Brucella abortus is a Gram-negative bacterium and one of the causative agents of brucellosis. Cattle and other livestock are the major host species for the bacteria B. abortus. It is usually found to colonize in the liver and spleen.
When cattle have still births and are carrying this disease, other animals nearby can get infected if they ingest it or otherwise come into contact with fluids containing the bacteria. Ticks are another source of transmission for B. abortus.