Poor resource quality lowers transmission potential by changing foraging behaviour

Resource quality can have conflicting effects on the spread of disease. High quality resources could hinder disease spread by promoting host immune function. Alternatively, high quality food might enhance the spread of disease through other traits of hosts or parasites. Thus, to assess how resource quality shapes epidemics, we need to delineate mechanisms by which food quality affects key epidemiological traits. Here, we disentangle effects of food quality on ‘transmission potential’ – a key component of parasite fitness that combines transmission rate and parasite production – using a zooplankton host and fungal parasite. We estimated the components of transmission potential (i.e., parasite encounter rate, susceptibility, and yield of parasite propagules) for hosts fed a high quality green alga and a low quality cyanobacterium. A focal experiment was designed to disentangle food quality effects on various components of transmission potential. The low quality resource decreased transmis...