Experimental evidence of a pathogen invasion threshold

Area of Science:

• Ecology
• Epidemiology
• Pathogen Dynamics

Background:

• Host density thresholds are key in disease ecology, separating endemic and disease-free states.
• Evidence for thresholds is mixed, particularly for wildlife and environmentally transmitted pathogens.

Purpose of the Study:

• To experimentally demonstrate a host density threshold for an environmentally transmitted pathogen.
• To assess the predictive power of epidemiological models for invasion thresholds.

Main Methods:

• Combined epidemiological modeling with microcosm experiments using Daphnia dentifera and Metschnikowia bicuspidata.
• Varied host densities across a range (20-640 hosts/L) to observe pathogen invasion dynamics.

Main Results:

• Clearly demonstrated a host density threshold for pathogen invasion in a replicated experimental system.
• Epidemiological model simulations, independently parameterized, qualitatively predicted the observed invasion thresholds.
• Parameter variability had minor effects, but systematic changes could shift thresholds.

Conclusions:

• Provides one of the first clear experimental confirmations of pathogen invasion thresholds.
• Suggests that independently constructed epidemiological models can predict these thresholds, aiding disease management strategies.