Bacterial and Viral Diversity of Didelphid Opossums from Brazil

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.

Epigenetic clock and methylation studies in marsupials: opossums, Tasmanian devils, kangaroos, and wallabies

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.

Interferon gamma protective against Sarcocystis neurona encephalitis in susceptible murine model

Sarcocystis neurona is the predominant etiological agent of the infectious equine neurologic disease, equine protozoal myeloencephalitis (EPM), which is prevalent in the United States. A wealth of knowledge about S. neurona biology and its life cycle has accumulated over the last several decades. However, much remains unknown about the aberrant equine host's immune response to S. neurona and the relatively high prevalence of exposure to the protozoa but relatively infrequent occurrence of clinical neurologic disease. Mouse models simulating EPM are commonly used to study the disease due to numerous challenges associated with studying the disease in horses. The critical role of the cytokine, interferon gamma (IFNγ), in protection against S. neurona encephalitis has been well established as Ifnγ^-/- mice are highly susceptible to S. neurona encephalitis. However, there are discrepancies in the literature regarding S. neurona disease susceptibility in lymphocyte deficient mice, lacking T-lymphocytes and their associated Ifnγ production. In the current study, we investigated S. neurona encephalitis susceptibility in 2 genetically different strains of lymphocyte null mice, C57Bl/6 (B6).scid and Balb/c.scid. The B6.scid mouse was determined to be susceptible to S. neurona encephalitis as 100 % of infected mice developed neurologic disease within 60 days post infection (DPI). The Balb/c.scid mouse was nearly disease resistant as only 10 % of mice developed neurologic disease 60 DPI. Encephalitis was histologically demonstrable and S. neurona was identified in cerebellar samples collected from B6.scid but absent in Balb/c.scid mice. To further investigate the importance of T-lymphocyte derived Ifnγ, T- lymphocytes were adoptively transferred into B6.scid mice. The adoptive transfer of Ifnγ competent T- lymphocytes offered complete protection against S. neurona encephalitis but transfer of Ifnγ deficient T- lymphocytes did not with 100 % of these recipient mice succumbing to S. neruona encephalitis. Histological analysis of collected cerebellar samples confirmed the presences of S. neurona and encephalitis in recipient mice that developed neurologic disease. These studies show that the background strain is critical in studying SCID susceptibility to S. neurona disease and suggest a protective role of Ifnγ producing T- lymphocytes in S. neurona encephalitis susceptible mice.

from white-eared opossum (Didelphis albiventris)

The order Piroplasmida encompasses tick-borne pathogens of veterinary and medical importance positioned in two main families: Babesiidae and Theileriidae. Even though previous studies carried out in Brazil recorded the occurrence of piroplasmid species circulating in small mammals, 18S RNA gene sequences were only partially sequenced, preventing the assessment of their phylogenetic positioning. The current study aimed to detect and characterize, using morphological, molecular, and bioinformatic approaches, piroplasmids from wild mammals and associated ticks sampled in Central-Western Brazil. Out of 67 Didelphis albiventris sampled, 22 (16.4%) were positive for piroplasmids by PCR. In contrast, none of the 48 small rodents and 14 capybaras (Hydrochoerus hydrochaeris) was PCR-positive. Four Amblyomma dubitatum ticks-one from Rattus rattus, one from H. hydrochaeris, and two from D. albiventris-out of 114 Amblyomma spp. DNA samples were positive for piroplasmids by PCR. The phylogenetic inference performed using the near-complete 18S rRNA gene positioned the putative novel piroplasmid species detected in D. albiventris and associated A. dubitatum ticks near to Babesia sensu lato clade (Western group-cluster III) and distant from the Australian marsupial-associated piroplasms. Phylogenetic inferences based on two additional molecular markers, namely hsp-70 and cox-1, supported the near-complete 18S rRNA gene phylogenetic inference. Finally, the partial 18S rRNA gene sequences detected in ticks from rodents (R. rattus and H. hydrochaeris) showed 97.2-99.4% identity with the Piroplasmida previously detected in a capybara from Brazil, raising evidence that a still uncharacterized piroplasmid species has been identified in the capybara, the largest rodent species from South America.

Didelphis albiventris as a carrier of Leptospira sp. in the central nervous tissue in the semiarid region of Northeast, Brazil

Leptospirosis has been investigated in several species of wild animals. The white-eared opossum (Didelphis albiventris) is a mammal common in the brazilian semi-arid, so, this study aimed to investigate its role in the occurrence of the leptospirosis in the region Northeast of Brazil. 12 animals were used, from which samples were collected for the attempt of isolation, molecular detection and serological examination. There was no microbial growth, nor were any anti-Leptospira sp. antibodies found in the serological samples. The PCR detected leptospiric DNA in the central nervous system (CNS) of five animals (41.7 %). The gene in one of the samples was sequenced and showed identity with Leptospira interrogans. The presence of Leptospira sp. in the CNS of Didelphis albiventris does not allow the characterization of the studied animals as reservoirs with potential for transmission of the pathogen in the region, however it represents a site that needs to be further investigated.

Genetic diversity and lack of molecular evidence for hemoplasma cross-species transmission between wild and synanthropic mammals from Central-Western Brazil

Globally, hemotropic mycoplasmas (hemoplasmas) comprise an emerging or remerging bacteria group that attaches to red blood cells of several mammal's species and in some cases, causing hemolytic anemia. Herein, we assessed the occurrence, genetic diversity, the factors coupled to mammals infection, and the phylogeographic distribution of hemoplasmas in sylvatic and synanthropic mammals and their associated ectoparasites from Brazil. We collected spleen and/or blood samples from synanthropic rodents (Rattus rattus [N = 39] and Mus musculus [N = 9]), sylvatic rodents (Hydrochoerus hydrochaeris [N = 14]) and opossums (Didelphis albiventris [N = 43]). In addition, ticks (Amblyomma spp. [N = 270] and lice (Polyplax spinulosa [N = 6]) specimens were also sampled. Using a PCR targeting the 16S rRNA region, out of 48 small rodents, 14 capybaras and 43 opossums DNA samples, hemoplasma DNA was found in 25%, 50%, and 32.5% animals, respectively. Besides, we reported hemoplasma DNA in Amblyomma sp. (22.2% [2/9]) and lice (100% [2/2]) pools samples from rats, and one female A. sculptum DNA sample (3% [1/33]) obtained from a capybara. Additionally, and in agreement with ML analysis, the network analyses showed a clear phylogenetic separation among the hemoplasmas genotypes found in the different host species sampled, thus, suggesting the absence of cross-species hemoplasmas transmission between the mammals trapped. Finally, using the NTC network analysis, we reported the same 16S rRNA Mycoplasma genotype circulating in Rattus sampled in Brazil, Hungary, and Japan.

Sarcocystis neurona-Induced Myeloencephalitis Relapse Following Anticoccidial Treatment

Sarcocystis neurona is a ubiquitous parasite in the eastern United States, which is the principal causative agent in the neurologic disorder equine protozoal myeloencephalitis (EPM). While much is known about this protozoa's life cycle in its natural host, the opossum (Didelphis virginiana), little is known of how it acts in the aberrant equine host, which displays a high incidence of exposure with a relatively low rate of morbidity. For this study, we employed the popular interferon gamma knockout mouse model to determine the potential for recrudescence of S. neurona infection after treatment with the anticoccidial drug diclazuril. Mice were infected with S. neurona merozoites, and 7-days post-infection (DPI) they were treated with diclazuril for 30 or 60 days or not treated at all. All infected non-treated mice developed neurologic signs consistent with S. neurona infection within 30 DPI. All diclazuril-treated infected mice remained clinically normal while on treatment but developed neurologic signs within 60 days of treatment cessation. Histological examination of cerebella from all infected mice demonstrated characteristic lesions of S. neurona infection, regardless of treatment status. Cerebellar samples collected from infected treated mice, displaying neurologic signs, produced viable S. neurona in culture. However, cerebellar samples collected from infected and neurologically normal mice at the end of a 30-day treatment period did not produce viable S. neurona in culture. Analysis of the humoral immune response in infected mice showed that during treatment IgM antibody production decreased, suggesting the organism was sequestered from immune surveillance. The cessation of treatment and subsequent development of neurologic disease resulted in increased IgM antibody production, suggesting recognition by the immune system at that time. Based on the study results the authors propose that diclazuril was able to inhibit the replication and migration of S. neurona but not fully eliminate the parasite, suggesting recrudescence of infection after treatment is possible.

Leptospira reservoirs among wildlife in Brazil: Beyond rodents

Leptospirosis is a disease of great importance in tropical regions. Infection occurs mainly through contact with water contaminated with the urine of infected animals, especially that of rodents. Despite the diversity and abundance of wild fauna in Brazil, little is known about the role of other wild species in the epidemiology of leptospirosis. This study aimed to investigate new reservoirs of Leptospira among wildlife in Brazil, using serological and molecular diagnoses in a large-sized sample. Biological samples were collected from 309 free-ranging mammals, belonging to 16 species. The majority of the animals included were opossums (Didelphis albiventris) and coatis (Nasua nasua). Blood and urine samples were subjected to the microscopic agglutination test (MAT) and real-time PCR, respectively. Genetic characterization of genomospecies was performed using PCR amplicons. Statistical analysis was applied to test associations between positive diagnoses and age, sex, season and type of environment. The prevalence of infection found via MAT and PCR was 11% and 5.5%, respectively. If these tests are taken to be complementary, the overall prevalence was 16%. The most common serogroups were Djasiman and Australis, while L. santarosai was the prevalent genomospecies. Significant differences in prevalence between animal species were observed. Greater risk of infection was detected among adult opossums than among young ones. The influence of each serogroup and genomospecies was tested for the same variables, and this revealed higher risk of infection by L. santarosai among male opossums than among females. The present study highlights the exposure and carrier status of several wild species in Brazil and it indicates that coatis and other carnivores are priorities for further investigations.

Transcriptomic insights into the genetic basis of mammalian limb diversity

Background

From bat wings to whale flippers, limb diversification has been crucial to the evolutionary success of mammals. We performed the first transcriptome-wide study of limb development in multiple species to explore the hypothesis that mammalian limb diversification has proceeded through the differential expression of conserved shared genes, rather than by major changes to limb patterning. Specifically, we investigated the manner in which the expression of shared genes has evolved within and among mammalian species.

Results

We assembled and compared transcriptomes of bat, mouse, opossum, and pig fore- and hind limbs at the ridge, bud, and paddle stages of development. Results suggest that gene expression patterns exhibit larger variation among species during later than earlier stages of limb development, while within species results are more mixed. Consistent with the former, results also suggest that genes expressed at later developmental stages tend to have a younger evolutionary age than genes expressed at earlier stages. A suite of key limb-patterning genes was identified as being differentially expressed among the homologous limbs of all species. However, only a small subset of shared genes is differentially expressed in the fore- and hind limbs of all examined species. Similarly, a small subset of shared genes is differentially expressed within the fore- and hind limb of a single species and among the forelimbs of different species.

Conclusions

Taken together, results of this study do not support the existence of a phylotypic period of limb development ending at chondrogenesis, but do support the hypothesis that the hierarchical nature of development translates into increasing variation among species as development progresses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-0902-6) contains supplementary material, which is available to authorized users.

Sarcocystis neurona manipulation using culture-derived merozoites for bradyzoite and sporocyst production

Equine protozoal myeloencephalitis (EPM) remains a significant central nervous system disease of horses in the American continents. Sarcocystis neurona is considered the primary causative agent and its intermediate life stages are carried by a wide host-range including raccoons (Procyon lotor) in North America. S. neurona sarcocysts mature in raccoon skeletal muscle and can produce central nervous system disease in raccoons, mirroring the clinical presentation in horses. The study aimed to develop laboratory tools whereby the life cycle and various life stages of S. neurona could be better studied and manipulated using in vitro and in vivo systems and compare the biology of two independent isolates. This study utilized culture-derived parasites from S. neurona strains derived from a raccoon or from a horse to initiate raccoon infections. Raccoon tissues, including fresh and cryopreserved tissues, were used to establish opossum (Didelphis virginiana) infections, which then shed sporocyts with retained biological activity to cause encephalitis in mice. These results demonstrate that sarcocysts can be generated using in vitro-derived S. neurona merozoites, including an isolate originally derived from a naturally infected horse with clinical EPM. This study indicates the life cycle can be significantly manipulated in the laboratory without affecting subsequent stage development, allowing further purification of strains and artificial maintenance of the life cycle.

Reproductive Disorders of Marsupials

Marsupial reproduction differs significantly in anatomy and physiology from that of placental mammals. The gastrointestinal and urogenital tracts empty into a cloaca. Reproductive parameters include gestation and pouch time, as the fetus develops outside of the uterus. Captive marsupials discussed include sugar gliders), short-tailed opossums, Virginia opossums, and Tammar and Bennett's wallabies. Common disease conditions include joey eviction, pouch infections, mastitis, metritis, prostatitis, penile necrosis, and neoplasia. Common surgeries include penile amputation, castration, and ovario-vaginal-hysterectomy or ovario-hysterectomy. Therapeutics used for these conditions are presented.

Identification of the mRNA encoding interleukin-6 and its receptor, interleukin-6 receptor α, in five marsupial species

Expressed coding sequences for interleukin-6 (IL-6) and interleukin-6 receptor α (IL-6R) were examined in five marsupial species. Full length expressed coding sequences for IL-6 and IL-6R were identified and characterized in the gray short-tailed opossum (Monodelphis domestica). For IL-6, ∼225 bp fragments of the mRNA sequence were identified in the red-tailed phascogale (Phascogale calura), kultarr (Antechinomys laniger), and stripe-faced dunnart (Sminthopsis macroura), while ∼563 bp fragments of mRNA encoding IL-6R were identified in the red-tailed phascogale, kultarr, stripe-face dunnart and fat-tailed dunnart (Sminthopsis crassicaudata). Relative expression levels of IL-6 and IL-6R were examined in the heart, muscle, lung, liver, spleen and kidney of adult red-tailed phascogales, and IL-6 gene expression was found to be significantly higher in the lung and spleen than the other tissues examined, while the expression of IL-6R was significantly higher in the liver, lung and spleen. These results now serve as a reference point for examining the role and levels of IL-6 and IL-6R in the health and disease of these marsupial species. The pro-tumorigenic nature of IL-6 is of particular interest, and the identification of these IL-6 and IL-6R coding sequences provides a platform for further work to evaluate the potential role of IL-6 in marsupial cancers.

The evolution of basal progenitors in the developing non-mammalian brain

The amplification of distinct neural stem/progenitor cell subtypes during embryogenesis is essential for the intricate brain structures present in various vertebrate species. For example, in both mammals and birds, proliferative neuronal progenitors transiently appear on the basal side of the ventricular zone of the telencephalon (basal progenitors), where they contribute to the enlargement of the neocortex and its homologous structures. In placental mammals, this proliferative cell population can be subdivided into several groups that include Tbr2⁺ intermediate progenitors and basal radial glial cells (bRGs). Here, we report that basal progenitors in the developing avian pallium show unique morphological and molecular characteristics that resemble the characteristics of bRGs, a progenitor population that is abundant in gyrencephalic mammalian neocortex. Manipulation of LGN (Leu-Gly-Asn repeat-enriched protein) and Cdk4/cyclin D1, both essential regulators of neural progenitor dynamics, revealed that basal progenitors and Tbr2⁺ cells are distinct cell lineages in the developing avian telencephalon. Furthermore, we identified a small population of subapical mitotic cells in the developing brains of a wide variety of amniotes and amphibians. Our results suggest that unique progenitor subtypes are amplified in mammalian and avian lineages by modifying common mechanisms of neural stem/progenitor regulation during amniote brain evolution.

Highlighted article: In the developing chick pallium, a basal progenitor population resembles mammalian cortical basal radial glia, suggesting a more ancient evolutionary origin for this cell type.

Differential morphology of the superior olivary complex of Meriones unguiculatus and Monodelphis domestica revealed by calcium-binding proteins

In mammals, the superior olivary complex (SOC) of the brainstem is composed of nuclei that integrate afferent auditory originating from both ears. Here, the expression of different calcium-binding proteins in subnuclei of the SOC was studied in distantly related mammals, the Mongolian gerbil (Meriones unguiculatus) and the gray short-tailed opossum (Monodelphis domestica) to get a better understanding of the basal nuclear organization of the SOC. Combined immunofluorescence labeling of the calcium-binding proteins (CaBPs) parvalbumin, calbindin-D28k, and calretinin as well as pan-neuronal markers displayed characteristic distribution patterns highlighting details of neuronal architecture of SOC nuclei. Parvalbumin was found in almost all neurons of SOC nuclei in both species, while calbindin and calretinin were restricted to specific cell types and axonal terminal fields. In both species, calbindin displayed a ubiquitous and mostly selective distribution in neurons of the medial nucleus of trapezoid body (MNTB) including their terminal axonal fields in different SOC targets. In Meriones, calretinin and calbindin showed non-overlapping expression patterns in neuron somata and terminal fields throughout the SOC. In Monodelphis, co-expression of calbindin and calretinin was observed in the MNTB, and hence both CaBPs were also co-localized in terminal fields within the adjacent SOC nuclei. The distribution patterns of CaBPs in both species are discussed with respect to the intrinsic neuronal SOC circuits as part of the auditory brainstem system that underlie the binaural integrative processing of acoustic signals as the basis for localization and discrimination of auditory objects.

Equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis (EPM) can be caused by either of 2 related protozoan parasites, Sarcocystis neurona and Neospora hughesi, although S. neurona is the most frequent etiologic pathogen. Horses are commonly infected, but clinical disease occurs infrequently; the factors influencing disease occurrence are not well understood. Risk factors for the development of EPM include the presence of opossums and prior stressful health-related events. Attempts to reproduce EPM experimentally have reliably induced antibody responses in challenged horses but have not consistently produced acute neurologic disease. Diagnosis and options for treatment of EPM have improved over the past decade.

Captive marsupial nutrition

Marsupials comprise an interesting group of mammals, which are increasingly being kept as pets. Few actual feeding trials have been published, although many anecdotal diets have years of usage with good success. Marsupials have dental and digestive tract adaptations that allow them to use specific niches in their environments. Knowing the diet in the wild is instrumental in designing diets used in captivity.

Morphologic characterization and distribution of endocrine cells in the large intestine of the opossum Didelphis aurita (Wied-Neuwied, 1826)

This study was designed to investigate the morphology and distribution of argyrophil, argentaffins, and insulin-immunoreactive endocrine cells in the large intestine of the opossum Didelphis aurita. Fragments of the large intestine of 10 male specimens of the opossum D. aurita were collected, processed, and submitted for histochemistry, immunohistochemistry, and scanning electron microscopy. The tunics of the large intestine of D. aurita presented morphological characteristics that have already been described for eutherian mammals. The morphometric data showed that the inner circular layer of all portions and regions analyzed is thicker relative to the longitudinal layer, and these layers in the rectum are thicker compared to the cecum and ascending colon. The majority of mucus-secreting cells have acid and neutral mucins, suggesting that the production of mucus is mixed. The number of these cells increases in the region of the cecum toward the rectum. Important findings include the occurrence of argyrophil, argentaffins, and insulin-immunoreactive endocrine cells in all segments of the large intestine of the opossum (D. aurita). To the best of our knowledge, this is the first report about the presence of insulin-immunoreactive endocrine cells in the large intestine of the opossum (D. aurita).

The laboratory opossum (Monodelphis domestica) as a natural mammalian model for human cancer research

This study established that human cancer cells (A375 melanoma, HT-29 colon cancer, PC-3p prostate cancer) that were xenografted into suckling opossums could proliferate and globally metastasize as early as 11 days after injection. Light and electron microscopic examinations (HT-29 colon cancer) determined that the cellular features exhibited by the xenogeneic human tumors grown in laboratory opossums were consistent with those observed in tumors removed from humans. The tumor induction rate, patterns of tumor growth and regression, and types of host immune responses against the xenografted tumors were influenced by injection dosages, injection sites and injection ages of suckling opossums. The results highlight the value of the opossum model as a natural in vivo system for investigating human cancer growth, metastasis and apoptosis at the cellular and molecular levels; enhancing identification of tumor associated antigens or T cell epitopes through use of humoral and cellular expression cloning techniques; elucidating mechanisms utilized by tumor cells to evade host immunosurveillance; and devising diagnostic and therapeutic methods for cancer treatment.