Yes, we have all read about canine brucellosis.
That disease has been eliminated from our dogs in the U.S., right? So why are we bringing this topic up again – we are tired of hearing about it by now, aren’t we?
Sadly, canine brucellosis is not gone from the U.S. It is not only still here, but it is here again. We have it indigenous in a small population of breeding dogs native to the U.S. But we have also seen it re-introduced into the U.S. through imported dogs that are not required to be screened for this disease.
What is Canine Brucellosis?
Starting at the beginning, canine brucellosis is caused by a bacteria called Brucella Canis. There are other strains of brucellosis that affect ruminants such as cattle, sheep, and goats. Most of the recent cases of brucellosis in dogs are canine in origin. But brucellosis can affect other canines, such as fox and coyotes in our wildlife population. Like Brucella abortus, the cattle version of brucellosis, which has been harbored in the wildlife populations of bison and buffalo in the Great Plains states, it may be difficult to eradicate because of this wildlife population reservoir. But that doesn’t mean we shouldn’t be vigilant.
On May 29, 2019, canine brucellosis was reported to have been imported into Wisconsin in a group of 26 South Korean dogs legally brought into the U.S. through Canada. While the group was awaiting importation, one dog in the group died. Symptoms and gender of this dog have not been reported. However, a veterinarian in Canada tested this dog and found it was positive for canine brucellosis. By the time the test results were available, the dogs had already moved into a Wisconsin shelter and had been co-mingled with approximately 100 other dogs. Two of the primary exposed group were also found to be positive – it is not clear if they were exposed while in South Korea or during transport and housing. Worse yet, these dogs (both the primary exposed group and the secondary exposed group) had been placed in the homes of the general public. Quarantine and repeated testing are currently underway; results are not yet available.
On May 5, 2019, a kennel in Marian County Iowa was determined to have dogs on site infected with canine brucellosis.
What’s the Big Deal?
The big deal about this is multi-level.
- Canine brucellosis is a zoonotic disease. This means the disease can be spread to humans and is known as undulant fever. Once in the human, the disease may never be eliminated – it hangs out in the bone marrow of the unfortunate recipient for the rest of their lives, causing waxing and waning symptoms that include fever, aches, and symptoms similar to that of influenza. It is of particular concern in the very young, the very old, patients who are immunocompromised such as patients on chemotherapy, steroids, other immunosuppressive drugs, and patients with diseases such as the human AIDS virus. Women who are pregnant can lose a pregnancy – and when you consider most caretakers of dogs in shelters, humane societies, rescue organizations, dog breeding kennels are young females of child-bearing age, this is especially worrisome. Granted, canine brucellosis is not commonly transmitted to people but the literature has multiple instances of human disease. One of the earliest cases reported was in an air-conditioner repairman who was exposed when he crawled under a porch and was exposed to an affected bitch and her litter. You don’t want yourself or a loved one in the footnote of the next published journal reporting zoonotic transmission.
- Dogs that are found to have serial positive test results are usually euthanized. This decision is made at the local level, by the state Veterinarian where the dog(s) are housed. In most states, this is a reportable disease – this means if your veterinarian finds your dog to have a positive brucellosis test result on a confirmatory test, your veterinarian is required to contact your State Veterinarian. In most states, there are written requirements for how individual and groups of affected dogs need to be managed. You don’t get to decide – it is in the hands of the authorities. Spaying and neutering along with long-term use of antibiotics are not 100% effective in managing this nasty bacterial infection. For this reason, euthanasia of all persistently infected dogs is frequently the outcome.
- Should you be one of the really compassionate people who find themselves involved in rescue dog transport or housing, or fostering dogs, you may be putting your personal dogs at risk. Even spayed and neutered dogs can contract and spread this disease.
- If you are not only helping these dogs but you are also a dog breeder, you may be putting your entire breeding program at risk. If you have introduced an infected dog into your car, home or kennel, you may have just destroyed a 40 year or longer breeding program.
- If you are involved in any part of handling rescue or relocated dogs, require that the organization managing their rehoming screen for this important infectious disease BEFORE you touch the dog, put the dog in your vehicle, or bring the dog(s) into your home, yard and/or kennel.
As previously stated, much has been written about canine brucellosis. This is a bacterial, infectious disease that can be spread both venereally and through handling placentas and other body secretions. Brucellosis causes reproductive failure in male and female dogs. Many infected dogs will appear to be in normal health. In females, they can have apparent missed breedings, puppies aborted prematurely, full term but weak puppies that fail to thrive or normal puppies. In males, they can experience swollen and painful testicles, failure to settle bitches, and inadequate semen quality. Brucella Canis has been reported to spread in frozen canine semen.
Testing for Brucella Canis
All dogs should be tested for Brucella Canis (B. canis) prior to using them for breeding dogs and/or moving in and out of your kennels. Testing can be done at your veterinary clinic or reference lab. The screening test is an RSAT test – a rapid slide agglutination test, which takes approximately 2 minutes. This test is very sensitive, meaning it is unlikely you would have a diseased dog test negative unless very early in the course of the disease. However, it is not very specific, meaning you can have a relatively high number of false positive tests. If the test is positive, there is a second step in the test kit that should automatically be run.
If both the first and second step are positive, follow up confirmatory tests need to be run at a reference lab. Cornell Veterinary Lab runs a test called AGID – this is usually the next test run if both steps of the RSAT test are positive. Most pathologists still consider blood cultures to be the gold standard of testing for brucellosis. Because brucella organisms grow slowly, this testing can take weeks to months. There is also a PCR test for brucella – this test looks for the DNA of the bacterial organism.
Should the reference lab test be positive, prepare for communications with your state veterinarian.
In summary, handle any dog that is not spayed or neutered as if it could be Brucella positive. You can’t be too careful.
Test frequently – you won’t save money by skipping testing. There is no cure for canine brucellosis. It is best to screen frequently and carefully to avoid this tragic scenario.
About the author: Marty Greer, DVM, JD has run the Veterinary Village Small Animal Clinic in Wisconsin since 1982. She is an expert in canine reproduction, is author of Canine Reproduction and Neonatology and a frequent lecturer on the subject. Dr. Greer also studied law at Marquette University and is a partner in Animal Legal Resources, LLC and is a board member of the National Animal Interest Alliance.