Brucellosis

What it is

Brucellosis is a zoonotic infection transmitted to humans by contact with fluids from infected animals, whether sheep, cattle, goats, pigs or others, or with derived food products such as unpasteurized milk and cheese. Brucella melitensis, a gram-negative coccobacilli, is the organism that causes it. Through history the disease has taken many different names, including Mediterranean, Maltese or Crimean fever, and undulant fever.

Causes and risk

Human brucellosis is the most common zoonosis worldwide. It is most commonly seen in the Mediterranean countries, the Balkans, the Persian Gulf, the Middle East, and Central and South America. Contaminated sheep and goat milk with B. melitensis appears to be the leading source of human brucellosis worldwide, and humans are accidental hosts who can develop the disease from contact with tissues rich in erythritol and from shedding of organisms in milk, urine and birth products from goats and sheep.

Other routes of transmission are direct contact with infected animals or their secretions through bruises and lacerations on the skin, inhalation of infected aerosols, and conjunctival inoculation, an occupational hazard that includes lab workers. The same animal contact raises another organism to be told apart from it: Coxiella burnetii, a gram-negative intracellular bacterium that causes Q fever, whose human infections are associated with contact with infected cattle, sheep, goats, dogs and cats.