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Trypanosoma cruzi, a zoonotic protozoan parasite, infects a wide range of mammals. The southern United States has endemic sylvatic transmission cycles maintained by several species of wildlife and domestic dogs. We hypothesized that urban-dwelling opossums (Didelphis virginiana) in South Texas are infected with T. cruzi, and that tissue pathology would be associated with infection. In 2017, we collected blood, heart tissue and anal gland secretions from 100 wild opossums across three seasons that were trapped by animal control in South Texas. In addition, anal gland tissue and intercostal muscle were collected from 43 of the 100 opossums for which time allowed the extra tissue collection. All blood, tissue, and secretion samples were screened for T. cruzi DNA using qPCR with confirmation of positive status achieved through one or more additional PCR assays, including a qPCR to determine the parasite discrete typing unit (DTU). T. cruzi DNA was detected in at least one tissue of 15% of the opossums sampled: blood clot (9%), heart tissue (10%), anal gland secretions (12%), intercostal muscle (16.3%), and anal gland tissue (11.6%). Infection was detected in two or more different tissue types in nine of the opossums. The 35 tissues for which parasite DTU was determined were exclusively ‘Tcl’- a DTU previously associated with locally-acquired human disease in the United States. T. cruzi-positive opossums were nearly 14 times more likely to exhibit significant heart lesions on histopathology (lympoplasmacytic inflammation±fibrosis) when compared to negative opossums (OR = 13.56, CI = 1.23–751.28, p-value = 0.03). Three triatomines were opportunistically collected from the study site, of which two were infected (66.7%), and bloodmeal analysis revealed canine, opossum, and human bloodmeals. Given the presence of parasite in opossum blood, unique potential for shedding of parasite in anal glad secretions, and evidence of vectors feeding on opossums, it is likely that opossums serve as wild reservoirs around urban dwellings in South Texas., Graphical abstract Image 1, Highlights • Trypanosoma cruzi type ‘TcI’ DNA was detected in 15% of opossums from South Texas. • Infected tissues included blood, heart, skeletal muscle, and anal glands and secretions. • Heart pathology occurred more frequently in opossums with infected tissues. • Local triatomines were found to feed on opossum, dog, and human. • Urban opossums likely serve as T. cruzi reservoirs in the US.

Considered ecologically generalist, Didelphis albiventris is reported as reservoir for different species of parasites, especially Trypanosoma cruzi. However, the knowledge about the influence of T. cruzi on hematological parameters of free-living opossum remains scarce. The present study aimed to evaluate the influence of T. cruzi on hematological parameters of white-ear opossums (D. albiventris) from Campo Grande, Mato Grosso do Sul, Brazil. The blood samples and biometric data were collected from 40 opossums captured by Tomahawk and Sherman traps in six urban forest fragments located in the city. The health of these animals was inferred, mainly, by means of blood parameters (PCV, RBC, WBC, MCV and WBC differential). Molecular detection of T. cruzi infection was performed by nested polymerase chain reaction (nPCR), using 18S and 24Sα rDNA region as target. Paired-t-test and simple linear regression were used for statistical analysis. No significant difference was observed between the averages of hematological variables in relation to gender and body condition. The molecular diagnosis showed that 32.5% (13/40) of the opossums were infected by T. cruzi, which presented lymphocytosis (3.4 ± 1.5) and eosinophilia (0.09 ± 0.13). Path analysis showed that T. cruzi infection resulted in increased numbers of lymphocytes and indirectly decreased the body condition of opossums. Moreover T. cruzi infection resulted in a direct effect on decrease of MCV. Overall, our results suggest that T. cruzi infection may represent a risk to health of opossums since the lymphocytosis may cause a secondary damage on body condition of infected animals., Graphical abstract Image 1, Highlights • Trypanosoma cruzi infection may pose a risk to health of opossums. • Lymphocytosis may cause a secondary damage on body condition of infected animals. • D. albiventris is an important host of T. cruzi in the Campo Grande city.

Guanylin (GN) and uroguanylin (UGN) peptides were first discovered as ligands of the guanylyl/guanylate cyclase C receptor (GC-C) in the rat in 1992 and in the opossum in 1993, respectively. The discoveries were brought about on the basis of the anticipation of the existence of endogenous ligand(s) that mimic structurally enterotoxigenic E. coli heat-stable enterotoxin (ST), a previously-known exogenous ligand of GC-C1.

In Colombia, dogs and opossum are the most important mammals in domestic and sylvatic T. cruzi transmission. However, the role of both species has not been evaluated in areas where both species converge in the peridomestic area. To evaluate the infection status of domestic and wild mammals in peridomestic habitats of Puerto Valdivia, Antioquia Department. The infection of domestic dogs and small wild mammals was performed by hemoculture, molecular and serological methods. Additionally, the infection in children under 15 years old and triatomine searches was carried out. We found that 16.07% and 34% dogs, and 59.1% and 61.1% Didelphis marsupialis were found positive by molecular and serological methods respectively. Moreover, in 25% and 75% of the infected dogs were detected TcIDom and TcI sylvatic, respectively, while all the D. marsupialis were infected with TcI. Six Rattus rattus and three Proechimys semispinosus were captured but without T. cruzi infection. Finally, none of the 82 children were positive and no triatomine bugs were captured. D. marsupialis and domestics dogs have an important role in the transmission of T. cruzi suggesting a potential risk in T. cruzi transitions areas.

UGN is a peptide hormone consisting of 15–17 aa residues. UGN binds to GC-C to produce cGMP for the regulation of ion and water transport in the intestine and kidney. Opossum lymphoguanylin could be closer to UGN than to GN regarding its characteristics and phylogenetic position, and thus is described here.

This chapter summarized our knowledge of two genera ( Besnoitia , Toxoplasma ) within the second subfamily of the Sarcocystidae (Toxoplasmatinae) that infect marsupials. The history of the discovery and naming of Besnoitia from American marsupials is presented. Besnoitia darlingi is the only species to infect marsupials, and it is found only in about four American opossum species; no Besnoitia species are yet reported from Australian marsupials. Pathology of B. darlingi in opossums seems to be variable in time and space and dependent upon the host it infects.

Plasma cholesterol levels among individuals vary considerably in response to diet. However, the genes that influence this response are largely unknown. Non-HDL (V+LDL) cholesterol levels vary dramatically among gray, short-tailed opossums fed an atherogenic diet, and we previously reported that two quantitative trait loci (QTLs) influenced V+LDL cholesterol on two diets. We used hypothesis-free, genome-wide linkage analyses on data from 325 pedigreed opossums and located one QTL for V+LDL cholesterol on the basal diet on opossum chromosome 1q [logarithm of the odds (LOD) = 3.11, genomic P = 0.019] and another QTL for V+LDL on the atherogenic diet (i.e., high levels of cholesterol and fat) on chromosome 8 (LOD = 9.88, genomic P = 5 x 10(-9)). We then employed a novel strategy involving combined analyses of genomic resources, expression analysis, sequencing, and genotyping to identify candidate genes for the chromosome 8 QTL. A polymorphism in ABCB4 was strongly associated (P = 9 x 10(-14)) with the plasma V+LDL cholesterol concentrations on the high-cholesterol, high-fat diet. The results of this study indicate that genetic variation in ABCB4, or closely linked genes, is responsible for the dramatic differences among opossums in their V+LDL cholesterol response to an atherogenic diet.

and then levels off to a concentration which is about half of the maximum [10]. Nothing is known about its function; pepsinogen B has never been found in species other than pig and dog, in spite of intensive research on gastric extracts from cow and human. However, pepsinogen B accounts for 30% of the total pepsinogen level in dog gastric mucosa indicating a dominating role in digestion [7]. Some databases have mis-registered opossum progastricsin (Q689Z7) as pepsin B and the name has been used incorrectly in rattail for what presumably is a pepsin [4].

Publisher Summary This chapter provides illustrations of the humeri of human, horse, bear, cow, pig, dog, white-tailed deer, sheep, goat, turkey, duck, raccoon, cat, opossum, rabbit, and chicken. Anterior and posterior views of the human humeri are included, as are the cranial and caudal views of the non-human animals.

Publisher Summary This chapter provides illustrations of the tibiae of human, horse, bear, cow, pig, dog, white-tailed deer, sheep, goat, turkey, duck, raccoon, cat, opossum, rabbit, and chicken. It includes anterior and posterior views of the human tibiae, and the cranial and caudal views of the non-human animals.

In this chapter, the postcranial skeleton of an opossum is compared to that of a newborn human. The chapter begins with lateral and ventral views of the opossum’s cranium and images of the maxillary and mandibular dentition. The opossum’s limb bones are then compared to those of a newborn human, including both cranial (anterior) and caudal (posterior) views. The chapter concludes with images of the scapula, pelvis, and selected vertebrae.

Publisher Summary This chapter provides illustrations of the crania of humans, horse, black bear, cow, deer, pig, sheep, goat, dog, cat, rabbit, duck, chicken, opossum, and raccoon. The skulls are shown in lateral and ventral views. It also illustrates the frontals and maxillae of a human newborn.

In this chapter, the ulnae and radii of human, horse, bear, cow, pig, dog, white-tailed deer, sheep, goat, turkey, duck, raccoon, cat, opossum, rabbit, and chicken are presented. Anterior and posterior views of the human ulnae and radii are included, as are the cranial and caudal views of the non-human animals.

Archaeologists and forensic anthropologists are often called on to distinguish the remains of adult and juvenile humans from those of other vertebrates. This guide is designed as an aid to help experienced osteologists distinguish human skeletal remains from those of other common North American mammals and birds. In addition to adult and juvenile human skeletons, we have chosen to illustrate the skeletons of the most common Old World domestic animals and birds (cattle, horse, sheep, goat, pig, dog, cat, rabbit, turkey, duck, and chicken) as well as wild mammals that are frequently recovered from archaeological and forensic contexts in eastern North America (bear, white-tailed deer, raccoon, and opossum).

Publisher Summary This chapter provides illustrations of the femora of human, horse, bear, cow, pig, dog, white-tailed deer, sheep, goat, turkey, duck, raccoon, cat, opossum, rabbit, and chicken. It includes the anterior and posterior views of the human femora, and the cranial and caudal views of the non-human animals.

The gray short-tailed opossum is one of the most widely studied of all marsupials and an important model for study of olfactory communication, particularly as it relates to pheromonal activation of reproduction. Males respond to differentially to female skin gland secretions and urine from anestrous females, while females respond only skin gland secretions, particularly that of the suprasternal gland. Divergent responses by male and female opossums to odors from these different body sources are most likely related to sex-specific production and deposition of chemical signals in this species. Female opossums do not have an estrous cycle but are stimulated to estrus by male pheromone. Females nuzzle scent marks from male suprasternal gland secretions, and thereby facilitate delivery of a nonvolatile estrus-inducing pheromone to the chemosensory epithelium of vomeronasal organ. Neuroendocrine correlates of pheromonal induction of estrus include elevated plasma estradiol and upregulation of progesterone receptors in hypothalamic regions that control reproductive behavior.

Free vulpecholic acid (1 alpha,3 alpha,7 alpha-trihydroxy-5 beta-cholan-24-oic) is the major biliary component of the Australian opossum (Trichosurus vulpecula), accompanied only by a few percent of its taurine conjugate. In order to exclude a microbial involvement in its formation (i.e., secondary origin) four sets of experiments were performed. It was found that a) the level of vulpecholic acid remained unchanged in the bile of opossums fed with neomycin and kanamycin for 7 days prior to bile collection; b) it also remained unchanged after long bile drainage; c) in opossums prepared with biliary cannula, intraportally injected [24-14C]chenodeoxycholic acid was transformed to [24-14C]vulpecholic acid; and d) in a similar experiment, the detectable transformation of [1 alpha,2 alpha-3H2]cholesterol to vulpecholic acid was observed. In experiment c) 28-66% of the administered radioactivity was secreted in 2 h in the form of free biliary vulpecholic and chenodeoxycholic acids. Only a trace amount of the corresponding taurine conjugates (approximately 0.4%) was formed. Moreover, rapidly declining specific radioactivity of the unconjugated chenodeoxycholic acid indicated its probable participation in the native formation of vulpecholic acid.

Publisher Summary This chapter reviews the regeneration in the central nervous system (CNS) of the newly born opossum. It describes the preparation, its survival in culture and the time course of repair after a lesion. A remarkable preparation for studying development and repair is the CNS of the newborn opossum that removed in its entirety, survives in culture for more than 1 week. In suitable medium, cells continue to divide, mature, and reflex activity is maintained. Moreover, nerve fibers grow rapidly, reliably and extensively across lesions made in the spinal cord. Restoration of conduction has been demonstrated by recording electrically; labeled fibers have been observed directly by light and electron microscopy as they traverse the lesion. Similar experiments have also been made in embryonic (E15) rat CNS in culture. The chapter also considers what mechanisms might favor the extensive repair occurring in early life that becomes inhibited at later stages of development. It analyses the mechanisms that favor repair in younger opossums and that prevent it in their older siblings.

Publisher Summary In mammals, such as opossums, there may be evidence of a thalamo-non-cortical projection caught in the process of becoming a thalamocortical projection. This chapter explores in what ways the two parts of the medial geniculate (MG) is similar or different. For evidence of homology in the projections afferent to the MG, an injection of retrograde tracer in the MG of Monodelphis shows: (1) labeled cells in the inferior colliculus and, therefore, the presence of ascending projections from the colliculus, and (2) labeled cells in the thalamic reticular nucleus and, therefore, the presence of direct projections from that nucleus. Following a large injection of WGA-HRP into the medial geniculate of Monodelphis, labeled neurons are seen in each division of the inferior colliculus. The same injection also shows many retrogradely labeled cell bodies in the thalamic reticular nucleus. On the basis of the presence of these two classes of afferents, therefore, MG in the opossum appears to be a typical mammalian MG. In addition, this same technical procedure also shows orthogradely labeled terminals in the thalamic reticular nucleus—that is, the presence of a reciprocal projection between MG and reticular nucleus—a character typical of MG in placental mammals.

Publisher Summary The discrepancy among different species regarding the presence and distribution of γ-aminobutyric acid (GABA)ergic interneurons raises the question of whether thalamic interneurons can be considered a marker of thalamic evolution. This chapter explores this issue, using different mammals, such as bat, mouse, rat, guinea pig, and rabbit. The chapter, based on cytoarchitectural and immunocytochemical data, demonstrates that animals developed in different eras rearranged their intrathalamic networks by modifying the content and distribution of GABAergic neurons. From opossum to man, there is a progressive increase in the number of GABAergic neurons in the thalamus, associated with a decreased GABA/non-GABA ratio. The three systems, cortex, Rt, and dorsal thalamus, containing GABAergic interneurons are interconnected and evolve in parallel.

Publisher Summary This chapter discusses the extrinsic connections of the neostriatum (NS). The NS or striatum consists of the nucleus caudatus and putamen, which are separated by the fibers of the internal capsule in higher mammals. In all mammals, these nuclei are entirely covered by the cerebral cortex and subcortical white matter, and they are contiguous rostroventrally with the nucleus accumbens septi or the fundus striati. They harbor radial bundles of very thin fibers, which account for their striatal appearance. The principles of the topographical organization of the corticostriatal afferents were clearly established from the degeneration studies. In the opossum, rabbit and cat fibers from every cortical area terminate in both the putamen and the caudate. In all species studied, the cortical fibers show a distinct mediolateral, dorsoventral, and anteroposterior organization.

Publisher Summary This chapter discusses the development of descending spinal connections. The opossum is a good model for developmental studies. The development of the opossum's nervous system is quite protracted in comparison to that of placental mammals. The opossum's hindlimbs are little more than buds at birth and do not become motile for 7–10 days postnatally. The development of hindlimb motility and the influence of descending pathways on that motility can be divided into three stages: (1) stage I begins at birth (or conception) and ends when spontaneous hindlimb movements first appear (postnatal day 7–10), (2) stage II begins with the onset of hindlimb motility and ends approximately 20 days later (50–60 mm snout-rump length) when that motility can be altered by transecting the spinal cord at thoracic levels, and (3) stage III begins when hindlimb movements can first be affected by thoracic transection and continues until the animal can support its weight and ambulate (90–120 mm S-R length, estimated to have been 60–75 days in the pouch). Axons from the reticular formation, raphe nuclei, coeruleus complex, vestibular nuclei, and red nucleus invade most of the lumbosacral areas innervated in the adult animal before transecting them produces noticeable change in hindlimb motility.

Publisher Summary This chapter discusses the immunologic differentiation in ontology. The differentiation of cells in the fetus with respect to the formation of different classes of immunoglobulins is similar in many respects to that seen in the adult. Prior to experimental antigenic stimulation of the fetus of most species, the formation of ϒM-globulins can usually be detected in the fetal tissue, and in some species, ϒG-globulin formation has been observed. The initial immunologic responses of the immature opossum appear to be very closely associated with the first appearance of thymocytes in this animal and with the development of primitive lymph nodes in the cervical region. One of the most striking findings to emerge from studies on the development of immunologic capabilities by the mammalian fetus is that maturation does not appear as a transition from a previously postulated immunologic null state to one of general competence. It rather appears to develop in a series of discrete steps peculiar to each species, and highly dependent upon the antigen employed. No correlation could be made between the position of an antigen in the hierarchy of immunogenicity and its chemical nature, its size, or the sensitivity of the assay system employed to detect the antibodies formed against it.