Brucellosis is a zoonotic disease that affects humans, cattle, small ruminants, pigs and dogs. Brucellosis in humans is usually a result of occupational exposure to infected animals, but infections can also occur from ingesting contaminated dairy products.

Causative agent

The Brucella bacterium is a small, Gram-negative, coccobacillus. They are facultative intracellular parasites, capable of growing and reproducing inside of host cells, specifically phagocytic cells. The most relevant species are B. melitensis (in goats, occasionally sheep), B. abortus (in cattle, bison, buffalo), B. suis (in pigs), and B. canis (in dogs).


Brucellosis is present worldwide, though some high-income countries having a Brucellosis-free status for some or all Brucella species. 


Brucellosis is ranked among the most economically important zoonoses globally. More than 500,000 new human cases are reported each year worldwide.  The primary livestock-based economic losses arise from abortions and decrease in milk production, however, farmers are also sometimes forced to depopulate their herd in order to eliminate the disease. The annual impact of Brucellosis to Small Scale Producers across Sub-Saharan Africa and South Asia is estimated at USD $500 million per year.


Infection occurs by ingestion, through mucous membranes, or through broken skin. The bacteria are shed from an infected animal at the time of calving or abortion. It is present in milk and in both male and female reproductive tracts. Brucella can survive in manure, hay, dust, and soil for several months. Eradication efforts are complicated by the presence of the pathogen in the wild animal populations. 

Clinical signs

Brucella causes chronic disease that, if not treated, persists for life. The most common clinical signs are abortions, stillbirths, reduced milk production, and infertility. Occasionally, testes inflammation, lameness, abscess formation, and paralysis have been observed.


Serological testing as well as tests on milk support surveillance work, and also individual animal testing for both trade and disease control purposes. 

Vaccination is also used in some endemic areas to reduce the incidence of infection. 


For further information, view our Brucellosis product development work.