Is the local environment more important than within-host interactions in determining coinfection?

Area of Science:

• Ecology
• Parasitology
• Evolutionary Biology

Background:

• Coinfection prevalence varies across environments and often occurs sequentially.
• Distinguishing environmental influences from within-host parasite interactions is crucial for understanding coinfection dynamics.

Purpose of the Study:

• To develop a framework for disentangling environmental and within-host factors in sequential coinfection.
• To investigate the roles of local environment and primary water mite infection in secondary gregarine infection in damselflies.

Main Methods:

• Surveyed five damselfly species across multiple lakes.
• Quantified primary ectoparasitic water mite and secondary endoparasitic gregarine infections.
• Analyzed the influence of environmental factors (e.g., pH) and primary infection on coinfection probability and intensity.

Main Results:

• Coinfection probability decreased with increasing pH for all host species.
• No evidence of water mite mediation between pH and gregarine infection was found.
• Gregarine infection intensity correlated directly with local environmental factors, with varying predictor influences.

Conclusions:

• The local environment significantly shapes infection dynamics that precede coinfection.
• Within-host interactions between water mites and gregarines did not appear to mediate the observed environmental effects.
• The conceptual framework can be applied to other systems to study host-parasite interactions in complex communities.