Brucella canis otherwise known as Canine Brucellosis, is a small, rough intracellular Gram-negative bacteria, which was first isolated in the United States in 1966 following the documentation of mass beagle abortions.
- canis, like other Brucella species adheres to mucous membranes, then spreads to the lymph nodes and appears in the blood within 7-30 days post-infection with an affinity for organs such as the prostate, uterus, and placenta. B. caniscan persist in the blood and secretions for years as well as in the lymph nodes and internal organs, such as the vagina and uterine in the female dog and testicles and seminal fluids in the male dog.
Canids are the natural hosts of the bacteria. Transmission between dogs occurs via mucous membranes, so the bacteria can enter the body through the nose, mouth, conjunctiva of the eye and the vagina. The majority of bacteria in infected dogs are secreted in semen and vaginal secretions and therefore the disease is mainly sexually transmitted. Bacteria may also be present in milk, urine and saliva meaning any body fluids can infect another dog.
When an infected bitch aborts, the disease can spread throughout a kennel extremely rapidly. Infected bitches may deliver both living and dead puppies. The surviving puppies will be born infected and will shed bacteria in their secretions.
Transmission between dogs through objects is also possible, although the survival of B. canis in the environment is relatively low and can be easily destroyed by common disinfectants such as ammonium, bleach, alcohol, iodine, etc. The disease usually spreads in kennels and in places where dogs are in high-density, and is less common among privately kept dogs.
Clinical signs: The severity of the disease is proportionally related to the number of bacteria that enters the dog’s body. Usually clinical signs are absent in a non-gravid bitch, and are difficult to notice during a physical examination. B. canis affects the reproductive system both in female and male dogs, and is characterized by reproductive disturbances.
Since B. canis causes an acute necrotizing inflammation of the uterus, litters are commonly aborted, usually in the last two weeks of gestation, or the puppies often die shortly after birth. A bitch that aborts after 45 days of gestation should be highly suspected of Brucellosis. Usually the fetuses are partially decayed and accompanied by a gray to green vaginal discharge. This discharge may contain very high numbers of the bacteria. If embryos die early, they may be reabsorbed and the female may never appear to be pregnant at all. In males, there are often no signs, except for advanced cases when the testicles may be uneven in size (see table 1).
Table 1. Major Clinical Signs
|Both||Mild or no signs.
Usually no fever.
|Female||Lymphadenopathy or no signs.
Fertility problems (conceiving or keeping pregnant).
|Pregnant female||Abortion in a late gestation stage.
A brown or greenish-gray vaginal discharge.
|Male||Lymphadenopathy, epididymitis, testicular abnormalities, infertility, enlarged scrotum.|
|Surviving pups||General lymphadenopathy, persistent globulinemia, transient fever, leukocytosis, seizures.|
Other signs may appear, including discospondylitis, splenomegaly, ocular disorders and other more rear signs such as osteomyelitis, meningitis and CNS signs. When blood tests are normal and there is splenomegaly and/or lymph-adenomegaly with discospondylitis, a brucellosis infection can be suspected.
Preferred Method of Diagnosis: The diagnosis of Canine Brucellosis is largely based on serology. Some dogs seroconvert as soon as 2-4 weeks after infection but others may not have detectable titers until 3-4 months post-infection. Chronically infected animals can sometimes be seronegative. Therefore, it is preferred that serology testing be performed in infected bitches during estrus, pregnancy, or after an abortion, when the antibody levels tend to be higher. Since most serological methods have been proven to produce false positive results, it is recommended to confirm infection by either taking a B. canis culture or performing a PCR test. Once the disease is confirmed and a decision is made with the veterinarian, it is recommended to keep the dog isolated and take precautions while handling it.
ImmunoComb Canine Brucella Antibody Test Kit[RN1] :
Detecting and treating B.canis can be challenging. Biogal’s ImmunoComb serology test detects and measures multiple antibodies and produces extremely accurate semi-quantitative results. The test is based on a solid phase “dot”-ELISA technology. Following an infection, significant levels of IgG anti-B. canis antibodies are produced. The intensity of the test’s spots’ colors corresponds directly with the antibody level in the test sample (from a score of S1 to S6. S3 being the positive reference spot).
Table 2. Interpreting the Results
|0||Neg.||Healthy Dog||Undetectable levels of IgG antibodies to B. canis.||Recheck before the next breeding|
|Suspected Dog||Retest in 7-10 days.|
|1-2||Low Pos.||Healthy Dog
||Insignificant levels of IgG antibodies to B. canis.
Results may be non-specific.
|Recheck before the next breeding|
|Suspected Dog||Retest in 7-10 days.|
|3||Med. Pos.||Healthy Dog
|Positive IgG titer confirms exposure to B. canis.||Perform confirmatory B. canis isolation.
Isolate the dog, until a decision regarding the dog’s fate is made.
|³4||High Pos.||Healthy Dog
||Significant IgG titer confirms exposure to B. canis.
||Perform confirmatory B. canis isolation. Isolate the dog, until a decision regarding the dog’s fate is made.|
Main Application: Screening for previous exposure to B. canis. Negative results confirm the absence of antibodies. A rising titer between two tests taken 7-14 weeks apart is highly suggestive of a recent infection.
If the test result is negative in a puppy up to the age of six months, the chance of infection is extremely low. Upon receiving a positive result another verification test should be performed through another method, due to the possible false positive results. If, however, the result of the verification test is positive, the puppy should be retested at the age of six months, since the positive result may have been obtained from the presence of maternal antibodies, which should disappear by this age.
Managing B. canis outbreaks depends greatly on the dog’s geographical region and whether the disease is considered a “reportable disease.” In general, although euthanasia serves as a strict approach, it is still accepted due to the risk to canine and human populations.
Other approaches include a combination between a surgical removal of the reproductive tissues of the ovary or uterus, testes and epididymis and a multiple antibiotics treatment. It is recommended to combine antibiotics from the tetracycline family with additional antibiotics from other families such as quinolones or aminoglycosides, for a minimum of 6-8 weeks. Unfortunately, even then the treatment fails to completely eliminate the bacteria in most cases and recurrences are possible. Therefore testing should be performed at the end of the treatment, and at a 3-month interval thereafter, until serological results are negative on at list two successive tests.
In conclusion, there is no denying Canine Brucellosis’ diagnosis and treatment can be complicated. Not only do many infected dogs show no clinical signs, bacteria are rapidly transmitted and very persistent even after treatment, and B. Canis can be transmitted to humans. Therefore, it is highly recommended to screen all dogs as a routine procedure, particularly those in breeding kennels and in places where dogs are kept together.
CBC Recommendations (2012)
OIE Publication (2018).
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Mazar, S., Rudnik, M., Nir, L. (2007). Comparison of the Canine Brucella Antibody ImmunoComb® Test Kit to the Immunofluorescence Assay. An unpublished study.
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