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SUMMARYRatio-dependent models set up a challenging issue for their rich dynamics incomparison to preydependent models. Little attention has been paid so far to describe the importance of transmissible disease in ecological situation by considering ratio-dependent models. In this paper, by assuming the predator response function as ratio-dependent, we consider a model of a system of three non-linear di erential equations describing the time evolution of susceptible and infected Tilapia ÿsh population and their predator, the Pelican. Existence and stability analysis of di erent equilibria of the system lead to di erent realistic thresholds in terms of system parameters. The condition for extinction of the species is also worked out. Our analytical and numerical studies may be helpful to chalk out suitable control strategies for minimizing the extinction of the Pelicans. We also suggest that supply of alternative food source for predator population may be used as a possible solution to save the predator from their extinction.

A predator-prey model with disease in the prey population is proposed and analysed. The mode of disease transmission plays an important role in such dynamics. Keeping this factor in mind, we observe the dynamics of such a system for simple mass action incidence and standard incidence. Our observations indicate that the phenomenon of rarity or non-occurrence of chaos in our proposed model is well defined if the mode of disease transmission follows standard incidence. Moreover, using the method of Latin hypercube sampling, we show that the region of stability increases if the disease transmission follows the standard incidence law.

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A simple predator–prey system with disease in prey population and alternative food for the predator is proposed and analyzed. The main objective of the present investigation is to observe the conditions for which the disease in prey population will be controlled. It is observed that supply of alternative food to the predator population can make the system disease free. Enrichment also plays an important role in suppressing the infected population in the presence of alternative food. However, in the absence of predator population, enrichment increases the disease prevalence instead of reducing it. We finally conclude that supply of alternative food to the predator provides a healthy disease free system.

The present paper deals with the problem of a predator-prey system with disease in the prey population. We observe the dynamics of such a system under the influence of severe as well as unnoticeable parasite attack and also alternative food sources for predator population. We assume the predator population will prefer only infected population for their diet as those are more vulnerable. Local and global stability of the system around the biological feasible equilibria are studied. The conditions for which all three species will persist are worked out. Our results indicate that in the case of severe parasite attack, the predator population will prefer the alternative food source and not the infected one. But the strategy is reversed in the case of unnoticeable parasite attack.

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