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Flea-borne diseases are endemic in Texas, U.S.A., with an increasing incidence of flea-borne typhus and cat scratch disease. Knowledge of flea natural history could provide information to protect public health, yet many knowledge gaps remain outside of plague-endemic regions. Our objective was to characterize seasonal activity patterns of fleas on common mammalian wildlife species and test fleas and wildlife for Rickettsia and Bartonella pathogens. We performed one year of monthly trapping for rodents and medium-sized mammals in a national forest with high recreational use and urban encroachment in East Texas. From 90 mammal captures representing seven species, 101 fleas were collected representing Polygenis spp., Ctenocephalides felis, and Orchopeas species. Virginia opossums (Didelphis virginianus) hosted 99% of the collected fleas (100 fleas) and a single flea was on an eastern woodrat (Neotoma floridana). Flea infestation prevalence of opossums was 79% (23/29). Mean flea abundance was 4.39 fleas, with intensity peaking in spring. One cat flea removed from an opossum was positive for Bartonella henselae. Furthermore, we identified tissue or blood of four raccoons (Procyon lotor) and one golden mouse (Ochrotomys nuttalli) positive for Rickettsia amblyommatis. These findings provide an ecological basis for the maintenance of vectors and pathogens from sylvatic settings. [ABSTRACT FROM AUTHOR]

Background: The common opossum (Didelphis marsupialis) is a generalist species that hosts several parasites. Nevertheless, no information is available on the specific parasites that this species may host when it inhabits urban areas. Objective: To evaluate the presence and frequency of gastrointestinal parasites of urban opossums in the Aburrá Valley, Antioquia, Colombia. Methods: A total of 70 opossums were captured in six protected urban areas using Tomahawk traps during six months. From these animals we obtained 65 fecal samples which were fixed wit SAF solution and analyzed with direct smear and sedimentation techniques. Results: Sixty-one samples were positive for, at least, one parasite (93.9%) and 60 were positive for two or more parasites, averaging five parasites per animal. We observed nematodes in 58 samples (89.2%), protozoa in 46 samples (70.7%), acanthocephalans in 29 samples (44.6%), and cestodes in eight samples (12.3%). The most frequent parasite was Aspidodera spp. in 80% of the samples. In addition, this is the first study reporting the presence of eggs of Toxocara spp., Hymenolepis spp., an Oxyuridae parasite, and coccidians Eimeria didelphidis, E. caluromydis, and E. marmosopos in D. marsupialis. The latter is also reported in Colombia for the first time. Toxacara spp. is common to dogs and cats, while Hymenolepis and Oxiuridae are common to rodents. We found no association between parasites and sex or life stage of opossums, nor to the urban area of origin. Conclusions: Urban opossums in the Aburrá Valley host a high frequency and diversity of gastrointestinal parasites compared to other areas in Latin America. Some parasites are reported here for the first time. [ABSTRACT FROM AUTHOR]

Opossums (marsupials of the Didelphidae family) retain a generalized masticatory apparatus and tribosphenic molars, often used as models to understand the evolution of mastication in early therian mammals. Like all marsupials, their growth goes through a stage when pups complete their development while permanently attached to the mother's teats before weaning and starting feeding on their own. Yet, while the masticatory muscles of adults are known, as is the ontogeny of the cranium and mandible, the ontogenetic changes in the masticatory muscles remain unknown. Here we describe for the first time the changes in the masticatory muscles observed in lactating pups, and weaned juveniles, subadults, and adults in the White‐eared opossum, Didelphis albiventris, through dissection of 25 specimens and quantification of relative muscle masses, lines of actions and mechanical advantages whenever possible. We also assessed the scaling patterns of muscle masses and mechanical advantages through ontogeny. The main changes, as expected, were found between suckling and weaned specimens, although some changes still occurred from juveniles to adults. The adult adductor musculature is similar to the other Didelphis species already known, with a dominant m. temporalis that originates on the lateral wall of the skull, up to the sagittal and nuchal crests, and fills the zygomatic arch when inserting into the lateral and medial surfaces of the coronoid process, respectively through the pars superficialis and pars profunda. The m. masseter is also subdivided in superficial and deep bundles which originate posteriorly in the maxilla and zygomatic arch, and insert into the angular process and masseteric fossa in the mandible. The m. pterygoideus medialis originates from the palatine, the pterygoid bone and the alisphenoid, and it inserts on the angular process medially. Suckling pups showed muscles with more restricted attachments, reduced muscle lines of action, and less diversity in the fiber orientation. The absence of the postorbital constriction also resulted in a distinct morphology of the m. temporalis pars profunda, through two bundles, one anterior and one posterior, which insert more inferiorly into the mandible. These major changes can be related to the onset of mastication and to size‐related changes in growing weaned age classes. In general, all adductor muscles grew with positive allometry, and increased their fixation areas through, in part, the development of specific regions of the cranium and mandible. Their lines of action also increase and diversify along ontogeny. These changes can be related to the functional requirements for fixation during lactation, which shift to adduction and mastication movements after weaning. [ABSTRACT FROM AUTHOR]

Parasites are key players in ecosystems, influencing population sizes and food webs, yet the impact of environmental factors on their diversity is not well understood. The Atlantic rainforest in Brazil, particularly the Parque Estadual das Fontes do Ipiranga (PEFI), exemplifies a biodiversity hotspot facing significant deforestation, housing diverse animal species such as the synanthropic Brazilian common opossum (Didelphis aurita), which serves as a reservoir for multiple zoonotic pathogens. In this study, we investigated parasite diversity, abundance, prevalence, and richness in free-living D. aurita in the PEFI, São Paulo, Brazil. From January 2015 to January 2017, 101 fecal samples of D. aurita were collected in two areas of PEFI, at the Instituto de Pesquisas Ambientais (IPA) and the Parque de Ciência e Tecnologia (Cientec), and analyzed using three different parasitological methods. In total, 99% of the samples were positive for at least one parasite. The most prevalent parasite belonged to the order Strongylida (82%), followed by Cruzia sp. (77%), the latter having a significantly higher prevalence at IPA. In contrast, Acanthocephala showed greater prevalence at Cientec. Co-infections were common, with some individuals harboring up to seven different parasites. Our findings reveal significant parasite diversity in the D. aurita population at PEFI, including both helminths and protozoan trophozoites, some of which are reported for the first time in this host species. Further research is essential for accurate species identification of the observed parasites. [ABSTRACT FROM AUTHOR]

Abstract To understand the ecoepidemiology of fleas and their interactions with domestic and wild animals, it is necessary to decode the cycles of flea abundance in relation to host species and environmental factors. The province of Misiones, known for its biodiversity and land use changes, provides an excellent study location. We assessed the diversity, prevalence, abundance, and parasitic intensity of fleas collected from 1153 rodents and opossums in various environments in the Upper Paraná Atlantic Forest of Argentina, considering phytogeography and land use. Our findings were consistent with previous studies conducted in humid regions of Argentina and the Atlantic Forest in Brazil. Hosts with high population density exhibited greater flea prevalence and abundance, and widely distributed hosts showed higher flea species richness and diversity. Significant similarities in flea similarity indices among phytogeographic areas, especially in forest. Environments with an anthropogenic gradient exhibited marked dissimilarities, with higher species richness and diversity in less disturbed sites. These parameters may be influenced by the presence of polyxenous Ctenocephalides, Polygenis, and Adoratopsylla fleas co-infesting opossum in urban areas. These findings provide valuable insights into the ecoepidemiology of fleas, their relationships with host species, and the impact of environmental factors in a strategic Atlantic forest ecoregion.

Natural processes and patterns are altered by human activity at different spatial and temporal scales, affecting species assemblages and population traits, modifying mechanisms or regulating dynamics at different scales. However, little is known about the influence of landscape structure on small mammal assemblages and populations on farms. Thus, in this work, we aimed to study the effect of landscape and environmental characteristics at the farm scale on the assemblage and populations of native and introduced small mammals in pig and dairy farms located in Buenos Aires province, Argentina. Our results showed that farms in contexts of higher environmental diversity at the landscape scale have higher species richness. Our results also showed that variations in assemblage composition were associated with the quantity of water body surfaces, cattle food, small mammal refugia, and impervious surfaces at the farm scale—and with woodland, grassland, and natural vegetation cover at the landscape scale. The abundance of commensal murids was higher on farms near towns, with higher vegetation cover at the farm scale and/or in landscape contexts with fewer crops. The abundance of Akodon azarae was higher on farms with a lower amount of cattle food at the farm scale and crop patches in the landscape. The abundance of Didelphis albiventris was higher during spring on farms with a low proportion of bare ground, while that of Lutreolina crassicaudata was higher on farms with high vegetation cover and a lower number of water body surfaces. These results show the relevance of multiscale determinants in the development of ecologically based management strategies to control pest small mammals. [ABSTRACT FROM AUTHOR]

Abstract The Brazilian tick fauna currently comprises 77 valid species categorized into two families: Ixodidae (53 species) and Argasidae (24 species). In the state of Alagoas, only six Ixodid ticks have been reported to date, with no previous reports of ticks in the Argasidae family. Here, we assessed 33 White-eared Opossum (Didelphis albiventris Lund, 1840) rescued in the metropolitan region of Maceió and referred to the Wild Animal Screening Center (Cetas) in the city. Upon arrival, the animals were examined for ectoparasites within 24 hours. In total, 10/33 (30%) opossums were found to be infested by 26 larvae of the argasid tick Ornithodoros mimon Kohls, Clifford & Jones, 1969. Morphological identification of ticks was corroborated by generating partial sequences of the mitochondrial 16S rRNA gene from three tick specimens. This study marks the first report of an argasid tick in the state of Alagoas. Future studies should investigate whether populations of both O. mimon ticks and their host, D. albiventris, in the state of Alagoas carry potential zoonotic agents capable of causing tick-borne diseases.

Introduction: The gray short-tailed opossum, Monodelhis domestica (M. domestica), is a widely used marsupial model species that presents unique advantages for neurodevelopmental studies. Notably their extremely altricial birth allows manipulation of postnatal pups at timepoints equivalent to embryonic stages of placental mammals. A robust literature exists on the development of short-tailed opossums, but many researchers working in the more conventional model species of mice and rats may find it daunting to identify the appropriate age at which to conduct experiments. Methods: Here, we present detailed staging diagrams taken from photographic observations of 40 individual pups, in 6 litters, over 25 timepoints across postnatal development. We also present a comparative neurodevelopmental timeline of short-tailed opossums (M. domestica), the house mouse (Mus musculus), and the laboratory rat (Rattus norvegicus) during embryonic as well as postnatal development, using timepoints taken from this study and a review of existing literature, and use this dataset to present statistical models comparing the opossum to the rat and mouse. Results: One aim of this research was to aid in testing the generalizability of results found in rodents to other mammalian brains, such as the more distantly related metatherians. However, this broad dataset also allows the identification of potential heterochronies in opossum development compared to rats and mice. In contrast to previous work, we found broad similarity between the pace of opossum neural development with that of rats and mice. We also found that development of some systems was accelerated in the opossum, such as the forelimb motor plant, oral motor control, and some aspects of the olfactory system, while the development of the cortex, some aspects of the retina, and other aspects of the olfactory system are delayed compared to the rat and mouse. Discussion: The pace of opossum development is broadly similar to that of mice and rats, which underscores the usefulness of this species as a compliment to the more commonly used rodents. Many features that differ the most between opossums and rats and mice were either clustered around the day of birth and were features that have functional importance for the pup immediately after or during birth, or were features that have reduced functional importance for the pup until later in postnatal development, given that it is initially attached to the mother. [ABSTRACT FROM AUTHOR]

In marsupials, upper-layer cortical neurons derived from the progenitors of the subventricular zone of the lateral ventricle (SVZ) mature morphologically and send their axons to form interhemispheric connections through the anterior commissure. In contrast, eutherians have evolved a new extra callosal pathway, the corpus callosum, that interconnects both hemispheres. In this study, we aimed to examine neurogenesis during the formation of cortical upper layers, including their morphological maturation in a marsupial species, namely the opossum (Monodelphis domestica). Furthermore, we studied how the axons of upper layers neurons pass through the anterior commissure of the opossum, which connects neocortical areas. We showed that upper-layer II/III neurons were generated within at least seven days in the opossum neocortex. Surprisingly, these neurons expressed special AT-rich sequence binding protein 2 (Satb2) and neuropilin 1 interacting protein (Nrp1), which are proteins known to be essential for the formation of the corpus callosum in eutherians. This indicates that extrinsic, but not intrinsic, cues could be key players in guiding the axons of newly generated cortical neurons in the opossum. Although oligodendrocyte precursor cells were present in the neocortex and anterior commissure, newly generated upper-layer neurons sent unmyelinated axons to the anterior commissure. We also found numerous GFAP-expressing progenitor cells in both brain structures, the neocortex and the anterior commissure. However, at P12–P17 in the opossums, a small population of astrocytes was observed only in the midline area of the anterior commissure. We postulate that in the opossum, midline astrocytes allow neocortical axons to be guided to cross the midline, as this structure resembles the glial wedge required by fibers to cross the midline area of the corpus callosum in the rodent. [ABSTRACT FROM AUTHOR]

(1) Background: Central nervous system (CNS) development is characterized by dynamic changes in cell proliferation and differentiation. Key regulators of these transitions are the transcription factors such as SOX2 and SOX9. SOX2 is involved in the maintenance of progenitor cell state and neural stem cell multipotency, while SOX9, expressed in neurogenic niches, plays an important role in neuron/glia switch with predominant expression in astrocytes in the adult brain. (2) Methods: To validate SOX2 and SOX9 expression patterns in developing opossum (Monodelphis domestica) cortex, we used immunohistochemistry (IHC) and the isotropic fractionator method on fixed cortical tissue from comparable postnatal ages, as well as dissociated primary neuronal cultures. (3) Results: Neurons positive for both neuronal (TUJ1 or NeuN) and stem cell (SOX2) markers were identified, and their presence was confirmed with all methods and postnatal age groups (P4-6, P6-18, and P30) analyzed. SOX9 showed exclusive staining in non-neuronal cells, and it was coexpressed with SOX2. (4) Conclusions: The persistence of SOX2 expression in developing cortical neurons of M. domestica during the first postnatal month implies the functional role of SOX2 during neuronal differentiation and maturation, which was not previously reported in opossums. [ABSTRACT FROM AUTHOR]

The white‐eared opossum (Didelphis albiventris) is a Neotropical marsupial that occurs in the Brazilian territory. The larynx is an important organ of vocalization in mammals, although, other laryngeal functions are more fundamental for survival of mammals than phonation. The anatomical knowledge of respiratory structures is pivotal for a better understanding of the species. Thus, this study aimed to examine the larynx of the white‐eared opossum by gross anatomy, computed tomography and histological description. For this, 10 adult (six females and four males) white‐eared opossums (D. albiventris) were used. The white‐eared opossum larynx was formed by epiglottis, thyroid, cricoids and arytenoid cartilages and a corniculate process. There is a similarity between the larynx of this marsupial and those reported in other wild mammals, regarding the number of cartilages and their location. Histologically, the epiglottis consisted of elastic cartilage and thyroid, cricoid and arytenoid cartilages were composed of hyaline cartilage. The epiglottis protruded rostrally into the nasal part of the pharynx, above the soft palate, and this is probably a marsupial characteristic as the fact that the thyroid and cricoid cartilages were ventrally fused. The hyoid apparatus was similar to that of other animals, with the same bony constitution, but with a greatly reduced stylohyoid bone. Histologically, the larynx was similar to those of other species such as koala, armadillo, crab‐eating foxes and giant anteaters. The knowledge of the larynx morphology is important for the anatomical features of the species and clinical and surgical procedures, such as endotracheal intubation. [ABSTRACT FROM AUTHOR]

The opossum (Monodelphis domestica), with its sequenced genome, ease of laboratory care and experimental manipulation, and unique biology, is the most used laboratory marsupial. Using the mammalian methylation array, we generated DNA methylation data from n = 100 opossum samples from the ear, liver, and tail. We contrasted postnatal development and later aging effects in the opossum methylome with those in mouse (Mus musculus, C57BL/6 J strain) and other marsupial species such as Tasmanian devil, kangaroos, and wallabies. While the opossum methylome is similar to that of mouse during postnatal development, it is distinct from that shared by other mammals when it comes to the age-related gain of methylation at target sites of polycomb repressive complex 2. Our immunohistochemical staining results provide additional support for the hypothesis that PRC2 activity increases with later aging in mouse tissues but remains constant in opossum tissues. We present several epigenetic clocks for opossums that are distinguished by their compatibility with tissue type (pan-tissue and blood clock) and species (opossum and human). Two dual-species human-opossum pan-tissue clocks accurately measure chronological age and relative age, respectively. The human-opossum epigenetic clocks are expected to provide a significant boost to the attractiveness of opossum as a biological model. Additional epigenetic clocks for Tasmanian devil, red kangaroos and other species of the genus Macropus may aid species conservation efforts.

Opossums are considered resistant to rabies. Nonhematophagous bats are reservoirs of rabies in urban areas of South America. We analyzed bats and opossums tested for rabies during 2021 in a highly urbanized city in Brazil to understand spillover in an urban setting. Wildlife surveillance is necessary to prevent rabies in humans and domestic animals.

Parasites are key players in ecosystems, influencing population sizes and food webs, yet the impact of environmental factors on their diversity is not well understood. The Atlantic rainforest in Brazil, particularly the Parque Estadual das Fontes do Ipiranga (PEFI), exemplifies a biodiversity hotspot facing significant deforestation, housing diverse animal species such as the synanthropic Brazilian common opossum (Didelphis aurita), which serves as a reservoir for multiple zoonotic pathogens. In this study, we investigated parasite diversity, abundance, prevalence, and richness in free-living D. aurita in the PEFI, São Paulo, Brazil. From January 2015 to January 2017, 101 fecal samples of D. aurita were collected in two areas of PEFI, at the Instituto de Pesquisas Ambientais (IPA) and the Parque de Ciência e Tecnologia (Cientec), and analyzed using three different parasitological methods. In total, 99% of the samples were positive for at least one parasite. The most prevalent parasite belonged to the order Strongylida (82%), followed by Cruzia sp. (77%), the latter having a significantly higher prevalence at IPA. In contrast, Acanthocephala showed greater prevalence at Cientec. Co-infections were common, with some individuals harboring up to seven different parasites. Our findings reveal significant parasite diversity in the D. aurita population at PEFI, including both helminths and protozoan trophozoites, some of which are reported for the first time in this host species. Further research is essential for accurate species identification of the observed parasites.

Didelphis virginiana (the Virginia opossum) is often used as an extant model for understanding feeding behaviour in Mesozoic mammaliaforms, primarily due to their morphological similarities, including an unfused mandibular symphysis and tribosphenic molars. However, the three-dimensional jaw kinematics of opossum chewing have not yet been fully quantified. We used biplanar videofluoroscopy and the X-Ray Reconstruction of Moving Morphology workflow to quantify mandibular kinematics in four wild-caught opossums feeding on hard (almonds) and soft (cheese cubes) foods. These data were used to test hypotheses regarding the importance of roll versus yaw in chewing by early mammals, and the impact of food material properties (FMPs) on jaw kinematics. The magnitude of roll exceeds that of yaw, but both are necessary for tooth-tooth or tooth-food-tooth contact between complex occlusal surfaces. We confirmed the utility of the four vertical kinematic gape cycle phases identified in tetrapods but we further defined two more in order to capture non-vertical kinematics. Statistical tests support the separation of chew cycle phases into two functional groups: occlusal and non-occlusal phases. The separation of slow close into two (occlusal) phases gives quantitative kinematic support for the long-hypothesized multifunctionality of the tribosphenic molar. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'. [ABSTRACT FROM AUTHOR]

Marsupials belonging to the Didelphis genus are widely distributed in the American Continent, and Didelphis albiventris and Didelphis aurita, are common in all of their areas of distribution in Brazil. Here we describe the bacterial and viral diversity of samples from opossums captured in three forest fragments in the State of São Paulo, Brazil. Microbiomes from the same body site were more similar across species and sampling sites while oral swabs presented higher bacterial diversity than rectal swabs. We also identified sequences related to bacterial species involved in zoonotic diseases. The detection of pathogens in such abundant mammal species warns for the possibility of emergence in other species. [ABSTRACT FROM AUTHOR]

We developed a venipuncture technique of the ventral caudal vein in conscious Virginia opossums (Didelphis virginiana) in cage traps, enabling blood sampling without anesthesia. Blood samples were successfully collected from all 28 opossums in this study by this technique. Draw volume of <0.1 mL occurred in only four opossums (14%). [ABSTRACT FROM AUTHOR]

Abstract Morphological studies provide knowledge that allow us to understand how animals interact with the natural environment or the captivity. The goal of this study was to describe the origin and antimeric distribution of lumbosacral plexus nerves in Didelphis aurita and D. albiventris. Fourteen adult cadavers of D. aurita, seven males and seven females, and 13 adult cadavers of D. albiventris, nine males and four females were used. The specimens were sexed, identified, fixed and dissected until the origins of the lumbosacral plexus nerves were exposed. Data were represented as absolute frequency and simple percentage. The lumbosacral plexuses derived a trunk for the femoral and obturator nerves from the ventral branches of L3-L4 (75%) in D. aurita, and in D. albiventris the femoral nerve of L3-L4 (73.1%) and the obturator nerve of L3-L4 (61.5%). In both species, formation of a lumbosacral trunk derived from L5-L6-S1 occurred in 78.6% of D. aurita and 61.5% of D. albiventris. The origin and distribution of lumbosacral plexus nerves of the studied species present similarities with domestic and wild eutherian mammals.

[Display omitted] • The basic neuroanatomy of the hypothalamus is highly conserved across all mammalian species. • Adult neurogenesis occurs in the hypothalamus of many mammalian species, including marsupials, but its rate is low. • Newly generated neurons are incorporated into the neural circuits of the hypothalamus, thereby inducing brain plasticity. In mammals, adult neurogenesis was first demonstrated in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus of the hippocampal formation. Further research showed that adult neurogenesis persists in other brain structures, such as the cerebral cortex, piriform cortex, striatum, amygdala, and hypothalamus. However, the origin of newly generated cells in these structures is not clear. Accumulating evidence indicates that newly generated neurons in the striatum or amygdala are derived from the SVZ, while in the adult hypothalamus, the proliferation of progenitor cells occurs in the ependymal cells lining the third ventricle, which give rise to new neurons. The heterogeneous cellular organization of the ependymal layer of the hypothalamus leads to different conclusions regarding the type of hypothalamic progenitor cells. In addition, adult hypothalamic neurogenesis occurs at low levels. Based on comparative and functional approaches, we synthesize the knowledge of newly generated cells in the adult hypothalamus. The aim of this review is to provide new insights on adult neurogenesis in the mammalian hypothalamus, with particular attention given to marsupial species. We highlight the number of adult-born neurons in various hypothalamic nuclei, debating whether their low number has an impact on hypothalamic function. [ABSTRACT FROM AUTHOR]

(1) Background: Central nervous system (CNS) development is characterized by dynamic changes in cell proliferation and differentiation. Key regulators of these transitions are the transcription factors such as SOX2 and SOX9. SOX2 is involved in the maintenance of progenitor cell state and neural stem cell multipotency, while SOX9, expressed in neurogenic niches, plays an important role in neuron/glia switch with predominant expression in astrocytes in the adult brain. (2) Methods: To validate SOX2 and SOX9 expression patterns in developing opossum (Monodelphis domestica) cortex, we used immunohistochemistry (IHC) and the isotropic fractionator method on fixed cortical tissue from comparable postnatal ages, as well as dissociated primary neuronal cultures. (3) Results: Neurons positive for both neuronal (TUJ1 or NeuN) and stem cell (SOX2) markers were identified, and their presence was confirmed with all methods and postnatal age groups (P4-6, P6-18, and P30) analyzed. SOX9 showed exclusive staining in non-neuronal cells, and it was coexpressed with SOX2. (4) Conclusions: The persistence of SOX2 expression in developing cortical neurons of M. domestica during the first postnatal month implies the functional role of SOX2 during neuronal differentiation and maturation, which was not previously reported in opossums.

Genomic imprinting is a parent-of-origin-specific expression phenomenon that plays fundamental roles in many biological processes. In animals, imprinting is only observed in therian mammals, with ∼200 imprinted genes known in humans and mice. The imprinting pattern in marsupials has been minimally investigated by examining orthologs to known eutherian imprinted genes. To identify marsupial-specific imprinting in an unbiased way, we performed RNA-seq studies on samples of fetal brain and placenta from the reciprocal cross progeny of two laboratory opossum stocks. We inferred allele-specific expression for >3,000 expressed genes and discovered/validated 13 imprinted genes, including three previously known imprinted genes, Igf2r , Peg10 , and H19. We estimate that marsupials imprint ∼60 autosomal genes, which is a much smaller set compared with eutherians. Among the nine novel imprinted genes, three noncoding RNAs have no known homologs in eutherian mammals, while the remaining genes have important functions in pluripotency, transcription regulation, nucleolar homeostasis, and neural differentiation. Methylation analyses at promoter CpG islands revealed differentially methylated regions in five of these marsupial-specific imprinted genes, suggesting that differential methylation is a common mechanism in the epigenetic regulation of marsupial imprinting. Clustering and co-regulation were observed at marsupial imprinting loci Pou5f3 - Npdc1 and Nkrfl - Ipncr2 , but eutherian-type multi-gene imprinting clusters were not detected. Also differing from eutherian mammals, the brain and placenta imprinting profiles are remarkably similar in opossums, presumably due to the shared origin of these organs from the trophectoderm. Our results contribute to a fuller understanding of the origin, evolution, and mechanisms of genomic imprinting in therian mammals. [ABSTRACT FROM AUTHOR]

A severe epidemic erupted in Coyoacán at the southern end of Lake Texcoco, in Central Mexico, around 1330. Chroniclers of the 16th century reported that after disrupted fish supply, the inhabitants of Coyoacán had suffered high morbidity and mortality. They developed edema of their eyelids, face, and feet, and hemorrhagic diarrhea. Many died, mainly the young and the old. Pregnant women miscarried. The disease is classically considered an illness of nutritional origin. However, its clinical picture and the circumstances of its emergence are remarkably consistent with an outbreak of foodborne Chagas disease, possibly acquired upon the hunting and consumption of alternative food sources, such as infected opossums (Didelphis spp.), unique reservoirs of Trypanosoma cruzi. [ABSTRACT FROM AUTHOR]

El uso de la cola por parte de los marsupiales neotropicales para transporte de material vegetal ha sido poco documentado. Usando cámaras trampa instaladas en la Reserva de la Biosfera La Encrucijada, Chiapas, México, documentamos el uso de la cola prensil para el transporte de material vegetal en Philander opossum y Didelphis marsupialis. Estos registros muestran la importancia de los monitoreos con fototrampeo para determinar conductas de los marsupiales neotropicales poco conocidas

In mammals, neurogenesis occurs during both embryonic and postnatal development. In eutherians, most brain structures develop embryonically; conversely, in marsupials, a number of brain structures develop after birth. The exception is the generation of granule cells in the dentate gyrus, olfactory bulb, and cerebellum of eutherian species. The formation of these structures starts during embryogenesis and continues postnatally. In both eutherians and marsupials, neurogenesis continues in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus of the hippocampal formation throughout life. The majority of proliferated cells from the SVZ migrate to the olfactory bulb, whereas, in the dentate gyrus, cells reside within this structure after division and differentiation into neurons. A key aim of this review is to evaluate advances in understanding developmental neurogenesis that occurs postnatally in both marsupials and eutherians, with a particular emphasis on the generation of granule cells during the formation of the olfactory bulb, dentate gyrus, and cerebellum. We debate the significance of immature neurons in the piriform cortex of young mammals. We also synthesize the knowledge of adult neurogenesis in the olfactory bulb and the dentate gyrus of marsupials by considering whether adult-born neurons are essential for the functioning of a given area. [ABSTRACT FROM AUTHOR]

Oral rabies vaccination (ORV) is the primary tool for landscape level control and elimination of rabies virus in terrestrial wildlife species. However, there is currently a limited understanding of how different baiting strategies influence raccoon (Procyon lotor) uptake of ORV baits in non-agricultural habitats in the Southeastern United States, which may hinder the refinement of ORV management for raccoons in this region. Using a combination of new and existing data, we investigated the role of baited area (0.16 vs 3 km2), bait density (75 vs 150 baits/km2) and season (spring vs fall) on placebo ORV bait uptake by raccoons in four rural, non-agricultural habitats in the southeastern United States (bottomland hardwood forest, upland pine forest, riparian forest, and isolated wetlands). Increasing the baited area to 3 km2 increased the proportion of raccoons that consumed baits by 140 % in riparian forests and decreased the proportion consuming baits by 70 % in bottomland hardwood forests. A greater proportion of raccoons consumed baits in riparian habitat in spring compared to fall, but bait density did not influence uptake in either season in this habitat. Increasing the bait density during spring in bottomland hardwoods increased the proportion of raccoons that consumed baits by 270 %, but there was no effect of increasing bait density in bottomland hardwoods during fall. We suggest that variation in habitat contiguity and seasonal resource availability influence how raccoons utilize these habitats which in turn impacts habitat-specific ORV bait uptake. The estimated proportion of raccoons that consumed baits did not exceed 60 % for any treatment, and for most treatments was less than 40 %. These low uptake rates indicate a need for research into additional strategies to maximize raccoon uptake of ORV baits across rural, non-agricultural southeastern landscapes. • Role of oral rabies vaccine (ORV) bait density, area, and season on raccoon uptake varied by habitat. • Variation in bait uptake likely results from differences in how raccoons utilize these habitats. • Raccoons consumed more ORV baits than opossums, but uptake was low overall. [ABSTRACT FROM AUTHOR]

Zoonoses are diseases or infections naturally transmissible from vertebrate animals to humans, and can be bacterial, viral or parasitic. The growth of urbanization, industrialization and the advance of agriculture and livestock facilitate the spread of infectious and parasitic agents from wild animals to the human population and to their domestic animals. Among the various reservoirs of zoonotic agents, we find that didelphid species, due to their high capacity for adaptation in urban environments, as an important study case. We reviewed the literature data on the pathogens, including with zoonotic potential of marsupial species occurring in Brazil, accounted for infections by agents that we categorized into Bacteria, Viruses, Protozoa, and Helminths. Aiming identifies possible knowledge gaps, we also surveyed the origin of studied samples and the institutions leading the researches on host didelphids. Among the hosts, the genus Didelphis in the cycles of these agents stands out. Moreover, we found that the majority of reported cases are in the Southeastern Brazil, mean the data from other Brazilian localities and didelphid species could be underestimated. Most studies took place in graduate programs of public research institutions, emphasizing the importance of the funding public research for the Brazilian scientific development. [ABSTRACT FROM AUTHOR]

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Opossums are considered resistant to rabies. Nonhematophagous bats are reservoirs of rabies in urban areas of South America. We analyzed bats and opossums tested for rabies during 2021 in a highly urbanized city in Brazil to understand spillover in an urban setting. Wildlife surveillance is necessary to prevent rabies in humans and domestic animals.

We describe the pathology of natural infection with highly pathogenic avian influenza A(H5N1) virus of Eurasian lineage Goose/Guangdong clade 2.3.4.4b in 67 wild terrestrial mammals throughout the United States during April 1‒July 21, 2022. Affected mammals include 50 red foxes (Vulpes vulpes), 6 striped skunks (Mephitis mephitis), 4 raccoons (Procyon lotor), 2 bobcats (Lynx rufus), 2 Virginia opossums (Didelphis virginiana), 1 coyote (Canis latrans), 1 fisher (Pekania pennanti), and 1 gray fox (Urocyon cinereoargenteus). Infected mammals showed primarily neurologic signs. Necrotizing meningoencephalitis, interstitial pneumonia, and myocardial necrosis were the most common lesions; however, species variations in lesion distribution were observed. Genotype analysis of sequences from 48 animals indicates that these cases represent spillover infections from wild birds.

• Detection of Babesia sp. belonging to "South American Marsupialia" piroplasmid clade;. • Detection of a putative novel Ehrlichia genotype in opossums;. • First molecular detection of hemoplasmas in D. marsupialis ;. • A putative new genotype closely related with Hepatozoon felis was detected in opossums;. • Copositivity between different agents was found in three opossums. Opossums are synanthropic marsupials able to interchange among wild, peri‑urban and urban environments, playing an epidemiologically important role as hosts for emerging pathogens and ectoparasites of relevance in public health. The present study aimed to detect and molecularly characterize vector-borne agents in a population of common opossums (Didelphis marsupialis) from the Island of São Luís do Maranhão, northeastern Brazil. Of the 45 animals analyzed, one (2.22%) was positive in the nested PCR assay based on the 18S rRNA gene of piroplasmids. The obtained sequence was phylogenetically positioned in a clade containing sequences of Babesia sp. previously detected in Didelphis aurita, Didelphis albiventris and associated ticks from Brazil. Eight (17.77%) samples were positive in PCR for Ehrlichia spp. based on the dsb gene; four samples were sequenced and positioned into a new clade, sister to E. minasensis and Ehrlichia sp. clade detected in Superorder Xenarthra mammals. No samples tested positive in the screening PCR assays based on the 16S rRNA gene of Anaplasma spp. Two samples were positive in the qPCR for Bartonella spp. based on the nuoG gene. Seven animals (15.56%) were positive in the nPCR based on the 16S rRNA gene of hemoplasmas. Of these, three were positive in a PCR based on the 23S rRNA gene. The phylogenies based on both 16S rRNA and 23S rRNA genes corroborated to each other and positioned the sequences in the same clade of hemoplasmas previously detected in D. aurita and D. albiventris sampled in Brazil. Finally, three (6.66%) animals were positive in the PCR for Hepatozoon spp.; the obtained 18S rRNA sequence was positioned into the H. felis clade.The present study showed, for the first time, the circulation of piroplasmids, Hepatozoon spp., Ehrlichia spp., hemoplasmas and Bartonella spp. in D. marsupialis sampled in northeastern Brazil, with description of putative novel genotypes of Ehrlichia and Hepatozoon and copositivity by different vector-borne agents. The present work consolidates the "South American Marsupialia" piroplasmid clade, adding one more genotype of Babesia sp. to this clade. [ABSTRACT FROM AUTHOR]