Brucella spp

From Dog
Aborted canine fetus as a result of B. canis infection[1]
Scrotal edema consequent to venereal spread of B. canis[2]

Brucella spp are a Gram-negative facultative intracellular zoonotic alphaproteobacteria which causes canine brucellosis in many countries worldwide.

Species which are pathogenic to dogs include:

  • Brucella canis
  • Brucella abortus
  • Brucella suis[3]
  • Brucella melitensis[4]

Infection with B. canis is common in Central and South America, southern USA and Canada[5]. It has also been reported across Europe, Asia-pacific and South Africa[6]. From epidemiological surveys, co-infection with other hemoplasmas such as Leishmania spp is common.

Brucella canis infection can be clinically unapparent in dogs, and be transmitted to humans[7]. Humans become infected through the consumption of infected, unpasteurized animal milk and milk products, through direct contact with infected animal parts, through ruptures of skin and mucous membranes and through the inhalation of infected aerosolized particles[8].

Dogs become infected with Brucella spp via the oropharynx, venereal spread or conjunctiva[9]. The parasite survives within phagocytes, thus avoiding the host defense mechanisms, but induces a Th1 or Th2 helper-cell response[10]. The bacteria are subsequently disseminated via phagocytes to lymph nodes, spleen and genital organs but most organs can become infected[11]. Bacteremia occurs 1 to 4 weeks after the infection and persists for at least 6 months, then recurs intermittently for up to 5 years[12].

Some species, such as B. suis and B. melitensis occur through dogs exposed to pig. B. suis infections in dogs have not yet been reported as zoonotic to humans, unlike B. melitensis, which can infect humans[13].

Dogs are most commonly infected by contact with vaginal discharges at estrus or after abortions, or by ingesting infected placentas or fetuses. Brucella abortus infection is usually a result of dogs being fed fetuses from cows[14]. The mechanism of spread of B. suis is unknown is more pathogenic to humans than B. canis, and its mechanisms of pathogenesis in dogs can vary, the same recommendations might not be true for B. suis–infected dogs. Given the serious zoonotic implications of these bacteria, euthanasia may be advocated by regulatory agencies and physicians treating exposed humans.

Clinical signs may often be undetected, but infertility, reduced litter size, abortion and neonatal deaths are common[15]. Subsequent lymphadenopathy, vaginitis, epididymitis and posthitis are common and need to be distinguished from canine herpesvirus[16]. Chronically infected dogs are often oligo- or azoospermic, and infertile[17].

Other symptoms have been reported, such as osteomyelitis, endocarditis, chronic meningitis, endophthalmitis[18] and anterior uveitis[19].

Diagnosis is based on blood cultures, standard slide and tube agglutination tests taken from blood or vaginal/preputial swabs[20]. Agglutination assays are not specific compared with ELISA assays[21], and PCR assays is usually required for definitive speciation[22][23]. Blood cultures can often be negative yet positive with PCR, underlying the important of correct detection methods[24].

Treatment involves a 4 - 6 weeks course of enrofloxacin, trimethoprim-sulfamethoxazole, doxycycline or clindamycin. Clinically, no antibiotic treatment has been shown to eliminate the infection in all treated animals[25]. Spaying or neutering to prevent breeding is advisable but might not be completely effective.

In outbreaks in a kennel situation, infected dogs should be quarantined and, if necessary, euthanized after showing positive test results[26].

The premises should also be thoroughly disinfected before restocking.


  1. Vetnext
  2. Iowa State Univ
  3. Ramamoorthy S et al (2011) Brucella suis infection in dogs, Georgia, USA. Emerg Infect Dis 17(12):2386-2387
  4. Hinić V et al (2010) Brucellosis in a dog caused by Brucella melitensis Rev 1. Vet Microbiol 141(3-4):391-392
  5. Bosu WT & Prescott JF (1980) A serological survey of dogs for Brucella canis in southwestern Ontario. Can Vet J 21:198–200
  6. Holst BS et al (2012) The first case of Brucella canis in Sweden: background, case report and recommendations from a northern European perspective. Acta Vet Scand 54:18
  7. Kim JS et al (2012) Complete Genome Sequence of Brucella canis Strain HSK A52141, Isolated from the Blood of an Infected Dog. J Bacteriol 194(18):5134
  8. Haque N et al (2011) An overview of Brucellosis. Mymensingh Med J 20(4):742-747
  9. Carmichael LE & Kenney RM (1970) Canine brucellosis: the clinical disease, pathogenesis, and immune response. J Am Vet Med Assoc 156:1726–1734
  10. Baldwin CL & Goenka R (2006) Host immune responses to the intracellular bacteria Brucella: does the bacteria instruct the host to facilitate chronic infection? Crit Rev Immunol 26:407–442
  11. Serikawa T & Muraguchi T (1979) Significance of urine in transmission of canine brucellosis. Nihon Juigaku Zasshi 41:607–616
  12. Carmichael LE et al (1984) Problems in the serodiagnosis of canine brucellosis: dog responses to cell wall and internal antigens of Brucella canis. Dev Biol Stand 56:371–383
  13. Seleem MN et al (2010) Brucellosis: a re-emerging zoonosis. Vet Microbiol 140:392–398
  14. Cadmus SI et al (2011) Seroprevalence of Brucella abortus and B. canis in household dogs in southwestern Nigeria: a preliminary report. J S Afr Vet Assoc 82(1):56-57
  15. Makloski CL (2011) Canine brucellosis management. Vet Clin North Am Small Anim Pract 41(6):1209-1219
  16. Dahlbom M et al (2009) Seroprevalence of canine herpesvirus-1 and Brucella canis in Finnish breeding kennels with and without reproductive problems. Reprod Domest Anim 44(1):128-131
  17. Carmichael LE (1976) Canine brucellosis: An annotated review with selected cautionary comments. Theriogenology 6:105–116
  18. Ledbetter EC et al (2009) Brucella canis endophthalmitis in 3 dogs: clinical features, diagnosis, and treatment. Vet Ophthalmol 12(3):183-191
  19. Ledbetter EC et al (2009) Brucella canis endophthalmitis in 3 dogs: clinical features, diagnosis, and treatment. Vet Ophthalmol 12:183–191
  20. Keid LB et al (2007) A polymerase chain reaction for detection of Brucella canis in vaginal swabs of naturally infected bitches. Theriogenology 68(9):1260-1270
  21. Barkha S et al (2011) Immunochemical characterization of antigens of Brucella canis and their use in seroprevalence study of canine brucellosis. Asian Pac J Trop Med 4(11):857-861
  22. Hinić V et al (2008) Novel identification and differentiation of Brucella melitensis, B. abortus, B. suis, B. ovis, B. canis, and B. neotomae suitable for both conventional and real-time PCR systems. J Microbiol Methods 75(2):375-378
  23. Sayan M et al (2011) Investigation of Brucella canis seropositivity by in-house slide agglutination test antigen in healthy blood donors. Mikrobiyol Bul 45(4):655-663
  24. Truong LQ et al (2011) Epidemiological survey for Brucella in wildlife and stray dogs, a cat and rodents captured on farms. J Vet Med Sci 73(12):1597-1601
  25. Wanke MM et al (2006) Use of enrofloxacin in the treatment of canine brucellosis in a dog kennel (clinical trial) Theriogenology 66:1573–1578
  26. Communication of the Georgia Department of Community Health (DCH) Division of Public Health Brucellosis; information for dog owner, 2011. cited 2011 Aug 25