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).

Geography

Brucellosis is present worldwide, with some high-income countries having a Brucellosis-free status.

Impact

Brucellosis is ranked among the most economically important zoonoses globally. Apart from economic losses from abortions and in milk production, farmers are sometimes forced to depopulate their herd in order to eliminate the disease. The total yearly cost of the disease is estimated to be US $452 million.

Epidemiology

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 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.

Control

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

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