Print PageWe developed a spatially-explicit, agent-based simulation to examine the trade-off between risk of predation and disease transmission that occurs when susceptible hosts avoid diseased conspecifics, a behavior exhibited by juvenile Panulirus argus in response to conspecifics infected with Panulirus argus Virus 1 (PaV1). Because the virus also infects asocial, early benthic phase juveniles (EBJs) through an unknown mechanism, we included a density-independent infection mechanism, representative of environmental exposure. We also simulated the arrival of the disease with new cohorts of postlarvae, a consequence of the openness of this population that is characteristic of many marine systems. Last, we examined the effect of loss of sponges used by juvenile spiny lobster due to harmful algal blooms, which changes the pattern of lobster cohabitation.
Results/Conclusions
We found that without disease avoidance, outbreaks occurred rapidly, growing in intensity and duration until, by the end of 10 simulated years, PaV1 was maintained continuously at unrealistically high levels. Disease avoidance reduced simulated outbreak intensities and durations, and in the absence of other transmission pathways, resulted in extinction of the disease within five years. However, both EBJ infection mechanisms were capable of maintaining the disease, even at the highest level of disease avoidance, due to the long period between exposure and death. Loss of shelter did not significantly increase PaV1 transmission or persistence because increased predation and large-scale movement of lobsters quickly reduced local lobster populations. Thus, avoidance of diseased conspecifics may select against high virulence and promote alternative transmission modes, resulting in a more resilient system.
