Lagenidium giganteum is a spore-producing, aquatic oomycete of the southeastern United States. Lagenidium commonly infects the extremities, mammary region, perineum, and trunk. Cutaneous and subcutaneous lesions are progressive, multifocal, firm, and ulcerative. Occult lesions in the thorax or abdomen may involve lymph nodes, great vessels, or lungs. Histologically, pyogranulomatous and eosinophilic inflammation are accompanied by extracellular, negatively staining hyphae with non-parallel walls, spherical to bulbous dilatations, and irregular right-angle branching. Lagenidium hyphae are larger and more visible in hematoxylin and eosin sections when compared with P. insidiosum. Hyphae stain with Grocott’s methenamine silver (Image 1). Ancillary testing is necessary for definitive identification.
Hemorrhagic bowel syndrome (HBS) is a sporadic and fatal disease of predominantly lactating dairy cattle, characterized by segmental hemorrhage and luminal clot formation in the small intestine. Although, Clostridium perfringens and Aspergillus fumigatus have been associated with HBS, the pathogenesis and cause are currently unknown. In this study, 18 naturally occurring cases of HBS (7 necropsied immediately following euthanasia, 11 with 12-48 hour postmortem intervals) were investigated to characterize the pathology and the intestinal microbiome. Hemorrhagic bowel syndrome was characterized by a single small-intestinal, intramucosal hematoma with dissection of the lamina muscularis mucosae. In most cases necropsied immediately after euthanasia (4/7), the intestinal mucosa proximal to the hematoma contained 9 to 14, dispersed, solitary or clustered, erosions or lacerations measuring 4 to 45 mm. In 77% (37/48) of these mucosal lesions, microscopic splitting of the lamina muscularis mucosae comparable to the hematoma was present. These findings suggest the intramucosal hematoma to originate from small mucosal erosions through dissecting hemorrhage within the lamina muscularis mucosae. No invasive fungal growth was observed in any tissue. Bacteriological cultivation and nanopore sequencing showed a polymicrobial population at the hematoma and unaffected intestine, with mostly mild presence of C perfringens at selective culture. Gross and microscopic lesions, as well as the culture and sequencing results, were not in support of involvement of C perfringens or A fumigatus in the pathogenesis of HBS.
Lipopolysaccharide (LPS) has dose-dependent biphasic functions (cell protective versus cell toxic). To clarify the different effects of LPS on liver homeostasis or liver diseases, comparisons were made between low and high doses of LPS, in terms of the mutual relation of hepatic macrophages, autophagy, and damage-associated molecular patterns (DAMPs) in male F344/DuCrlCrlj rats. Rats injected with low dose (0.1 mg/kg) or high dose (2.0 mg/kg) of LPS were examined at 6, 10, and 24 hours following single injections. Histologically, focal hepatocellular necrosis was occasionally present in high-dose animals, whereas there were no significant changes in low-dose animals. In low-dose animals, Kupffer cells reacting to CD163 and CD204 were hypertrophic and regarded as M2 macrophages, which promote resolution of inflammation and tissue repair, whereas in high-dose animals, infiltration of M1 macrophages expressing CD68 and major histocompatibility complex class II, which enhance cell injury, was seen. Hepatocytes with high-mobility-group box-1 (HMGB1) (one of DAMPs)-positive cytoplasmic granules appeared more frequently in high-dose animals than in low-dose animals, indicating the translocation of nuclear HMGB1 into the cytoplasm. However, although light-chain 3 beta–positive autophagosomes in hepatocytes increased in both doses, abnormally vacuolated autophagosomes were only seen in injured hepatocytes in the high-dose group, indicating possible extracellular release of HMGB1, which might result in cell injury and inflammation. These findings suggested that low-dose LPS induced a favorable mutual relationship among hepatic macrophages, autophagy, and DAMPs leading to cytoprotection of hepatocytes, whereas failures of the relationship in high-dose LPS caused hepatocyte injury.
The amoeba Malpighamoeba mellificae is the etiologic agent of amoebic (amoeba) disease of Western honey bees (Apis mellifera). M. mellificae damages the Malpighian tubules, which is believed to weaken and kill the host bee. Here, the authors describe the detection of this organism in a honey bee colony in the Yukon Territory, Canada. The Malpighian tubules of 14% (7/50) of the adult worker bees were discolored dark brown. Fifteen bees screened using conventional polymerase chain reaction for the 18S gene of M. mellificae were positive for the pathogen. Histologically, the lumens of Malpighian tubules were packed with amoebae, causing dilation of the tubules and attenuation and loss of the tubular epithelium. This phylogenetic analysis places M. mellificae in a new clade, a sister group to the Entamoebidae. This work provides a foundation for further investigation into the distribution, prevalence, and pathology associated with M. mellificae infection.
Aspergillosis of gorgonian sea fans is a Caribbean-wide disease characterized by focal, annular purple pigmentation with central tissue loss. We applied a holistic diagnostic approach including histopathology and a combination of culture and direct molecular identification of fungi to evaluate these lesions with the goal of determining the diversity of associated micro-organisms and pathology. Biopsies were collected from 14 sea fans without gross lesions and 44 sea fans with lesions grossly consistent with aspergillosis in shallow fringing reefs of St. Kitts. Histologically, the tissue loss margin had exposure of the axis and amoebocyte encapsulation with abundant mixed micro-organisms. Polyp loss, gastrodermal necrosis, and coenenchymal amoebocytosis were at the lesion interface (purpled area transitioning to grossly normal tissue) with algae (n = 21), fungus-like hyphae (n = 20), ciliate protists (n = 16), cyanobacteria (n = 15), labyrinthulomycetes (n = 5), or no micro-organisms (n = 8). Slender, septate hyaline hyphae predominated over other morphological categories, but were confined to the axis with little host response other than periaxial melanization. Hyphae were absent in 6 lesioned sea fans and present in 5 control biopsies, questioning their pathogenicity and necessary role in lesion causation. From cultivation, different fungi were isolated and identified by sequencing of the nuclear ribosomal internal transcribed spacer region. In addition, 2 primer pairs were used in a nested format to increase the sensitivity for direct amplification and identification of fungi from lesions, thereby circumventing cultivation. Results suggest mixed and opportunistic infections in sea fans with these lesions, requiring longitudinal or experimental studies to better determine the pathogenesis.
This short account cannot do justice to the long and rich history of the genesis and evolution of invertebrate pathology. The emphasis in the succeeding text, therefore, is to draw attention to the early dawning of interest in the lives—and in the deaths— of “les petites bêtes” (as the French entomologist Jean-Henri Fabre [1823–1915] termed them) and to summarize, with examples, advances in knowledge over the centuries that led to the emergence of the discipline of “invertebrate pathology” as we know it now. As the following text illustrates, the subject did not evolve spontaneously. Its growth mirrored the history of other forms of pathology whereby initial studies on anatomy and physiology, often supplemented by behavioral observations, led to an understanding of the causes and mechanisms of disease in a wide range of taxa.
This report describes a unique pattern of alopecia in 8 American red squirrels (Tamiasciurus hudsonicus) from 2013 to 2021. All animals were juveniles; 6 were female and 2 were male. Seven presented between September and November, and one presented in April. All squirrels had widespread, bilaterally symmetric, noninflammatory, well-demarcated alopecia involving the entire trunk and legs and normal hair on their muzzle and dorsal surfaces of their paws. Six months later, a normal hair coat had grown on 2 of the animals, which were littermates. Hair fully grew 2 months later in another animal. Histopathology of the alopecic skin was performed in 7 of 8 animals. The following changes were noted: bent and coiled hairs, perforating folliculitis, melanin clumping, and distortion of hair shafts. Based on features of follicular dysplasia and apparent seasonality, this condition has some similarities to canine seasonal flank alopecia. A genetic etiology is suspected.
Freshwater mussels are one of the most imperiled groups of organisms in the world, and more than 30 species have gone extinct in the last century. While habitat alteration and destruction have contributed to the declines, the role of disease in mortality events is unclear. In an effort to involve veterinary pathologists in disease surveillance and the investigation of freshwater mussel mortality events, we provide information on the conservation status of unionids, sample collection and processing techniques, and unique and confounding anatomical and physiological differences. We review the published accounts of pathology and infectious agents described in freshwater mussels including neoplasms, viruses, bacteria, fungi, fungal-like agents, ciliated protists, Aspidogastrea, Digenea, Nematoda, Acari, Diptera, and Odonata. Of the identified infectious agents, a single viral disease, Hyriopsis cumingii plague disease, that occurs only in cultured mussels is known to cause high mortality. Parasites including ciliates, trematodes, nematodes, mites, and insects may decrease host fitness, but are not known to cause mortality. Many of the published reports identify infectious agents at the light or ultrastructural microscopy level with no lesion or molecular characterization. Although metagenomic analyses provide sequence information for infectious agents, studies often fail to link the agents to tissue changes at the light or ultrastructural level or confirm their role in disease. Pathologists can bridge this gap between identification of infectious agents and confirmation of disease, participate in disease surveillance to ensure successful propagation programs necessary to restore decimated populations, and investigate mussel mortality events to document pathology and identify causality.
Fungi are among the most common infectious agents affecting the skin of animals. The skin can serve as a port of entry for fungal infections, which can eventually become disseminated. In some regions of the world, oomycetes, such as Pythium and Lagenidium, are also responsible for a significant number of severe cutaneous infections. Histologic evaluation of fungal morphology, including size, shape, septation, branching, and budding characteristics, combined with the distribution of inflammatory infiltrates within different skin layers can potentially identify etiologic agents, guiding selection of antifungals and additional diagnostics. Fungal infections of the skin surface are typically caused by Malassezia and rarely Candida, with opportunistic fungi also capable of colonizing the skin surface, especially when the barrier is broken. Folliculocentric infections, caused by dermatophytes, result in mild to severe inflammation and can occasionally penetrate deep into the skin. A wide range of fungi, including agents of hyalohyphomycosis, phaeohyphomycosis, and dimorphic fungal infections, as well as oomycetes, result in nodular cutaneous and subcutaneous lesions. With the occasional exception of dimorphic fungi, fungal speciation often requires cultures performed on fresh tissues. However, molecular techniques such as pan-fungal polymerase chain reaction on paraffin blocks is becoming an increasingly useful tool to distinguish between cutaneous fungal pathogens. This review focuses on describing the clinical and histologic features of the most common fungal and oomycete infections affecting the skin of animals, divided according to distribution patterns of lesions and fungal or oomycete morphology.
Primary central nervous system (CNS) neoplasms are uncommonly diagnosed in cats. The majority of primary feline CNS neoplasms described in the veterinary literature consist of meningioma and glioma occurring mainly in the brain and less often in the spinal cord. Although most neoplasms can be diagnosed based on routine histologic evaluation, less typical tumors need to be further characterized using immunohistochemistry. This review compiles the relevant information about the most common primary CNS neoplasms of cats available in the veterinary literature, aiming to serve as a converging source of information for the topic.
Disease caused by the archetypical amdoparvovirus (APV), Aleutian mink disease virus (AMDV), has been well studied, but APV infections in other carnivores are poorly understood. Skunk amdoparvovirus (SKAV), one of a handful of newly discovered APVs, is apparently species-specific in striped skunks (Mephitis mephitis) and has a high prevalence across North America. We have evaluated the infection status and viral tissue distribution in a cohort of 26 free-ranging California skunks from a single rehabilitation facility who were euthanized due to poor prognosis for recovery from neurologic disease. SKAV was detected in the majority of this cohort, and virus was associated with a spectrum of lesions including tubulointerstitial nephritis, meningoencephalitis, myocarditis, and arteritis. Affected tissue and patterns of inflammation were partially overlapping with those of AMDV infection but were notably distinct in the kidney.
During meat inspections in pigs, dystrophinopathies are among the muscle lesions targeted for disposal. In this study, the authors examined the lesions and the distribution of dystrophin expression in 25 pigs with dystrophinopathy. In addition, complementary deoxyribonucleic acid (cDNA) sequencing and western blotting were performed in 6 of the 25 cases, all of which were characterized by degeneration, necrosis, and fat replacement of muscle fibers. Comparing the results of immunohistochemistry with anti-dystrophin antibodies that recognized at different sites in the protein, the authors noted that the loss of dystrophin expression was most pronounced in the C-terminus-recognizing antibody (19/25 cases). The authors detected 5 missense mutations and 3 types of shortened transcripts generated by the skipping of exons in the cDNA, which were associated with the pathogenesis. One missense mutation had been reported previously, whereas the remaining mutations identified had not been previously documented in pigs. In the cases with shortened transcripts, normal-sized transcripts were detected together with the defective transcripts, suggesting that these mutations were caused by splicing abnormalities. In addition, they were in-frame mutations, all of which have similar pathogeneses of Becker muscular dystrophy in humans. These cases were 6 months of age and exhibited macroscopic discoloration, fatty replacement, and muscle degeneration, suggesting that the effect of these mutations on skeletal muscle was significant.
Avian chlamydiosis is a common disease found in domesticated and nondomesticated avian species caused by several species of chlamydiae including but not limited to Chlamydia psittaci, Chlamydia avium, Chlamydia gallinacea, Chlamydia buteonis, and Chlamydia ibidis. Generally, early in the disease course, birds present with mild nonspecific clinical signs associated with gastrointestinal and respiratory tract disease. During end-stage disease, birds may present in a severe state of emaciation, dehydration, and/or acute death with no known history of prior illness. Between 2000 and 2009, 14 unusual cases of avian chlamydiosis were submitted to the California Animal Health and Food Safety Laboratory System. Histologic lesions noted in the 14 birds included meningoencephalomyelitis (3 of 13, 23%), otitis media (3 of 8), bursitis (9 of 11, 81%), nephritis (8 of 13, 61%), and orchitis (1 of 8). Corresponding immunopositive chlamydiae intracytoplasmic inclusions were detected in all tissues. Positive immunolabeling was detected in optic nerves (5 of 10, 50%), meninges (5 of 13, 38%), and endothelial cells (14 of 14, 100%) in the absence of significant microscopic lesions. This study highlights unusual gross, histological, and immunohistochemical findings of chlamydiosis in psittacines and highlights the importance of a thorough diagnostic approach when confirming or excluding chlamydiosis in psittacine birds.
Lymphoglandular complexes are components of the gut-associated lymphoid tissue that are characterized by submucosal lymphoid aggregates invested by projections of mucosal epithelium. Reports of pathology involving these structures are rare in both human and veterinary literature. Here, the authors report 2 cases of rectal masses excised from dogs following a period of tenesmus and hematochezia. In both animals, the masses were composed of lymphoid tissue closely encompassing tubuloacinar structures. Immunohistochemistry and polymerase chain reaction antigen receptor rearrangement testing demonstrated that the lymphoid population was polyclonal, comprising T and B cells arranged in loosely follicular aggregates centered on the epithelial foci. In light of these findings, a diagnosis of lymphoglandular complex nodular hyperplasia was reported. To the authors’ knowledge, this is the first report of this condition in dogs.
Pedigree analysis, clinical, gross, microscopic, ultrastructural, and lipidomic findings in 4 female superb bird-of-paradise (SBOP, Lophorina superba) siblings led to the diagnosis of a primary inherited glycerolipid storage disease. These birds were the offspring of a related breeding pair (inbreeding coefficient = 0.1797) and are the only known SBOPs to display this constellation of lesions. The birds ranged from 0.75 to 4.3 years of age at the time of death. Two birds were euthanized and 1 died naturally due to the disease, and 1 died of head trauma with no prior clinical signs. Macroscopic findings included hepatomegaly and pallor (4/4), cardiac and renal pallor (2/4), and coelomic effusion (1/4). Microscopic examination found marked tissue distortion due to cytoplasmic lipid vacuoles in hepatocytes (4/4), cardiomyocytes (4/4), renal tubular epithelial cells (4/4), parathyroid gland principal cells (2/2), exocrine pancreatic cells (3/3), and the glandular cells of the ventriculus and proventriculus (3/3). Ultrastructurally, the lipids were deposited in single to coalescing or fused droplets lined by an inconspicuous or discontinuous monolayer membrane. Lipidomic profiling found that the cytoplasmic lipid deposits were primarily composed of triacylglycerols. Future work, including sequencing of the SBOP genome and genotyping, will be required to definitively determine the underlying genetic mechanism of this disease.
Leptomeningeal gliomatosis (LG) is characterized by extensive dissemination of neoplastic glial cells in the subarachnoid space either without an intraparenchymal glioma (primary LG or PLG) or secondary to an intraparenchymal glioma (secondary LG or SLG). Given the low frequency of LG in human and veterinary medicine, specific diagnostic criteria are lacking. Here, we describe 14 cases of canine LG that were retrospectively identified from 6 academic institutions. The mean age of affected dogs was 7.3 years and over 90% of patients were brachycephalic. Clinical signs were variable and progressive. Relevant magnetic resonance image findings in 7/14 dogs included meningeal enhancement of affected areas and/or intraparenchymal masses. All affected dogs were euthanized because of the poor prognosis. Gross changes were reported in 12/14 cases and consisted mainly of gelatinous leptomeningeal thickening in the brain (6/12 cases) or spinal cord (2/12 cases) and 1 or multiple, gelatinous, gray to red intraparenchymal masses in the brain (6/12 cases). Histologically, all leptomeningeal neoplasms and intraparenchymal gliomas were morphologically consistent with oligodendrogliomas. Widespread nuclear immunolabeling for OLIG2 was observed in all neoplasms. The absence of an intraparenchymal glioma was consistent with PLG in 3 cases. The remaining 11 cases were diagnosed as SLG.
Primary pulmonary neoplasms in cattle are rare. There are few studies on the pathological findings of these neoplasms in this species. This study aimed to describe the histological and immunohistochemical findings of primary and metastatic pulmonary carcinomas in cattle. We conducted a retrospective study of 19 cases of epithelial neoplasms with pulmonary involvement. Histologically, most of the neoplasms were classified as primary pulmonary neoplasms, including different adenocarcinoma subtypes (4/19, 21%) and adenosquamous carcinomas (3/19, 16%), followed by squamous cell carcinoma (6/19, 32%), metastatic uterine adenocarcinoma (4/19, 21%), metastatic hepatocellular carcinoma (1/19, 5%), and metastatic cholangiocarcinoma (1/19, 5%). By immunohistochemistry, all neoplasms were positive for pancytokeratin, and 4/19 (21%) were positive for vimentin. Primary pulmonary neoplasms had immunoreactivity for thyroid transcription factor-1 (6/7), while only 2 of these cases were positive for napsin A. All cases with squamous differentiation (9/9) had immunoreactivity for cytokeratin (CK) 5/6, while only 7 of these cases were positive for p40. CK20, CK7, and CK8/18 showed varied immunoreactivity in the primary and metastatic pulmonary carcinomas but were important markers to confirm the diagnosis of primary mucinous adenocarcinoma and metastatic cholangiocarcinoma. HepPar-1 was only positive in the metastatic hepatocellular carcinoma. The limited number of cases of metastatic uterine adenocarcinomas in this study precluded identification of a specific immunophenotype for this tumor. Immunohistochemistry proved to be an important tool to confirm the proper classification of these neoplasms.
The aim of the work was to study the features of the rabies epizootic process manifestation in the territory of the Rostov region. To achieve the intended aim the comprehensive epizootological research and the retrospective epizootological analysis were carried out based on the veterinary reports of the Rostov Region State Budgetary Institution «Rostov Regional Station for Animal Diseases Combating, with Anti-Epizootic Squad» and the Rostov Region Veterinary Medicine Directorate. In the result of research it was found that for the period from 2018 to 2021, 35 rabies epizootic foci were registered within the territory of 24 municipalities of the Rostov region. During this period of time the disease was detected in 8 species of domestic and wild animals. The main reservoir and source of rabies infection causative agent in this territorial entity of the Russian Federation are dogs (31.4 %), foxes (22.8 %), cats (14.3 %), cattle (14.3 %) and jackals (8.5 %); single cases of the disease (8.7 % in total) were detected among wolves, martens and horses. When analysing the annual dynamics of the rabies incidence in animals, the clear-cut seasonality of the disease is discovered. The disease is mainly recorded in the autumn-spring period, whereby the seasonal dynamics has the two-peak character with two highest points in April and November. Such seasonal fluctuations are explained by the breeding biology of wild carnivores, such as foxes and jackals, with wolves and martens involved in the epizootic process. The unstable and tense rabies epizootic situation in the Rostov region indicates the need to regulate the number of wild carnivores on its territory and to carry out planned activities on their immunization.
Immuno-oncology research has brought to light the paradoxical role of immune cells in the induction and elimination of cancer. Programmed cell death protein 1 (PD1), expressed by tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PDL1), expressed by tumor cells, are immune checkpoint proteins that regulate the antitumor adaptive immune response. This study aimed to validate commercially available PDL1 antibodies in canine tissue and then, applying standardized methods and scoring systems used in human pathology, evaluate PDL1 immunopositivity in different types of canine tumors. To demonstrate cross-reactivity, a monoclonal antibody (22C3) and polyclonal antibody (cod. A1645) were tested by western blot. Cross-reactivity in canine tissue cell extracts was observed for both antibodies; however, the polyclonal antibody (cod. A1645) demonstrated higher signal specificity. Canine tumor histotypes were selected based on the human counterparts known to express PDL1. Immunohistochemistry was performed on 168 tumors with the polyclonal anti-PDL1 antibody. Only membranous labeling was considered positive. PDL1 labeling was detected both in neoplastic and infiltrating immune cells. The following tumors were immunopositive: melanomas (17 of 17; 100%), renal cell carcinomas (4 of 17; 24%), squamous cell carcinomas (3 of 17; 18%), lymphomas (2 of 14; 14%), urothelial carcinomas (2 of 18; 11%), pulmonary carcinomas (2 of 20; 10%), and mammary carcinomas (1 of 31; 3%). Gastric (0 of 10; 0%) and intestinal carcinomas (0 of 24; 0%) were negative. The findings of this study suggest that PDL1 is expressed in some canine tumors, with high prevalence in melanomas.
Equine parvovirus-hepatitis (EqPV-H) is the causative agent of Theiler's disease, or severe acute hepatic necrosis, in horses. However, it is poorly understood whether EqPV-H is associated with other histologic findings in horses with clinical liver disease. The objective of this study was to examine the prevalence and severity of EqPV-H infections in diagnostic liver samples. Archived formalin-fixed, paraffin-embedded (FFPE) liver samples (n = 98) from Cornell University and University of California, Davis, collected between 2007 and 2022 were evaluated for 15 individual histologic features and by EqPV-H in situ hybridization. EqPV-H was detected in 48% (n = 47) of samples. The most common histologic features of EqPV-H-positive samples included individual hepatocyte death (n = 40, 85%), lobular infiltrates (n = 38, 80%), portal infiltrates (n = 35, 74%), and ductular reaction (n = 33, 70%). Centrilobular necrosis, portal infiltrate, and individual hepatocyte death were positively associated with high viral load. Neutrophil infiltrates, bridging fibrosis, and portal edema were negatively associated with a high viral load. Only 4 of 49 tested samples were positive for equine hepacivirus by polymerase chain reaction (PCR), but the PCR assay was unreliable for FFPE tissues. In summary, this study demonstrates that EqPV-H is common in a variety of liver pathologies and should be considered as a differential diagnosis in cases of hepatitis other than Theiler's disease.
