Chytridiomycosis, the disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has devastated global amphibian biodiversity. Nevertheless, some hosts avoid disease after Bd exposure even as others experience near-complete extirpation. It remains unclear whether the amphibian adaptive immune system plays a role in Bd defence. Here, we describe gene expression in two host species—one susceptible to chytridiomycosis and one resistant—following exposure to two Bd isolates that differ in virulence. Susceptible wood frogs (Rana sylvatica) had high infection loads and mortality when exposed to the more virulent Bd isolate but lower infection loads and no fatal disease when exposed to the less virulent isolate. Resistant American bullfrogs (R. catesbeiana) had high survival across treatments and rapidly cleared Bd infection or avoided infection entirely. We found widespread upregulation of adaptive immune genes and downregulation of important metabolic and cellular maintenance components in wood frogs after Bd exposure, whereas American bullfrogs showed little gene expression change and no evidence of an adaptive immune response. Wood frog responses suggest that adaptive immune defences may be ineffective against virulent Bd isolates that can cause rapid physiological dysfunction. By contrast, American bullfrogs exhibited robust resistance to Bd that is likely attributable, at least in part, to their continued upkeep of metabolic and skin integrity pathways as well as greater antimicrobial peptide expression compared to wood frogs, regardless of exposure. Greater understanding of these defences will ultimately help conservationists manage chytridiomycosis.

OBJECTIVE To determine survival time and metastatic rate for dogs with early-stage anal sac adenocarcinoma (ASACA) treated with surgery alone and assess whether specific clinical, pathological, or immunohistochemical factors were predictive of outcome for those dogs. DESIGN Retrospective case series. ANIMALS 34 dogs with early-stage, nonmetastatic ASACA that were treated with surgery only. PROCEDURES Medical record databases of 2 referral hospitals were searched to identify dogs examined between 2002 and 2013 that had a diagnosis of nonmetastatic ASACA that was < 3.2 cm at its largest diameter. Only dogs that received surgical treatment alone were included in the study. For each dog, information extracted from the medical record included signalment, clinical and diagnostic test findings, tumor characteristics, and outcome. When available, archived tumor specimens were histologically reviewed and tumor characteristics were described; Ki-67 and E-cadherin expressions were evaluated by use of immunohistochemical methods. Clinical, pathological, and immunohistochemical factors were assessed for associations with survival time and tumor recurrence and metastasis rates. RESULTS Median survival time was 1,237 days. Seven dogs had tumor recurrence and 9 dogs developed metastatic disease at a median of 354 and 589 days, respectively, after primary tumor removal. Cellular pleomorphism was positively associated with development of metastatic disease. No other factors evaluated were associated with outcome. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated dogs with early-stage nonmetastatic ASACA generally had a favorable outcome following surgical removal of the primary tumor alone. Routine rectal examination may be a simple and useful method for detection of dogs with early-stage ASACA.

Liposarcoma, rhabdomyosarcoma, and hibernoma share some overlapping histologic and immunohistochemical features. Although immunohistochemistry (IHC) is commonly used in the diagnosis of these neoplasms, expression of muscle markers has been reported in human liposarcoma and canine hibernoma in addition to rhabdomyosarcoma. Thus, these neoplasms are a diagnostic challenge but important to distinguish because of differences in prognosis and treatment. Rhabdomyosarcoma and liposarcoma are both malignant, but rhabdomyosarcoma has a higher potential for metastasis. In contrast, hibernomas are benign with low risk of recurrence. This study investigated expression of the muscle markers desmin, myogenin, and α-smooth muscle actin (α-SMA) and the brown fat marker uncoupling protein 1 (UCP1) in 25 cases of canine liposarcoma using IHC. Oil red O histochemistry was performed to confirm the presence of lipid and the diagnosis of liposarcoma in cases that were not well-differentiated. The 25 cases included 15 well-differentiated, 5 pleomorphic, 3 myxoid, and 2 dedifferentiated subtypes of liposarcoma. By IHC, 23 of 25 expressed UCP1, 7 of 25 expressed α-SMA, 7 of 25 expressed desmin, and 3 of 25 expressed myogenin with no clear relationship of antigen expression and tumor subtype. These findings clarify the immunohistochemical profile of canine liposarcoma and suggest overlap in the expression of several muscle antigens and UCP1 between liposarcoma, hibernoma, and rhabdomyosarcoma.

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This retrospective study summarizes 11 cases of end-stage renal disease (ESRD) in captive polar bears (Ursus maritimus) from eight zoologic institutions across the United States and Canada. Ten bears were female, one was male, and the mean age at the time of death was 24 yr old. The most common clinical signs were lethargy, inappetence, and polyuria-polydipsia. Biochemical findings included azotemia, anemia, hyperphosphatemia, and isosthenuria. Histologic examination commonly showed glomerulonephropathies and interstitial fibrosis. Based on submissions to a private diagnostic institution over a 16-yr period, ESRD was the most commonly diagnosed cause of death or euthanasia in captive polar bears in the United States, with an estimated prevalence of over 20%. Further research is needed to discern the etiology of this apparently common disease of captive polar bears.