Brucellosis: A Review

Abstract

Brucellosis is caused by bacteria of the genus Brucella and remains as a major zoonosis world wide. The disease is characterized by abortion, retained placenta and to lesser extent, orchitis and infection of accessory sex glands in males. Brucellosis is not a sustainable disease in humans. The source of human infection always resides in domestic or wild animal reservoirs. The disease is prevalent in the most countries of the world. Although many countries have eradicated Brucella abortus from cattle, in some areas Brucella melitensis has emerged as a major cause of infection in this species as well as in sheep and goats because of much focus on eradication of bovine brucellosis rather the ovine and caprine brucellosis. New Brucella strains or species may emerge and existing Brucella species adapt to changing social, cultural, travel and agricultural environment. Brucella suis is also emerging as an agent of infection in cattle, thus extending its opportunities to infect humans. Marine mammal brucellosis, due to two new proposed Brucella species i.e. B. cetaceae and B. pinnipediae, represents a new zoonotic threat for humans. Pathogenicity is related to production of lipopolysaccharides containing a poly N-formyl perosamine O chain, Cu-Zn superoxide dismutase, erythrulose phosphate dehydrogenase, stress-induced proteins related to intracellular survival and adenine and guanine monophosphate inhibitors of phagocyte functions. Protective immunity is conferred by antibody to lipopolysaccharide and T-cell-mediated macrophage activation triggered by protein antigens. Diagnosis still centers on isolation of the organism and serologic test results, especially enzyme immunoassay. Species and biovars should be identified by phage lysis, and by cultural, biochemical and serological criteria. Polymerase chain reaction (PCR) can provide both a complementary and biotyping method based on specific genomic sequences.