How do predicted ecological niches of the mpox virus compare with that of 99 mammal species?

In a recent study posted to the bioRxiv* preprint server, researchers compared ecological niches to identify probable mpox virus (MPXV) reservoir hosts.

Background

Mpox is an evolving zoonotic disease endemic to West and Central African rainforests. It is characterized by swollen lymph nodes, fever, and fatigue, which is subsequently characterized by a rash with macular lesions advancing from papules to vesicles, pustules, and scabs on the face, feet, and hands, for two to four weeks. The mortality rate varies from 1% to 3% in West Africa to 5% to 10% in Central Africa.

Although the MPX virus has been detected in numerous mammalian species, most are probably secondary hosts, while the reservoir host has yet to be found.

About the study

In the present study, researchers anticipated that the MPXV reservoir is comprised of one or more rainforest mammal species with a comparable geographic distribution to that of MPXV.

The study concentrated on all mammalian species for which biological data, such as viral isolation, MPXV deoxyribonucleic acid (DNA) sequencing, polymerase chain reaction (PCR) amplification, and anti-Orthopoxvirus (OPXV) antibody detection, supported their involvement as either reservoir or secondary hosts. To reduce the impact of taxonomic difficulties at the species level, the team examined every species of all 14 genera.

Using the R package spocc, the team acquired species occurrence information from the Integrated Digitized Biocollections (IdIgBio), Global Biodiversity Information Facility (GBIF), VertNet, and Inaturalist to recreate the ecological niche corresponding to mammal species.

All of these databases contain records of the occurrence of mammalian species. However, each has its own particularity. To recreate the biological niche of MPXV, the team required case occurrence data. Human index cases that were proven by PCR, DNA sequencing, or MPXV isolation to have been infected from any animal source.

All 103 person records utilized in this study were index cases with a documented village of origin having global positioning system (GPS) coordinates. The predominance of a species was computed as a proportion of the species' geographic spread. The team recreated ecological niches using occurrence records and covariates.

Results

MPXV's ecological niche was predicted using 96 records of occurrence and an area under curve (AUC) of 0.956%. The niche outlined a wide geographical region that spans the West and Central African rainforests. Furthermore, three isolated regions in East Africa had some support, such as one region from Ethiopia, one located east of Lake Victoria in Kenya, and one from the Eastern African Coastal Forest of Tanzania near Dar es Salaam.

In West Africa, the distribution was discontinuous, having a void in the southern regions of Benin and Togo. In Central Africa, the niche encompasses the entirety of the Congo Basin, except for a substantial portion of eastern Equatorial Africa, encompassing eastern as well as southern Gabon and the southern Democratic Republic of the Congo.

The 14 genera identified as hosts for MPXV were from four mammalian orders and 11 families, including Macroscelidea, Primates, and Rodentia. In Africa, 14 genera were represented by 213 species having occurrence records. In international databases, the team discovered fewer than 14 occurrence records corresponding to 112 species categorized as restricted-range, and 17 occurrence records related to one species categorized as widespread, Crocidura viara. Therefore, predicting the ecological niche for these 113 species was impossible.

Based on analyses of niche overlap noted among MPXV and mammal species, the top ten species were Graphiurus lorraineus, Funisciurus anerythrus, Funisciurus pyrropus, Stochomys longicaudatus, Heliosciurus rufobrachium, Malacomys longipes, Oenomys hypoxanthos, Pan troglodytes, Crocidura olivieri, and Crocid. All of these species share a niche with MPXV found in Central as well as West Africa, except for O. hypoxanthus and M. longipes, which are mostly found in Central Africa. C. theresa is virtually exclusively found in West Africa.

Conclusion

The study findings showed that the MPXV niche encompasses three African rainforests, including the Congo Basin and the lower and upper Guinean forests. Furthermore, four mammal species that had the greatest niche overlap with that of MPXV were arboreal rodents. Finally, the team noted that F. anerythrus was the most likely MPXV reservoir.

*Important notice

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Bhavana Kunkalikar

Bhavana Kunkalikar is a medical writer based in Goa, India. Her academic background is in Pharmaceutical sciences and she holds a Bachelor's degree in Pharmacy. Her educational background allowed her to foster an interest in anatomical and physiological sciences. Her college project work based on ‘The manifestations and causes of sickle cell anemia’ formed the stepping stone to a life-long fascination with human pathophysiology.