Brucella is not transmitted from a sick person to a healthy person. The reservoir and source of infection are domestic animals (sheep, goats, cows, pigs, less often dogs).
Infection with brucellosis from sick animals occurs by contact, food and air routes. Infection by contact occurs especially often when amniotic fluid gets on the skin (help with calving, lambing, when caring for newborn calves, lambs). Veterinarians, calves, shepherds, etc. are often infected. Infection can also occur through contact with the meat of infected animals, with manure.