Are local plague endemicity and ecological characteristics of vectors and reservoirs related? A case study in north-east Tanzania

摘要

The pattern of plague endemicity in Tanzania is characterized by continuous re-appearance of the disease in some locations, while in other neighbouring villages the disease has never or seldom been observed. To understand the reasons for this pattern, we studied small mammals and fleas species composition, diversity and relative abundances in two plague-endemic and two plague-free locations. We asked (a) whether fleas more abundant in plague-endemic locations differ in their characteristic abundance and the degree of their host specificity from fleas most abundant in plague-free locations and (b) whether hosts more abundant in plague-endemic locations differ in the diversity of their flea assemblages from hosts most abundant in plague-free locations. We characterized (a) host species by species richness and degree of taxonomic relatedness of its flea assemblages and (b) each flea species by its mean abundance and size, and degree of taxonomic relatedness of its host spectrum and compared their relative abundances between locations. No significant difference between plague-endemic and plague-free locations in either host density or any variable related to flea abundance or diversity was found. However, there was marginally significant effect of taxonomic distinctness of a flea assemblage harboured by a host on its probability to be more abundant in either plague-endemic or plague-free locations. Furthermore, hosts more abundant in plague-endemic locations tended to harbour closely-related fleas. Finally, while opportunistic and specialist fleas were equally distributed in both sets of locations, fleas exploiting distantly-related hosts were found mainly in plague-free locations during the rainy season. We suggest that the observed patterns might arise due to seasonal and spatial differences in local microclimatic conditions and landscape connectivity