Elizabeth W. Howerth

A 9‐year‐old Warmblood gelding presented to the University of Georgia Veterinary Teaching Hospital with colic, lethargy and decreased appetite for approximately 1 week. Round cell neoplasia was prioritised after abdominal sonography and cytology of abdominal fluid. The morphological diagnosis after postmortem examination and histopathology was extramedullary plasma cell tumour of the heart, small intestine, large intestine, spleen, diaphragm, urinary bladder and skeletal muscle.

Galectins play an important role in intestinal immune modulation. Little is known about galectin expression in the normal gastrointestinal tract (GIT) of dogs or their potential role in canine immunosuppressant-responsive (IR) chronic inflammatory enteropathy (CIE). In this study, we described and compared the expression of galectins in the stomach, duodenum, ileum, and colon of dogs without CIE-IR (healthy dogs) ( n = 5) and dogs with CIE-IR ( n = 7). Cellular localization of galectins was evaluated using immunohistochemistry quantified with open-source digital pathology software (QuPath). Immunoreactivity in the normal GIT was intense for Gal-2, weak for Gal-3, and moderate for Gal-4. Gal-2 was expressed throughout the gastric mucosa, including epithelium, pits, glands, and lamina propria, whereas Gal-3 and Gal-4 were expressed in the lower two-thirds of the mucosa. In healthy dogs, inflammatory cells, myenteric plexus neurons, and smooth muscle cells were immunoreactive for the examined galectins, whereas enteroendocrine and goblet cells were only immunoreactive for Gal-4. Quantitatively, Gal-2 expression was significantly higher than Gal-3 and Gal-4 in the stomach and duodenum ( P < .05) and higher than Gal-3 in the ileum. In the colon, Gal-2 and Gal-4 expressions were significantly ( P < .05) higher than Gal-3. The expressions of Gal-2, Gal-3, and Gal-4 in duodenum, ileum, and colon of dogs with CIE-IR were significantly ( P < .05) lower than in healthy dogs. A potential role for Gal-2, Gal-3, and Gal-4 in GIT immune regulation and their involvement in the pathogenesis of CIE-IR in dogs is possible and warrants further study.

Chiropterans exhibit remarkable immunological adaptations that facilitate their function as competent reservoir hosts for diverse high-consequence zoonotic viruses while maintaining apparent clinical health. The Egyptian rousette ( Rousettus aegyptiacus ), a frugivorous pteropodid species, represents the sole confirmed natural reservoir for Marburg and Ravn viruses (family Filoviridae), yet comprehensive characterization of its lymphoid system architecture remains absent from the literature. This investigation presents the first systematic gross, histological, and immunohistochemical atlas of lymphoid tissues in this epidemiologically critical species, encompassing primary (bone marrow, thymus) and secondary lymphoid tissues (lymph nodes, spleen, mucosa-associated lymphoid tissue). Tissues from fetal, juvenile, and adult specimens were systematically evaluated to characterize age-related variations in lymphoid architecture and cellular composition dynamics. Immunohistochemical analyses employing cross-reactive antibodies against CD3, CD79a, Iba1, and Granzyme B elucidated the spatial distribution and organizational patterns of key lymphocyte populations and antigen-presenting cells across distinct lymphoid compartments. While overall lymphoid tissue organization demonstrated conservation relative to other mammalian species, several distinctive morphological features were identified, including prominently developed splenic marginal zones, extensive gut-associated lymphoid tissue networks, and organized nasopharyngeal and bronchial lymphoid structures. These anatomical specializations likely represent species-specific evolutionary adaptations underlying viral tolerance mechanisms and immunological equilibrium maintenance during persistent viral exposure. This comprehensive atlas provides an essential foundational resource for veterinary pathologists, comparative immunologists, and infectious disease investigators conducting research with R. aegyptiacus bat populations. By establishing anatomically and immunologically detailed reference standards for lymphoid tissues in this critical reservoir species, this work supports interpretation of experimental infection studies and may help guide future investigations of host–pathogen interactions, reservoir competence, and zoonotic spillover dynamics at wildlife–human interfaces.

The Egyptian rousette ( Rousettus aegyptiacus ) has garnered escalating scientific interest owing to its remarkable physiological adaptations, its role as a natural reservoir for emerging zoonotic pathogens, and its potential as a model organism for comparative mammalian investigations. Despite this interest, comprehensive descriptions of normal tissue architecture in this species remain limited and fragmented, hindering interpretation of experimental and spontaneous disease processes. Here, we present a comprehensive histologic atlas derived from wild-caught Egyptian rousette specimens, documenting normal tissue architecture across major organ systems and establishing a standardized reference for future investigations. To contextualize these findings, we also integrate previously published descriptions of Egyptian rousette anatomy and histology, providing a consolidated summary of existing knowledge. This atlas serves as a foundational reference for studies of physiology, immunobiology, and pathology in Egyptian rousettes, facilitating comparative analyses, supporting investigations of host-pathogen interactions, and advancing broader understanding of chiropteran biology relevant to biomedical research, wildlife health, and public health surveillance.

The emergence of significant viral pathogens and their escalating threats to human and animal health have intensified scientific interest in bats as disease vectors and natural reservoir hosts. Among chiropteran species, the Egyptian rousette ( Rousettus aegyptiacus ) assumes particular epidemiological significance as the established natural reservoir for orthomarburgviruses, encompassing the two recognized members Marburg virus and Ravn virus. While contemporary research predominantly emphasizes the detection and characterization of specific zoonotic agents within these populations, fundamental knowledge regarding their baseline pathology and the comprehensive impacts of disease on morbidity remains limited. Pathological investigations of free-ranging bat populations face inherent methodological constraints, frequently hampered by insufficient sample sizes or selection bias toward compromised specimens (e.g., moribund or deceased animals). This study addresses these limitations through comprehensive post-mortem examination and histologic evaluation of 69 free-ranging Egyptian rousettes from Uganda. These specimens were procured during systematic efforts to identify filoviral reservoir hosts, thereby providing an unprecedented opportunity to investigate spontaneous disease processes within an ostensibly healthy, representative population. Gross pathological examination identified lesions in 85.5% (59/69) of specimens, including scarring and fibrosis of the plagiopatagium and dactylopatagium (85.5%; 59/69), focal fibrotic nodules (17.4%; 12/69), and lacerations (17.4%; 12/69) within wing membranes. Histopathological analysis demonstrated the universal presence of microscopic alterations (100%; 69/69), with a cumulative total of 794 discrete lesions documented across 28 organ systems. The liver emerged as the most frequently affected organ, along with multiorgan perivascular cellular aggregates (both 81.2%; 56/69). This investigation represents the first comprehensive characterization of naturally occurring pathological processes in free-ranging Egyptian rousettes from Uganda. Elucidating the intrinsic factors that modulate reservoir species health is fundamental to understanding zoonotic disease spillover dynamics and developing evidence-based strategies for mitigating future outbreak risks in human and susceptible animal populations.

A 5‐year‐old, male, English Cream Golden Retriever dog with a 3‐month history of left thoracic limb lameness was presented to the University of Georgia Veterinary Teaching Hospital. Physical examination was unremarkable. Neurological examination indicated a left peripheral C6‒T2 lesion, but further diagnostics were declined in favour of empirical treatment with corticosteroids. Two months later, the patient had not improved, and a palpable mass was found in the left axilla on physical examination. Due to poor prognosis, euthanasia was elected. Postmortem MRI revealed a left brachial plexus mass extending up the left C7 spinal nerve into the spinal cord. At necropsy, pulmonary metastasis was found. A malignant nerve sheath tumour was diagnosed via histopathology.

Objective: To evaluate the correlation between cytology and histopathology of splenic masses or nodular lesions in dogs. Methods: Retrospective medical record review from January 2014 to July 2022 of dogs that had a splenic mass or nodular lesion and cytologic and histopathologic evaluation within 90 days of each other. Slide review was conducted by a single pathologist from each subspecialty and recorded as neoplastic, possibly neoplastic, or nonneoplastic. Results: 33 dogs were included and had a median of 4 days (range, 0 to 90 days) between cytologic and histopathologic evaluation. Cytologic and histopathologic results agreed in 18 of 33 dogs (55%; 12 nonneoplastic and 6 neoplastic), although the type of neoplasm differed in one of these (sarcoma vs lymphoma). There was disagreement in 8 of 33 dogs (24%; 7 neoplastic on histopathology and nonneoplastic on cytology, 1 nonneoplastic on histopathology and neoplastic on cytology). When including a possibly neoplastic cytologic diagnosis as neoplastic, there was agreement in 22 of 33 dogs (67%) and disagreement in 11 of 33 dogs (33%). In dogs with a neoplastic or possibly neoplastic cytologic diagnosis, 10 of 14 (71%) were neoplastic on histopathology. In dogs with a nonneoplastic cytologic diagnosis, 12 of 19 (63%) were nonneoplastic on histopathology. Conclusions: Cytologic diagnosis correlated with histopathologic diagnosis of splenic masses or nodular lesions in 55% to 67% of dogs. Cytology was accurate in 71% of neoplastic and 63% of nonneoplastic splenic masses or nodular lesions. Clinical Relevance: There is poor to fair agreement between cytology and histopathology in dogs with splenic masses or nodular lesions. A neoplastic cytologic diagnosis more commonly agrees with histopathology than a nonneoplastic diagnosis.

While most cases of human muscle-invasive bladder cancer (MIBC) are diagnosed as conventional urothelial carcinoma (UC), there is growing recognition of histologic subtypes and divergent differentiation within conventional UC. In this study, 31 dogs with UC (33 slides) were evaluated for histologic subtypes and divergent differentiation, as specified by the recent World Health Organization update on the classification of urinary bladder cancers. Slides were reviewed by a medical uropathologist and 3 board-certified veterinary pathologists and assessed for expression of uroplakin III, vimentin, and E-cadherin. All tumors were classified as UC. Fifteen cases were identified as conventional UC. Among the remainder, 8 displayed glandular differentiation, 4 were classified as sarcomatoid UC, 2 showed squamous differentiation, 1 case was classified as a large nested subtype, and 1 case was classified as a tubular/microcystic subtype. This study found a higher frequency of certain histologic subtypes and divergent differentiation in canine UC, particularly sarcomatoid UC and UC with glandular differentiation, compared to previous reports of both canine UC and human MIBC. The relatively high prevalence of the sarcomatoid UC and UC with glandular differentiation in dogs observed in this study suggests that canine UC may serve as a valuable translational model for evaluating novel therapeutic agents, particularly for these rare and aggressive subtypes in humans.

Iron overload is a leading cause of morbidity and mortality in Egyptian rousette bats (ERBs; Rousettus aegyptiacus ) within managed care settings. We compared hepatic iron accumulation and tissue damage in samples collected from managed care bats in a zoo setting, a research colony, and a free-ranging population with the goal of determining if iron overload was a potential cause of morbidity for free-ranging ERBs. Livers from 20 zoo bats, 8 research colony bats, and 69 free-ranging bats were histologically evaluated for fibrosis, necrosis, and iron accumulation in hepatocytes and Kupffer cells. Hemochromatosis was identified only in the zoo population, with hemosiderosis identified in all research colony bats and many free-ranging bats. There were statistically significant associations between age classification, population, and diagnosis and between Marburg virus infection status and histologic liver iron scores. In addition, there were positive associations with statistical significance between age class (juvenile, adult) and histologic iron scores and between population type (zoo bats > research colony bats > free-ranging bats) and histologic iron scores. Excessive hepatic iron storage does not appear to be a source of morbidity within free-ranging ERB populations.