Evolution of pathogen tolerance and reproductive trade-off implications

Area of Science:

• Ecology
• Epidemiology
• Evolutionary Biology

Background:

• Amphibian populations face severe declines due to pathogens like Batrachochytrium dendrobatidis (Bd).
• Host populations exhibit variations in defense strategies, such as disease tolerance, which can be heritable.

Purpose of the Study:

• To develop and analyze an epidemic model incorporating pathogen pools and diverse host defense strategies.
• To investigate the impact of host disease tolerance and potential trade-offs on epidemic dynamics and host-pathogen coexistence.

Main Methods:

• Developed a mathematical model for epidemic spread considering pathogen load and host tolerance levels.
• Analyzed the basic reproduction number and stability of disease-free and pandemic equilibria.
• Incorporated a trade-off between disease tolerance and reproductive rate.

Main Results:

• The basic reproduction number is a weighted average of individual numbers across tolerance classes.
• In the absence of trade-offs, host defense strategies can coexist, with higher tolerance leading to stable persistence or extinction.
• A trade-off between tolerance and reproduction alters coexistence dynamics, potentially enriching pandemic equilibria.

Conclusions:

• Host defense strategies and their heritability significantly influence epidemic outcomes.
• The stability of pandemic equilibria depends on the balance between disease tolerance and reproductive costs.
• Understanding these dynamics is crucial for amphibian conservation efforts facing infectious diseases.