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ABSTRACT The hairy-tailed bolo mouse, Necromys lasiurus (Lund, 1841), which is typical of the Cerrado (CE), has been recorded in some open areas within the Atlantic Forest (AF) domain of the Brazilian state of Rio de Janeiro (RJ). In the CE, N. lasiurus is a known reservoir of zoonotic agents, and is the reservoir of an orthohantavirus genotype, Araraquara virus (ARAV), the etiological agent of Hantavirus Pulmonary Syndrome (HPS). Given this, the presence of N. lasiurus has potentially negative implications for public health in the state, and therefore it is important to elucidate the origin of its populations in RJ and their connections with populations outside the AF known to carry the ARAV. In the present study we combined phylogenetic and phylogeographic approaches to elucidate the evolutionary history of N. lasiurus populations in RJ, and to test if their dispersal into the AF domain is recent or ancient. These analyses were based on sequences of the mitochondrial Cytochrome b gene, obtained from N. lasiurus specimens from the Atlantic Forest of Rio de Janeiro (AF-RJ), together with all the sequences of this gene available for N. lasiurus in GenBank. In addition to the phylogenetic and phylogeographic analyses, the sequences were used to test among five hypothetical demographic scenarios, proposed to explain the evolutionary history of the hairy-tailed bolo mouse in the state of RJ. The results of all the analyses indicated that populations from AF and the Arid Diagonal (AD) of South America, which includes the CE, diverged in the Late Pleistocene but reconnected in the Holocene. The RJ population (AF-RJ) resulted from this recent genetic admixture among diverging populations from AF and AD. Despite the recent reconnection, no evidence has been found that the AF-RJ N. lasiurus population acts as a reservoir of ARAV, although the continued genetic connectivity with those from AD highlight the need to reinforce the public health monitoring of orthohantavirus in this rodent, especially given the potential spillover of other genotypes. Overall, then, the results of the present study provide important new insights into the evolutionary history of N. lasiurus, which should contribute to the surveillance of orthohantaviruses, and the development of more effective measures for the prevention and control of this zoonosis.

Hantavirus Pulmonary Syndrome (HPS) is a disease caused by Hantavirus, which are negative-sense RNA viruses in the family Bunyaviridae that are highly virulent to humans. Numerous factors modify risk of Hantavirus transmission and consequent HPS risk. Human-driven landscape change can foster transmission risk by increasing numbers of habitat generalist rodent species that serve as the principal reservoir host. Climate can also affect rodent population dynamics and Hantavirus survival, and a number of social factors can influence probability of HPS transmission to humans. Evaluating contributions of these factors to HPS risk may enable predictions of future outbreaks, and is critical to development of effective public health strategies. Here we rely on a Bayesian model to quantify associations between annual HPS incidence across the state of São Paulo, Brazil (1993-2012) and climate variables (annual precipitation, annual mean temperature), landscape structure metrics (proportion of native habitat cover, number of forest fragments, proportion of area planted with sugarcane), and social factors (number of men older than 14 years and Human Development Index). We built separate models for the main two biomes of the state (cerrado and Atlantic forest). In both biomes Hantavirus risk increased with proportion of land cultivated for sugarcane and HDI, but proportion of forest cover, annual mean temperature, and population at risk also showed positive relationships in the Atlantic forest. Our analysis provides the first evidence that social, landscape, and climate factors are associated with HPS incidence in the Neotropics. Our risk map can be used to support the adoption of preventive measures and optimize the allocation of resources to avoid disease propagation, especially in municipalities that show medium to high HPS risk (> 5% of risk), and aimed at sugarcane workers, minimizing the risk of future HPS outbreaks.

The lymphocytic choriomeningitis virus (LCMV) is an under-investigated rodent-borne arenavirus primarily associated with its natural reservoir, the cosmopolitan rodent Mus musculus. Although widely distributed in mice worldwide, human cases are rare, likely under-reported, and often misdiagnosed. While typically asymptomatic or self-limiting, infection can progress to neurological disease, severe congenital outcomes, or fatal illness in transplant recipients. Despite its public health relevance, this study provides the first detection and characterization of LCMV in Brazil. We analyzed 236 rodent serum samples and 78 tissue samples from synanthropic rodents (Mus musculus, Rattus rattus, and Rattus norvegicus) collected during seven independent expeditions across the state of Rio de Janeiro, Southeastern Brazil. Using ELISAs, IgG anti-LCMV antibodies were detected in 20% of rodents, including two R. rattus (2/10), two R. norvegicus (2/95), and forty-five M. musculus (45/131). The LCMV’s RNA was amplified and partially sequenced from fourteen M. musculus, and complete S segment sequences were obtained from two mouse samples. Phylogenetic analyses revealed that these Brazilian strains belong to lineage I, which is composed of strains that induce disease in humans. Our results underscore the importance of implementing integrated surveillance for this zoonosis in Brazil.

Bats are known as potential carriers of different pathogens; these animals have been identified worldwide as an important reservoir of different species of Leptospira. Therefore, there has been an increasing interest in studying leptospirosis in neotropical bats in the Amazon. This region is a fertile ground for zoonotic diseases, given the intense process of deforestation, urbanization, opening of new agricultural frontiers, predatory hunting, effects of climate change, and loss of biodiversity. Based on this, the aim of the present study was to investigate the frequency of infection associated with the genetic characterization of pathogenic Leptospira spp. in bats inhabiting diverse landscapes in the southwestern region of the Amazon. To conduct the study, mist nets were installed to capture bats. Kidney samples were submitted to LipL32-polymerase chain reaction and secY gene sequencing. Our results showed that 21% of neotropical evaluated bats in Southwestern Amazon were infected with Leptospira spp. Positive animals were found in rural, urban, periurban, and control areas. Sanguinivores had the highest frequency of positives, followed by insectivores and frugivorous bats. The species of L. interrogans and a potential new Leptospira species were identified. The frequency of Leptospira in bats was not influenced by landscape type, suggesting these pathogens may not be affected by landscape changes. The findings suggest that bats may serve as potential reservoirs of Leptospira in diverse landscapes. The presence of Leptospira in bats appears to be independent of the type of land use, implying that these pathogens may not be affected by small-scale changes in the environment.

Parasites are important components of the immense n-dimensional trophic network that connects all living beings because they, among others, forge biodiversity and deeply influence ecological evolution and host behavior. In this sense, the influence of Trypanosomatidae remains unknown. The aim of this study was to determine trypanosomatid infection and richness in rats, opossums, and dogs in the semiarid Caatinga biome. We submitted DNA samples from trypanosomatids obtained through axenic cultures of the blood of these mammals to mini exon multiplex-PCR, Sanger, and next-generation sequencing targeting the 18S rDNA gene. Phylogenetic analyses were performed to identify genetic diversity in the Trypanosomatidae family. Shannon, Simpson, equability, and beta-diversity indices were calculated per location and per mammalian host. Dogs were surveyed for trypanosomatid infection through hemocultures and serological assays. The examined mammal species of this area of the Caatinga biome exhibited an enormous trypanosomatid species/genotypes richness. Ten denoised Operational Taxonomic Units (ZOTUs), including three species ( Trypanosoma cruzi , Trypanosoma rangeli and Crithidia mellificae ) and one Trypanosoma sp. five genotypes/lineages ( T. cruzi DTU TcI, TcII, and TcIV; T. rangeli A and B) and four DTU TcI haplotypes (ZOTU1, ZOTU2, ZOTU5, and ZOTU10 merged), as well as 13 Amplicon Sequence Variants (ASVs), including five species ( T. cruzi , T. rangeli , C. mellificae , Trypanosoma dionisii , and Trypanosoma lainsoni ), five genotypes/lineages (same as the ZOTUs) and six DTU TcI haplotypes (ASV, ASV1, ASV2, ASV3, ASV5 and ASV13), were identified in single and mixed infections. We observed that trypanosomatids present a broad host spectrum given that species related to a single host are found in other mammals from different taxa. Concomitant infections between trypanosomatids and new host-parasite relationships have been reported, and this immense diversity in mammals raised questions, such as how this can influence the course of the infection in these animals and its transmissibility. Dogs demonstrated a high infection rate by T. cruzi as observed by positive serological results (92% in 2005 and 76% in 2007). The absence of positive parasitological tests confirmed their poor infectivity potential but their importance as sentinel hosts of T. cruzi transmission.

Leptospirosis is a neglected zoonosis frequently reported worldwide, caused by a spirochete of the genus Leptospira. It is capable of infecting domestic animals, free-living animals, and humans. Among wild animals, the role of bats in the epidemiology of leptospirosis has been investigated but is far from being elucidated. The Amazonian biome has the ideal conditions for maintaining and disseminating leptospires and, despite efforts that have been made to better understand leptospires’ occurrence in wild animals in the region, few studies aimed to explore and genetically characterize leptospires in bats. Based on this, the aim of the present study is to deeper investigate and genetically characterize leptospires detected in bats from the southwest Amazon. Animals were trapped by mist netting at five sites in the state of Acre, Brazil. Kidney samples were obtained and stored for molecular analysis. Polymerase chain reaction (PCR) was conducted first based on the LipL32 gene, and positive samples were submitted to rrs and secY-PCR and sequencing. Sequences were then submitted to phylogenetic analyses through multiple bioinformatic tools. The rrs sequences from the present study formed one single haplotype, different from any other previously deposited, grouped in a highly supported cluster with sequences from bats from Madagascar and China. The initial secY screening revealed no identity with previously deposited sequences. The phylogenetic trees revealed the sequences from the present study in an isolated branch, clearly separated from all previously known pathogenic Leptospira spp., suggesting the existence of a potentially undescribed species. The haplotype network including only leptospires from the Amazon region confirmed two new haplotypes from the same taxon unity, isolated from the others, with a probable origin of the species from L. noguchii. The characterization of this potentially new species in bats reinforces the complexity of the transmission dynamics of leptospires, including wild, periurban, and urban environments, emphasizing the need for an integrative look at leptospirosis vigilance within the context of One Health.

Background Trypanosoma cruzi infection via oral route results in outbreaks or cases of acute Chagas disease (ACD) in different Brazilian regions and poses a novel epidemiological scenario. In the Espírito Santo state (southeastern Brazil), a fatal case of a patient with ACD led us to investigate the enzootic scenario to avoid the development of new cases. At the studied locality, Triatoma vitticeps exhibited high T. cruzi infection rates and frequently invaded residences. Methods Sylvatic and domestic mammals in the Rio da Prata locality, where the ACD case occurred, and in four surrounding areas (Baia Nova, Buenos Aires, Santa Rita and Todos os Santos) were examined and underwent parasitological and serological tests. Triatomines were collected for a fecal material exam, culturing and mini-exon gene molecular characterization, followed by RFLP-PCR of H3/Alul. Paraffin-embedded cardiac tissue of a patient was washed with xylene to remove paraffin and DNA was extracted using the phenol-chloroform method. For genotype characterization, PCR was performed to amplify the 1f8, GPI and 18S rRNA genes. In the case of V7V8 SSU rRNA, the PCR products were molecularly cloned. PCR products were sequenced and compared to sequences in GenBank. Phylogenetic analysis using maximum likelihood method with 1000 bootstrap replicates was performed. Results None of the animals showed positive hemocultures. Three rodents and two dogs showed signs of infection, as inferred from borderline serological titers. T. vitticeps was the only triatomine species identified and showed T. cruzi infection by DTUs TcI and TcIV. The analysis of cardiac tissue DNA showed mixed infection by T. cruzi (DTUs I, II, III and IV) and Trypanosoma dionisii . Conclusions Each case or outbreak of ACD should be analyzed as a particular epidemiological occurrence. The results indicated that mixed infections in humans may play a role in pathogenicity and may be more common than is currently recognized. Direct molecular characterization from biological samples is essential because this procedure avoids parasite selection. T. dionisii may under certain and unknown circumstances infect humans. The distribution of T. cruzi DTUS TcIII and TcIV in Brazilian biomes is broader than has been assumed to date.

Trypanosomatids are hemoflagellate parasites that even though they have been increasingly studied, many aspects of their biology and taxonomy remain unknown. The aim of this study was to investigate the Trypanosoma sp. transmission cycle in nonflying small mammals in an area where a case of acute Chagas disease occurred in Mangaratiba municipality, Rio de Janeiro state. Three expeditions were conducted in the area: the first in 2012, soon after the human case, and two others in 2015. Sylvatic mammals were captured and submitted to blood collection for trypanosomatid parasitological and serological exams. Dogs from the surrounding areas where the sylvatic mammals were captured were also tested for T. cruzi infection. DNA samples were extracted from blood clots and positive hemocultures, submitted to polymerase chain reaction targeting SSU rDNA and gGAPDH genes, sequenced and phylogenetic analysed. Twenty-one wild mammals were captured in 2012, mainly rodents, and 17 mammals, mainly marsupials, were captured in the two expeditions conducted in 2015. Only four rodents demonstrated borderline serological T. cruzi test (IFAT), two in 2012 and two in 2015. Trypanosoma janseni was the main Trypanosoma species identified, and isolates were obtained solely from Didelphis aurita . In addition to biological differences, molecular differences are suggestive of genetic diversity in this flagellate species. Trypanosoma sp. DID was identified in blood clots from D. aurita in single and mixed infections with T. janseni . Concerning dogs, 12 presented mostly borderline serological titers for T. cruzi and no positive hemoculture. In blood clots from 11 dogs, T. cruzi DNA was detected and characterized as TcI (n = 9) or TcII (n = 2). Infections by Trypanosoma rangeli lineage E (n = 2) and, for the first time, Trypanosoma caninum , Trypanosoma dionisii , and Crithidia mellificae (n = 1 each) were also detected in dogs. We concluded that despite the low mammalian species richness and degraded environment, a high Trypanosoma species richness species was being transmitted with the predominance of T. janseni and not T. cruzi , as would be expected in a locality of an acute case of Chagas disease.

Wild animals are infected by diverse parasites, but how they influence host health is poorly understood. We examined the relationship of trypanosomatids and gastrointestinal parasites with health of wild brown-nosed coatis (Nasua nasua) from the Brazilian Pantanal. We used coati body condition and hematological parameters as response variables in linear models that were compared using an information theoretic approach. Predictors were high/low parasitemias by Trypanosoma cruzi and T. evansi, and indices representing the abundance of distinct groups of gastrointestinal parasites. We also analyzed how host health changed with host sex and reproductive seasonality. Hemoparasites was best related to coati body condition and hematological indices, whereas abundance of gastrointestinal parasites was relatively less associated with coati health. Additionally, some associations were best predicted by models that incorporated reproductive seasonality and host sex. Overall, we observed a lower health condition during the breeding season, when coatis are under reproductive stress and may be less able to handle infection. In addition, females seem to handle infection better than males. Body condition was lower in coatis with high parasitemias of T. evansi, especially during the reproductive season. Total red blood cell counts, packed cell volume, platelets and eosinophils were also lower in animals with high T. evansi parasitemias. Total white blood cell counts and mature neutrophils were lower in animals with high parasitemias for both Trypanosoma species, with neutrophils decreasing mainly during the reproductive season. Overall, decreases in hematological parameters of females with T. evansi high parasitemias were less evident. For T. cruzi, monocytes decreased in individuals with high parasitemias. High abundances of microfilariae in the bloodstream, and cestode eggs and coccidian oocysts in feces were also associated with coati blood parameters. This study shows the potential value of examining hematological parameters as an approach to better understand the ecological relevance of parasite-host interactions.

Background Phylogeny, combined with trait-based measures, offers insights into parasite sharing among hosts. However, the specific traits that mediate transmission and the aspects of host community diversity that most effectively explain parasite infection rates remain unclear, even for the Bartonella genus, a vector-borne bacteria that causes persistent blood infections in vertebrates. Methods This study investigated the association between rodent host traits and Bartonella infection, as well as how rodent community diversity affects the odds of infection in the Atlantic Forest, using generalized linear models. Additionally, we assessed how host traits and phylogenetic similarities influence Bartonella infection among mammal species in Brazil. To this end, rodents were sampled from ten municipalities in Rio de Janeiro, southeastern Brazil. Then, we calculated several diversity indices for each community, including Rényi’s diversity profiles, Fisher’s alpha, Rao’s quadratic entropy (RaoQ), Functional Diversity (FDis), Functional Richness (FRic), and Functional Evenness (FEve). Finally, we compiled a network encompassing all known interactions between mammal species and Bartonella lineages recorded in Brazil. Results We found no significant relationship between diversity indices and the odds of Bartonella infection in rodent communities. Furthermore, there was no statistical support for the influence of individual-level traits (e.g., body length, sex, and age) or species-level ecological traits (e.g., locomotor habitat, dietary guild, and activity period) on Bartonella infection in rodents. A country-scale analysis, considering all mammal species, revealed no effect of host traits or phylogeny on Bartonella infection. Conclusions This study highlighted wild mammals that share Bartonella lineages with livestock, synanthropic, and domestic animals, underscoring the complexity of their maintenance cycle within the One Health framework. A key question arising from our findings is whether molecular host–cell interactions outweigh host body mass and ecological traits in influencing Bartonella infection, potentially opening new avenues for understanding host–parasite relationships and infection ecology. Graphical Abstract