Infectious disease in consumer populations: dynamic consequences of resource-mediated transmission and infectiousness

摘要

Nonhost species can strongly affect the timing and progression of epidemics. One central interaction-between hosts, their resources, and parasites-remains surprisingly underdeveloped from a theoretical perspective. Furthermore, key epidemiological traits that govern disease spread are known to depend on resource density. We tackle both issues here using models that fuse consumer-resource and epidemiological theory. Motivated by recent studies of a phytoplankton-zooplankton-fungus system, we derive and analyze a family of dynamic models for parasite spread among consumers in which transmission depends on consumer (host) and resource densities. These models yield four key insights. First, host-resource cycling can lower mean host density and inhibit parasite invasion. Second, host-resource cycling can create Allee effects (bistability) if parasites increase mean host density by reducing the amplitude of host-resource cycles. Third, parasites can stabilize host-resource cycles; however, host-resource cycling can also cause disease cycling. Fourth, resource dependence of epidemiological traits helps to govern the relative dominance of these different behaviors. However, these resource dependencies largely have quantitative rather than qualitative effects on these three-species dynamics. Given the extent of these results, host-resource-parasite interactions should become more fundamental components of the burgeoning theory for the community ecology of infectious diseases.