Final answer:
Strangles is the bacterial disease that is easily transmitted between horses through contaminated humans or objects.
Step-by-step explanation:
The bacterial disease that is spread by contaminated humans or objects and can be easily transmitted between horses is Strangles. This disease is caused by the bacterium Streptococcus equi and can lead to severe inflammation of the lymph nodes in the upper respiratory tract. Horses with strangles often have nasal discharge and may develop abscesses. It is highly contagious, and strict biosecurity measures are necessary to prevent its spread.