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Related Experiment Video

Updated: Sep 26, 2025

Tractable Mammalian Cell Infections with Protozoan-primed Bacteria

Tractable Mammalian Cell Infections with Protozoan-primed Bacteria

Published on: April 2, 2013

Virulence evolution during a naturally occurring parasite outbreak.

Camden D Gowler¹, Haley Essington¹, Bruce O'Brien¹

¹Department of Ecology and Evolutionary Biology, University of Michigan, 48104 Ann Arbor, MI USA.

Evolutionary Ecology

|April 18, 2022

Summary

This summary is machine-generated.

In a natural Daphnia-Pasteuria epidemic, the parasite Pasteuria ramosa evolved to produce fewer spores, despite no changes in virulence. This suggests ecological factors may drive parasite evolution during epidemics.

Keywords:

Daphnia dentifera Eco-evolution Infectivity Pasteuria ramosa Resistance Virulence

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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

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Area of Science:

Evolutionary Biology
Ecology
Microbiology

Background:

Virulence, a pathogen's harm to its host, is crucial in host-pathogen interactions but poorly understood.
Virulence can evolve rapidly based on ecological context, with theory predicting changes with host density.
Empirical evidence for virulence evolution in natural epidemics is limited.

Purpose of the Study:

To investigate virulence evolution in a natural epidemic setting.
To examine the host-pathogen dynamics in the Daphnia-Pasteuria model system.
To identify changes in parasite virulence and spore production during an outbreak.

Main Methods:

Field observations of a natural Daphnia-Pasteuria ramosa outbreak in Daphnia dentifera.
Laboratory assays of infected and uninfected Daphnia hosts.
Quantification of host lifespan, reproduction, resistance, parasite infectivity, and parasite spore yield.

Main Results:

Infection prevalence peaked at 40%, with a subsequent decline in host density.
Infected hosts showed reduced lifespan and reproduction compared to controls.
No significant changes were detected in host resistance or parasite infectivity.
The parasite evolved to produce significantly fewer spores in infected hosts over the epidemic.

Conclusions:

The study provides empirical evidence of parasite evolution during a natural epidemic.
Despite no detectable shifts in virulence, Pasteuria ramosa evolved reduced spore production.
This evolution may be linked to ecological trade-offs, such as environmental mortality rates influencing parasite reproductive strategies.