Human density is associated with the increased prevalence of a generalist zoonotic parasite in mammalian wildlife

Abstract

Macroecological approaches can provide valuable insight into the epidemiology of globally distributed, multi-host pathogens. Toxoplasma gondii is a zoonotic protozoan that infects any warm-blooded animal, including humans, in almost every ecosystem worldwide. There is substantial geographical variation in T. gondii prevalence in wildlife populations and the mechanisms driving this variation are poorly understood. We implemented Bayesian phylogenetic mixed models to determine the association between species’ ecology, phylogeny and climatic and anthropogenic factors on T. gondii prevalence. Toxoplasma gondii prevalence data were compiled for free-ranging wild mammal species from 202 published studies, encompassing 45 079 individuals from 54 taxonomic families and 238 species. We found that T. gondii prevalence was positively associated with human population density and warmer temperatures at the sampling location. Terrestrial species had a lower overall prevalence, but there were no consistent patterns between trophic level and prevalence. The relationship between human density and T. gondii prevalence is probably mediated by higher domestic cat abundance and landscape degradation leading to increased environmental oocyst contamination. Landscape restoration and limiting free-roaming in domestic cats could synergistically increase the resiliency of wildlife populations and reduce wildlife and human infection risks from one of the world's most common parasitic infections.

Seroprevalence and risk factors of Toxoplasma gondii infection in captive giant panda (Ailuropoda melanoleuca)

“…Toxoplasmosis is a disease that results from infection with the Toxoplasma gondii , which can cause death in wildlife ( Rouatbi et al., 2019 ; Wilson et al., 2021 ). It is also a potentially serious threat to giant pandas, which can cause reproductive disorder and even death.…”

Parasite and pathogen prevalence in our closest animal companions is determined by accessibility of sanitation services

“…Companion animals have strong associations with both humans (Chomel and Sun 2011, Zhang et al 2019) and wildlife (Medina et al 2011, Young et al 2011, Hughes and Macdonald 2013, Loss et al 2013, Plaza et al 2018), making them an important bridge host (i.e., a link that transmits pathogens between a reservoir host population and some target host population; Caron et al 2015) for many diseases between humans and wildlife (Ellwanger and Chies 2019). Parasite and pathogen vectoring from companion animals to wildlife has also received much attention, and many species of conservation concern are at risk for health problems from parasites and pathogens of companion animals (Salb et al 2008, Day 2011, Wilson et al 2021). Thus, in addition to reducing exposure of parasites and pathogens to humans, improving sanitation could be a sound conservation strategy for reducing exposure of wildlife to infectious agents in the environment.…”

Applications of conceptual models from lifecourse epidemiology in ecology and evolutionary biology

“…A doubling of infection in older hyaenas suggests that the parasite is transmitted via the consumption of infected meat [ 66 ]. A recent meta-analysis reported that proximity to human populations is a risk factor for T. gondii infection due to higher exposure to cats, the definitive host of the parasite [ 68 ]. Based on these data we may hypothesize a causal relationship between risk factors and infection with T. gondii that follows the Chains of Risk with Trigger Effect paradigm.…”