Global Patterns of Zoonotic Disease in Mammals

Abstract

As the frequency and prevalence of zoonotic diseases increase worldwide, investigating how mammal host distributions determine patterns of human disease and predicting which regions are at greatest risk for future zoonotic disease emergence are two goals which both require better understanding of the current distributions of zoonotic hosts and pathogens. We review here the existing data about mammalian host species, comparing and contrasting these patterns against global maps of zoonotic hosts from all 27 orders of terrestrial mammals. We discuss the zoonotic potential of host species from the top six most species-rich mammal groups, and review the literature to identify analytical and conceptual gaps that must be addressed to improve our ability to generate testable predictions about zoonotic diseases originating from wild mammals.

Keywords: biogeography; hotspot; infectious disease; macroecology; prediction; risk.

Figure 1

Geographic Ranges of Zoonotic Mammal Hosts. Mammal reservoirs of zoonotic diseases are globally distributed, with noteworthy hotspots in Amazonia and Eurasia. Overlapping geographic ranges of mammal species recognized to carry one or more zoonotic diseases, with counts of unique host species (gold bars) and unique zoonotic pathogens (red bars) found within 30° latitudinal and longitudinal bands. This map depicts 5007 total wild mammal species from 27 orders.

Figure 2

The Number of Zoonotic Hosts Increases with Total Species Richness of the Order. Zoonotic diseases are found in the majority of terrestrial mammal orders (21/27), with the most species-rich orders containing the greatest diversity of zoonoses. This split bar plot shows the total number of host species (black and grey) and the fraction of species that are confirmed zoonotic hosts for one or more zoonotic diseases (grey). The number above each bar represents a tally of the total unique zoonoses per order. Mammal orders are arranged in descending order of species richness. The number of zoonotic host species in each order is represented by scatterplots, with the most-speciose orders being contained in the blue boxes (top right; regression R² = 0.81) and all other orders in the orange boxes (bottom right; regression R² = 0.63).

Figure 3

Key Figure: Global Hotspots of Zoonoses Are Driven by Differences in the Distribution of Zoonotic Hosts from Specific Clades Mapping overlapping geographic ranges of mammal species recognized to carry one or more zoonotic diseases highlights regions of high and low zoonotic host diversity arising from particular clades. Mammal zoonotic host richness is depicted by color for carnivores, bats (Chiroptera), primates, rodents, shrews and moles (Soricomorpha), and the hoofed mammals (ungulates, which combine the orders Perissodactyla and Artiodactyla and exclude domesticated species).

Figure 4

Overlapping Geographic Ranges of Zoonotic Diseases Carried by Wild Terrestrial Mammal Host Species from 27 Orders.

Figure 5

Zoonoses Caused by the Four Major Pathogen Types Are Globally Distributed, with Notable Hotspots for Bacteria and Helminths in North America and Eurasia. (A) Richness patterns are depicted by pathogen type in descending order: bacteria, viruses, helminths, protozoa. (B) A histogram showing the number of unique zoonoses caused by each pathogen types in the six most species-rich mammal groups: the carnivores, bats (Chiroptera), primates, rodents, shrews and moles (Soricomorpha), and the hoofed mammals (ungulates, which combine the orders Perissodactyla and Artiodactyla and exclude domesticated species).