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Masticatory myositis is an autoimmune neuromuscular disorder that affects the muscles of mastication. The affected individual has difficulties in opening or closing the mouth, pain, and swelling in the acute phase, and significant atrophy of the affected musculature in the chronic phase. A guinea pig ( Cavia porcellus ) with a history of chronic hyporexia, recurrent cheek teeth overgrowth, and loss of facial silhouette, was suspected of having masticatory myositis. The disease was confirmed by computed tomography and histopathological examination of muscle fragments. The patient was treated with a protocol involving corticosteroids and gabapentin, and occlusal correction procedures., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Mouse kidney parvovirus (MKPV) infection can cause significant morbidity and mortality by inducing moderate to severe inclusion body nephropathy and kidney fibrosis in aged immunodeficient mice. However, MKPV infection in immunocompetent mice is associated with histopathologic findings ranging from absent to minimal or moderate lymphoplasmacytic interstitial nephritis without inclusion body in most cases. We surveyed the prevalence of MKPV via PCR from August 2019 through January 2021, using feces, kidneys, and livers collected and pooled from 2 sentinel mice [Crl:CD1(ICR)] (CD1) per surveillance cage (a total of 212 cages). CD1 mice used as dirty-bedding sentinels were housed for 6 mo in a separate cage on the same rack as colony mice used in research at the Massachusetts Institute of Technology and at the Whitehead Institute for Biomedical Research. MKPV quantitative PCR positivity was 16.04%, 14.62%, and 10.02% for feces, kidney, and liver, respectively. The aggregate prevalence of MKPV was 22.64% (48 of 212 samples). Thirty-three of 103 rooms (32.04%) were MKPV positive. MKPV-positive kidneys had more severe chronic lymphoplasmacytic interstitial nephritis (CLIN) than MKPV-negative kidneys; however, there was no significant difference in hepatic lesions between MKPV-positive and -negative livers. Although no overt intranuclear inclusion body nephropathy was noted in MKPV-positive CD1 kidneys, MKPV RNA was sporadically detected within tubular epithelial cells in MKPV-positive kidneys but not in MKPV-positive livers. Our study indicates that MKPV can be easily transmitted through soiled bedding. It highlights that CD1 mice can be used as sentinels to detect MKPV, emphasizing the importance of monitoring MKPV distribution using quantitative PCR in sentinel mice if MKPV needs to be excluded from a colony. Importantly, as MKPV infection is associated with mild to moderate CLIN, MKPV can potentially confound the interpretation of in vivo biomedical data.

A 4-year 9-month-old Amami spiny rat reared in a zoo died following a history of anorexia, weight loss, and respiratory distress. At necropsy, neoplastic tissues were found along the pleura and adhered to the thoracic wall, heart, and lungs. Histologically, the tumor was composed of diffuse, patternless sheets of large round to polygonal neoplastic cells with abundant eosinophilic cytoplasm, and multinucleated giant cells were often present. Metastatic lesions were observed in the abdominal lymph nodes. Neoplastic cells were immunopositive for vimentin, Iba-1, and CD204, and negative for E-cadherin and S100. Based on these findings, the tumor was diagnosed as histiocytic sarcoma. Compression of the lungs by the tumor may have caused respiratory failure and led to death.

A case of cutaneous asthenia in a Campbell's dwarf hamster is described. The animal was found to have hyperextensible skin, glaucoma and lens dislocation. Histopathological examination revealed an irregular, haphazard arrangement of collagen fibres in the dermis. The animal underwent surgical reduction of the skin folds which provided only temporary relief., (© 2024 ESVD and ACVD.)

Rodents are typically viewed as asymptomatic reservoirs for leptospirosis infection, as clinical disease in rodents is rarely described. This report includes three separate cases of leptospirosis in Patagonian maras ( Dolichotis patagonum ) over a 3-yr period in multiple locations within a single zoo. All three cases presented with varying clinical signs including lethargy, conjunctival hyperemia, hyperbilirubinemia, and presumed renal azotemia. Infection with Leptospira spp. was diagnosed antemortem by PCR on whole blood ( n = 1, Case 1) or urine ( n = 2, Cases 2 and 3). Leptospira antibody titers measured by serum microagglutination testing ( n = 3) were elevated or increased in all three animals over a 1-3-wk period for Leptospira serovars Bratislava and Hardjo (Case 1) and Grippotyphosa (Case 2 and 3). Two of the three animals responded to treatment with penicillin and doxycycline and supportive care, whereas one animal did not respond to treatment. Postmortem findings in this individual included conjunctivitis, chemosis, dehydration, icterus, tricavitary serosanguinous effusions, necrotizing hepatitis, diffuse pulmonary congestion, and edema. Immunohistochemical examination identified scattered Leptospira organisms within hepatocytes and renal tubular epithelial cells. A wild raccoon ( Procyon lotor ) at the institution tested positive by PCR on kidney tissue for the same Leptospira spp. serovar and was the suspected source of infection. This case series highlights the clinical importance of leptospirosis as a differential for Patagonian maras presenting with lethargy, ocular signs, acute hepatic disease, and azotemia.

Biopsy data on externally palpable masses in pet rats (Rattus norvegicus) were retrieved from the archives of a large commercial pathology laboratory between November 2013 and July 2021. A total of 330 samples were submitted from 292 individual animals. Of the 330 samples submitted, 182 (55.2%) were of mammary gland origin and the majority were benign neoplasms, with fibroadenoma most frequent. Of the remaining 148 samples, 101 were neoplastic in nature, with 76 tumours classified as mesenchymal, 23 as epithelial and two classified only as malignant neoplasia not otherwise specified. Malignant neoplasms accounted for 88 of these non-mammary masses, with the most diagnosed tumours including soft tissue sarcoma (including fibrosarcoma) and sarcomas not otherwise specified., Competing Interests: Declaration of competing interests The authors declared no conflicts of interest in relation to the research, authorship or publication of this article., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Spontaneous choriocarcinomas are rare, highly vascular, malignant trophoblastic tumors that occur in humans and animals. This report describes the unusual spontaneous presentation of 4 choriocarcinomas within the subcutaneous tissues of 4, multiparous but nongravid, Amargosa voles ( Microtus californicus scirpensis ) from a captive breeding colony. Two subcutaneous neoplasms were composed of multifocal discohesive and infiltrative aggregates of medium to large trophoblasts and cytotrophoblasts within a fibrovascular stroma. Neoplastic cells were associated with variably sized thrombi and cavitary areas of hemorrhage and necrosis. Two subcutaneous tumors were predominantly composed of expansile, blood-filled, cystic spaces lined by neoplastic cytotrophoblasts and occasionally contained medium to large trophoblasts. Trophoblasts and cytotrophoblasts were positive for pancytokeratin and cytokeratin 8/18, negative for alpha-fetoprotein, and contained intracytoplasmic Periodic acid-Schiff (PAS)-positive glycogen in all 4 tumors. In species with hemochorial placentation, migration of trophoblasts into maternal circulation with embolization to distant nonreproductive tissues occurs and may explain the unusual subcutaneous distribution of these 4 tumors. The 2 multiloculated paucicellular tumors may represent an early stage of neoplastic transformation. To the authors' knowledge, this is the first report characterizing choriocarcinomas in extrareproductive sites in rodents., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Structural plasticity is critical for the functional diversity of neurons in the brain. Experimental autoimmune encephalomyelitis (EAE) is the most commonly used model for multiple sclerosis (MS), successfully mimicking its key pathological features (inflammation, demyelination, axonal loss, and gliosis) and clinical symptoms (motor and non-motor dysfunctions). Recent studies have demonstrated the importance of synaptic plasticity in EAE pathogenesis. In the present study, we investigated the features of behavioral alteration and hippocampal structural plasticity in EAE-affected mice in the early phase (11 days post-immunization, DPI) and chronic phase (28 DPI). EAE-affected mice exhibited hippocampus-related behavioral dysfunction in the open field test during both early and chronic phases. Dendritic complexity was largely affected in the cornu ammonis 1 (CA1) and CA3 apical and dentate gyrus (DG) subregions of the hippocampus during the chronic phase, while this effect was only noted in the CA1 apical subregion in the early phase. Moreover, dendritic spine density was reduced in the hippocampal CA1 and CA3 apical/basal and DG subregions in the early phase of EAE, but only reduced in the DG subregion during the chronic phase. Furthermore, mRNA levels of proinflammatory cytokines ( Il1β , Tnfα , and Ifnγ ) and glial cell markers ( Gfap and Cd68 ) were significantly increased, whereas the expression of activity-regulated cytoskeleton-associated protein (ARC) was reduced during the chronic phase. Similarly, exposure to the aforementioned cytokines in primary cultures of hippocampal neurons reduced dendritic complexity and ARC expression. Primary cultures of hippocampal neurons also showed significantly reduced extracellular signal-regulated kinase (ERK) phosphorylation upon treatment with proinflammatory cytokines. Collectively, these results suggest that autoimmune neuroinflammation alters structural plasticity in the hippocampus, possibly through the ERK-ARC pathway, indicating that this alteration may be associated with hippocampal dysfunctions in EAE.

Spinal cord ischemia-reperfusion injury (SCII) ranks as the common complication after aortic surgery, usually leading to devastating post-operative paraplegia. Microglia over-activation and neuronal cell loss are key pathological features of SCII. Curcumin is involved in several I/R injuries. However, its underlying mechanism in SCII remains elusive. Here, curcumin attenuated oxygen and glucose deprivation/reoxygenation (OGD/R)-induced oxidative injury in PC12 neuronal cells by increasing cell viability, inhibiting cell apoptosis, lactate dehydrogenase, malondialdehyde levels, but elevating anti-oxidative superoxide dismutase and glutathione peroxidase levels. Furthermore, curcumin restrained OGD/R-evoked microglia M1 activation by decreasing microglia M1 polarization marker IBA-1 and iNOS transcripts. Moreover, the increased inflammatory cytokine levels of TNF-α and IL-6 in microglia under OGD/R conditions were suppressed after curcumin treatment. Importantly, neuronal cells incubated with a conditioned medium from OGD/R-treated microglia exhibited lower cell viability and higher apoptotic ratio, which were overturned when microglia were treated with curcumin. Intriguingly, curcumin could inhibit the activation of the NF-κB pathway by Nrf2 enhancement in OGD/R-treated PC12 cells and microglia. Notably, targeting Nrf2 signaling reversed the protective efficacy of curcumin against OGD/R-evoked oxidative insult in neuronal, microglia M1 activation, inflammatory response, and microglial activation-evoked neuronal death. In vivo, curcumin improved histopathologic injury and neurologic motor function in SCII rats and attenuated oxidative stress, microglia activation and neuroinflammation in spinal cord tissues, and activation of the Nrf2/NF-κB pathway. Thus, curcumin may alleviate SCII by mitigating I/R-evoked oxidative injury in neuron and microglia activation-induced neuroinflammation and neuron death through Nrf2/NF-κB signaling, supporting a promising therapeutic agent for SCII., (© 2024. The Society for In Vitro Biology.)

Niemann-Pick disease type C1 (NPC1) is a lysosomal lipid storage disease caused by NPC1 gene mutation. Our previous study found that, compared with wild-type (Npc1 +/+ ) mice, the renal volume and weight of Npc1 gene mutant (Npc1 -/- ) mice were significantly reduced. We speculate that Npc1 gene mutations may affect the basic structure of the kidneys of Npc1 -/- mice, and thus affect their function. Therefore, we randomly selected postnatal Day 28 (P28) and P56 Npc1 +/+ and Npc1 -/- mice, and observed the renal structure and pathological changes by haematoxylin-eosin staining. The level of renal fibrosis was detected by immunofluorescence histochemical techniques, and western blotting was used to detect the expression levels of apoptosis-related proteins and canonical Wnt signalling pathway related proteins. The results showed that compared with Npc1 +/+ mice, the kidneys of P28 and P56 Npc1 -/- mice underwent apoptosis and fibrosis; furthermore, there were obvious vacuoles in the cytoplasm of renal tubular epithelial cells of P56 Npc1 -/- mice, the cell bodies were loose and foam-like, and the canonical Wnt signalling pathway was abnormally activated. These results showed that Npc1 gene mutation can cause pathological changes in the kidneys of mice. As age increased, vacuoles developed in the cytoplasm of renal tubular epithelial cells, and apoptosis of renal cells, abnormal activation of the Wnt signalling pathway, and promotion of renal fibrosis increased., (© 2023 Stichting International Foundation for Animal Genetics.)

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., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

We describe gross and histopathological features of multiple ocular and neuro-ophthalmic abnormalities in a fox squirrel (Sciurus niger). Ophthalmic findings included severe bilateral microphthalmos, with the right eye more affected than the left. Histopathology confirmed severe microphthalmia, aphakia, disorganized retinal tissue and small optic nerves, as well as agenesis of the optic chiasm and optic tract. This combination of neuro-ophthalmic abnormalities has not been previously described in wild animals., Competing Interests: Declaration of competing interests The authors declared no conflicts of interest with respect to the research, authorship or publication of this article., (Published by Elsevier Ltd.)

A 10.5-y-old intact female capybara ( Hydrochoerus hydrochaeris ) with a history of chronic weight loss was euthanized following discovery by palpation of a large intra-abdominal mass. Postmortem examination revealed a large, firm, tan mass expanding the uterine body and extensively adhered to the jejunum and abdominal wall. Numerous pinpoint to 3-cm diameter, tan-to-red, raised masses were present throughout the parietal peritoneum, liver, lungs, and intestinal serosa. Histologic examination of the uterine mass revealed well-differentiated smooth muscle intermixed with abundant collagen, interspersed with a highly anaplastic spindle cell population extending to the serosa; the masses in the lung, liver, and peritoneum were histologically very similar to the anaplastic uterine spindle cells. Immunohistochemical staining of the uterus and lung confirmed smooth muscle origin of the anaplastic cells. To our knowledge, leiomyosarcoma has not been reported previously in a capybara, and the widespread metastases in this case represent an unusually aggressive presentation of this rare malignancy. The animal also had an incidental dermal histiocytoma, a tumor that has also not been reported previously in this species, to our knowledge.

Objective: To describe the clinical presentation, treatment, and treatment outcomes for companion rats (Rattus norvegicus) diagnosed with lymphoma., Animals: All rats that presented to the exotics service and underwent postmortem examination during the time period of 2008 through 2020 were evaluated., Procedures: The medical records of 35 rats were evaluated for an ante- or postmortem diagnosis of lymphoma. Cases with a diagnosis of lymphoma were further reviewed for signalment, presenting complaint, clinical signs observed on physical exam, diagnostic testing performed, and treatments administered. Postmortem gross and histologic findings were reviewed., Results: 7 out of 35 rats were diagnosed with lymphoma, either ante-mortem or postmortem. The most common presenting complaint that was present in all rats with lymphoma was respiratory abnormalities. Five out of 7 rats had radiographs performed, all of which had abnormalities noted in the thoracic cavity including pulmonary nodules, cranial mediastinal widening, or alteration to the cardiac silhouette. Diagnosis via cytologic aspirates was performed in 2 cases and each was diagnostic for lymphoma; however, even with treatment, survival time following initiation of chemotherapy was short (less than or equal to 24 days). The definitive diagnosis in the remainder of the cases was via necropsy., Clinical Relevance: Results suggest that lymphoma is a common neoplastic disease in rats and a thorough diagnostic work-up is indicated in any rat that presents for general malaise or respiratory signs.

The presence of Mycobacterium lepromatosis and Mycobacterium leprae in Eurasian red squirrel ( Sciurus vulgaris , ERS) carcasses throughout the British Isles, and leprosy as a disease, have recently been reported using histological and molecular diagnostic methods. In 2016, the first longitudinal study of ERS affected by leprosy was initiated. One of the main challenges was the reliable diagnosis of leprosy in live ERS, which is important for (a) welfare and case management and (b) surveillance or pretranslocation screening efforts. We explored diagnostic methods ranging from detailed clinical assessment and informative categorization of observed lesions, thermal imaging, serology (antiphenolic glycolipid-I antibody [αPGL-I] detection) to molecular methods (polymerase chain reaction [PCR]). For PCR the ear was established as the optimal sampling site. Based on the experiences from this 2-yr study we propose an objective categorization system for clinical lesions and a diagnostic framework for the combination of the diagnostic tools we found to be effective in live ERS: clinical assessment, αPGL-I serology, and PCR. Thermal imaging did not offer additional information for leprosy diagnostics in ERS. We propose an amended definition of leprosy lesions in ERS as "skin areas of local hair loss, in which a firm-rubbery, glossy swelling develops, that may ulcerate" and standardized terminology for describing ERS leprosy status. The information presented forms the basis of a consistent, reliable diagnostic and reporting system for leprosy cases in ERS.

The diagnosis and treatment of respiratory disease in pet guinea pigs, chinchillas, and degus still face profoundly serious challenges owing to their relatively small size, conspicuous clinical signs, difficulty for sampling, and insufficient scientific evidence to correlate signs and particular pathologies. This article is intended to summarize the available information on the relevant anatomy, physiology, and respiratory pathology in these species., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Air pollution has been associated with neuroinflammatory processes and is considered a risk factor for the development of neurodegenerative diseases. Volcanic environments are considered a natural source of air pollution. However, the effects of natural source air pollution on the central nervous system (CNS) have not been reported, despite the fact that up to 10% of the world's population lives near a historically active volcano. In order to assess the response of the CNS to such exposure, our study was conducted in the island of Sao Miguel (Azores, Portugal) in two different areas: Furnas, which is volcanically active one, and compared to Rabo de Peixe, a reference site without manifestations of active volcanism using Mus musculus as a bioindicator species. To evaluate the state of the astroglial population in the dentate gyrus in both samples, the number of astrocytes was determined using immunofluorescence methods (anti-GFAP and anti-GS). In addition, the astrocytic branches in that hippocampal area were examined. Our results showed an increase in GFAP+ astrocytes and a reduction in GS+ astrocytes in Furnas-exposed mice compared to animals from Rabo de Peixe. In addition, astrocytes in the dentate gyrus of chronically exposed animals exhibited longer branches compared to those residing at the reference site. Thus, reactive astrogliosis and astrocyte dysfunction are found in mice living in an active volcanic environment.

A mortality event of nine threatened smoky mice (Pseudomys fumeus) occurred in January 2020 at a captive breeding facility in southeastern Australia that was affected at the time by hazardous levels of bushfire smoke, despite being more than 20 km from the nearest fire. Pathologic and clinical observations indicated smoke inhalation was the cause of death. All animals had significant pulmonary lesions, notably pulmonary edema and congestion, and moderate amounts of dark brown to black pigmented intracellular and extracellular particles from <0.5-2.5 µm in diameter were observed in the central or hilar region of the lungs of four of six animals examined histologically. Deaths occurred between three and 30 d after exposure to smoke and, for seven animals in outdoor acclimatization enclosures, were associated with very high ambient temperature (>40 C). Similar mortalities did not occur in co-located parrots, suggesting differing species sensitivity to smoke inhalation. Our findings highlight the potential for smoke to be an underdiagnosed cause of mortality in free-ranging wildlife during bushfires and for bushfires to affect wildlife populations outside of burnt areas, including in unburnt refugia. Conservation interventions for wildlife after bushfires should consider and, where possible, mitigate the risk of animals dying due to increased respiratory demand following smoke inhalation injury., (© Wildlife Disease Association 2021.)

The review covers select disease conditions most frequently described in aging rodents (rats, mice, hamsters, guinea pigs), rabbits, and ferrets. The conditions are categorized by general organ systems, infectious diseases, and neoplasms. Two data systems, the Veterinary Medical Teaching Hospital and Comparative Pathology Laboratory at the University of California, Davis and Zoo/Exotic Pathology Service, Citrus Heights, California were used in the determining disease conditions to describe., Competing Interests: Disclosure The authors have no commercial or financial conflicts of interest nor any funding sources., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Chagas disease is a public health problem in America. Its parasite, Trypanosoma cruzi, presents different discrete typing units (DTUs), colonizes organs of mammalian hosts in chronic infections, and presents tropism for particular organs in experimental infections. We evaluated T. cruzi tropism towards organs on the naturally infected rodent Octodon degus, identifying the parasites' DTUs, by means of conventional PCR and hybridization. Almost all the analyzed organs presented T. cruzi. More than 42% of the tested oesophagus, skin, skeletal muscle, brain and intestine showed T. cruzi DNA. Other nine types of organs were infected in over 15%. These results suggest that there is some tropism by T. cruzi in chronically infected O. degus. DTU TcV was present in 92.5% of infected organs with identified DTUs; this DTU is frequently reported in human infections in the Southern Cone of South America. Few organs showed mixed DTU infections. This is one of the few reports on the outcome of chronic natural T. cruzi-infection in wild mammal hosts exposed to naturally infected vectors., Competing Interests: Declaration of competing interest The authors state that they do not have conflict of interest., (Copyright © 2020. Published by Elsevier Inc.)

During a 6-mo period, two 5-6 mo old female chinchillas ( Chinchilla lanigera ) were examined at the University of Colorado Anschutz Medical Campus after the discovery of firm, nonmobile masses in the left ventral cervical and left axillary region. Other than these findings and mild weight loss, both chinchillas' physical exams were normal. Bloodwork revealed an inflammatory leukogram characterized by leukocytosis, toxic neutrophils, lymphopenia, and monocytosis with mild, nonregenerative anemia. At necropsy, both masses were identified as abscesses. Streptococcus equi, subspecies zooepidemicus ( S. zooepidemicus ) was isolated in pure culture. Histology of the lungs, liver, spleen, and kidneys showed a marked increase in the numbers of both polymorphonuclear leukocytes and lymphocytes. Both animals were deemed unsuitable for research and were euthanized under isoflurane anesthesia by an intracardiac injection of pentobarbital sodium solution. S. zooepidemicus is an opportunistic, commensal organism found in the upper respiratory tract of horses. This organism has been documented to cause disease in other species and is zoonotic. Infections in humans have been reported, resulting in glomerulonephritis, endocarditis, septic arthritis, osteomyelitis, meningitis, and death. To aid in diagnosis and prospective surveillance of this bacteria, oral and nasal swabs were collected from the remaining cohort of chinchillas, and a qPCR screening assay was implemented. Within 12 mo, 4 of 41 additional females tested positive by culture or qPCR, resulting in a disease prevalence of 14% (6 of 43). However, only 2 of the additional 4 S. zooepidemicus positive animals developed clinical signs. The potential for the spread of infection, zoonosis, and adverse effects on research demonstrate that surveillance for S. zooepidemicus should be considered in a biomedical research environment.

As part of research and wildlife disease surveillance efforts, we performed necropsy examinations of 125 free-ranging ( n = 114) and captive ( n = 11) prairie dogs in Colorado from 2009 to 2017. From these cases, we identified three cases of thymic lymphoma in free-ranging Gunnison's prairie dogs ( Cynomys gunnisoni ), and we identified a novel retroviral sequence associated with these tumors. The viral sequence is 7700 nucleotides in length and exhibits a genetic organization that is consistent with the characteristics of a type D betaretrovirus. The proposed name of this virus is Gunnison's prairie dog retrovirus (GPDRV). We screened all 125 prairie dogs for the presence of GPDRV using PCR with envelope-specific primers and DNA extracted from spleen samples. Samples were from Gunnison's prairie dogs ( n = 59), black-tailed prairie dogs ( Cynomys ludovicianus ) ( n = 40), and white-tailed prairie dogs ( Cynomys leucurus ) ( n = 26). We identified GPDRV in a total of 7/125 (5.6%) samples including all three of the prairie dogs with thymic lymphoma, as well as spleen from an additional four Gunnison's prairie dogs with no tumors recognized at necropsy. None of the GPDRV-negative Gunnison's prairie dogs had thymic lymphomas. We also identified a related, apparently endogenous retroviral sequence in all prairie dog samples. These results suggest that GPDRV infection may lead to development of thymic lymphoma in Gunnison's prairie dogs.

Oxidative damage is often linked to reproduction; however, reproducing female Damaraland mole-rats (Fukomys damarensis) exhibit a reduction in oxidative damage relative to their non-reproductive, anovulatory, cohorts. Specifically, liver concentrations of malondialdehyde, a biomarker for lipid peroxidation, are significantly lower in reproducing females. We examined liver histology in reproductive, anovulatory and recently ovulating non-reproductive females, demonstrating an accumulation of lipid droplets only in the livers of anovulatory females and no fibrosis, cell death or inflammatory infiltrates in any group. Our observations suggest that anovulatory females experience a form of non-alcoholic fatty liver disease, which is reversed once they commence ovulation. We propose hormonal interactions that may underlie our observations.

Myoepitheliomas of the salivary glands have been described in laboratory mice, but not in rats. A 20-week-old Wistar (Han) female rat developed a white to grey firm mass at the left side of the neck. Histologically, the mass was unencapsulated and infiltrated the adjacent tissue. The tumour parenchyma was cell rich without acinar or tubular architecture. The tumour showed a palisading basal cell pattern adjacent to blood vessels. There were areas of necrosis filled with cellular debris. The tumour cells showed strong immunohistochemical labelling for pan-cytokeratin types I and II (AE1/AE3), pan-cytokeratin (cytokeratins 1, 5, 6 and 8), cytokeratin 5, cytokeratin 14, vimentin and podoplanin, and only very slight positivity for cytokeratin 8 in small areas. There was no expression of smooth muscle actin. Based on the histological appearance and the immunohistochemistry, the tumour was diagnosed as a malignant myoepithelioma of the parotid gland originating from the parotid duct., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Causes of morbidity and mortality and a survey of infectious disease agents were collated from wild and colony-raised endangered Amargosa voles ( Microtus californicus scirpensis ). Six voles from the wild and 295 voles in the captive-breeding colony were included in the study upon identification of an infectious agent during screening, identification of clinical signs of disease, or finding a pathological condition or infectious agent on necropsy. Findings included 28 significant or incidental pathological conditions of seven organ systems and 19 parasitic, viral, bacterial, or fungal agents. Several voles captured in the wild had fungal osteomyelitis of the tail that disseminated systemically in a vole brought from the wild to the colony and may have been caused by a Penicillium sp. Three voles reintroduced from the colony to the wild experienced inanition and subsequent severe hepatic and moderate renal tubular lipidosis. The most common significant pathological conditions in colony-reared voles were chronic interstitial nephritis with proteinosis; cardiomyopathy; trichobezoars that, in intestines or cecocolic junctions, sometimes induced local rupture or infarction with peritonitis; multifocal gastrointestinal ulceration and colibacillosis; acute renal tubular necrosis or nephritis; sepsis; hepatic and renal lipidosis; molar apical elongation sometimes progressing to invasion of the calvarium; and mammary tumors. Uncommon diagnoses included intervertebral disc disease; microvascular dysplasia; and multifocal bacterial abscessation. Common or clinically important infectious agents included Demodex sp. mites in hair follicles, Demodex sp. in esophageal mucosa, and an outbreak of tropical rat mites thought to have been introduced via the straw bedding; gastrointestinal Helicobacter sp.; attaching and effacing Escherichia coli ; and Citrobacter braakii , a possible zoonotic bacterium. This survey of species-specific diseases and pathogens was possible because the established health surveillance program that is part of the species recovery plan allowed for monitoring of voles throughout the duration of their natural life spans in captivity.

Genetically engineered mouse lines on a C57BL/6J background are widely employed as preclinical models to study neurodegenerative human disorders and brain tumors. However, because of the lack of comprehensive data on the spontaneous background neuropathology of the C57BL/6J strain, discriminating between naturally occurring changes and lesions caused by experimental mutations can be challenging. In this context, this study aims at defining the spectrum and frequency of spontaneous brain changes in a large cohort of C57BL/6J mice and their association with specific biological variables, including age and sex. Brains from 203 experimentally naive and clinically unremarkable C57BL/6J mice were collected and analyzed by means of histopathology and immunohistochemistry. Mice ranged in age from 3 to 110 weeks with 89 females, 111 males, and 3 unknowns. Sixteen different spontaneous lesion categories were described in this cohort. Age-related neurodegenerative and/or neuroinflammatory findings represented the most common pathologic changes and included (1) Hirano-like inclusions in the thalamic neurons, (2) neuroaxonal dystrophy in the medulla oblongata, (3) periodic acid-Schiff-positive granular deposits in the neuropil of the hippocampus, and (4) progressive neuroinflammation characterized by microgliosis and astrogliosis. Neoplastic conditions, developmental abnormalities, and circulatory disorders were rarely observed incidental findings. In conclusion, this study describes spontaneous age-related brain lesions of the C57BL/6J mouse and provides a reference for evaluating and interpreting the neuropathological phenotype in genetically engineered mouse models developed and maintained on this congenic background.

The naked mole-rat (NMR; Heterocephalus glaber )-a small, eusocial, subterranean rodent native to East Africa-is distinguished by its capability to live long and resist changes associated with the aging process. Notably, a growing amount of research has been dedicated to NMRs' multifactorial capacity to resist cancer. Since 2016, however, zoos have begun to document various neoplasms in a handful of individuals. We present herein radiographic, gross anatomic, and histopathologic features of a case of a sacral chordoma in a geriatric female. Chordomas originate in notochordal remnants. These spinal tumors are most commonly seen in ferrets; chordomas are rare in humans, can be difficult to treat, and need wide surgical margins.

A spontaneously arising, loss-of-function mutation in the RNA binding motif protein 20 ( Rbm20 ) gene, which encodes a nuclear splicing protein, was previously identified as the underlying reason for expression of an abnormally large TITIN (TTN) protein in a rat model of cardiomyopathy. An outbreak of Pseudomonas aeruginosa led to submission of rats with dyspnea, sneezing, lethargy, nasal discharge, and/or unexpected death for diagnostic evaluation. Necropsy revealed underlying megaesophagus in Rbm20 -/- rats. Further phenotyping of this rat strain and determination of the size of esophageal TTN was undertaken. The Rbm20 -defective rats developed megaesophagus at an early age (26 weeks) with high frequency (13/32, 41%). They also often exhibited secondary rhinitis (9/32, 28%), aspiration pneumonia (8/32, 25%), and otitis media/interna (6/32, 19%). In addition, these rats had a high prevalence of hydronephrosis (13/32, 41%). RBM20 is involved in splicing multiple RNA transcripts, one of which is the muscle-specific protein TTN. Rbm20 mutations are a significant cause of dilated cardiomyopathy in humans. In Rbm20 -defective rats, TTN size was significantly increased in the skeletal muscle of the esophagus. Megaesophagus in this rat strain (maintained on a mixed genetic background) is hypothesized to result from altered TTN stretch signaling in esophageal skeletal muscle. This study describes a novel mechanism for the development of megaesophagus, which may be useful for understanding the pathogenesis of megaesophagus in humans and offers insights into potential myogenic causes of this condition. This is the first report of megaesophagus and other noncardiac pathogenic changes associated with mutation of Rbm20 in any species.

The NOD.Cg- Prkdc scid Il2rg tm1Wjl /SzJ strain (NOD scid gamma, NSG) is a severely immunodeficient inbred laboratory mouse used for preclinical studies because it is amenable to engraftment with human cells. Combining scid and Il2rg null mutations results in severe immunodeficiency by impairing the maturation, survival, and functionality of interleukin 2-dependent immune cells, including T, B, and natural killer lymphocytes. While NSG mice are reportedly resistant to developing spontaneous lymphomas/leukemias, there are reports of hematopoietic cancers developing. In this study, we characterized the immunophenotype of spontaneous lymphoma/leukemia in 12 NSG mice (20 to 38 weeks old). The mice had a combination of grossly enlarged thymus, spleen, or lymph nodes and variable histologic involvement of the bone marrow and other tissues. All 12 lymphomas were diffusely CD3, TDT, and CD4 positive, and 11 of 12 were also positive for CD8, which together was consistent with precursor T-cell lymphoblastic lymphoma/leukemia (pre-T-LBL). A subset of NSG tissues from all mice and neoplastic lymphocytes from 8 of 12 cases had strong immunoreactivity for retroviral p30 core protein, suggesting an association with a viral infection. These data highlight that NSG mice may develop T-cell lymphoma at low frequency, necessitating the recognition of this spontaneously arising disease when interpreting studies.

Toxoplasma gondii infection was diagnosed in 2 captive Patagonian maras ( Dolichotis patagonum ). One animal developed fatal systemic toxoplasmosis and had concurrent localized bacterial and fungal infections; its daughter remained clinically healthy. Microscopic findings included acute, coagulative necrosis, lymphohistiocytic inflammatory infiltrates, and extra- and intracellular parasites in the liver, myocardium, urinary bladder, and adrenal glands of the diseased animal. PCR and subsequent genotyping of parasites from fresh tissue from both cases revealed infection with T. gondii genotype II. Direct agglutination testing of blood from the healthy individual revealed high levels of T. gondii IgG antibodies. T. gondii is a potential cause of disease and lethality in captive and wild Patagonian maras, and toxoplasmosis should be considered when managing and providing veterinary care for this species.

A 2-year-old male Djungarian hamster (Phodopus sungorus) and a 1-year-old male Roborovski hamster (Phodopus roborovskii) were presented with expansile subcutaneous masses. The well-demarcated, firm, grey, multilobulated nodules displayed an homogeneous, white-grey cut surface. Histological examination revealed a neoplasm of variable cellularity consisting of spindle-shaped to polygonal 'ganglion cell-like' cells with abundant, amphophilic, vacuolated cytoplasm. Immunohistochemically, the tumour cells were labelled intensely for vimentin and nestin, moderately for neuron specific enolase and weakly for melan-A. The histological and immunohistochemical findings were suggestive of an atypical fibroma with evidence of a neuroectodermal phenotype., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

During a screen for vascular phenotypes in aged laboratory mice, a unique discrete phenotype of hyaline arteriolosclerosis of the intertubular arteries and arterioles of the testes was identified in several inbred strains. Lesions were limited to the testes and did not occur as part of any renal, systemic, or pulmonary arteriopathy or vasculitis phenotype. There was no evidence of systemic or pulmonary hypertension, and lesions did not occur in ovaries of females. Frequency was highest in males of the SM/J (27/30, 90%) and WSB/EiJ (19/26, 73%) strains, aged 383 to 847 days. Lesions were sporadically present in males from several other inbred strains at a much lower (<20%) frequency. The risk of testicular hyaline arteriolosclerosis is at least partially underpinned by a genetic predisposition that is not associated with other vascular lesions (including vasculitis), separating out the etiology of this form and site of arteriolosclerosis from other related conditions that often co-occur in other strains of mice and in humans. Because of their genetic uniformity and controlled dietary and environmental conditions, mice are an excellent model to dissect the pathogenesis of human disease conditions. In this study, a discrete genetically driven phenotype of testicular hyaline arteriolosclerosis in aging mice was identified. These observations open the possibility of identifying the underlying genetic variant(s) associated with the predisposition and therefore allowing future interrogation of the pathogenesis of this condition.

An adult female Cape porcupine ( Hystrix africaeaustralis ) was presented because of marked abdominal distension, acute dyspnea, and lethargy. Physical examination and standard radiographs revealed marked and diffuse gaseous dilation of the stomach and intestines of undetermined origin. The porcupine died despite medical therapy and surgical intervention. Postmortem examination revealed chronic fungal ( Aspergillus flavus ) rhinitis. Given that rodents are obligate nasal breathers, the rhinitis likely resulted in substantial upper airway obstruction leading to aerophagia.

H1 parvovirus (H1PV) infection in rats is of concern to the research community as infection may compromise rodent-based experiments. The aim of this study was to evaluate the influence of H1PV infection on rat gut microbiota. Inbred Wistar rats were infected with H1PV by routine gavage and clinical signs were recorded. Gross anatomical and histopathological examination of the gut was performed, as was immune cytokine analysis. The cecal contents were also collected for 16S rRNA sequencing. Gross anatomical examination showed distention of the ileum associated with flatulence after infection, while histopathological examination showed hyperemia and inflammatory cell infiltration in the ileum. Upregulation of the interleukin-6 in sera in H1PV infected rats was also detected. The gut microbiota had been significantly changed in H1PV infected rats: there was a reduction in several bacteria species including probiotic bacteria from the genera Parabacteroides and Butyricicoccus, while others were increased, including those from the genera Methanobrevibacter and Syntrophococcus. Taken together, these results demonstrate that chronic H1PV infection in rats leads to gastrointestinal inflammation with flatulence. The gut microbiota alterations were associated with decreased polymorphisms, reduced abundance of probiotic bacteria and increased abundance of methane-producing bacteria., (© FEMS 2019.)

Canine brucellosis, caused by Brucella canis, is a disease of dogs and represents a public health concern as it can be transmitted to humans. Canine brucellosis is on the rise in the United States and there is currently no vaccine for use in dogs. Mice have been extensively utilized to investigate host-pathogen interactions and vaccine candidates for smooth Brucella species and could serve a similar role for studying B. canis. However, comparatively little is known about B. canis infection in mice. The objective of this study was to characterize the kinetics of colonization and pathogenicity of B. canis in mice in order to evaluate the mouse as a model for studying this pathogen. C57BL/6 mice were inoculated intraperitoneally with 105, 107, or 109 CFU of Brucella canis RM6/66 and euthanized 1-, 2-, 4-, 6-, 9-, and 12-weeks post-inoculation. B. canis induced splenomegaly in mice infected with 109 CFU at 1- and 2 weeks post-inoculation while no gross lesions were observed in other dose groups. Infection at the two higher doses resulted in dose-dependent granulomatous hepatitis and histiocytic infiltration of the spleen and mesenteric lymph nodes by 1-2 weeks. B. canis was cultured from the liver, spleen, uterus, bone marrow, lung, and kidney in all groups with colonization declining at a slow but steady rate throughout the experiment. Clearance was achieved by 9 weeks 105 CFU group and by 12 weeks in the 107 CFU group, while B. canis persisted in the spleen until 12 weeks in the highest dose group. Although B. canis does not demonstrate significant replication in C57BL/6 mice, it has the ability to establish an infection, induce splenomegaly, and persist for several weeks in multiple organs. Moreover, 1 x 107 CFU appears to be a suitable challenge dose for investigating vaccine safety., Competing Interests: The authors have declared that no competing interests exist.

We describe a black-tailed prairie dog (Cynomys ludovicianus) with a benign biphasic nodular tumour that recurred as a malignant biphasic tumour at the same site 2 years after resection. Both tumours were biphasic with regard to the glandular epithelium and basal cells and contained little of the mucus, cartilage or fibrous tissue that characterize pleomorphic adenoma and carcinoma ex-pleomorphic adenoma. Both the first and second tumours exhibited histopathological features similar to those exhibited by human basal cell adenoma and adenocarcinoma, respectively. Both were resected and the animal was alive with no recurrence or metastasis at the time of writing, 9 months after the second surgery., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

To achieve a contemporary understanding of the common and rare lesions that affect wild, urban Norway rats ( Rattus norvegicus), we conducted a detailed pathology analysis of 672 rats from Vancouver, British Columbia, Canada. Grossly evident lesions, such as wounds, abscesses, and neoplasms, were present in 71 of 672 rats (11%) and tended to be severe. The most common and significant lesions were infectious and inflammatory, most often affecting the respiratory tract and associated with bite wounds. We assessed a subset of rats (up to n = 406 per tissue) for the presence of microscopic lesions in a variety of organ systems. The most frequent lesions that could impact individual rat health included cardiomyopathy (128 of 406; 32%), chronic respiratory tract infections as indicated by pulmonary inducible bronchus-associated lymphoid tissue (270 of 403; 67%), tracheitis (192 of 372; 52%), and thyroid follicular hyperplasia (142 of 279; 51%). We isolated 21 bacterial species from purulent lesions in rats with bacterial infections, the most frequent of which were Escherichia coli, Enterococcus sp., and Staphylococcus aureus. Parasitic diseases in rats resulted from infection with several invasive nematodes: Capillaria hepatica in the liver (242 of 672; 36%), Eucoleus sp. in the upper gastrointestinal tract (164 of 399; 41%), and Trichosomoides crassicauda in the urinary bladder (59 of 194; 30%). Neoplastic, congenital, and degenerative lesions were rare, which likely reflects their adverse effect on survival in the urban environment. Our results establish a baseline of expected lesions in wild urban rats, which may have implications for urban rat and zoonotic pathogen ecology, as well as rat control in cities worldwide.

Calodium hepaticum (Trichinellida: Capillaridae) is a parasitic nematode of mammals distributed worldwide. Although this parasite can infect the liver of a wide diversity of mammals (including humans), it is mostly associated with Muroidea hosts. Sigmodontinae rodents were recently recognized as important hosts of this parasite in Argentina, but the impact of this parasitism on these hosts has not been established. Here we report results of histopathological analyses of 40 livers of Akodon azarae infected with C. hepaticum. Lesions were classified into 4 categories: level 0, absence of lesions; level 1, with focal granulomatous hepatitis; level 2, presence of multifocal granulomatous hepatitis, fibrosis and focal necrosis with neutrophils, and level 3, absence of intact adult parasites, diffuse distribution, necrosis, and fibrosis. Most samples presented lesions of level 2 (55%), but all categories of lesions were found. This is the first study to describe the lesions caused by C. hepaticum in the liver of Sigmodontinae rodents, and the results suggest that infection by this parasite is costly to A. azarae populations.

Background: Several species of nematodes included in the superfamily Metastrongyloidea are recognized agents of parasitic infections in felines. Aelurostrongylus abstrusus is the most prevalent species affecting the respiratory system of domestic cats. The route of infection in cats is supposed to be through ingestion of gastropod intermediate or paratenic hosts. However, because gastropods are not the preferred preys of cats, rodents were suggested to play an important role as paratenic hosts in the biological cycle of A. abstrusus and in the epidemiology of aelurostrongylosis., Results: Two studies were conducted to document histopathological tissue lesions in mice experimentally infected with A. abstrusus third-stage larvae (L3) (Study 1), and to determine larval counts in their organs (Study 2). Additionally, cats were fed with experimentally infected mice to assess their infectivity. Aelurostrongylus abstrusus L3 were recovered from the liver, spleen, brain, skeletal muscle and gastrointestinal tract tissues by artificial digestion, and heart, spleen and brain tested positive for A. abstrusus at molecular diagnosis. Multifocal encephalitis and meningitis and glial nodules were the most common histopathological lesions found in mice inoculated with A. abstrusus. All cats shed first-stage larvae of A. abstrusus after ingestion of mice inoculated with this nematode., Conclusions: In this study, we provide information on the anatomical localization, histopathological alterations and rate of recovery of A. abstrusus L3 in mice, and confirm their infectivity to cats (definitive hosts) after feeding on infected mice (paratenic hosts). Data presented here add knowledge to further understand the biology of A. abstrusus in mice and underline the importance of mice as paratenic hosts of this nematode for the infection of cats.

Toxoplasma gondii is an apicomplexan parasite that infects almost all warm-blooded animals. Little is known about how the parasite virulence in mice extrapolates to other relevant hosts. In the current study, in vitro phenotype and in vivo behavior in mice and sheep of a type II T. gondii isolate (TgShSp1) were compared with the reference type II T. gondii isolate (TgME49). The results of in vitro assays and the intraperitoneal inoculation of tachyzoites in mice indicated an enhanced virulence for the laboratory isolate, TgME49, compared to the recently obtained TgShSp1 isolate. TgShSp1 proliferated at a slower rate and had delayed lysis plaque formation compared to TgME49, but it formed more cyst-like structures in vitro . No mortality was observed in adult mice after infection with 1-10 5 tachyzoites intraperitoneally or with 25-2,000 oocysts orally of TgShSp1. In sheep orally challenged with oocysts, TgME49 infection resulted in sporadically higher rectal temperatures and higher parasite load in cotyledons from ewes that gave birth and brain tissues of the respective lambs, but no differences between these two isolates were found on fetal/lamb mortality or lesions and number of T. gondii -positive lambs. The congenital infection after challenge at mid-pregnancy with TgShSp1, measured as offspring mortality and vertical transmission, was different depending on the challenged host. In mice, mortality in 50% of the pups was observed when a dam was challenged with a high oocyst dose (500 TgShSp1 oocysts), whereas in sheep infected with the same dose of oocysts, mortality occurred in all fetuses. Likewise, mortality of 9 and 27% of the pups was observed in mice after infection with 100 and 25 TgShSp1 oocysts, respectively, while in sheep, infection with 50 and 10 TgShSp1 oocysts triggered mortality in 68 and 66% of the fetuses/lambs. Differences in vertical transmission in the surviving offspring were only found with the lower oocyst doses (100% after infection with 10 TgShSp1 oocysts in sheep and only 37% in mice after infection with 25 TgShSp1 oocysts). In conclusion, virulence in mice of T. gondii type II isolates may not be a good indicator to predict the outcome of infection in pregnant sheep.

This article presents the historical control data of spontaneous tumors in Tg.rasH2 published in 2013 (2004-2012) and compares and contrasts it to more recent data collected from 2013 to 2018, reporting differences in the average percentage incidences or incidence ranges as well as the incidence of new tumors. In 2013, we published a comprehensive review of spontaneous tumors in Tg.rasH2 mice used in 26-week carcinogenicity studies, which included data from control dose groups from 26 studies and a total of 710 mice per sex. The total database, now including the more recent data, has nearly doubled the number of animals, completing to date a total of 52 studies in males and 51 studies in females for a total of 1,615 male mice and 1,560 female mice, respectively. In this article, we compare the data collected from 2004 to 2012 against the data collected from 2013 to 2018 and the overall tumor incidence change.

The circulation of mammarenaviruses in rodent populations of the Mekong region has recently been established, with a genetic variant of Wēnzhōu virus, Cardamones virus, detected in two Rattus species. This study tests the potential teratogenic effects of Wēnzhōu infection on the development of a Murid rodent, Rattus exulans. Using direct virus detection, morphological records and comparative analyses, a link was demonstrated between host infection status and host morphologies (the spleen irrespective of weight, the skull shape and the cranial cavity volume) at the level of the individual (females only). This study demonstrates that mammarenavirus infections can impact natural host physiology and/or affect developmental processes. The presence of an infecting micro-parasite during the development of the rat may lead to a physiological trade-off between immunity and brain size. Alternatively, replication of virus in specialized organs can result in selective morphologic abnormalities and lesions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Odontoameloblastomas (previously incorporated within ameloblastic odontomas) are matrix-producing odontogenic mixed tumors and are closely related in histologic appearance to the 2 other types of matrix-producing odontogenic mixed tumors: odontomas and ameloblastic fibro-odontomas. The presence or absence of intralesional, induced non-neoplastic tissue must be accounted for in the diagnosis. Herein we describe a naturally occurring odontoameloblastoma with extensive chondroid cementum deposition in a guinea pig ( Cavia porcellus). Microscopically, the mass featured palisading neoplastic odontogenic epithelium closely apposed to ribbons and rings of a pink dental matrix (dentinoid), alongside extensive sheets and aggregates of chondroid cementum. The final diagnosis was an odontoameloblastoma given the abundance of odontogenic epithelium in association with dentinoid but a paucity of pulp ectomesenchyme. Chondroid cementum is an expected anatomical feature of cavies, and its presence within the odontoameloblastoma was interpreted as a response of the ectomesenchyme of the dental follicle to the described neoplasm. Our case illustrates the inductive capabilities of odontoameloblastomas while highlighting species-specific anatomy that has resulted in a histologic appearance unique to cavies and provides imaging and histologic data to aid diagnosis of these challenging lesions.

A 3-year-old intact female guinea pig (Cavia porcellus) was presented for acute anorexia. Medical and surgical treatments for cystitis and ovarian cysts, respectively, did not prevent continuous weight loss. Computed tomography and histopathological analysis revealed a chondroblastic osteosarcoma of the right middle ear, which has not been reported in this species.

Sprague-Dawley rats are amongst the most widely used animals in biomedical research and malignant lymphoma has long been known to be a frequent neoplasm in these animals. A 9-month-old male control Sprague-Dawley rat from a toxicity study showed gelatinous material in the cranial cavity and dark, thickened cerebral meninges at necropsy. At microscopic evaluation of the temporal bone, neoplastic lymphocytes were seen invading several structures of the middle ear. The neoplastic cells appeared to extend from the marrow of the temporal bone, covered the dorsal part of the tympanic cavity wall, and surrounded and infiltrated the base of the tensor tympani muscle as well as the chorda tympani branch of the facial nerve. The lymphoma was generalized; neoplastic lymphocytes were also noted in numerous other tissues. Literature regarding neoplasms of the middle and inner ear in animals is scarce and, to our knowledge, this is the first report of a lymphoma involving the middle ear of a rat.

Molar apical elongation (MAE) was the leading cause for euthanasia or death in a captive breeding colony of endangered Amargosa voles ( Microtus californicus scirpensis). Clinical signs included ocular discharge, abnormal mastication, dyspnea, abnormal mentation, weight loss, and death. Although the severity varied, all molars in all quadrants were affected. When severe, the overgrown molar reserve crown and apex protruded into the nasal meatuses, the orbit, the calvarial vault and through the ventral margin of the mandible. Overall prevalence in the colony was 63% (92/146 voles) and increased to 77% in aged voles (>1 year). Mean age of onset was 5.3 months (1.7-11.2 months). Progression to extreme severity occurred over 1 to 3 months. Mean survival was 10.9 months (7.1-21.7 months). Histologically, the lesion was characterized by odontogenic hyperplasia and dysplasia. MAE was also documented in museum specimens of 2 other M. californicus subspecies ( M. californicus californicus, M. californicus vallicola) and 3 other Microtus species ( M. montanus, M. pennsylvanicus, M. socialis). In the M. californicus californicus collection, overall prevalence was 35.1% (129/368 skulls) and increased to 77.3% in aged voles (>1 year). A probable genetic influence was identified in the museum collection of M. californicus californicus. The etiopathogenesis of MAE is likely multifactorial, due to (1) inherent continuous odontogenic proliferation, (2) inadequate occlusal attrition, and (3) possible heritable disease susceptibility. In captivity, dietary or other management of occlusal attrition to prevent or delay MAE is a fundamental concern.

A 2-mo-old Vancouver Island marmot ( Marmota vancouverensis), housed at a quarantined breeding facility, presented for acute obtundation and vestibular ataxia. Physical examination revealed poor growth compared with littermates, poor nutritional condition, and mild dehydration. The animal's condition deteriorated over 24 hr, and it was euthanized following the development of generalized seizures. No gross abnormalities were observed upon postmortem evaluation. Histologic evaluation revealed severe, multifocal, granulomatous and lymphoplasmacytic meningoencephalomyelitis and interstitial nephritis, with intralesional, intracytoplasmic spore-filled, parasitophorous vacuoles and segmental, multi-organ, fibrinoid vasculitis (disseminated encephalitozoonosis). The etiologic agent was evident by hematoxylin and eosin and Gram-chromotrope stains, and confirmed as Encephalitozoon cuniculi by polymerase chain reaction on brain tissue. Sequencing of the internal transcribed spacer region of the rRNA gene showed 100% homology with E. cuniculi strain IV, which is a newly described genotype. This is the first report of encephalitozoonosis in this critically endangered species.