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1. Unraveling the Mechanistic Links Between Species Diversity and Infection Risk From Zoonotic Pathogens With Direct Transmission Among Reservoir Hosts: Rodent‐Orthohantavirus Systems as Models

   https://doi.org/10.1002/ece3.71597  

   Eleftheriou, Andreas; Luis, Angela D (June 2025, Ecology and Evolution)

   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. 

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2. A protocol for biodiversity-informed wildlife disease surveillance

   https://doi.org/10.32942/X21D36  

   Catchen, Michael; Banville, Francis; Boutin, Amélie; Brookson, Cole; Carlson, Colin; Dansereau, Gabriel; Gibb, Rory; Houle, Marianne; Kaza, Benjamin; Robertson, Hailey; et al (December 2025, PLOS Ecosystems)

   Land use and climate change are increasing the risk of spillover of zoonotic disease into human populations. However, we lack actionable information about the prevalence of pathogens in wildlife populations for most of the globe, challenging our ability to implement strategies to prevent zoonoses. Even when this data exists, it has historically been sampled opportunistically and without guidance based on known geographic distributions of hosts of zoonotic pathogens. Biosurveillance is essential to mitigating zoonotic spillover risk, but given the expensive nature of monitoring pathogens in wildlife, we need to be strategic about deciding where and what to sample to obtain as much useful information as possible. The field of biodiversity monitoring has established many practices that can directly inform optimal biosurveillance efforts. One such concept is the Biodiversity Observation Network (or BON), which aims to select monitoring locations that most effectively and efficiently capture the status and trends of biodiversity. We present a protocol for integrating data on host biodiversity into sampling priority for wildlife disease surveillance based on host species distribution models, with optional potential to integrate pathogen prevalence data (if available). This protocol has the flexibility to target different forms of sampling (collecting host occurrence vs pathogen prevalence data) to adapt to different levels of data availability, but still makes adaptive sampling recommendations based on a principled understanding of host distribution and pathogen biology.We illustrate this flexibility with two case studies, prioritizing sampling for Hanta- and Arena-viridae in rodents in India and South Korea, respectively representing data poor and data rich contexts. We view this framework as a basis for integrating long-term biosurveillance and biodiversity monitoring programs, and maximizing the useful information available for public health decision making. 

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3. A general framework for modeling pathogen transmission in co‐roosting host communities

   https://doi.org/10.1002/ecy.70326  

   Simonis, Molly C; Becker, Daniel J (February 2026, Ecology)

   Abstract Cross‐species transmission of pathogens can be facilitated by frequent contact among wildlife. Cross‐species transmission is often driven by phylogenetic similarity between host species, but the role this plays when multiple host species co‐roost is unknown. We developed a generalizable framework for understanding how cross‐species transmission is driven by contact among co‐roosting species spanning evolutionary similarities and the net impact on roost‐level infection prevalence. We developed ordinary differential equation models describing population and infection dynamics between two and three co‐roosting species. We derived conditions for pathogen invasion and parameterized models using co‐roosting Neotropical bat systems, with interspecific transmission exponentially declining with phylogenetic distance. To assess the relative contribution of contact rates and phylogenetic similarity, we co‐varied intraspecific transmission rates and phylogenetic distances while considering sensitivity to epidemiological structure and pathogen traits. For both susceptible–infected–recovered–susceptible and susceptible–infected–latent–infected models, we show that relatedness between co‐roosting hosts facilitates pathogen invasion, particularly for poorly transmissible pathogens with short durations of infection and immunity or latency. These models converged on similar equilibria, and roost‐level prevalence was greatest when hosts were most closely related. However, we also identified regions of parameter space where roost‐level prevalence increased when hosts were distantly related. Our generalizable models are adaptable to other co‐roosting systems with low‐virulence pathogens that are directly transmitted and inform our understanding of pathogen spillover. 

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4. Novel pathogen introduction triggers rapid evolution in animal social movement strategies

   https://doi.org/10.7554/eLife.81805  

   Gupte, Pratik Rajan; Albery, Gregory F; Gismann, Jakob; Sweeny, Amy; Weissing, Franz J (August 2023, eLife)

   Animal sociality emerges from individual decisions on how to balance the costs and benefits of being sociable. Novel pathogens introduced into wildlife populations should increase the costs of sociality, selecting against gregariousness. Using an individual-based model that captures essential features of pathogen transmission among social hosts, we show how novel pathogen introduction provokes the rapid evolutionary emergence and coexistence of distinct social movement strategies. These strategies differ in how they trade the benefits of social information against the risk of infection. Overall, pathogen-risk-adapted populations move more and have fewer associations with other individuals than their pathogen-risk-naive ancestors, reducing disease spread. Host evolution to be less social can be sufficient to cause a pathogen to be eliminated from a population, which is followed by a rapid recovery in social tendency. Our conceptual model is broadly applicable to a wide range of potential host–pathogen introductions and offers initial predictions for the eco-evolutionary consequences of wildlife pathogen spillover scenarios and a template for the development of theory in the ecology and evolution of animals’ movement decisions. 

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5. Macro-parasites and micro-parasites co-exist in rodent communities but are associated with different community-level parameters

   https://doi.org/10.1016/j.ijppaw.2023.08.006  

   Salomon, Jordan; Sambado, Samantha B.; Crews, Arielle; Sidhu, Sukhman; Seredian, Eric; Almarinez, Adrienne; Grgich, Rachel; Swei, Andrea (August 2023, International Journal for Parasitology: Parasites and Wildlife)

   Wildlife species are often heavily parasitized by multiple infections simultaneously. Yet research on sylvatic transmission cycles, tend to focus on host interactions with a single parasite and neglects the influence of co- infections by other pathogens and parasites. Co-infections between macro-parasites and micro-parasites can alter mechanisms that regulate pathogenesis and are important for understanding disease emergence and dy- namics. Wildlife rodent hosts in the Lyme disease system are infected with macro-parasites (i.e., ticks and hel- minths) and micro-parasites (i.e., Borrelia spp.), however, there has not been a study that investigates the interaction of all three parasites (i.e., I. pacificus, Borrelia spp., and helminths) and how these co-infections impact prevalence of micro-parasites. We live-trapped rodents in ten sites in northern California to collect feces, blood, ear tissue, and attached ticks. These samples were used to test for infection status of Borrelia species (i.e., micro- parasite), and describe the burden of ticks and helminths (i.e., macro-parasites). We found that some rodent hosts were co-infected with all three parasites, however, the burden or presence of concurrent macro-parasites were not associated with Borrelia infections. For macro-parasites, we found that tick burdens were positively associ- ated with rodent Shannon diversity while negatively associated with predator diversity, whereas helminth burdens were not significantly associated with any host community metric. Ticks and tick-borne pathogens are associated with rodent host diversity, predator diversity, and abiotic factors. However, it is still unknown what factors helminths are associated with on the community level. Understanding the mechanisms that influence co- infections of multiple types of parasites within and across hosts is an increasingly critical component of characterizing zoonotic disease transmission and maintenance. 

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