Merck Manual

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Professional Version

Overview of Brucellosis in Dogs


Paul Nicoletti

, DVM, MS, DACVPM (Deceased), College of Veterinary Medicine, University of Florida

Reviewed/Revised Jul 2013 | Modified Oct 2022

Although dogs occasionally become infected with Brucella abortus, B suis, or B melitensis, these sporadic occurrences typically are closely associated with exposure to infected domestic livestock ( see Brucellosis in Large Animals Brucellosis in Large Animals ).

B canis is a cause of abortion at 45–55 days of gestation in kenneled dogs. Dogs are the only definitive host of this organism. Infection has caused a reduction of 75% in the number of pups weaned in some breeding kennels. The disease disseminates rapidly among closely confined dogs, especially at time of breeding or when abortions occur. Transmission occurs via ingestion of contaminated materials or venereal routes. Urine transmission has been reported but seems to be unusual. Both sexes appear to be equally susceptible.

Primary signs are abortion during the last trimester of pregnancy without premonitory signs, stillbirths, and conception failures. Prolonged vaginal discharge usually follows abortion. Abortions may occur during subsequent pregnancies. Infected dogs may develop generalized lymphadenitis and frequently epididymitis, periorchitis, and prostatitis. Spondylitis and uveitis are occasional complications. Bacteremia is frequent and persists for ~18 mo after exposure. Fever is not characteristic.

Diagnosis is based on isolation and identification of the causative agent or by serology. The organisms can usually be readily isolated from vaginal exudate, aborted pups, blood, milk, or semen of infected dogs. The most widely used serologic test is an agglutination test by a tube or slide method. Nonspecific agglutination reactions occur in some dogs. To eliminate nonspecific antibody reactions, the serum is treated with 2-mercaptoethanol and retested. An agar gel immunodiffusion test performed in some laboratories is quite specific. Other tests, such as immunofluorescence and ELISA, have been used sometimes.

Attempts at immunization have not been successful. Control is based on elimination or isolation of infected dogs identified by positive cultural or serologic tests at monthly intervals. Incidence of infection is much lower in kennels where dogs are caged individually. Longterm therapy, eg, with a combination regimen of streptomycin or gentamicin and tetracycline, has been successful in many cases. Neutering of infected dogs is sometimes an alternative to euthanasia.

Prevention of canine brucellosis is done by testing before entry and breeding. The disease is reportable in some states. B canis is zoonotic, although cases of human infection are rare and less severe than those caused by the smooth species of the genus. The true incidence is unknown. Diagnostic tests used for smooth species do not cross-react with those for rough species; this may result in a missed diagnosis. In addition, signs of B canis infections may resemble those of other diseases. Appropriate measures to prevent exposure should be taken.

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