An official website of the United States government
Abstract Biodiversity has been linked to reduced disease transmission through the dilution effect process. Traditional ecological measures of biological diversity, such as species richness, are most commonly used to test for the dilution effect. However, such metrics of species diversity do not consider the evolutionary relationship between species, which has important implications for host immune processes and disease transmission. Phylogenetic diversity incorporates the evolutionary relationships of a wildlife community. Host reservoir competency is partly determined by their capacity to mount effective immune responses, which may be phylogenetically determined. As a result, phylogenetic diversity may be a better metric to evaluate the relationship between host diversity and disease transmission, given that closely related species may have more similar pathogen competencies than distantly related ones. Few studies have examined the relationship between phylogenetic diversity and disease transmission, particularly in vector‐borne transmission systems. This study seeks to quantify phylogenetic diversity in the western United States Lyme disease system, where the causal agentBorrelia burgdorferiis vectored by the western black‐legged tick,Ixodes pacificus.We empirically measured mammalian diversity and tick data over seven years. We collected data on ticks, host community, and infection prevalence withBorrelia burgdorferiand constructed generalized linear mixed‐effect models to evaluate the utility of phylogenetic diversity in predicting the prevalence of a tick‐borne pathogen. We found that phylogenetic diversity metrics improved our disease prediction models. Predictions of the overall density and infection prevalence of ticks were improved by the addition of phylogenetic metrics, whereas the density of infected nymphs was solely predicted by a phylogenetic metric over traditional species diversity or richness. Our study found that phylogenetic diversity improves statistical predictions of the Lyme disease pathogen and entomological risk in the western United States and may be informative in other contexts and systems as well.
more »
« less
Functional vertebrate group diversity differentially impacts vector‐borne pathogen transmission and genetic diversity
Abstract Anthropogenic land use change has led to considerable biodiversity loss, affecting ecosystem functions with unresolved consequences for zoonotic disease transmission. Functional diversity is understudied but potentially important for understanding the role of biodiversity because many zoonotic disease systems are maintained by species with different roles in disease transmission. Here, we explore how functional groups and pathogen genetic diversity influence transmission and human disease risk within the Lyme disease system. Our field and molecular ecology study examined ticks and vertebrates across a fragmented landscape and evaluated several metrics of disease risk. For predicting vector and infected vector density, rodent host richness had a positive effect and was most important, but vector infection prevalence was best predicted by rodent and predator richness together, reflecting how indirect effects may alter tick–host interactions and disease risk. These results indicate that examining species richness generally may obscure important interactions driven by richness within functional groups. Pathogen genotype richness was best predicted by overall vertebrate richness, providing support for the multiple niche polymorphism hypothesis. Our study offers an important perspective on the relationship between biodiversity and disease risk, suggesting that richness within functional groups may offer more nuanced insight into pathogen transmission dynamics than overall biodiversity.
more »
« less
- Award ID(s):
- 1750037
- PAR ID:
- 10668854
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 16
- Issue:
- 6
- ISSN:
- 2150-8925
- Page Range / eLocation ID:
- 70292
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
To explain patterns between anthropogenic loss of species diversity and the rise in the number of novel zoonotic diseases, the “dilution effect” hypothesis predicts that with lower species diversity, infection risk will increase. The underlying mechanisms have been largely investigated in systems where pathogen transmission is vector‐borne or environmental. Relatively less research has been conducted in systems where transmission is direct, such as with orthohantaviruses (hereafter hantaviruses) and their rodent reservoir hosts. These systems are commonly cited as supporting a negative diversity‐disease pattern. To motivate empirical research on underlying mechanisms driving this pattern, we extend a mechanistic framework that links species diversity and infection prevalence of directly transmitted zoonotic pathogens by using rodent‐hantavirus systems in the Americas as models. Additionally, we summarize empirical studies, synthesize mechanistic evidence, and identify knowledge gaps. Our findings suggest that host regulation is a key mechanism likely to drive diversity‐disease patterns in rodent‐hantavirus systems of the Americas. Other mechanisms have received less empirical support but also less attention. Although host regulation likely functions via density‐dependent transmission, and can thus change contact rates among hosts, consequences to other mechanisms have been neglected. As observed in rodent‐hantavirus systems in the Americas, we propose that for a negative diversity‐disease pattern to manifest, the primary reservoir host species should be resilient to anthropogenic disturbance but also vulnerable to competition, predation, or both, and the “diversity” measure should be associated with host density.more » « less
-
Abstract Pathogen spillover corresponds to the transmission of a pathogen or parasite from an original host species to a novel host species, preluding disease emergence. Understanding the interacting factors that lead to pathogen transmission in a zoonotic cycle could help identify novel hosts of pathogens and the patterns that lead to disease emergence. We hypothesize that ecological and biogeographic factors drive host encounters, infection susceptibility, and cross‐species spillover transmission. Using a rodent–ectoparasite system in the Neotropics, with shared ectoparasite associations as a proxy for ecological interaction between rodent species, we assessed relationships between rodents using geographic range, phylogenetic relatedness, and ectoparasite associations to determine the roles of generalist and specialist hosts in the transmission cycle of hantavirus. A total of 50 rodent species were ranked on their centrality in a network model based on ectoparasites sharing. Geographic proximity and phylogenetic relatedness were predictors for rodents to share ectoparasite species and were associated with shorter network path distance between rodents through shared ectoparasites. The rodent–ectoparasite network model successfully predicted independent data of seven known hantavirus hosts. The model predicted five novel rodent species as potential, unrecognized hantavirus hosts in South America. Findings suggest that ectoparasite data, geographic range, and phylogenetic relatedness of wildlife species could help predict novel hosts susceptible to infection and possible transmission of zoonotic pathogens. Hantavirus is a high‐consequence zoonotic pathogen with documented animal‐to‐animal, animal‐to‐human, and human‐to‐human transmission. Predictions of new rodent hosts can guide active epidemiological surveillance in specific areas and wildlife species to mitigate hantavirus spillover transmission risk from rodents to humans. This study supports the idea that ectoparasite relationships among rodents are a proxy of host species interactions and can inform transmission cycles of diverse pathogens circulating in wildlife disease systems, including wildlife viruses with epidemic potential, such as hantavirus.more » « less
-
Synopsis The emergence of infectious diseases is largely driven by spillover events from animal communities into human populations, with zoonotic pathogens accounting for 75% of novel infectious agents. In recent years, the incidence and prevalence of these pathogens have been on the rise, and efforts to understand the underlying ecological principles responsible for the reported increases have highlighted the role of biodiversity loss as a major contributing factor. Despite its role in pathogen emergence, how biodiversity is measured can differ drastically and may underlie variability in study results, making the impacts of biodiversity on pathogen behavior difficult to untangle. Here, we first examine how landscape parameters affect disease transmission and then evaluate metrics used in various disease systems to discuss the ways that different aspects of biodiversity, such as functional, phylogenetic, and trophic diversity, can provide novel insight into the relationship between host communities and disease emergence and transmission. We focus on the tick-borne pathogen that causes Lyme disease in this review and discuss how functional, trophic, and phylogenetic diversity can improve our understanding of the relationship between host community structure and disease transmission. The growing public health burden of tick-borne diseases necessitates holistic thinking to inform actions to decrease the risk of disease to humans and protect natural communities.more » « less
-
Abstract Understanding the community ecology of vector-borne and zoonotic diseases, and how it may shift transmission risk as it responds to environmental change, has become a central focus in disease ecology. Yet, it has been challenging to link the ecology of disease with reported human incidence. Here, we bridge the gap between local-scale community ecology and large-scale disease epidemiology, drawing from a priori knowledge of tick-pathogen-host ecology to model spatially-explicit Lyme disease (LD) risk, and human Lyme disease incidence (LDI) in California. We first use a species distribution modeling approach to model disease risk with variables capturing climate, vegetation, and ecology of key reservoir host species, and host species richness. We then use our modeled disease risk to predict human disease incidence at the zip code level across California. Our results suggest the ecology of key reservoir hosts—particularly dusky-footed woodrats—is central to disease risk posed by ticks, but that host community richness is not strongly associated with tick infection. Predicted disease risk, which is most strongly influenced by the ecology of dusky-footed woodrats, in turn is a strong predictor of human LDI. This relationship holds in the Wildland-Urban Interface, but not in open access public lands, and is stronger in northern California than in the state as a whole. This suggests peridomestic exposure to infected ticks may be more important to LD epidemiology in California than recreational exposure, and underlines the importance of the community ecology of LD in determining human transmission risk throughout this LD endemic region of far western North America. More targeted tick and pathogen surveillance, coupled with studies of human and tick behavior could improve understanding of key risk factors and inform public health interventions. Moreover, longitudinal surveillance data could further improve forecasts of disease risk in response to global environmental change.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ecs2.70292
