Influencing random transmission is a neutral character in hosts

Area of Science:

• Evolutionary Biology
• Epidemiology
• Behavioral Ecology

Background:

• Widespread notion suggests hosts evolve to obstruct virulent parasite transmission.
• Host-parasite interactions are complex, influenced by transmission routes and genetic relatedness.
• Parasite manipulation can enhance transmission, potentially overriding host defenses.

Purpose of the Study:

• To investigate host selection pressures related to virulent parasite transmission.
• To determine if hosts are necessarily selected to obstruct parasite transmission.
• To analyze the impact of transmission routes (random, kin-biased, non-kin-biased) on host-parasite coevolution.

Main Methods:

• Development of an individual-based model for host-parasite assemblages.
• Simulation of parasite transmission dynamics under different transmission route biases.
• Analysis of selection pressures on host counteradaptations and parasite virulence.

Main Results:

• Random transmission routes do not select hosts for obstructing parasites; host transmission ability is neutral.
• Vertically biased (kin) transmission selects hosts to decrease parasite transmission and parasites to decrease virulence.
• Horizontally biased (non-kin) transmission selects hosts to increase parasite transmission, aligning host and parasite interests.

Conclusions:

• Host selection against virulent parasites depends critically on transmission routes.
• Horizontally biased transmission can lead to increased host emigration and transmission at a distance.
• Findings advance understanding of contagious pathogen epidemiology and host social/sexual behavior evolution.