Brucella is a facultative intracellular pathogen. It uses its virulence factors, including effectors translocated by the VirB type IV secretion system, to block host cell defences and create a novel intracellular niche which allows it to survive and replicate in host macrophages. In animals the bacterium causes infectious abortion and other reproductive problems while in man the disease is also known as Malta or undulant Fever. Brucellosis is an important zoonosis and the disease in man is very severe and is contracted following direct contact with infected animals or following the ingestion dairy products derived from infected animals. Brucellosis has a world-wide impact in terms of its epidemiology, human health risks and its impact on trade. The greatest impact of brucellosis is in the poorer, rural areas of the world, without the funds, nor the infrastructure to establish surveillance and eradication programs.