Pathology of Diseases of Geriatric Exotic Mammals

Neoplasia in pet guinea pigs: a retrospective analysis of 2,474 autopsy examinations

Neoplasia is a common disease in guinea pigs (Cavia porcellus); however, few studies have evaluated the prevalence of neoplasia in all organ systems. We retrospectively analyzed the tumor prevalence in pet guinea pigs and the frequency of metastasis in a multi-institutional study population of 2,474 autopsy cases. Tumors were found in 508 guinea pigs (prevalence: 20.5%), of which 95 cases had >1 tumor, resulting in a total of 627 tumors. The tumor prevalence increased from 1.4% in animals <0.5-y-old to 53.6% for guinea pigs >5-y-old. The most common tumor type was lymphoma or leukemia, affecting 174 guinea pigs (tumor prevalence: 7.0%). Lymphomas or leukemias were disseminated to various organs and/or lymph nodes in 146 (83.9%) cases and localized to 1 organ or 1 lymph node in 28 (16.1%) cases. Primary non-lymphoid tumors were most frequent in the female genital tract (62 of 1,235 cases, mostly uterus), respiratory system (116 of 2,474), skin including mammary gland (81 of 2,474), endocrine system (66 of 2,474, mostly thyroid gland), and alimentary tract (35 of 2,474). Tumors of the alimentary tract were dominated by gastrointestinal stromal tumors. Metastasis was detected in 42 of 453 non-lymphoid tumors (9.3%), with a surprisingly low frequency for pulmonary carcinoma and splenic hemangiosarcoma compared to other species. Our postmortem study demonstrates a high prevalence of disseminated lymphoma or leukemia in pet guinea pigs at the time of death or euthanasia. Additional studies are needed to further characterize these tumors.

Clinicopathologic findings and causes of mortality in 100 pet rabbits from the Canary Islands, Spain, 2011-2022

The European domestic rabbit (Oryctolagus cuniculus domesticus) is commonly kept as a pet, with increasing popularity among pet owners. Despite the increasing body of information on lagomorph medicine and pathology, comprehensive published compilations of causes of mortality in pet rabbits are limited. We analyzed health disorders, pathology findings, and most probable causes of death in 100 pet rabbits submitted to the Anatomopathological Diagnostic Service of the Veterinary School of the University of Las Palmas de Gran Canaria, Canary Islands, Spain, from 2011 to 2022. We reviewed clinical data and gross and histopathologic findings to classify the various disorders into infectious (n = 39), noninfectious (n = 45), and idiopathic conditions (n = 16). Within infectious disease processes, Encephalitozoon cuniculi infection (n = 14) and rabbit hemorrhagic viral disease (n = 14) had the highest prevalence. Regarding the noninfectious conditions, perioperative mortality (n = 10), gastrointestinal syndrome (n = 7), and trauma (n = 6) were the most common clinicopathologic entities observed.

Respiratory Distress Caused by Neoplastic Upper Respiratory Tract Obstructions in 2 Pet Rats (Rattus norvegicus domestica)

Respiratory disease is one of the primary reasons for pet owners to seek veterinary attention for their rats. While chronic respiratory disease complex is most often responsible for respiratory signs in pet rats and is well characterized, upper respiratory obstructive disease has been rarely reported in the literature. This report describes 2 pet fancy rats (Rattus norvegicus domestica) presenting with a several day history of progressive respiratory signs that were minimally responsive to supportive therapies, including antibiotics, nonsteroidal anti-inflammatories, and fluid and oxygen support. Survey radiographs were performed under sedation in both cases. In the first case, no cause for the clinical signs could be identified, in part due to suboptimal radiographic positioning, although severe aerophagia was noted. In the second case, cervical tracheal luminal narrowing and increased soft tissue opacity along the walls of the trachea were identified. Both rats declined while under sedation, resulting in cardiopulmonary arrest in the first case and humane euthanasia in the second. On necropsy, the first case had a oropharyngeal squamous cell carcinoma originating from the Zymbal's gland, which was obstructing the larynx. The second case had an intra-luminal tracheal mass obstructing the airway. This was mostly likely B-cell lymphoma or a plasma cell tumor, although definitive diagnosis was unable to be obtained. For future such cases empiric management of respiratory disease in rats with antimicrobials, anti-inflammatories, and supportive care is often appropriate based on the high prevalence of infectious agents, however, other noninfectious causes should be considered, such as neoplastic processes leading to upper airway obstructive disease and diagnostic imaging may be indicated.

Demography, disorders and mortality of pet hamsters under primary veterinary care in the United Kingdom in 2016

BACKGROUND

Hamsters are popular pets worldwide but there is limited evidence on the overall health issues of pet hamsters. This study aimed to characterise the demography, disorder prevalence and mortality of pet hamsters in the United Kingdom.

METHOD

The VetCompass study included anonymised clinical records of 16,605 hamsters.

RESULTS

The most common hamster species were Syrian (golden) (Mesocricetus auratus) (n=12,197, 73.45%), Djungarian (winter white dwarf) (Phodopus sungorus) (2286, 13.77%) and Roborovski hamsters (Phodopus roborovskii) (1054, 6.35%). The most prevalent precise-level disorders recorded across all hamsters were a presentation categorised as 'wet tail' (n=293, 7.33%), disorder undiagnosed (292, 7.30%), bite injuries from other hamsters (235, 5.88%), overgrown nail(s) (165, 4.13%), overgrown incisor(s) (159, 3.98%) and traumatic injury (152, 3.80%). The most prevalent disorders groups across all species of hamster were traumatic injury (n=616, 15.41%), enteropathy (450, 11.26%), ophthalmological disorder (445, 11.13%), skin disorder (362, 9.05%) and mass (361, 9.03%). The median age at death across all hamsters was 1.75 years (interquartile range: 0.83 to 2.20, range: 0.01 to 3.65). The most common causes of death at a precise level were wet tail (7.88%, 95% confidence interval: 6.35 to 9.66), abdominal mass (6.40%, 95% confidence interval: 5.01 to 8.03), neoplasia (5.38%, 95% confidence interval: 4.11 to 6.90) and dyspnoea (3.99%, 95% confidence interval: 2.9 to 5.34).

CONCLUSION

This study provides veterinary professionals, educators, welfare scientists and owners with an evidence base on pet hamster health. A greater understanding of the common disorders of pet hamsters can support veterinary professionals to communicate more effectively with owners on key issues and outcomes to expect from hamster ownership.

Leiomyosarcoma with widespread metastases in a capybara

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.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.