Interactions between frequency-dependent and vertical transmission in host-parasite systems

Area of Science:

• Ecology
• Evolutionary Biology
• Epidemiology

Background:

• Host-pathogen dynamics are crucial for understanding disease persistence and evolution.
• Frequency-dependent horizontal transmission and vertical transmission are key modes influencing these dynamics.
• Previous models often simplify or omit the combined effects of these transmission routes.

Purpose of the Study:

• To investigate host-pathogen coexistence under combined frequency-dependent horizontal and vertical transmission.
• To compare the impact of uniparental versus biparental vertical transmission on parasite invasion and coexistence.
• To assess how host density-dependent regulation affects these host-pathogen interactions.

Main Methods:

• Development and analysis of two mathematical models of host-pathogen dynamics.
• Model 1: Frequency-dependent horizontal transmission with uniparental vertical transmission.
• Model 2: Frequency-dependent horizontal transmission with biparental vertical transmission.

Main Results:

• Vertical transmission significantly broadens the conditions for parasite invasion.
• Host-parasite coexistence is influenced by the mode of density-dependent host regulation.
• Parasite strains with biparental vertical transmission can drive strains with only horizontal transmission to extinction.
• Biparental vertical transmission can maintain a parasite at a stable equilibrium, contrary to uniparental transmission alone.

Conclusions:

• Combined vertical and horizontal transmission modes can lead to broader host-pathogen coexistence.
• Biparental vertical transmission is a potent mechanism for parasite maintenance and can alter competitive dynamics.
• Findings support the ecological relevance of sexual transmission alongside vertical transmission in natural systems with high host reproductive rates.