023.

     

    

    Fig. 4: DOL has asked for increased surveillance testing for B. canis for the past 2 years.  In FY 22, 7/1/2021-6/30/2022, a large majority of overall testing was performed through rescue/shelter facilities.  However, the Owned Dog category yielded a higher percentage of non-negative results, likely because this group represented more symptomatic dogs.

     

    GUIDANCE FOR TESTING/SURVEILLANCE OF ANIMALS IN SHELTER/RESCUE CHANNELS

    DOL would like veterinarians and animal caretakers who work with and live with dogs from high-risk populations to be aware of the potential disease risk. Through education and surveillance testing, our goal is to reduce the number of positive animals placed into homes, thereby reducing the risk to human health. We encourage animal shelters, animal rescue organizations and concerned animal owners to work with a local veterinarian when trying to evaluate risk for B. canis.

    The DOL considers high-risk dogs and/or dogs that should be tested to be:

    • An animal that originates from a population with a high number of intact, stray dogs.
    • New intake at a shelter/rescue of a mature, intact animal if testing history is unavailable.
    • Dogs with exposure to a known B. canis positive dog.
    • Periparturient dogs that were not tested prior to breeding.
    • Sexually intact dogs as part of a routine pre-breeding exam.
    • Dogs with symptoms consistent with B. canis infection which cannot be explained by other disease.

    The symptoms associated with B. canis include:

    • Reproductive abnormalities: abortion, stillbirth, weak puppies that die soon after birth, infertility
    • Genital abnormalities: orchitis, epididymitis, scrotal edema
    • Discospondylitis
    • Lymphadenitis
    • Unexplained lameness or pain
    • Uveitis
    • Lethargy
    • Anorexia

    * Many patients with B. canis are asymptomatic

    High-risk dogs and dogs presenting with clinical signs should be screened for B. canis. Because B. canis, like other Brucella species is difficult to diagnose, DOL has developed a flow chart to help guide screening programs. The flow chart can be accessed here.

     

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  • GUIDANCE FOR TESTING/SURVEILLANCE OF DOGS IN BREEDING KENNELS

     

    Due to the increased concern for B. canis infection throughout the state, DOL recommends that breeding kennels perform screening tests of all dogs over 6 months of age at least once every year. If there are any reproductive abnormalities within the breeding group B. canis screening tests should be performed. If an intact male or female has left the kennel for any reason other than a veterinary visit, the dog should be tested 8 weeks after returning to the kennel.

    If a positive result is obtained, that dog should be isolated and classified as a Brucella suspect. The suspect dog should have a recheck after 30-60 days using the same test and laboratory as the first test. If the recheck is still positive, then additional testing is recommended for confirmation of disease.

    Additional information on best practices for prevention and control of B. canis in a breeding kennel can be found here.

     

    Brucella canis TESTING OPTIONS

    Brucella testing is a serial testing process. A serial testing process starts with a screening test followed by a confirmatory test of all non-negative samples. The purpose of a screening test is to detect ANY potential positive animal. This means there WILL BE nonspecific reactors, which require additional testing for definitive diagnosis.  Serial testing improves diagnostic specificity and positive predictive value of a test process and asks the animal to “prove” it is affected by the condition being tested.

    DOL recommends starting with the B. canis ELISA test that is offered through MVDL, which has few false negatives. A positive result on the B. canis ELISA test may indicate: a true infection, titers due to exposure (or from maternal antibodies if <6 months old), or cross-reaction to another pathogen. A negative result on the ELISA is considered a true negative unless the patient exhibits symptoms that are not explained by another disease. See the following table for additional testing information.

    DIAGNOSTIC OPTIONS

    Diagnostic Options

    Test	Sample	Sensitivity Specificity	Turnaround time	Comments/Links
    B. ovis/canis ELISA performed at MVDL *Recommended screening test*	Serum	Sn = 70% Sp = 97%	1-7 days	Good screening test Improved sensitivity and specificity compared to agglutination reactions Potentially better for detecting IgG response Diagnostic Lab Bureau (mt.gov)
    Indirect Fluroescent Antibody (IFA) performed at MVDL, IDEXX, Antech, and many others	Serum	Positive Predictive Value = 99%	1-3 business days	Detects presence of antibodies after 8-12 weeks Diagnostic Lab Bureau (mt.gov)
    Multiplex performed at Cornell	Serum	Sn = 95%	1 business day for negative results	Brucella Multiplex Testing for Dogs | Cornell University College of Veterinary Medicine Good screening test More costly than ELISA
    Agar Gel Immunodiffusion (AGID) performed at Cornell	Serum	Sn = 53% Sp = >99%		Changes to Brucella canis Serology Testing | Cornell University College of Veterinary Medicine Detects presence of antibodies after 8-12 weeks Only performed if Cornell Multiplex test is non-negative
    Brucella Culture performed at NVSL	Blood, urine, tissues, reproductive fluids		5-14 days	Fastidious, slow growing organism Slow turnaround, may require speciation by NVSL Negative does not rule out infection Positive is definitive
    PCR performed at Kansas State	Blood, reproductive fluids	Sn = 80-100% Sp = 92-100%	3-4 business days	False negatives possible due to intermittent bacteremia, inadequate extraction techniques Contamination can cause false positives 5x more sensitive than culture Poor screening test Catalog Item Details (k-state.edu)

     

    LABORATORY CRITERIA FOR DIAGNOSIS and CASE DEFINITIONS

    Diagnostic Criteria

    Diagnostic Criteria

    Definitive Diagnosis: Culture positive PCR positive Rise in B. canis antibodies on ELISA retest AND positive IFA OR positive AGID * Negative results on definitive testing are not considered true negatives

    Presumptive Diagnosis: Positive initial ELISA (S/P >0.8) Positive IFA Positive AGID

     

    Case Definitions

    Confirmed: definitive laboratory evidence with/without clinically compatible illness*

    Probable: presumptive laboratory evidence with/without clinically compatible illness*

    Suspect: - Clinical symptoms consistent with B. canis infection with negative screening test but no other diagnosis can be made Or - Asymptomatic patient with positive ELISA and decreasing S/P value on recheck.

    Case Definitions

    * Clinically compatible illness includes symptoms consistent with B. canis infection and/or presence of risk factors for B. canis infection and/or epidemiologically linked to a confirmed case

     

    MANAGEMENT RECOMMENDATIONS

    Unfortunately, the primary management recommendation for positive B. canis cases is euthanasia. B. canis is not curable, not a benign disease in the dog, and is a zoonotic risk. Sterilization (if intact), lifelong antibiotic treatment, isolation in the home, and routine testing are offered as a second management option though treating B. canis cases is challenging, can be expensive, and is not be considered curative. The bacterium can sequester in areas, such as the prostate, making it difficult for antibiotics to penetrate and eliminate all the organism. Recrudescence may be observed when administration of antibiotics is discontinued resulting in long-term treatment with combinations of medically important antibiotics. Ultimately, many cases result in euthanasia of the animal due to the secondary clinical signs that cannot be effectively treated.

    An owner that chooses not to euthanize his/her B. canis positive dog has the responsibility to limit the spread of this disease: Prevention and Control Guidance is located here.

    DOL currently recommends that shelter/rescue dogs that test positive for B. canis (even if test performed is considered a screening test) are euthanized.  An alternative option is to hold, isolate, and retest after 30-60 days. Dogs presenting to a shelter/rescue with any risk factors should be tested prior to adoption and, when possible, immediately upon intake and isolated until results obtained. B. canis infected dogs should not be placed in foster care nor adopted.  Should a B. canis positive dog be placed in a home, the adoptees must sign a disease disclosure document showing their understanding of the infection and potential risks to family members. Similarly, veterinarians have the responsibility to discuss the risks with owned dogs that test positive and provide disclosure paperwork.

     

    HUMAN HEALTH RISK

    The zoonotic risk of B. canis is not fully understood and human cases are likely under-diagnosed. While human infections appear uncommon, people who have a compromised immune system, young children, pregnant women, or persons with artificial heart valves are at risk of severe disease if they acquire the infection. Refer to the MT Department of Public Health and Human Services (DPHHS) document Canine Brucellosis-Q and A for Dog Owners for more information. Please contact your local public health office or physician with questions about the zoonotic risk.

    People who are in contact with breeding dogs, newborn puppies, or aborted fetuses should always practice good hygiene. In general, all animal caretakers should wear gloves when handling bodily fluids from an animal and should regularly wash hands with soap and water. More information on disease prevention can be found in the Compendium of Veterinary Standard Precautions for Zoonotic Disease Prevention in Veterinary Personnel. 

     

    ADDITIONAL RESOURCES

    Disease Information (PDF)
    Human Health Risk (PDF)
    Montana Veterinary Medical Association Resolution 2022 (PDF)
    USDA Best Practices for Brucella Canis in Breeding Facilities (PDF)