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===Pathogenesis and pathogenicity===
===Pathogenesis and pathogenicity===
*Brucellae that lack outer membrane LPS (rough colonies) are less virulent than those which possess it
*Penetrate nasal, oral or pharyngeal mucosa
*Penetrate nasal, oral or pharyngeal mucosa
*Phagocytosed and carried to regional lymph nodes
*Phagocytosed and carried to regional lymph nodes
*Survive and multiply in cells of the reticulo-endothelial system
*Smooth organisms survive and multiply in cells of the reticulo-endothelial system
*Inhibit lysosome-phagosome fusion
*Inhibit lysosome-phagosome fusion
*Superoxide dismutase and catalase production may resist oxidative killing
*Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced
*Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced
*Surviving organisms spread to other organs (liver, spleen, placenta) and cause granulomatous reactions
*Surviving organisms spread to other organs (liver, spleen, placenta) and cause granulomatous reactions
*Eythritol is a growth stimulant and attracts the bacteria to the bovine placenta
*Eythritol is a growth stimulant and attracts the bacteria to the placenta of cattle, sheep, goats and pigs; also found in mammary gland and epididymis, targets for brucellae
*Infection of foetus and abortion
*Infection of foetus and abortion
*May localise in joints or intervertebral discs in chronic infections
===Diagnosis===
===Diagnosis===
*Serological testing of milk (Milk Ring Test) and beef cattle (Rose Bengal Plate Test)
*Serological tests detect anti-lipopolysaccharide antibodies
*LPS antigen present in virulent as well as some vaccine strains therefore vaccination may confuse serological testing
*False positives due to cross-reaction with LPS in other bacteria
===Control===
*Vaccination:
*Vaccination:
**Strain S19, a live vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing
**Strain S19, a live vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing