Brucella include arthritis or epididymo-orchitis, spondylitis, neurobrucellosis, liver abscess formation, and endocarditis, the latter potentially fatal. Human brucellosis is usually not transmitted from human to human; people become infected by contact with fluids from infected animals (sheep, cattle, or pigs) or derived food products, such as unpasteurized milk and cheese. Brucellosis is also considered an occupational disease because of a higher incidence in people working with animals (slaughterhouse cases). People may also be infected by inhalation of contaminated dust or aerosols, and as such, the CDC has labeled "Brucella" species as highly weaponizable. Human and animal brucellosis share the persistence of
Swine brucellosis nickel transport, "nikA", is activated by metal ion deficiency and is expressed once in the phagosome. Nickel is essential for many enzymatic reactions, including ureolysis to produce ammonia which in turn may neutralize acidic pH. Since "B. suis" is unable to grow in a strongly acidic medium, it could be protected from acidification by the ammonia. Summary: The most frequent clinical sign following "B. suis" infection is abortion in pregnant females, reduced milk production, and infertility. Cattle can also be transiently infected when they share pasture or facilities with infected pigs, and "B. suis" can be transmitted by cow’s milk.