Brucellosis is an important venereal disease in many species. It does not usually come up in pet ownership because most pet dogs are not used for breeding. Once someone has decided to breed their dog, though, it behooves them to know all about this disease, particularly since it can be transmitted to humans.
ALL DOGS TO BE BRED SHOULD HAVE A BRUCELLOSIS TEST.
If you are planning to breed your dog, test your dog and insist that the owner
Active stud dogs should be tested every six months.
WHICH TYPE OF BRUCELLA
There are ten species of Brucella and while Brucella canis is of most concern for dogs; dogs can certainly become infected with Brucella abortus (from cattle), Brucella melitensis (from goats) and Brucella suis (from pigs) if they are allowed to drink contaminated milk or eat leftover birth membranes, contaminated meat, or aborted young. Other Brucella species are Brucella ovis, which affects only rams, Brucella neotomae, which affects desert mice, Brucella microti which affects rodents and voles, Brucella ceti and Brucella pinnipedialis, which affect marine mammals, and Brucella inopinata, which has only been found once in a human breast implant infection. Luckily for humans, Brucella canis causes much less serious disease in humans than do the livestock Brucellae but the health department still considers any Brucella infection reportable.
WHAT HAPPENS AFTER INFECTION?
The organism requires 3 weeks on the average to become evident in the bloodstream. After that it localizes in the reproductive or urinary tract and either continuously or periodically seeds the bloodstream from there. Lymph nodes can enlarge and possibly the spleen or liver can become inflamed but generally the infected adult dog does not seem sick in the short term. Chronic disease from long term immune stimulation can result. Diseases produced by this kind of long term inflammation can include::
Most of the time, the only sign is aborted pregnancy between the 45th and 59th day of pregnancy (relatively late in the pregnancy). Classically, the aborted pups appear to have died at least several days prior to abortion as they do not look freshly dead. Abortion does not always appear in this most common form, though. Sometimes, the pregnancy is lost so early in its course that the problem is mistaken for infertility. Sometimes puppies are still born. Sometimes they are born live and infected.
Direct culture of the organism from a dead puppy, infected dog’s blood or from secretion is confirmatory but the organism is difficult to isolate in this way. This means we usually depend on immunologic tests. Which test is selected depends on what the test is being used for.
SCREENING BEFORE BREEDING:
The RSAT (Rapid Slide Agglutination Test) is a screening test that can readily identify negative dogs. That is, if the test comes out negative, the dog can be considered negative. If the test comes out positive, further testing is needed. Up to 60% false positives occur. A test kit is available for use inside the veterinary hospital and some facilities can perform this test while you wait.
The IFA (Immunofluorescent Antibody) test is a similar screening test but it must be sent to the reference laboratory. The same guidelines apply: negative means negative, positive means do further tests.
First of all, the infected dog must be removed from the breeding program (spayed, neutered or euthanized) and isolated from any animals to be used for breeding. Ideally the dog would be permanently isolated from all other dogs so as not to transmit the infection at all. The dog can remain as a pet but probably should not be sold due to potential health risks to potential buyers. For pet dogs, a course of antibiotics can be given but since this bacterium is so good at hiding inside the host’s cells one can never assume it is ever truly gone. Some people keep their dogs on tetracycline for life. Dogs do recover from this infection without treatment but it can take up to five years. Naturally recovered dogs cannot be reinfected; antibiotic-treated dogs can be reinfected.
Treatment options for the initial course:
Doxycycline and an Aminoglycoside
Tetracycline and Streptomycin
In this regimen, tetracycline is given twice times daily for a month and injectable streptomycin is given daily for the first and last week of the month. In one study over half the dogs were considered cured with this regimen but currently streptomycin is difficult to come by (as it is considered very old fashioned and with few uses at this time).
Minocycline and Streptomycin
Minocycline is a derivative of tetracycline that can also be used to treat Brucellosis but it is not effective when used alone. Again, four weeks of treatment is needed. Minocycline is used once daily while the aminoglycoside is used daily during the first and last week.
Lack of availability of streptomycin has been a problem for the treatment of this condition. Aminoglycosides such as gentamycin have been proposed as substitutes but are not as effective. Quinolone antibiotics such as enrofloxacin have also been proposed as substitutes. These are much less toxic than aminoglycosides and may emerge as the best replacement for streptomycin.
Because of the potential for human exposure, euthanasia is encouraged for confirmed positive dogs. In some states, euthanasia of positive dogs is mandatory. If you choose to keep a positive dog for a pet, see the links below to minimize contact with infected body fluids.
KEEPING BRUCELLA OUT OF THE KENNEL
A new dog for a breeding kennel should be isolated for one month. Two Brucella tests 2-3 months apart should be adequate to confirm negativity (it takes 8-12 weeks from infection for tests to turn positive). If an infection is detected in a kennel, the entire kennel population should be evaluated and re-screened every 3 months. The kennel should be quarantined until all dogs have tested negative three times with 3 months between tests. Positive dogs should be removed from the kennel.
The potential for human disease is always present if one is living with a positive dog. Here are some links to help with more details:
Page last updated: 9/8/2019