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The world is facing a major pulse of ecological and social changes that may favor the risk of zoonotic outbreaks. Such risk facilitation may occur through the modification of the host’s community diversity and structure, leading to an increase in pathogen reservoirs and the contact rate between these reservoirs and humans. Here, we examined whether anthropization alters the relative abundance and richness of zoonotic reservoir and non-reservoir rodents in three Socio-Ecological Systems. We hypothesized that anthropization increases the relative abundance and richness of rodent reservoirs while decreasing non-reservoir species. We first developed an Anthropization index based on 15 quantitative socio-ecological variables classified into five groups: 1) Vegetation type, 2) Urbanization degree, 3) Water quality, 4) Potential contaminant sources, and 5) Others. We then monitored rodent communities in three regions of Northwestern Mexico (Baja California, Chihuahua, and Sonora). A total of 683 rodents of 14 genera and 27 species were captured, nine of which have been identified as reservoirs of zoonotic pathogens (359 individuals, 53%). In all regions, we found that as anthropization increased, the relative abundance of reservoir rodents increased; in contrast, the relative abundance of non-reservoir rodents decreased. In Sonora, reservoir richness increased with increasing anthropization, while in Baja California and Chihuahua non-reservoir richness decreased as anthropization increased. We also found a significant positive relationship between the anthropization degree and the abundance of house mice ( Mus musculus ) and deer mice ( Peromyscus maniculatus ), the most abundant reservoir species in the study. These findings support the hypothesis that reservoir species of zoonotic pathogens increase their abundance in disturbed environments, which may increase the risk of pathogen exposure to humans, while anthropization creates an environmental filtering that promotes the local extinction of non-reservoir species.

Billions of genomic sequences and records of species occurrence are available in public repositories (e.g. National Center for Biotechnology Information, NCBI and the Global Biodiversity Information Facility, GBIF). By implementing analytical tools from different scientific disciplines, data mining these databases can aid in the global surveillance of zoonotic pathogens that circulate among wildlife. We illustrate this by investigating the Hantavirus–rodent system in the Americas, i.e. New World Hantaviruses (NWH). First, we considered the circulation of pathogenic NWH among Cricetidae rodents, by inferring the phylogenetic links among 277 genomic samples of the S segment (N protein) of NWH found in 55 species. Second, we used machine learning to assess the impact of land use on the probability of presence of the rodent species linked with reservoirs of pathogenic Hantaviruses. Our results show that hosts are widely present across the Americas. Some hosts are present in the primary forest and agricultural land, but not in the secondary forest, whereas other hosts are present in secondary forest and agricultural land. The diversity of host species allows Hantavirus to circulate in a wide spectrum of habitats, in particular rural rather than urban. We highlight that public repositories of genomic data and species occurrence are very useful resources for monitoring potential enzootic transmission and spillover of zoonotic viruses in relation with the changes that humans produce in the biosphere.

Land-use change can raise the risk of human exposure to zoonotic diseases by increasing abundance of reservoir hosts. In this study, we conducted a meta-analysis on the associations between land-use change and the abundance of rodent species in relation to their reservoir status for rodent-borne diseases. Using the PREDICT database, we analyzed 58 case studies comprising 54 species from eight countries. In general, rodent reservoirs were significantly more abundant in modified habitats (anthropogenically altered sites), whereas non-reservoir species were more abundant in non-modified habitats. To our knowledge, this is the first meta-analysis that evaluates the response of rodents to land-use change with a focus on the potential implications for epidemiological risks. Our findings give further evidence that land-use change generally impacts biodiversity in ways that might imply higher risk of zoonotic pathogen transmission.

Rodent-borne hantaviruses are a group of zoonotic agents that cause hemorrhagic fever in humans. The transmission of hantaviruses among rodent hosts may be higher with the increase of reservoir host abundance in a given area (density-dependent transmission) and with the decrease of small mammal diversity (dilution effect phenomenon). These population and community parameters may be modified by habitat fragmentation; however, studies that focus on fragmentation and its effect on hantavirus infection risk are scarce. To further understanding of this issue, we assessed some population and community responses of rodents that may increase the risk for hantavirus transmission among wildlife hosts in the Americas. We conducted a meta-analysis of published studies to assess the responses of small mammals to fragmentation of native habitats, relative to patch size. Our analyses included five countries and 14 case studies for abundance of reservoir hosts (8 species) and 15 case studies for species richness. We found that a reduction of patch area due to habitat fragmentation is associated with increased reservoir host abundances and decreased small mammal richness, which is mainly due to the loss of non-host small mammals. According to these results, habitat fragmentation in the Americas should be considered as an epidemiological risk factor for hantavirus transmission to humans. These findings are important to assess potential risk of infection when fragmentation of native habitats occurs.

Background Invasive rats ( Rattus rattus and Rattus norvegicus ) are recognized hosts of zoonotic pathogens, including Trypanosoma cruzi , in human-modified landscapes. However, their role in non-domestic transmission cycles remains poorly understood, particularly in Mediterranean ecosystems near the southern limit of endemic Chagas disease. Here, we assessed the prevalence of T. cruzi infection in invasive rats across rural and natural habitats of central Chile. Methods Rodents were live-trapped in rural (non-peridomestic) and natural habitats during seasonal campaigns conducted between 2023 and 2025. Blood samples from invasive rats captured at 31 sites were screened for T. cruzi DNA using real-time PCR targeting parasite satellite DNA. Results A total of 789 invasive rats were analyzed, representing one of the most extensive molecular screenings of Rattus spp. conducted in rural and natural habitats of central Chile. Overall infection prevalence was extremely low (0.25%; 95% CI: 0.07–0.92%), with positive detections restricted to two R. rattus individuals captured in autumn within natural habitats. This low prevalence was consistent across habitats and seasons. Conclusions Invasive rats appear to play a limited role in non-domestic transmission under the ecological conditions surveyed and are unlikely to reliably reflect local parasite circulation. One plausible explanation is potentially limited spatial overlap between invasive rat populations and areas where sylvatic vectors are most abundant, although this requires empirical verification through concurrent vector surveys. These findings provide baseline evidence on the epidemiological role of invasive rats in Mediterranean ecosystems and may inform ecologically grounded surveillance strategies within a One Health framework.

Cyanobacterial harmful algal blooms are an increasing concern for wildlife health, particularly in eutrophic wetlands, yet well-documented avian cases supported by environmental, pathological, and toxicological evidence remain scarce. This study describes a sentinel case of probable microcystin toxicosis in a Red-gartered coot (Fulica armillata) from Laguna Petrel, a protected coastal wetland in central Chile, during a broader wildlife mortality event. Surface-water monitoring included nutrient analyses, in situ physicochemical measurements, phytoplankton assessment, and cyanotoxin quantification. The evaluated bird was documented alive with severe motor impairment, euthanized, and examined by gross necropsy, histopathology, and tissue toxicology. Water analyses showed elevated nutrients, persistently alkaline and highly productive conditions, marked dominance of Microcystis aeruginosa, and high concentrations of microcystin-LR, microcystin-RR, microcystin-YR, and nodularin. The bird showed marked hepatic lesions at necropsy, histopathological changes compatible with acute hepatotoxic injury, and detectable microcystin-LR in lyophilized liver tissue. Taken together, these findings support a diagnosis of probable microcystin toxicosis in this individual. This case highlights the value of waterfowl as sentinels of ecosystem health threats and underscores the importance of integrated monitoring in protected coastal wetlands potentially affected by toxic cyanobacterial blooms.

Andes south virus (ANDV) is the etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in Chile and southern Argentina. Farm and forestry workers have been identified as a group at high risk of acquiring HCPS caused by ANDV due to their close exposure to rodents or their secretions in rural areas. Therefore, investigation on the effect of landscape composition on ANDV in wild rodents becomes relevant for disease prevention and control. In this study, we analyzed the influence of Monterey pine (Pinus radiata) plantations, an important monoculture in the global forest industry, on small mammal assemblage and on ANDV seroprevalence and abundance of seropositive rodents from central Chile. Small mammals were sampled seasonally during 2 years in native forests, adult pine plantations and young pine plantations. A total of 1630 samples from seven rodent species were analyzed for antibody detection. ANDV seroprevalence and abundance of seropositive rodents were significantly higher in the native forest compared to pine plantations. Furthermore, Monterey pine plantations decrease the abundance and relative abundance of Oligoryzomys longicaudatus (the principal reservoir of ANDV) and do not change sex ratio and distribution of age classes of this rodent species, which are variables that are important for ANDV transmission. Our findings indicate that Monterey pine plantations would not pose a higher risk of human exposure to ANDV compared to the temperate native forest. Our results can be useful for hantavirus risks assessment in human-dominated areas where ANDV is endemic.

Background The degree of temporal overlap between sympatric wild hosts species and their behavioral interactions can be highly relevant to the transmission of pathogens. However, this topic has been scantly addressed. Furthermore, temporal overlap and interactions within an assemblage of wild rodents composed of native and introduced species have been rarely discussed worldwide. We assessed the nocturnal activity patterns and interactions between rodent taxa of an assemblage consisting of native species ( Oligoryzomys longicaudatus , Abrothrix hirta , and Abrothrix olivaceus ) and the introduced black rat ( Rattus rattus ) in a temperate forest from southern Chile. All rodent species in this study are known hosts for various zoonotic pathogens. Results We found a high nocturnal temporal overlap within the rodent assemblage. However, pairwise comparisons of temporal activity patterns indicated significant differences among all taxa. Rattus rattus showed aggressive behaviors against all native rodents more frequently than against their conspecifics. As for native rodents, agonistic behaviors were the most common interactions between individuals of the same taxon and between individuals of different taxa ( O. longicaudatus vs Abrothrix spp.). Conclusions Our findings reveal several interactions among rodent taxa that may have implications for pathogens such as hantaviruses, Leptospira spp., and vector-borne pathogens. Furthermore, their transmission may be facilitated by the temporal overlap observed between rodent taxa.

Background Rodents play essential ecological roles but are also significant reservoirs of zoonotic pathogens, posing risks to humans. Individuals with frequent occupational contact with rodents face an elevated risk of exposure to rodent-borne diseases. This study examines the knowledge, risk perceptions, and practices of Chilean environmental consultants (ECs) concerning rodents and rodent-borne diseases. Methods A 32-item questionnaire, which focused primarily on biologists, veterinarians, and environmental engineers, was administered. The questionnaire included closed, open-ended, and semi-open-ended questions. Data analyses, performed using R software, involved calculating frequencies and proportions for questions related to knowledge of rodents and rodent-borne diseases, rodent management and handling, biosafety procedures, and training. Additionally, generalized linear models (GLMs) were used to assess knowledge of rodent hosts and diseases, whereas correspondence analysis was used to examine associations between EC characteristics (undergraduate fields of study and years of experience) and responses regarding risk perception and the importance of zoonotic disease training. Results Completed questionnaires were received from 206 ECs. Although the ECs demonstrated a strong awareness of hantavirus cardiopulmonary syndrome, identifying it as a significant rodent-borne threat, knowledge gaps were evident regarding the specific role of certain rodent reservoir species and other rodent-borne diseases in Chile. For example, leptospirosis was well recognized, particularly among veterinarians, whereas emerging zoonoses such as scrub typhus was rarely mentioned. The study also revealed the frequent use of live trapping and direct handling of rodents, resulting in injuries to 32% of the respondents. Despite the widespread use of personal protective equipment, key elements such as respiratory protection and disposable suits were underutilized, and inadequate cleaning practices for traps were reported. Nevertheless, ECs expressed a willingness to participate in zoonotic disease training, underscoring the need for further education. Conclusions This study highlights the critical need for ongoing education for ECs on rodent reservoirs, diseases, and biosafety measures to enhance their safety and reduce the risk of zoonotic infections. The findings offer valuable insights for developing strategies aimed at improving awareness and strengthening biosafety practices within this occupational group.

Native forests have been replaced by forestry plantations worldwide, impacting biodiversity. However, the effect of this anthropogenic land-use change on parasitism is poorly understood. One of the most important land-use change in Chile is the replacement of native forests by Monterey pine (Pinus radiata) plantations. In this study, we analyzed the parasitism (presence and prevalence) of intestinal helminths from fecal samples of wild rodents in three habitat types: native forests and adult and young pine plantations in central Chile. Small mammals were sampled seasonally for two years, and a total of 1091 fecal samples from seven small mammal species were analyzed using coprological analysis. We found several helminth families and genera, some of them potentially zoonotic. In addition, new rodent–parasite associations were reported for the first time. The overall helminth prevalence was 16.95%, and an effect of habitat type on prevalence was not observed. Other factors were more relevant for prevalence such rodent species for Hymenolepis sp. and season for Physaloptera sp. Our findings indicate that pine plantations do not increase helminth prevalence in rodents compared to native forests.