Frugivory Richness Predicts Ebola Spillover in Africa

Mireya Dorado, a student at Northeastern University, worked in Dr. Patrick Stephen’s lab studying pathogen spillover

Ebola is a deadly filovirus that infects a variety of mammals including humans. Since the first documented outbreak i n 1976, there have been numerous field studies searching for the source of the spillover of Ebola. Only a few studies have directly investigated the effect of mammalian host biodiversity. These studies have been limited to the diversity of known Ebola hosts and bats. However due to Ebola’s broad host range, there has not been a systematic approach to which hosts may be important for spillover. Therefore, our goal was to determine whether and what aspects of mammalian diversity play a significant role in predicting Ebola spillover events. We calculated species richness of mammals in 50 kilometer by 50 kilometer grid cells across Africa. Statistical analyses were based on a presence absence approach, which compared species richness at sites of spillover t o pseudo-absence background locations. We used bagged logistic regression, a machine learning method, to create statistical models testing how well species richness of different mammal subgroups predicted spillover. Overall, we found that Cercopithecidae and Pteropodidae were the strongest taxonomic predictors of spillover (mean AUC=0.943 and 0.936 respectively), but diversity of frugivorous species was the best overall predictor (mean AUC=0.956). This strongly implicates a role of fruit in Ebola transmission and the significance of fruiting and masting seasons as ideal times for spread of infection.