Orthohantavirus infection in two rodent species that inhabit wetlands in the central-east region of Argentina

Hantavirus pulmonary syndrome (HPS) is an emerging infectious disease caused by orthohantaviruses associated to rodents of the Cricetidae family, Sigmodontinae subfamily, in the American continent. Previous research carried out in central-east region of Argentina, recorded potential orthohantavirus host rodents in diverse environments, but infected rodents were particularly present on Paraná wetlands islands. The aims of this research were (1) to determine the orthohantavirus host in the rodent community focused on islands of Paraná River Delta, an endemic zone of HPS, (2) to identify temporal and spatial factors associated with orthohantavirus prevalence variations, (3) to compare the individual characteristics of seropositive and seronegative rodents and, (4) to explore the association between orthohantavirus seroprevalence and rodent community characteristics in the Paraná River Delta, central-east region of Argentina. Capture of small rodents was done between August 2014 and May 2018 on seven islands located in central-east region of Argentina. In this HPS endemic zone, 14.9% of Oligoryzomys flavescens and 1.5% of Oxymycterus rufus of the sampled rodents had antibodies against orthohantavirus. The individuals that were more likely to become seropositive were the reproductively active adult males. Even though O. flavescens inhabit all islands, the seropositive individuals were only present in two of these, suggesting spatial heterogeneity in the viral distribution. We found that two months later of periods with low temperature, seroprevalence increased probably due to a higher proportion of adults in the population. Additionally, higher seroprevalence was associated with greater diversity of the rodent assemblage. This association could support the idea that a rescue effect or amplification of the prevalence of orthohantavirus would be taking place by means of secondary host as O. rufus, a novelty for this species and for the region. This finding may be significant if one takes into account that O. rufus was the second most abundant species in the area of islands studied and is one of the most abundant species on the islands and riparian sectors of the study zone. In conclusion, the relative risk of HPS could be high on wetlands of Paraná River Delta in the central-east region of Argentina where several favourable factors for the transmission of orthohantavirus are combined, such as the presence of several host species, two of them numerically dominant, high percentages of infection and a high degree of occupational exposure of the human population due to rural activities, the most frequently associated nationwide with HPS.

Maintenance of community function through compensation breaks down over time in a desert rodent community

Understanding the ecological processes that maintain community function in systems experiencing species loss, and how these processes change over time, is key to understanding the relationship between community structure and function and predicting how communities may respond to perturbations in the Anthropocene. Using a 30-year experiment on desert rodents, we show that the impact of species loss on community-level energy use has changed dramatically over time, due to changes in both species composition and in the degree of functional redundancy among the same set of species. Although strong compensation, initially driven by the dispersal of functionally redundant species to the local community, occurred in this system from 1996-2010, since 2010, compensation has broken down due to decreasing functional overlap within the same set of species. Simultaneously, long-term changes in sitewide community composition due to niche complementarity have decoupled the dynamics of compensation from the overall impact of species loss on community-level energy use. These results highlight the importance of explicitly long-term, metacommunity, and eco-evolutionary perspectives on compensatory dynamics, zero-sum constraints, and the link between species-level fluctuations and community function in a changing world.Original submissionThis submission analyzes long-term data on rodent community abundance and energy use from the Portal Project. Sections of this timeseries have been analyzed in numerous other publications, but this is the first to analyze data from 2007-2020 on compensation on experimental and control plots.No prior publicationThis submission is posted as a preprint on bioRxiv at [bioRxiv].Animal welfareRodent censuses were conducted with IACUC approval, most recently under protocol 201808839_01 at the University of Florida.Open researchAll data and code to reproduce these analyses are archived on Zenodo at https://doi.org/10.5281/zenodo.5544362 and https://doi.org/10.5281/zenodo.5539881.Analytic methodsAll analyses were conducted in R version 4.0.3.

Multiple Mammarenaviruses Circulating in Angolan Rodents

Rodents are a speciose group of mammals with strong zoonotic potential. Some parts of Africa are still underexplored for the occurrence of rodent-borne pathogens, despite this high potential. Angola is at the convergence of three major biogeographical regions of sub-Saharan Africa, each harbouring a specific rodent community. This rodent-rich area is, therefore, strategic for studying the diversity and evolution of rodent-borne viruses. In this study we examined 290 small mammals, almost all rodents, for the presence of mammarenavirus and hantavirus RNA. While no hantavirus was detected, we found three rodent species positive for distinct mammarenaviruses with a particularly high prevalence in Namaqua rock rats (Micaelamys namaquensis). We characterised four complete virus genomes, which showed typical mammarenavirus organisation. Phylogenetic and genetic distance analyses revealed: (i) the presence of a significantly divergent strain of Luna virus in Angolan representatives of the ubiquitous Natal multimammate mouse (Mastomys natalensis), (ii) a novel Okahandja-related virus associated with the Angolan lineage of Micaelamys namaquensis for which we propose the name Bitu virus (BITV) and (iii) the occurrence of a novel Mobala-like mammarenavirus in the grey-bellied pygmy mouse (Mus triton) for which we propose the name Kwanza virus (KWAV). This high virus diversity in a limited host sample size and in a relatively small geographical area supports the idea that Angola is a hotspot for mammarenavirus diversity.

Rats in the city: implications for zoonotic disease risk in an urbanizing world

Urbanization is rapidly transforming much of Southeast Asia, altering the structure and function of the landscape, as well as the frequency and intensity of the interactions between people, animals, and the environment. In this study, we began to explore the impact of urbanization on zoonotic disease risk by simultaneously characterizing changes in the abundance and diversity of reservoir hosts (rodents), ectoparasite vectors (ticks), and microbial pathogens across a gradient of urbanization in Malaysian Borneo. We found that although rodent species diversity decreased with increasing urbanization, two species appeared to thrive in anthropogenic environments: the invasive urban exploiter, Rattus rattus and the native urban adapter, Sundamys muelleri. R. rattus was strongly associated with the presence of built infrastructure across the gradient and dominated the urban rodent community where it was associated with high microbial diversity and multi-host zoonoses capable of environmental transmission, including Leptospira spp., and Toxoplasma gondii. In contrast, S. muelleri was restricted to sites with a significant vegetative component where it was found at high densities in the urban location. This species was strongly associated with the presence of ticks, including the medically important genera Ambylomma, Haemaphysalis, and Ixodes. Overall, our results demonstrate that the response to urbanization varies by species at all levels: host, ectoparasite, and microbe. This may lead to increased zoonotic disease risk in a subset of environments across urban and urbanizing landscapes that can be reduced through improved pest management and public health messaging.

Mixed Effects of Habitat Degradation and Resources on Hantaviruses in Sympatric Wild Rodent Reservoirs within a Neotropical Forest

Understanding the ecology of rodent-borne hantaviruses is critical to assessing the risk of spillover to humans. Longitudinal surveys have suggested that hantaviral prevalence in a given host population is tightly linked to rodent ecology and correlates with changes in the species composition of a rodent community over time and/or habitat composition. We tested two hypotheses to identify whether resource addition and/or habitat composition may affect hantavirus prevalence among two sympatric reservoir hosts in a neotropical forest: (i) increased food resources will alter the rodent community and thus hantaviral prevalence; and (ii) host abundance and viral seroprevalence will be associated with habitat composition. We established a baseline of rodent–virus prevalence in three grid pairs of distinct habitat compositions and subjected one grid of each pair to resource augmentation. Increased rodent species diversity was observed on grids where food was added versus untreated control grids during the first post-treatment sampling session. Resource augmentation changed species community composition, yet it did not affect the prevalence of hantavirus in the host population over time, nor was there evidence of a dilution effect. Secondly, we show that the prevalence of the virus in the respective reservoir hosts was associated with habitat composition at two spatial levels, independent of resource addition, supporting previous findings that habitat composition is a primary driver of the prevalence of hantaviruses in the neotropics.

Partitioning of trophic resource on example of the rodent community dwelling in the high mountain zone of the Eastern Caucasus

Quantitative and qualitative feeding characteristics of some rodent species co-living in the high mountain zone of the Eastern Caucasus (Republic of Daghestan) were investigated. The diet of S. uralensis consisted of 23 plant species, C. gud – 22 plant species, M. arvalis – 27 plant species, C. migtatorius – 26 plant species and D. nitedula – 19 plant species. The largest dietary breadths were M. arvalis and C. migtatorius and the least was S. uralensis. In spring, Carex spp. predominated in the diets of rodent species; in summer, the diets consisted mainly of cereals, and the autumn rodents diets consisted mainly of forbs and legumes. The maximum values of the dietary niches overlapping were found in pairs of the following species: S. uralensis C. gud, C. gud - C. migtatorius, M. arvalis C. migtatorius. Average values of the dietary niches overlapping for all rodents were 0.529, 0.277, 0.459, respectively, in spring, summer and autumn.