Integrating microclimate to understand vector development and disease patterns: challenges and lessons from plague in...

Plague, the zoonotic vector-borne disease caused by the bacterium Yersinia pestis, shows seasonal infection patterns across the Central Highlands of Madagascar. The disease persists within a complex ecological network involving host and vector species, all influenced by climate. Due to this complexity, links between climate, Y. pestis ecology and human infection remain incomplete. This study developed microclimate-based models to assess climatic impacts on growth cycles of plague vectors Xenopsylla cheopis and Synopsyllus fonquerniei. Using microclimatic modelling, the vector development index (VDI) was calculated to estimate annual developmental phases for each flea species. The uncorrected VDI suggested that development rates were highly variable for X. cheopis compared to S. fonquerniei, which shows greater temporal consistency. Elevated VDI slopes, representing an increased rate of vector development, correlated with plague cases across 61.8-14.7% of areas, implying possible climatic influence on vector-driven disease cycles. However, these associations were not maintained after adjusting modelled temperatures using limited field validation. These findings highlight the complex interactions between climate, vector dynamics and Y. pestis transmission, and emphasize the need for further investigation into burrow microclimates and their seasonal epidemiological roles.