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Background Research on cancer in wild animals provides important insights into the mechanisms of carcinogenesis. Histiocytic sarcomas comprise a rare malignant macrophage-dendritic cell lineage neoplasm in wildlife. This study reports a case of histiocytic sarcoma in the small intestine of a collared peccary ( Pecari tajacu ), describing its clinical, anatomopathological, and immunohistochemical aspects. Case presentation A six-year-old male collared peccary maintained in captivity at a facility in Northeastern Brazil presented progressive weight loss, diarrhea, anorexia, dyspnea, lethargy, abdominal distension, bristled fur, and pale mucous membranes. A complete blood count indicated a mild degree of anemia and moderate leukocytosis. Treatment included anti-inflammatories and antibiotics; however, on the 18th day after initial presentation, the animal was found dead in its enclosure. An anatomopathological examination revealed that the animal exhibited poor body condition, scant body fat with a gelatinous appearance, hydrothorax, pulmonary edema, and ascites. Thickening of the duodenal wall was observed, along with the presence of a yellowish-white tumor. Histopathological examination of the affected intestinal segment revealed a neoplastic proliferation of round cells with large, hyperchromatic nuclei, prominent nucleoli, and a high mitotic index (20 mitoses per high-power field). Numerous multinucleated and binucleated giant cells were present. The neoplastic cells extensively infiltrated all layers of the intestinal wall, from the mucosa to the serosa. Immunohistochemical analysis showed strong positivity for macrophage/mononuclear phagocytic lineage markers (CD18, IBA-1, and lysozyme), while negative for T-cell (CD3), B-cell (CD79), and plasma cell (MUM1) markers. The proliferation index assessed by Ki-67 was approximately 60%. Conclusions The histopathological and immunohistochemical findings confirmed the diagnosis of intestinal histiocytic sarcoma in a collared peccary, representing the first documented case of this neoplasm in this species.

Phylogenetically, the yolk sac is an ancient structure in vertebrate evolution and crucial in the placentation of viviparous animals, playing an essential role in embryogenesis. Considering that the yolk sac persists until birth in rodents, forming an active placenta, this study aimed to describe the yolk sac development process in red-rumped agoutis ( Dasyprocta leporina ) during the early gestation phase and associating the progression to morphological changes in other structures. To this end, six female red-rumped agoutis obtained from CEMAS-UFERSA were monitored for 24 h. The first gestation day was defined as 24 h post-copulation. Samplings were carried out on the 13th, 14th and 15th pregnancy days. Pregnant uteri were fixed in 8% paraformaldehyde for 72 h and histologically processed, with 5 μm sections stained with Hematoxylin-Eosin (HE) and analyzed under a light microscope. On the 13th day, the blastocyst is implanted on the antimesometrial side of the uterus, surrounded by uterine stromal cells organizing themselves around this structure. On the 14th day, the intramural wall between the uterus and the embryo begins to break down and the parietal yolk sac exhibits spindle cells, while the visceral yolk sac presents eosinophilic cuboidal cells. On the 15th day, the intramural layer is almost completely ruptured, revealing a vascular bed between the embryo and the decidua. The visceral yolk sac did not yet contain its characteristic villi at this stage. Blastocyst formation and yolk sac differentiation take place between the 13th and 15th pregnancy days. The yolk sac inversion process is also described, taking place between the 14th and 15th gestation days, which had not yet been documented for red-rumped agoutis.

The greater rhea, Rhea americana , is a wild ratite of high scientific importance and significant and zootechnical value, especially considering the current development state of Brazilian poultry production, where research aimed at increasing the productivity of these animals has become extremely relevant. Studies concerning fetal attachments and embryonic development are paramount, as they can provide essential information concerning reproductive and nutritional animal management. However, a lack of information on greater rhea fetal morphology is noted. Therefore, the aim of the present study was to establish a standard model for fetal attachments in this species. Greater rhea eggs were incubated from 0 to 36 days, and macroscopic and microscopic embryonic attachment characterizations were performed. Histologically, all embryonic annexes exhibit germ layers, namely the ectoderm (outer layer), mesoderm (middle layer) and endoderm (inner layer). The findings indicate that greater rhea development patterns are similar to other birds.

The black-rumped agouti (Dasyprocta prymnolopha, Wagler 1831) is currently under intense ecologic pressure, which has resulted in its disappearance from some regions of Brazil. Echocardiography is widely used in veterinary medicine but it is not yet part of the clinical routine for wild animals. The objective of the present study was to assess the applicability of the echocardiographic exam in nonanesthetized agouti and to establish normal reference values for echocardiographic measurements in bidimensional mode (2D), M-mode, and Doppler for this species, and a lead II electrocardiogram was simultaneously recorded. Twenty agouti were used in this study. All the echocardiographic measurements were positively correlated with weight (P < 0.05), and there were no significant differences between sexes (P > 0.05). Blood flow velocities in the pulmonary and aortic artery ranged from 67.32–71.28 cm/sec and 79.22–101.84 cm/sec, respectively. The isovolumic relaxation time was assessed in all the animals and ranged from 38.5 to 56.6 ms. The maximum value for the nonfused E and A waves and the Et and At waves was 158 beats/min for both. The results obtained for the morphologic and heart hemodynamic measurements can guide future studies and help in the clinical management of these animals in captivity.