Climatic variations and Yersinia pestis host-vector abundance: a case study in Ankazobe district to understand plague epidemiology in Madagascar.

BACKGROUND

Plague, a disease caused by the bacterium Yersinia pestis remains a major public health concern in Madagascar despite numerous multidisciplinary studies. The persistence of human plague infections is thought to be linked to fluctuations in mammalian host and flea populations, which are affected by climatic and environmental variations. This study explored local macro- and microclimatic variations along with mammal and flea population dynamics across different microhabitat types within plague endemic rural and forested habitats of Madagascar. Understanding these variables and their interdependent relationships may help us better understand the complexities of Y. pestis transmission in the Madagascan Highlands.

METHODS

Small mammals and their fleas were captured in different microhabitats within plague focus in the Ankazobe District of Madagascar. Simultaneously, climatic data including temperature and humidity, were collected to assess the potential relationship between flea population dynamics and climatic variations. Specialized equipment was used to monitor microclimate conditions across various microhabitat types and compare them with macroclimate. Monitoring was performed inside and outside rodent burrows located inside and outside houses and in adjacent forested areas.

RESULTS

A greater abundance of fleas was observed inside dwellings compared to other microhabitats, such as outside houses and forest, whereas small mammal species diversity was significantly higher in forest environments. We also revealed significant differences in microclimates across microhabitat types, with lower temperatures and higher humidity inside rodent burrows compared to outside burrows, outside houses and the forest. Inside houses, temperature variations were more stable although temperatures were higher and humidity lower inside rodent burrows compared to other microhabitats.

CONCLUSION

This study highlights microclimate variation across different microhabitat types, which also differ from the macroclimate, and maps small mammal and flea abundance to these locations. These data suggest that it is important to further explore the relationship between microclimatic variations in the different microhabitats and the dynamics of flea and rodent populations as potential markers for plague persistence and transmission in these endemic foci.