The causative agent of canine brucellosis is the bacteria, Brucella canis.
Transmission between dogs occurs via mucous membranes, so the bacteria may
enter the body through the nose, mouth, conjunctiva of the eye, and vagina. The
majority of bacteria in infected dogs are secreted in semen and vaginal secretions,
but bacteria may be present in milk, urine and saliva as well. Thus any bodily fluids
can infect another dog.
Clinical signs of infection are variable. Dogs with brucellosis may show mild or no
clinical signs of infection. No deaths have been reported with B. canis infection.
Lymph node enlargement is a common finding, affecting most lymph nodes in the
body. The spleen and liver may also become enlarged. Fever is uncommon. Clinical
signs may be subtle, such as poor hair coat, lack of energy, or exercise intolerance.
Arthritis may be present, especially in the back. Recurrent eye infections may be a
problem in the dog with brucellosis.
The most common sign of brucellosis infection in a healthy-appearing bitch is
abortion between days 45 to 59 of gestation. The vaginal discharge associated with
abortion is typically brown or greenish gray in color. This vaginal discharge and
fetuses contain large numbers of Brucella bacteria. Other dogs and humans should
not come in contact with these secretions. When an infected bitch aborts, spread
throughout a kennel can be very rapid. The persistent discharge after abortion
contains extremely high numbers of organisms for 4 to 6 weeks. Milk also serves as
another contaminant to the environment. Infected bitches may deliver both living and
dead puppies. These surviving puppies are infected and will shed bacteria in their
Bitches infected with B. canis may appear infertile. These bitches typically do
conceive a litter, but resorb the fetuses early during gestation. Brucellosis should
always be considered when a dog is examined for infertility.
The Rapid Slide Agglutination Test (RSAT) is a widely used screening test for
brucellosis in dogs. A blood sample is taken from the dog to be tested, and serum
is separated. Patient serum is mixed with heat-killed Brucella ovis on a microscope
slide. B. ovis is used because it is similar to B. canis. Agglutination of the serum
sample is suspicious for B. canis infection. This test is highly sensitive, and
false-positive reactions do occur. A false positive is a test that appears positive in a
dog that is not infected with the disease. These false-positive reactions are caused
by cross- reactions with Bordetella bronchiseptica (the kennel cough agent),
Pseudomonas, Moraxella, and other gram negative bacteria. Thus if the RSAT is
negative, it is safe to assume that the dog does not have brucellosis. However, if
RSAT is positive, further testing is necessary to determine if the patient is infected
with Brucella canis. Typically, the 2-mercaptoethanol tube agglutination test (2- ME
TAT) is used in these patients. Few false-positives result with this test. A dog that
tests positive with the 2-ME TAT should have the results confirmed using an agar
gel immunodiffusion test (AGID), or blood culture.
Dogs with brucellosis should never be used for breeding and euthanasia is the only
solution to the problem. These animals are a potential source of infection for other
dogs and humans. Combination therapy of aminoglycosides and tetracyclines has
been tried, but the treatment only makes the infected dog test "false" negative,
when in fact the dog is still very infectious and very much contagious. A breeding
bitch in a kennel should be permanently separated from the other dogs to minimize
the chance of spread. Euthanasia is the only true remedy for a dog that has tested
positive for brucellosis using the AGID test which is the blood culture. Remember
that a neutered, spayed, and/or antibiotic treated dog is still a source of infection to
other dogs and humans so this is not a proper option to exercise, even though some
vets are wrongly doing so.
Kennels with active stud dogs should never breed a male to an untested female.
The test on the female should be 7 days or less old and an original with the vet's
letterhead and showing an original signature, complete address, and current phone
number. Kennels should even test their own bitches before breeding them to their
own males since brucellosis is not simply a sexually transmitted disease; it can be
picked up anywhere that a healthy dog can come in contact with an infected dog's
bodily fluids which is everywhere other dogs go such as boarding kennels, dog
boxes, dog trailers, hunting fields, field trial club grounds, starting/running pens, and
even city parks.
Unfortunately, there is no vaccine available for the prevention or treatment of
brucellosis. Any new additions brought into the breeding kennel should be isolated
for at least one month, and should have two negative brucellosis tests one month
apart before being allowed into the kennel. Stud dogs that are actively breeding
should be tested at least once every three months. Dogs and bitches competing
regularly in field trials should be tested once per month and kept segregated from
the main kennel area where breeding studs, brood bitches, and puppies are kept.
Brucellosis-infected bitches should not be bred, even with artificial insemination, due
to the risk of contamination from vaginal discharge, milk, and puppies. If a dog or
bitch in the main kennel area does test positive for brucellosis, the entire kennel
must be tested. Several tests should be done on each dog, each one a month
apart, to make sure that all positive animals are identified, and then immediately
destroyed and properly disposed of.