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Updated: Aug 16, 2026
08:23
Phenotypic Analysis of Rodent Malaria Parasite Asexual and Sexual Blood Stages and Mosquito Stages
Published on: May 30, 2019
Age at First Reproduction Predicts Sex-Specific Parasite Infection Trajectories Through Adulthood
Francisco Ruiz-Raya1, Sarah J Burthe2, Hannah Ravenswater1
1Ashworth Laboratories, School of Biological Sciences, Institute of Ecology and Evolution University of Edinburgh Edinburgh UK.
Ecology and Evolution
|August 15, 2026
Summary
Age at first reproduction influences parasite burden trajectories differently in male and female European shags. Early reproduction in males correlates with declining parasite loads, while later reproduction is linked to increasing loads, highlighting sex-specific host-parasite dynamics.
Area of Science:
- Ecology
- Evolutionary Biology
- Parasitology
Background:
- Parasite infection intensity varies significantly across host individuals and life stages.
- Age-related changes in parasite burden can result from altered host behavior, physiology, or selective disappearance of heavily infected individuals.
- Age at first reproduction (AFR) is a key life-history trait influencing host-parasite dynamics throughout life.
Purpose of the Study:
- To investigate if AFR predicts within-individual changes in gastrointestinal nematode burden in European shags across adulthood.
- To determine if these age-related parasite infection trajectories differ between sexes.
Main Methods:
- Utilized 10 years of individual-based monitoring data from European shags.
- Quantified parasite burdens through repeated endoscopic examinations.
- Employed a within-subject centring approach to differentiate within-individual age effects from between-individual variation and account for selective disappearance.
Main Results:
- AFR predicted sex-specific infection trajectories in male shags; early/modal reproducers showed declining parasite burdens with age, while late reproducers exhibited increasing burdens.
- A marginal trend suggested potential selective disappearance in early-recruiting males.
- Female shags displayed consistent within-individual declines in parasite burden with age, irrespective of their AFR, with no evidence of selective disappearance.
Conclusions:
- This study provides the first evidence linking AFR to sex-specific parasite infection trajectories in a long-lived bird species.
- Early-life reproductive strategies significantly influence adult host-parasite dynamics in a sex-dependent manner.
- Longitudinal, within-individual analyses are crucial for uncovering mechanisms of host-parasite interactions that cross-sectional studies may miss.
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