Gross, microscopic, radiologic, echocardiographic and haematological findings in rats experimentally infected with Angiostrongylus cantonensis.

Although the gross and microscopic pathology in rats infected with Angiostrongylus cantonensis has been well described, corresponding changes detected using diagnostic imaging modalities have not been reported. This work describes the cardiopulmonary changes in mature Wistar rats chronically infected with moderate burdens of A. cantonensis using radiology, computed tomography (CT), CT angiography, echocardiography, necropsy and histological examinations. Haematology and coagulation studies were also performed. Thoracic radiography, CT and CT angiography showed moderately severe alveolar pulmonary patterns mainly affecting caudal portions of the caudal lung lobes and associated dilatation of the caudal lobar pulmonary arteries. Presumptive worm profiles could be detected using echocardiography, with worms seen in the right ventricular outflow tract or straddling either the pulmonary and/or the tricuspid valves. Extensive, multifocal, coalescing dark areas and multiple pale foci affecting the caudal lung lobes were observed at necropsy. Histologically, these were composed of numerous large, confluent granulomas and fibrotic nodules. Adult worms were found predominantly in the mid- to distal pulmonary arteries. An inflammatory leukogram, hyperproteinaemia and hyperfibrinogenaemia were found in most rats. These findings provide a comparative model for A. cantonensis in its accidental hosts, such as humans and dogs. In addition, the pathological and imaging changes are comparable to those seen in dogs infected with Angiostrongylus vasorum, suggesting rats infected with A. cantonensis could be a model for dogs with A. vasorum infection.

Multilobular tumor of bone on the forehead of a guinea pig.

Multilobular tumor of bone (MLTB) is an infrequent, slow-growing, bone neoplasm formed predominantly on the head. These tumors can behave as malignant neoplasms clinically and pathologically and can metastasize occasionally. No cases of MLTB in rodents have been reported, to our knowledge. We describe a novel case of an MLTB in a guinea pig. An adult guinea pig had an exophytic mass fixed on the frontal bone, maxilla, and nasal bone. On radiography, the mass had a spherical contour and variable density and was formed on the surface of the cranial bones. The mass was excised surgically. The cut surface was light-yellow to milky-white and had a granular texture with fine fibrous septa. Histologically, the neoplasm had a multilobular pattern, which consisted of many islands of bone and/or cartilage matrix surrounded by small cells and separated by fibrous septa, which closely resembles the equivalent neoplasm in dogs.

Non-aversive photographic measurement method for subcutaneous tumours in nude mice.

We have developed a new method for the measurement of subcutaneous tumour volume which consists in taking photographs of mice in their home cages, to refine the standard method of measurement with calipers. We consider this new method to be non-aversive, as it may be more compatible with mice behavioural preferences and, therefore, improve their welfare. Photographs are captured when mice voluntarily go into an acrylic tube containing graph paper that is later used as a scale. Tumour volumes measured with the caliper and the non-aversive photographic method were compared to those obtained by water displacement volume and weight. Behavioural and physiological changes were evaluated to assess animal welfare. Significant differences were found between measurements obtained with the caliper and the non-aversive photographic method, v. the reference volume acquired by water displacement (P < 0.001). Nevertheless, there was good consistency for these measurements when tumours were measured repeatedly, with all Intra-Class Correlation Coefficients above 0.95. Mice on which the non-aversive photographic method was employed were significantly less reluctant to establish contact with the experimenter (P < 0.001) and behaved less anxiously in a modified-Novelty Suppressed Feeding test. Particularly, statistically significant differences were found in connection with the latency to eat an almond piece (P < 0.05), the frequency of grooming (P < 0.001) and the frequency of defecation (P < 0.001). Corticosterone concentration in faeces and blood glucose were determined and no significant changes were found. Therefore, we propose the non-aversive photographic method to measure subcutaneous tumours as a way to refine methodologies in the field of experimental oncology.

Supernumerary Incisors in CB6F1 Mice Conditioned with Chemotherapy and Total Body Irradiation before Bone Marrow Transplantation.

Multiple adult female CB6F1 mice presented with supernumerary incisors after preconditioning with chemotherapy and total body irradiation for bone marrow transplantation (BMT). Mice received nonmyeloablative total body irradiation (3 Gy) and either cyclophosphamide or bendamustine, followed by BMT and posttransplantation cyclophosphamide or bendamustine. Here we describe the clinical presentation, µCT findings, and histopathologic evaluation of the affected mice. These analyses confirmed the gross diagnosis and revealed details of the abnormal tooth morphology. We surmise that the combination of total body irradiation and chemotherapy resulted in the abnormal formation of supernumerary incisors. Supernumerary teeth should be considered as a potential confounding factor in tracking weight loss after BMT. These conditions can be managed to allow animals to reach their intended scientific endpoint.

Chondroblastic osteosarcoma of the middle ear in a guinea pig (Cavia porcellus).

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.

Ostéosarcome chondroblastique de l'oreille moyenne chez un cobaye(Cavia porcellus). Un cobaye (Cavia porcellus) femelle de 3 ans a été présentée pour une anorexie d'apparition aiguë. Malgré la prise en charge médicale et chirurgicale d'une cystite et de kystes ovariens, l'individu continuait de perdre du poids. L'examen tomodensitométrique et l'analyse histologique ont mis en évidence un ostéosarcome chondroblastique de l'oreille moyenne, ce qui n'a jamais été rapporté dans cette espèce.(Traduit par Dre Ophélie Cojean).

Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig.

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.

Apical Elongation of Molar Teeth in Captive Microtus Voles.

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.

Effects of mammarenavirus infection (Wenzhou virus) on the morphology of Rattus exulans.

The circulation of mammarenaviruses in rodent populations of the Mekong region has recently been established, with a genetic variant of Wenzhou virus, Cardamones virus, detected in two Rattus species. This study tests the potential teratogenic effects of Wenzhou 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.

Urethral diverticulum and urolithiasis in a female guinea pig (Cavia porcellus).

CASE DESCRIPTION A 5-year-old sexually intact female guinea pig was evaluated because of mild dysuria and a subcutaneous mass located cranioventral to the urogenital openings. CLINICAL FINDINGS Non-contrast-enhanced CT and surgical exploration of the distal aspect of the urethra revealed a urethral diverticulum with an intraluminal urolith. Analysis revealed that the urolith was composed of calcium carbonate and struvite. TREATMENT AND OUTCOME The urolith was surgically removed and ablation of the urethral diverticulum was attempted. Approximately 3 months later, the guinea pig was reevaluated for masses in the perineal region, and positive-contrast urethrocystography revealed 2 uroliths present in the same diverticulum. Uroliths were manually expressed with the patient under general anesthesia. Approximately 2 weeks later, urethroplasty was performed to create an enlarged stoma with the diverticulum, thereby preventing urine from pooling in the diverticulum and potentially reducing the risk of future urolith formation. The urethroplasty site healed well with no reported complications or evidence of urolith recurrence 6 months after surgery. CLINICAL RELEVANCE Urolithiasis is common in guinea pigs, and urethral diverticulum and intraluminal urolith formation should be considered as a potential differential diagnosis for a subcutaneous mass along the distal aspect of the urethra. Creation of a urethral stoma from a urethral diverticulum via urethroplasty achieved a successful outcome in this patient.

COMPUTED TOMOGRAPHIC FEATURES OF INCISOR PSEUDO-ODONTOMAS IN PRAIRIE DOGS (CYNOMYS LUDOVICIANUS).

Maxillary incisor pseudo-odontomas are common in pet prairie dogs and can cause progressive respiratory obstruction, while mandibular pseudo-odontomas are rarely clinically significant. The aim of this retrospective cross-sectional study was to describe CT features of maxillary and mandibular incisor pseudo-odontomas vs. normal incisors in a group of pet prairie dogs. All pet prairie dogs with head CT scans acquired during the period of 2013-2015 were included. A veterinary radiologist who was aware of final diagnosis reviewed CT scans and recorded qualitative features of affected and normal incisors. Mean density values for the pulp cavity and palatal and buccal dentin were also recorded. A total of 16 prairie dogs were sampled (12 normal maxillary incisors, 20 confirmed maxillary incisor pseudo-odontomas, 20 normal mandibular incisors, 12 presumed mandibular incisor pseudo-odontomas). Maxillary incisors with confirmed pseudo-odontomas had a significantly hyperattenuating pulp and dentin in the reserve crown and apical zone, when compared to normal maxillary incisors. Pseudo-odontomas appeared as enlargements of the apical zone with a globular/multilobular hyperattenuating mass formation haphazardly arranged, encroaching on midline and growing caudally and ventrally. Presumed mandibular incisor pseudo-odontomas had similar CT characteristics. In 60% of prairie dogs with maxillary incisor pseudo-odontomas, the hard palate was deformed and the mass bulged into the oral cavity causing loss of the palatine bone. The common nasal meatus was partially or totally obliterated in 81.8% of prairie dogs with maxillary pseudo-odontomas. Findings supported the use of CT for characterizing extent of involvement and surgical planning in prairie dogs with pseudo-odontomas.

Anatomy and Disorders of the Oral Cavity of Chinchillas and Degus.

Dental disease is among the most common causes for chinchillas and degus to present to veterinarians. Most animals with dental disease present with weight loss, reduced food intake/anorexia, and drooling. Degus commonly present with dyspnea. Dental disease has been primarily referred to as elongation and malocclusion of the cheek teeth. Periodontal disease, caries, and tooth resorption are common diseases in chinchillas, but are missed frequently during routine intraoral examination, even performed under general anesthesia. A diagnostic evaluation, including endoscopy-guided intraoral examination and diagnostic imaging of the skull, is necessary to detect oral disorders and to perform the appropriate therapy.

Diagnostic Imaging of Dental Disease in Pet Rabbits and Rodents.

Diagnostic imaging techniques are of paramount importance for dentistry and oral disorders of rabbits, rodents, and other exotic companion mammals. Aside from standard radiography, stomatoscopy is a complementary tool allowing a thorough and detailed inspection of the oral cavity. Computed tomography (CT) generates multiple 2-dimensional views and 3-dimensional reconstructions providing superior diagnostic accuracy also useful for prognosis and treatment of advanced dental disease and its related complications. MRI is a diagnostic imaging technique additional to CT used primarily to enhance soft tissues, including complex odontogenic abscesses.

Anatomy and Disorders of the Oral Cavity of Rat-like and Squirrel-like Rodents.

The order Rodentia comprises more than 2000 species divided into 3 groups based on anatomic and functional differences of the masseter muscle. Myomorph and sciuromorph species have elodont incisors and anelodont cheek teeth, unlike hystrichomorph species which have full anelodont dentition. Diseases of incisors and cheek teeth of rat-like and squirrel-like rodents result in a wide variety of symptoms and clinical signs. Appropriate diagnostic testing and imaging techniques are required to obtain a definitive diagnosis, formulate a prognosis, and develop a treatment plan. A thorough review of elodontoma, odontoma, and pseudo-odontoma is provided, including treatment of pseudo-odontomas in prairie dogs.

Magnetic Resonance Imaging of Reptiles, Rodents, and Lagomorphs for Clinical Diagnosis and Animal Research.

MRI is a great diagnostic tool for evaluating exotic animals, particularly in clinical practice and in research with animal models. Here we review various aspects of MRI of reptiles, rodents, and lagomorphs, including the indications for this modality, the preparation of subjects, and protocols for imaging various organs and the musculoskeletal system. Protocols for the anesthesia and immobilization of subjects to facilitate their imaging are discussed also.

Elodontoma in captive southern red-backed voles (Myodes gapperi).

Five southern red-backed voles (Myodes gapperi) of the first generation of a wild-caught breeding colony were presented with lesions at the maxillary incisors consistent with elodontoma. The affected animals had a history of chronic weight loss, were >16 months of age, and were siblings. Radiographs of the head showed multiglobular to irregularly outlined mineral opacity masses at the apices of the maxillary incisors. On necropsy, maxillary incisor teeth were not grossly visible, and a gingival ulceration was observed at the expected site of eruption. Microscopically, the apical region of the maxillary incisors was thickened or replaced by irregular dental tissue masses consistent with elodontoma. This is the first report to describe elodontoma in red-backed voles.

Urethral obstruction by seminal coagulum is associated with medetomidine-ketamine anesthesia in male mice on C57BL/6J and mixed genetic backgrounds.

Male and female mice were anesthetized by intraperitoneal injection with a mixture delivering 0.5 mg/kg medetomidine and 50 mg/kg ketamine to achieve immobilization for whole-body radiographs and bone densitometry, as part of a phenotypic screen for bone and mineral disorders in mice carrying genetic modifications induced through mutagenesis with N'-ethyl-N'-nitrosourea. Morbidity and mortality occurred in 19 of 628 (3%) of male mice 24 to 72 h after a seemingly uneventful recovery from anesthesia. No morbidity or mortality occurred in 1564 female mice that were similar in age to the affected male mice and that underwent the same procedure. Of the 7 male mice that underwent postmortem examinations, 5 had urinary bladders grossly distended with urine and 1 had ascites. In addition, the pelvic or penile urethra in 5 of the examined male mice was obstructed with seminal coagulum associated with varying degrees of erosion of the urothelial lining and inflammation of the urethra. In 2 of these animals, from which plasma samples were recovered, azotemia, hyperphosphatemia, and hyperkalemia were present. The predilection for delayed morbidity and mortality in males after anesthesia suggests that anesthesia with 0.5 mg/kg medetomidine and 50 mg/kg ketamine is a potential risk factor for obstructive uropathy due to release of seminal coagulum. This adverse effect did not recur when we altered our anesthesia protocol to 10 mg/kg xylazine and 100 mg/kg ketamine.

Lumbar osteosarcoma in a chinchilla (Chinchilla laniger).

An 11-year-old male chinchilla was presented for investigation of progressive weight loss, apathy, anorexia, changes in faecal quality and alopecia on the tip of the tail. On clinical examination, a stiffness of the back legs was noted. Abdominal palpation revealed a hard immobile, irregular structure in the region of the last lumbar vertebrae. Subsequent radiography and ultrasonography suggested the presence of neoplasia. The following day the chinchilla was showing hindlimb paralysis, and there was severe self-trauma to the distal 5 cm of the tail. In view of the rapid clinical deterioration, the chinchilla was euthanased with the owner's consent. Macroscopic examination supported the clinical suspicion of neoplasia. Histopathological examination revealed a reactive osteoblastic osteosarcoma. To the author's knowledge, this is the first report of osteosarcoma in chinchillas.