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Das et al. (Biosystems, 95, 188-199, 2009) proposed and analyzed an eco-epidemiological model where the prey population was not only infected through contact but also got infection from external sources. Time delay effect is an important component in every biological systems and can not be ignored. The present paper modifies our previous investigation to observe the quantitative and qualitative behavior of the system with gestation delay. It is observed that for a lower infection rate, the system is stable for all delays; but for a higher infection rate, there exists several critical values of delay factor below and above which system is stable and unstable alternatively. It is also observed that delay prevents the extinction of predator population and outbreak of disease. Finally we observe that the instability arising from the gestation delay may be controlled if somehow the growth rate of predator population and external source of infection increase and predation rate for infected prey decreases. [ABSTRACT FROM AUTHOR]

Most of phytoplankton species are subjected to viral infection and the viral infection could be a factor regulating phytoplankton community structure and primary productivity in the oceans. Mode of viral transmission is an important issue in biological point of view while modeling plankton dynamics in the presence of highly abundant free viruses. In this paper we formulate a simple predator-prey model with a viral infection in prey. We assume that the phytoplankton population can be infected by external free viruses following saturating functional form. Our results suggest that the nutrient enrichment can decline disease prevalence and the infection disappears if the nutrient enrichment is above a threshold value. However virus replication and half saturation constant of viral infection also play an important role in persistence of infection. [ABSTRACT FROM AUTHOR]