Cutaneous melanoma in a ferret (Mustela putorius furo).

A 4-year-old spayed female ferret (Mustela putorius furo) was clinically evaluated for a slightly raised subcutaneous mass in the dorsal lumbar area. The mass was surgically excised and submitted for histopathologic evaluation. Histologically, the mass was composed of closely packeted large, atypical, polygonal to spindle-shaped cells arranged in sheets and short bundles. A few cells contained variable amounts of granular, brown to black intracytoplasmic pigment. Warthin-Starry and Fontana-Masson silver stains demonstrated variable numbers of fine black intracytoplasmic granules in most cells. The atypical cells stained positively for vimentin and S100 protein and negatively for cytokeratin and Melan A. Ultrastructurally, the neoplastic cells contained intracytoplasmic melanosomes in different stages of development. Compound melanosomes were not identified. To our knowledge, this report documents the first case of a spontaneous cutaneous melanoma in the ferret.

Neospora caninum in vitro: evidence that the destiny of a parasitophorous vacuole depends on the phenotype of the progenitor zoite.

We previously reported that Neospora caninum can be induced to express BAGI, a bradyzoite antigen, within 3 days of culture under stress conditions. The main goals of the present experiment were to increase the expression of BAGI in vitro (in part by extending cultures for 9 days), to observe parasitophorous vacuoles at various points of stage differentiation, and to test the ability of organisms produced in vitro to function like mature bradyzoites. Expression of BAG1 and of a tachyzoite antigen (NcSAGI) was monitored using a double-label immunofluorescence assay. For the purpose of this study, organisms expressing NcSAG1 were designated as tachyzoites, those expressing BAG1 were designated as bradyzoites, and those expressing both antigens were designated as intermediate zoites. The greatest percentage of intermediate zoites and bradyzoites (14%) occurred in bovine monocytes maintained for 9 days. These bradyzoites did not appear to be functionally mature; they did not induce patent infections in dogs. in contrast to bradyzoites that were produced in chronically infected mice. In vitro, large parasitophorous vacuoles contained either a pure population of tachyzoites or a mixture of tachyzoites and intermediate zoites, which is indicative of asynchronous stage conversion of organisms within a vacuole. Bradyzoites were first observed within small vacuoles on day 6. and bradyzoites never shared vacuoles with tachyzoites. This finding suggests that vacuoles containing bradyzoites may develop only if the cell is invaded by a zoite that has already begun bradyzoite differentiation. An alternative possibility is that cysts may develop if the establishing tachyzoite undergoes bradyzoite differentiation before multiplying. Cysts do not appear to arise from transformation of tachyzoites within large parasitophorous vacuoles.

Progression of an orbital T-cell rich B-cell lymphoma to a B-cell lymphoma in a dog.

An 11-year-old Shetland Sheepdog was presented for exophthalmos caused by a locally extensive, poorly defined mass located behind the right eye. The primary orbital mass was identified by light microscopy and immunohistochemistry as a T-cell rich B-cell lymphoma (TCRBCL) composed predominantly of BLA.36-positive large neoplastic lymphoid cells admixed with fewer CD3- and CD79a-positive small lymphocytes. The dog was treated for lymphoma, but 6 months after presentation it was euthanatized for suspected hepatic and gastrointestinal metastasis. Gross findings revealed an enlarged liver with multiple well-demarcated, randomly distributed 0.1-1.5-cm white nodules, five firm white submucosal jejunal nodules, and ileocecal, mediastinal, and hilar lymphadenopathy. Metastatic liver lesions consisted of sheets of monomorphic large neoplastic lymphoid cells that effaced and expanded portal and centrilobular zones. These cells were morphologically similar to the large neoplastic cells of the original orbital tumor and were CD3-negative and variably BLA.36-positive, consistent with B-cell lineage. Similar cells comprised the jejunal nodules and effaced the lymph nodes. The progression of TCRBCL to a diffuse B-cell lymphoma in this case is consistent with reported human cases and has not been previously reported in the dog.

Disseminated blastomycosis in two California sea lions (Zalophus californianus).

Two captive California sea lions (Zalophus californianus) from different facilities were diagnosed with disseminated blastomycosis. The first, a 12-yr-old male, died after a 3-wk history of progressive anorexia and lethargy. Gross examination revealed acute jejunitis with focal perforation and associated peritonitis, along with severe purulent bronchopneumonia. The second, a 15-yr-old female, was euthanized after a 2-wk history of severe cutaneous ulceration and declining clinical condition. Gross examination revealed severe pyogranulomatous bronchopneumonia and ulcerative dermatitis. Histopathologic examination in both individuals revealed severe multifocal subacute to chronic pyogranulomatous pneumonia associated with massive numbers of fungal organisms morphologically compatible with Blastomyces sp. Fungal organisms were 8-20-microm-diameter broad-based budding yeasts with thick, refractile, double-contoured walls. The male sea lion had multifocal transmural Blastomyces-induced enteritis with subsequent rupture and peritonitis. The organism was also present in the liver, with minimal associated inflammation. The female had severe multifocal pyogranulomatous ulcerative dermatitis associated with large numbers of intralesional fungal organisms. Dissemination to the spleen had occurred in both animals. A serologic immunodiffusion test for Blastomyces dermatitidis was positive in the male. The presumptive primary pathogen in both cases was Blastomyces dermatitidis.

Necrotizing mycotic vasculitis with cerebral infarction caused by Aspergillus niger in a horse with acute typholocolitis.

An 18-year-old Morgan mare was presented to the Veterinary Medical Teaching Hospital, University of Illinois, with a 10-day history of watery diarrhea, depression, and dysphagia. On admission, the animal was severely dehydrated, depressed, and unable to swallow and had no clinical signs of diarrhea. The respiratory and heart rate and body temperature were within normal limits. Following fluid therapy, the mare developed severe watery diarrhea and continued to be depressed, incoordinated, and dysphagic. The animal died on the fourth day after admission and was sent to the Laboratories of Veterinary Diagnostic Medicine for necropsy. Gross postmortem findings were consistent with an acute cerebral infarction in the right cerebral hemisphere, an acute necrotizing typhlocolitis, multifocal petechial and ecchymotic hemorrhages, enlarged and congested pars intermedia of the pituitary gland, and marked bilateral adrenocortical hyperplasia with multifocal areas of necrosis and hemorrhage. Histologic evaluation of the affected brain demonstrated an area of coagulative necrosis of the gray matter, with hemorrhage, vasculitis, and thrombosis. There were many fungal hyphae 3.5-6.0 microm, pale basophilic, septate, and occasionally branching at 45 degrees present in the arterial walls and throughout the necrotic tissue. Immunohistochemical analysis revealed Aspergillus niger as the etiologic agent responsible for the mycotic vasculitis and infarction in the brain. Bacteria culture and immunohistochemical staining of the colon and cecum failed to demonstrate specific pathogens.