Super-spreaders and super-shedders in a changing world

Levels of parasitism and the dynamics of helminth systems are subject to the impact of environmental conditions, such that we may expect long term increases in temperature to increase the force of infection and the parasite’s basic reproduction number, R₀.  We postulate that an increase in the force of infection will only lead to an increase in the mean intensity of adults when adult parasite mortality is not determined by acquired immunity. Long term trends in various species confirm these predictions. Indeed parasite development rate, transmission rate and contact rate between hosts may also vary, such that susceptibility covaries with transmissibility and these heterogeneities shape the dynamics.