Spontaneous Disease and Pathology of Naked Mole-Rats

Naked mole-rats are highly valuable research models and popular exhibition animals at zoos worldwide. Here, we provide comprehensive descriptions of common postmortem findings of naked mole-rats from both research colonies and populations managed in zoological institutions. Included are brief reviews of their natural history and related physiologic adaptations, unique anatomical features, gross and histologic lesions of common as well as rarely reported disease processes, and discussions of possible pathogeneses with recommendations for future investigations to fill knowledge gaps. Based on postmortem data of several hundreds of naked mole-rats in managed care, it is clear that cancer is extremely rare and infectious disease is infrequently reported. However, despite relatively benign aging phenotypes in this species, several degenerative processes have been nevertheless observed in older populations of naked mole-rats. As such, some potential diet and husbandry-related issues are discussed in addition to the one of the most prominent causes of morbidity and mortality, conspecific aggression and traumas. From this review of lesions and disease, it is clear that pathology, including histopathology, is integral to better understanding mechanisms of healthy aging and cancer resistance of these extraordinary rodents.

Rodentia

This chapter includes diseases of animals in the order Rodentia, in which there are over 2000 species representing 40% of all mammals. This incredibly diverse order includes members inhabiting every continent, either naturally or in human-made environments. While rodents have been the cause or implicated in disease transmission that has lead to human pandemics, such as the Black Death, and the decimation of certain animal species, like island-dwelling birds; genetically modified rodents have contributed significantly to the advancement of biomedical research and human health. There are more than 50 species of endangered rats, mice, voles, squirrels, and marmots. The recent extinction of the Bramble Cay melomys represents the first human-induced rodent extinction linked to climate change. Rodents are the reservoir host of several human and domestic pathogens of concern listed by OIE. Herein, we highlight those diseases of rodents that lead to clinically important gross and microscopic lesions.

Peritoneal sarcomatosis associated with telemetry implants in Sprague Dawley CD rats: a review of eight cases

Surgical implantation of radiotelemetric transmitters is a current practice to collect a variety of physiological parameters in unrestrained laboratory animals, and in rodents in particular. In this study, the incidence of peritoneal sarcomatosis arising secondary to surgically implanted telemetry devices (< 15% of implanted Sprague Dawley rats) is considered to represent a significant issue for both animal welfare and data validity in affected animals. Macroscopically, the telemetry-associated fibrosarcomas spread along the visceral and parietal peritoneum and mesentery surrounding abdominal organs. The histologic morphology of these sarcomas was typically an undifferentiated sarcoma, although well-differentiated fibrosarcomas and telangiectatic and pleomorphic variants were noted. Using special stains such as Masson's Trichrome demonstrated a collagenous extracellular matrix in 50% of these rats, which is consistent with a fibroblastic origin. Immunohistochemical studies clearly delineated the mesenchymal components of the sarcomas (fibroblasts and smooth muscle cells); one case, however, was diagnosed as an osteosarcoma.