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High virulence is associated with pathogen spreadability in a songbird-bacterial system
Dana M Hawley1, Courtney A Thomason1, Matt A Aberle1
1Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0131, USA.
Royal Society Open Science
|January 23, 2023
Summary
High virulence in pathogens like Mycoplasma gallisepticum can increase spreadability. Inflammation, not just host behavior, appears to drive this enhanced transmission between house finches.
Area of Science:
- Evolutionary biology
- Pathogen dynamics
- Disease ecology
Background:
- Understanding virulence evolution is crucial for directly transmitted pathogens.
- High pathogen loads within hosts often correlate with increased virulence.
- Virulence may also enhance pathogen spreadability, independent of host load.
Purpose of the Study:
- To investigate if components of virulence (conjunctival inflammation, behavioral changes) predict pathogen spreadability.
- To determine the mechanisms by which virulence influences pathogen transmission.
Main Methods:
- Using house finches experimentally infected with varying virulence strains of Mycoplasma gallisepticum.
- Applying ultraviolet powder to predict pathogen spreadability, measured by powder transfer between birds.
- Assessing conjunctival inflammation severity and host behavior (feeder use, social interactions).
Main Results:
- High-virulence Mycoplasma gallisepticum strains significantly increased powder spreadability compared to controls.
- Birds with high-virulence infections showed more severe conjunctival inflammation and spent more time on feeders.
- Inflammatory responses, rather than behavioral changes, were suggested to drive increased spreadability.
Conclusions:
- Inflammation associated with high pathogen virulence can facilitate spread to conspecifics.
- This mechanism may favor the evolution of virulence in this and other host-pathogen systems.
- Virulence evolution is influenced by factors beyond host mortality or morbidity.
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