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This paper presents a two stage SIS epidemiological model in animal population with bovine tuberculosis (BTB) in African buffalo as a guiding example. The proposed model is rigorously analyzed. The analysis reveals that the model exhibits the phenomenon of backward bifurcation, where a stable disease-free equilibrium (DFE) coexists with a stable endemic equilibrium (EE) when the associated reproduction number ( R v ) is less than unity. It is shown under two special cases of the presented model, that this phenomenon of backward bifurcation does not arise depending on vaccination coverage and efficacy of vaccine. Numerical simulations of the model show that, the use of an imperfect vaccine can lead to effective control of the disease if the vaccination coverage and the efficacy of vaccine are high enough. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a delayed SIRS epidemic model with saturation incidence and temporary immunity is investigated. The immunity gained by experiencing a disease is temporary, whenever infected the diseased individuals will return to the susceptible class after a fixed period. By analyzing the corresponding characteristic equations, the local stability of an endemic equilibrium and a disease-free equilibrium is discussed. By comparison arguments, it is proved that if the basic reproduction number is less than unity, the disease-free equilibrium is globally asymptotically stable. If the basic reproduction number is greater than unity, by means of an iteration technique, sufficient conditions are obtained for the global asymptotic stability of the endemic equilibrium. Numerical simulations are carried out to illustrate the main theoretical results. [Copyright &y& Elsevier]

Abstract: Based on [J. Zhang, M. Cerasuolo, P. Fergola, Z.E. Ma, On the influence of quorum sensing in the competition between bacteria and immune system (in press)], a bacteria-immunity model with periodically bacterial quorum sensing is formulated which describes the competition between bacteria and immune cells. A discrete delay is introduced to characterize the time in which bacteria receive signal molecules and combat with immune cells. In this paper, we focus on a subsystem of the bacteria-immunity model, investigate the existence and stability of the positively periodic solution, and discuss the existence of subharmonic bifurcation by the perturbation method. [Copyright &y& Elsevier]

Abstract: We develop and analyze a model for the interactions of T-cells, antigen presenting cells (APCs), and HIV-1. Our model consists of five components: APCs, resting helper T-cells, activated uninfected helper T-cells, activated and infected helper T-cells, and the free virus. We emphasize the impact of APCs during HIV infection and the cell-to-cell contact manner in the transference of HIV-1 in vivo. The existence and stability of the uninfected steady state and those of the infected steady states are discussed. The uniform persistence of the system is also obtained. As a novel approach, multiple exposures of HIV-1 are illustrated and discussed in the paper. Through numerical stimulations, we check the sensitivity of APCs and helper T-cells in impacting the infection outcome and obtain some relevant results. We also give the lowest infectioe dose for certain individuals. [Copyright &y& Elsevier]