Prairie Dogs, Persistent Plague, Flocking Fleas, and Pernicious Positive Feedback

Area of Science:

• Ecology
• Epidemiology
• Bacteriology

Background:

• Plague, caused by Yersinia pestis, is a significant global public health and ecological threat.
• Current understanding of Yersinia pestis transmission dynamics requires refinement.

Purpose of the Study:

• To review hypotheses on Yersinia pestis maintenance and transmission.
• To emphasize the role of positive feedback (PFB) cycles in epizootic plague.
• To explore potential triggers for plague epizootics.

Main Methods:

• Review of existing literature on Yersinia pestis.
• Analysis of recent data from North America on plague dynamics.
• Examination of factors influencing flea:host ratios.

Main Results:

• Evidence supports persistent transmission as a maintenance mechanism for Yersinia pestis.
• Synergistic positive feedback (PFB) cycles involving fleas, hosts, and the bacterium are central to epizootic plague.
• Increased flea:host ratios, potentially from human activities, may trigger epizootic transitions.

Conclusions:

• Positive feedback cycles are crucial for understanding epizootic plague dynamics.
• Epizootic eruptions may be a tolerated cost rather than an adaptive strategy for Yersinia pestis.
• The absence of epizootics does not negate ecological impact and may reduce public health risk.