Authors

Discussion

Plague, caused by the pathogenic bacterium Yersinia pestis, is endemic in Madagascar with several hundred human cases typically reported per year. The principal reservoir host for plague is Rattus rattus, with two flea vectors involved in transmission. These are: Xenopsylla cheopis, an invasive flea found throughout the island, and Synopsyllus fonquerniei, an endemic flea only present in the Central Highlands, where plague transmission mainly occurs. Understanding of the factors driving variation in the abundance of these two flea species is crucial for informing effective disease control strategies.

Using data from c. 100 sites across Madagascar, we used generalised linear mixed effects models to explore spatial (local habitat, bioclimatic region) and temporal (seasonal) variation in flea abundance. Consistent with previous research, X. cheopis was predominately collected inside dwellings, whilst S. fonquerniei was found almost exclusively in outdoor sites, with highest abundances in forest habitats.

The two vector species showed contrasting spatial and temporal patterns in abundance, with the endemic flea expressing particularly strong seasonal variation, likely due to its outdoor distribution. In terms of temporal patterns, S. fonquerniei demonstrated strong seasonal variation with its abundance peaking after the cool, dry winter. S. fonquerniei abundance was also higher in bioclimatic regions which have a distinct dry season, as well as regions with lower average summer temperatures. This further suggests an association between climate and abundance. X. cheopis showed less pronounced seasonal variation across the country, however a small amount of bioclimate-driven variation is observed.