Global dynamics of a multi-stage brucellosis model with distributed delays and indirect transmission.

The mechanisms of brucellosis transmission are diverse and complex, especially the role of young animals in the spread of brucellosis has not been well studied. In this article, a new deterministic system that incorporates various stages of susceptible individuals and time delay of infection is proposed. Under general biological assumptions, the qualitative properties and stability of the system are studied, the results illustrate that the global dynamics of equilibrium points depend on the basic reproduction number R₀: If R₀≤1, animal brucellosis will eventually die out; and if R₀>1, animal brucellosis is persistent and eventually tends to the endemic steady state. These results suggest that distributed time delay is harmless for the dynamics of the spread of brucellosis when R₀ is greater than one or less than or equal to one. Finally, periodic phenomena are found by numerical analysis if the assumptions are not true.