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Published on: March 16, 2019
Population dynamics of plague vector fleas in an endemic focus: implications for plague surveillance
Fanohinjanaharinirina Rasoamalala1,2, Katelyn Gostic3, Mamionah J Parany1,2
1Plague Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar.
Abstract:
Plague is a zoonotic vector-borne disease caused by the bacterium Yersinia pestis. In Madagascar, it persists in identified foci, where it is a threat to public health generally from September to April. A more complete understanding of how the disease persists could guide control strategies. Fleas are the main vector for transmission between small mammal hosts and humans, and fleas likely play a role in the maintenance of plague. This study characterized the dynamics of flea populations in plague foci alongside the occurrence of human cases. From 2018 to 2020, small mammals were trapped at sites in the central Highlands of Madagascar. A total of 2,762 small mammals were captured and 5,295 fleas were collected. The analysis examines 2 plague vector species in Madagascar (Synopsyllus fonquerniei and Xenopsylla cheopis). Generalized linear models were used to relate flea abundance to abiotic factors, with adjustments for trap location and flea species. We observed significant effects of abiotic factors on the abundance, intensity, and infestation rate by the outdoor-associated flea species, S. fonquerniei, but weak seasonality for the indoor-associated flea species, X. cheopis. A difference in the timing of peak abundance was observed between the 2 flea species during and outside the plague season. While the present study did not identify a clear link between flea population dynamics and plague maintenance, as only one collected X. cheopis was infected, the results presented herein can be used by local health authorities to improve monitoring and control strategies of plague vector fleas in Madagascar.
Insights
Plague, a zoonotic disease, persists in Madagascar. This study analyzed flea populations, revealing distinct seasonal patterns for outdoor (Synopsyllus fonquerniei) and indoor (Xenopsylla cheopis) flea species, aiding public health control strategies.
Area of Science:
- Vector-borne diseases
- Zoonotic disease epidemiology
- Environmental science and public health
Background:
- Plague, caused by Yersinia pestis, is a significant public health threat in Madagascar, particularly from September to April.
- Fleas are the primary vectors for plague transmission between small mammals and humans, playing a crucial role in disease maintenance.
- Understanding flea population dynamics is essential for developing effective plague control strategies.
Purpose of the Study:
- To investigate the population dynamics of key plague vector fleas in Madagascar.
- To correlate flea abundance and infestation rates with environmental factors.
- To inform public health interventions for plague control.
Main Methods:
- Field study conducted in plague foci in Madagascar's central Highlands from 2018 to 2020.
- Capture and collection of 2,762 small mammals and 5,295 fleas, focusing on Synopsyllus fonquerniei and Xenopsylla cheopis.
- Statistical analysis using generalized linear models to assess the impact of abiotic factors on flea abundance, intensity, and infestation rates.
Main Results:
- Significant influence of abiotic factors on the abundance, intensity, and infestation rates of the outdoor-associated flea S. fonquerniei.
- Weak seasonality observed for the indoor-associated flea X. cheopis.
- Distinct peak abundance timing differences between S. fonquerniei and X. cheopis during and outside the plague season.
Conclusions:
- Flea population dynamics show varying responses to environmental factors, with S. fonquerniei exhibiting stronger seasonality.
- While a direct link to plague maintenance was not definitively established (one infected X. cheopis found), findings support improved vector surveillance.
- Results provide valuable data for local health authorities to enhance monitoring and control of plague vector fleas in Madagascar.
