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| In recent years, ecological research has suggested several mechanisms by which biodiversity
might affect the risk of acquiring infectious diseases (i.e., the decoy, dilution or amplification
effects), but the topic remains controversial. While many experimental studies suggest a negative
relationship between biodiversity and disease, this relationship is inherently complex, and might
be negative, positive or neutral depending on the geographical scale and ecological context. Here,
applying a macroecological approach, we look for associations between diversity and disease by
comparing the distribution of human schistosomiasis and biogeographical patterns of freshwater
snail and mammal species richness in Uganda. We found that the association between estimated
snail richness and human infection was best described by a negative correlation in non-spatial
bi- and multivariate logistic mixed effect models. However, this association lost significance after
the inclusion of a spatial component in a full geostatistical model, highlighting the importance of
accounting for spatial correlation to obtain more precise parameter estimates. Furthermore, we
found no significant relationships between mammal richness and schistosomiasis risk. We discuss
the limitations of the data and methods used to test the decoy hypothesis for schistosomiasis, and
highlight key future research directions that can facilitate more powerful tests of the decoy effect in
snail-borne infections, at geographical scales that are relevant for public health and conservation. | |
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