Chaos and bistability in a delayed eco-epidemiological model with fear and Allee effects

Eco-epidemiological systems, in which infectious diseases interact with ecological processes such as predation and competition, exhibit rich and often counterintuitive dynamics. In predator–prey systems, where the prey population is subject to disease, additional ecological mechanisms such as the Allee effect and non-consumptive fear responses can critically influence stability, persistence and extinction outcomes. Furthermore, biological processes like predator gestation introduce time delays that can fundamentally alter system trajectories. In this study, we develop and analyze a nonlinear predatorpreydisease model incorporating (i) a strong Allee effect in the prey population, (ii) fear-mediated reductions in prey growth rates and (iii) an explicit gestation delay in predator reproduction. Analytical investigations are conducted to determine the existence and stability conditions of equilibria, extinction thresholds and bifurcation structures. The delay is treated as a bifurcation parameter to assess its influence on the stability of the coexistence equilibrium and the onset of oscillatory dynamics. Numerical simulations further reveal delay-induced destabilization, bistability and shifts in the basins of attraction. The results highlight how the combined effects of ecological constraints, behavioral adaptations and epidemiological factors shape the qualitative dynamics of eco-epidemiological systems, offering new insights into population persistence and control strategies.