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Flea diversity as an element for persistence of plague bacteria in an East African plague focus
Rebecca J Eisen1, Jeff N Borchert, Joseph T Mpanga
1Division of Vector Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America. dyn2@cdc.gov
Abstract:
Plague is a flea-borne rodent-associated zoonotic disease that is caused by Yersinia pestis and characterized by long quiescent periods punctuated by rapidly spreading epidemics and epizootics. How plague bacteria persist during inter-epizootic periods is poorly understood, yet is important for predicting when and where epizootics are likely to occur and for designing interventions aimed at local elimination of the pathogen. Existing hypotheses of how Y. pestis is maintained within plague foci typically center on host abundance or diversity, but little attention has been paid to the importance of flea diversity in enzootic maintenance. Our study compares host and flea abundance and diversity along an elevation gradient that spans from low elevation sites outside of a plague focus in the West Nile region of Uganda (~725-1160 m) to higher elevation sites within the focus (~1380-1630 m). Based on a year of sampling, we showed that host abundance and diversity, as well as total flea abundance on hosts was similar between sites inside compared with outside the plague focus. By contrast, flea diversity was significantly higher inside the focus than outside. Our study highlights the importance of considering flea diversity in models of Y. pestis persistence.
Insights
Plague bacteria persistence is poorly understood. This study found higher flea diversity, not host factors, within plague foci, suggesting flea diversity is key for Yersinia pestis maintenance.
Area of Science:
- Ecology
- Epidemiology
- Zoonotic Diseases
Background:
- Plague, caused by *Yersinia pestis*, is a zoonotic disease with poorly understood inter-epizootic persistence mechanisms.
- Current hypotheses focus on host abundance or diversity, neglecting the role of flea diversity in enzootic maintenance.
Purpose of the Study:
- To investigate the role of flea diversity in the enzootic maintenance of *Yersinia pestis*.
- To compare host and flea abundance and diversity in plague foci versus non-foci areas.
Main Methods:
- A year-long ecological study was conducted along an elevation gradient in Uganda.
- Sampling sites included areas within and outside a known plague focus.
- Host and flea abundance and diversity were assessed at different elevations.
Main Results:
- Host abundance and diversity, and total flea abundance on hosts, were similar between sites inside and outside the plague focus.
- Flea diversity was significantly higher within the plague focus compared to outside areas.
- These findings challenge existing models of plague persistence.
Conclusions:
- Flea diversity, rather than host abundance or diversity, appears to be a critical factor in the enzootic maintenance of *Yersinia pestis*.
- Future models predicting plague epizootics and guiding interventions should incorporate flea diversity.
- Understanding flea diversity is crucial for managing plague persistence and preventing outbreaks.
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