Schematic representation of the main ports of entry, dissemination and persistence foci, and excretion of Brucella

The main way of transmission for brucellae is through aerosols, for example through contact with abortion products with massive amounts of bacteria per gram. Hence, brucellae access the organism mainly through the oral and nasal mucosae, where they are internalised by phagocytes that fail to clear the infection. Brucella survive and replicate within these cells and, as a consequence, they disseminate through the organism, developing into a systemic infection. This way, Brucella can access their preferential organs for replication, such as the spleen or the reproductive organs (e.g., the placenta), resulting in abortion and excretion in the milk in females, further transmitting the infection to new individuals. (Created with Biorender.com).