Canine Brucellosis: Disease on the Rise?
Part 1, What is Canine Brucellosis and its Symptoms?
Debra M. Eldredge, DVM
Brucellosis is a disease bandied about casually by many dog fanciers. Breeders recommend that all bitches have a negative Brucellosis test before any breedings, but often skimp on testing the stud dogs. It seems like such a routine problem. In reality, a diagnosis of brucellosis can be a kennel wipeout, not just the loss of an individual litter.
Brucellosis is caused by a bacteria called Brucella canis. There are other versions of the brucella bacteria that primarily infect pigs, cattle, sheep and goats. All of the versions appear to be at least mildly infectious to other species, including humans, making this a zoonotic disease. A dog can be infected with other versions of the brucella bacteria as well as the canine type. The bovine version of brucellosis is a reportable disease in virtually every state, but even the canine version is reportable in some states.
According to the Iowa State Center for Food Security and Public Health, this bacteria has been identified in dogs with reproductive problems all over the world with the exception of New Zealand and Australia. A study from Cornell sights figures as high as 20 to 30 percent for Central/South American dogs. The same study mentions estimates of 7 to 8 percent in stray dogs in Japan and the southern United States. Another site mentions infection rates possibly as high as 8 to 10 percent of the dogs in the US.
In people, blood tests indicating exposure show that as of July 2009, 67.8 percent of Oklahoma’s human residents had been exposed to brucella bacteria (probably including all the variants, not just the canine version). There have been documented cases of people contracting the canine form of brucellosis, even from the “tamer” laboratory strain, but clinical disease is not very common. The people most at risk of illness are the elderly, very young and anyone with any immunocompromising illness. Still, it makes sense for everyone to wear gloves dealing with any aftereffects of an abortion and take precautions.
In a case in Argentina, six people were diagnosed with brucellosis from Brucella canis after exposure to a bitch and her three puppies who were positive for brucellosis. The bitch had problems with her previous two litters, but had never been tested. This litter consisted of five puppies — two born dead and the three puppies who were positive. The puppies had grown up and two of them were placed in homes where people became ill. A positive bacterial culture grown from the ill 17-month-old baby was the tip off to look at brucellosis.
Brucella canis is an intracellular bacteria which means it can be difficult to treat — especially if your goal is a cure. Because the bacteria “hides” inside cells, it is tough for antibiotics to attack and kill it. In dogs, the bacteria tends to settle in reproductive and urinary organs. The most common signs seen in dogs are associated with reproductive failures. Bitches may abort, generally later in the pregnancy, at approximately seven to nine weeks. If puppies are born alive, they are often weak and die soon after. A few pups may live and those pups often develop brucellosis later.
After the abortion, the bitch will drain infectious fluid for up to six or eight weeks. Many bitches do not appear particularly ill themselves, but they may have enlarged lymph nodes, may act depressed and may have a decreased appetite. Weight loss and exercise intolerance may be noticed.
In males, the scrotum may be swollen and warm to the touch from inflammation. Some dogs will lick or chew at the area, causing a skin rash. Over time, the testicles may atrophy and some males will become sterile. The prostate often acts as a safe harbor for bacteria, leaving male dogs to shed brucellosis for long periods of time — sometimes even after neutering.
In chronic cases, dogs may develop inflammation of the vertebrae in the spine, inflammation of the eyes, heart problems or inflamed brain layers. Some dogs never show any real signs of illness at all.
While the most common way of spreading brucellosis is through direct sexual contact, it can be spread via other methods. If the male is infected, using artificial insemination, either with fresh chilled or frozen semen, may infect the bitch. Most groups who freeze semen insist on a negative brucellosis before processing the sperm.
Infected bitches shed the bacteria in the fluids from their uteri and in urine. Males shed brucella in their semen and urine. Smaller amounts of the bacteria may be shed in fecal material, saliva and any discharges from the eyes and nose.
Clearly it makes sense to test any breeding stock before ANY breedings. Previously, recommendations were often made to check stud dogs yearly and bitches before any breeding. Males should also be checked before any breeding. Breeders have tended in the past to only test outside dogs involved in breedings, that is, if they were breeding one of their own bitches to one of their own stud dogs, they rarely checked for brucellosis. With the possibility of infection from sniffing brucellosis laden urine at any places where dogs may gather — shows, dog parks, etc., — it makes sense to test before any and every breeding.
What tests to run, what test results mean and how to proceed if you get a positive test result will be covered next time, along with the possible time bombs that could mean brucellosis epidemics in the US.
For more information:
Epidemiol. Infect. (2010), 138, 280–285.
IVIS — Recent Advances in Canine Infectious Disease — Canine Brucellosis Caused by Brucella canis by S. Shin and L.E. Michael
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