Identifying the Most Probable Mammal Reservoir Hosts for Monkeypox Virus Based on Ecological Niche Comparisons

Abstract

Previous human cases or epidemics have suggested that Monkeypox virus (MPXV) can be transmitted through contact with animals of African rainforests. Although MPXV has been identified in many mammal species, most are likely secondary hosts, and the reservoir host has yet to be discovered. In this study, we provide the full list of African mammal genera (and species) in which MPXV was previously detected, and predict the geographic distributions of all species of these genera based on museum specimens and an ecological niche modelling (ENM) method. Then, we reconstruct the ecological niche of MPXV using georeferenced data on animal MPXV sequences and human index cases, and conduct overlap analyses with the ecological niches inferred for 99 mammal species, in order to identify the most probable animal reservoir. Our results show that the MPXV niche covers three African rainforests: the Congo Basin, and Upper and Lower Guinean forests. The four mammal species showing the best niche overlap with MPXV are all arboreal rodents, including three squirrels: Funisciurus anerythrus, Funisciurus pyrropus, Heliosciurus rufobrachium, and Graphiurus lorraineus. We conclude that the most probable MPXV reservoir is F. anerythrus based on two niche overlap metrics, the areas of higher probabilities of occurrence, and available data on MPXV detection.

Keywords: Monkeypox; Sciuridae; animal reservoir; ecological niche model; evergreen forests; tropical Africa.

Figure 1

Ecological niches of Monkeypox virus (A) and the four mammal species showing the best overlap with it: Funisciurus anerythrus (C), Graphiurus lorraineus (D), Funisciurus pyrropus (E), and Heliosciurus rufobrachium (F). Black circles indicate localities used to build the distribution model. The probabilities of occurrence (p) are highlighted using different colours: blue grey for probabilities < 0.5; turquoise green for 0.5 < p < 0.75; yellowish green for 0.75 < p < 0.9; and yellow for p > 0.9. The red line is the IUCN distribution of the species [60]. Indicated at the left of the maps are the number of occurrence records (n) used to infer the ecological niche, and the Schoener’s D and Hellinger’s I values summarizing niche overlap between mammal species and MPXV. For convenience, we have included a map (B) showing the major biogeographic barriers, such as the Dahomey gap, rivers, and Cameroon volcanic line (CVL), and African rainforests (B), including the Upper Guinean forests (UGF) and Lower Guinean forests (LGF) in West Africa, the Atlantic Equatorial coastal forests (AECF) and Congolian lowland forests (CLF) in Central Africa, and the Eastern African coastal forests (EACF) in East Africa.

Figure 2

Ecological niches of mammal species ranked between the 5th and 10th positions for their overlap with the MPXV niche. Stochomys longicaudatus (A), Malacomys longipes (B), Pan troglodytes (C), Oenomys hypoxanthus (D), Crocidura olivieri (E), and Crocidura theresae (F). See legend of Figure 1 for more details.