Canine Brucellosis 
by Sarit Bechor, DVM 

Canine Brucellosis is an infectious disease, caused by Brucella canis, a gram negative intracellular bacteria. It affects the reproductive system in both male and female, and it has a worldwide distribution with a public health concern.  

Dealing with Brucellosis might be very frustrating. Control of the disease in kennels, where Brucellosis is detected, is difficult, time consuming and agonizing for all parts. Therapy with antibiotics adds to the frustration, since its efficiency is uncertain and success occurs only in some cases. Failure to control the disease might lead to a serious economic loss. Therefore it is mostly important to detect every infected individual, and eliminate it as soon as possible from the kennel or from other dogs.  

Transmission:
B. canis is transmitted by contact, by penetrating intact mucouse membrane, especially those of oral cavity, vagina, placenta and conjunctiva. The main contamination sources are vaginal secretion, both during estrus and parturition, abortion, and post-partum in the fetus, placenta and lochia. Most commonly transmission occur in a venereal manner, from an infected male dog to a susceptible bitch, or through contact with aborted material.  

Clinical Signs:
Usually clinical signs are absent in a male dog and in a non-gravid bitch, and are hard to be noticed during a physical examination. Brucella canis affects the reproductive system both in female and male dogs, and is characterized by reproductive disturbances.  

Litters are commonly aborted, usually in the last two weeks of gestation, or the puppies may 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. In both female and male, there may be some extragenital symptoms such as lymphadentitis and discospondylitis, but they are rare.  

Diagnosis:
Diagnosis is difficult because of unstable serum antibody titers that vary from  individual to individual as well as between different methods. Furthermore, many dogs remain asymptomatic despite being infected. Laboratory test confirmation is required when brucellosis is suspected.    

Serological Tests:
Rapid Slide Agglutination Test (RSAT) – this test is quick, but false positive results are too common (60% of positive were actually false positive [ivis]).
Tube Agglutination Test (TAT) – semiquantitative determination– with false positive results are similar to those in the RSAT.
Agar-gel Immunodiffusion (AGID) Cell Wall (somatic) Antigen – this is a very sensitive test, but its procedure and interpretation is very complex. It suffers from nonspecific reactions.  
Indirect Fluorescent Antibody Test (IFA) – this test is available and convenient for diagnostic laboratories, yet no data have been published about its accuracy.
The ImmunoComb^® Antibody Test Kit – provides quantitative results. It is user friendly, and can be performed in any place, either the vet’s clinic or in the kennel.

Since the only available serological kit today, in veterinary clinics, is based on RSAT, which as mentioned above, has too many false positive results, Biogal has chosen the assay that is used in most diagnostic labs in universities, the IFA, as a reference. In a comparative study, the ImmunoComb^® Canine Brucella Antibody Test Kit demonstrated specificity of 98% and sensitivity of 98%.   The ImmunoComb^® test is a modified ELISA, which can be described as an enzyme labeled “dot assay”, that detects antibody levels in serum or whole blood. The kit contains all necessary reagents for developing the kit.  

Applications:

• As a diagnostic tool, when Brucellosis is suspected (repeating abortions, apparently failure to conceive, etc.).
• As part of health control and disease prevention, all dogs (both female and male) must be routinely tested serologically before mating  (7 days at the most).
• Stud dogs, that actively breed, should be tested once in every 3 months.
• Before introducing any new dog into the kennel, serologic test must be taken out.
• In case of brucellosis breakout in kennels, periodic screening should be taken out (see below).
• All canine blood donors should be screened for Brucellosis.  

Interpretation & Recommendation:
Negative Result, ImmunoComb^® Score = 1, Titer  ≤1:50, Interpretation: Not infected, Recommendation: Get into periodic screening, as part of preventative program in breeding kennels. 

Suspicious Result, ImmunoComb^® Score = 2, Titer 1:50-1:200, Interpretation: Previous disease or very recent infection, Recommendation: Repeat serologic test in 4-6 wks. Quarantine in the meantime. 

Positive Result, ImmunoComb^® Score = 3 - 6, Titer ≥1:200, Interpretation: Consider infected, Recommendation: (Before any of the following, diagnosis must be verified by culturing the bacteria). Pet dog: castration and treatment. Breeding dog:  act according to local regulations and recommendation.
 
* In case of introducing a new dog, quarantine for 4 weeks, and only then test.

Prevention and Control:
The absence of clinical signs in males, as usually occurs, plus the fact that they play a main role in transmitting the infection to females through mating, makes prevention and control hard to achieve. To reduce the risk of infection, it is recommended to test females and males at least once a semester.  Every new dog (both sexes) should be examined and should be quarantined for 4-12 weeks before entering the kennel.

In infected kennels, both positive and negative tested dogs should be taken notice.  Any positive tested dog should be taken away from the kennel. A combination of antibiotics should be given as a treatment, rather than one kind of antibiotic. Negative tested dogs should be treated for 1 month with tetracycline and streptomycin and carry out monthly control for 3 months.

Kennel cleaning is very important in order to prevent recontamination. The first 5 months, post infection, are the most expected period for new cases to appear. In kennels where brucellosis is detected, a continuing program of every 3 months testing of all dogs is recommended for the first year post individual infection.          

References:
Brucellosis (canine). From: http://www.spc.int/rahs/Manual/Canine-Feline/BRUCELLOSIS(CANINE).HTM
Greene E. G. (2006). Infectious Diseases of the Dog and Cat, 3rd edition, Saunders publication. pp. 369-381.   
Shin, S. & Carmichael, L. E. (1999). Canine Brucellosis Caused by Brucella canis. From: http://www.ivis.org/advances/Infect_Dis_Carmichael/shin/ivis.pdf   
Wanke M. M. (2004). Canine Brucellosis. Animal Reproduction Science, 82-83, pp. 195-207.