Canine Brucellosis

Canine brucellosis is a contagious infection produced by a gram-negative coccobacilus called Brucella canis. Brucellosis can infect cattle, sheep, goats, dogs and humans as well as pigs. Cats, however, seem to be somewhat resistant to the bacteria. The main sources of infection are vaginal fluids of infected females and urine in males. Infection with Brucella canis in dogs leads to abortion, infection of the sexual organs in males, and infertility. There are six species of Brucella and the dog is mostly concerned with Brucella canis; however, dogs can become infected with Brucella abortus, Brucella melitensis and Brucella suis. Brucellosis can be contracted sexually but it can also be contracted by inhalation.

The most significant symptoms are late abortions in females, inflammation of the testicles in males and infertility in both sexes, as well as generalized inflammation of the lymph nodes, inflammation of the disk (discospondylitis) and uveitis. Signs may include fever, hind limb weakness, lethargy, and/or general lymph node swelling. In males, the primary sign of infection is inflammation of the testicles and reluctance to mate because of this inflammation. The dog may show no clinical signs, but still transmit the bacteria in semen or vaginal fluid.

Diagnosis The diagnosis of B. canis infection in dogs is based on bacteriological examination and serological methods

Treatment Brucellosis is difficult to treat. It may take a long period of antibiotic therapy to fully rid the dog of the bacteria. No antibiotic treatment is 100% effective and the infection often recurs in animals apparently treated successfully. Infected animals must be removed from the kennels and no longer used for breeding. Preferably, males should be castrated and females spayed.

Close contact between people and infected dogs increases the risk of transmission. Transmission of brucellosis from dogs to humans occurs, but it is quite rare. Although veterinarians exposed to blood of infected animals are at risk, pet owners are not considered to be at risk for infection. This is partly because it is unlikely that they will come in contact with blood, semen, or placenta of the dog. In humans, the disease can be very serious. Humans become infected when they handle birth fluids, or newborn puppies, from infected bitches, and fail to practice good hygienic practices. The disease in man is life-threatening with testicular swelling, recurrent fever and sometimes, disabling lesions of the spine. The bacteria may be cleared from the animal within a few days of treatment; however re-infection is common and some animal body fluids may be infectious for weeks. Immunocompromised persons (cancer patients, HIV-infected individuals, or transplantation patients) should not handle dogs known to be infected with B. canis. Depending on the timing of treatment and severity of illness, recovery may take a few weeks to several months.

Prevention Do not consume unpasteurized milk, cheese, or ice cream while traveling. If you are not sure that the dairy product is pasteurized, don't eat it. Hunters should use rubber gloves when handling internal organs of animals. There is no vaccine available for humans.

In humans brucellosis is also known as undulant fever or Mediterranean fever. B. melitensis, B. abortus and B. suis regularly cause human infection, but only rare infections with canine and marine species have been reported. Approximately 100 - 200 cases occur in the U.S. each year. People working in jobs requiring frequent contact with animals or meat—such as slaughterhouse workers, farmers, and veterinarians—are at high risk. The illness may be chronic and persist for years. Brucellosis is rare in the United States (except in the western states) and in visitors or immigrants from countries where it is prevalent (Spain, Mexico, South America, the Middle East). Since routine brucellosis diagnosis does not include B. canis investigation, infection with this species may be more widespread than is currently suspected. The RSAT (rapid slide agglutination test) could be a suitable screening test for the diagnosis of B. canis human brucellosis, and a supplementary technique, such as IELISA, performed on all positive RSAT samples that were negative by B. abortus antigen could confirm the diagnosis.