Forty-four primary feline vaccine-associated fibrosarcomas and 16 recurrences were examined histologically for detailed morphologic characterization with emphasis on tumor grade, presence of neoplastic multinucleated giant cells, presence and proportion of T and B lymphocytes within the tumor, and thin and intermediate filament contents of neoplastic and stromal cells. The microvascularity and proliferation rates of central and peripheral areas of the tumors were also quantified by computerized image analysis. For primary fibrosarcomas, 11 of 44 (25%) were grade I, 21 of 44 (47.7%) were grade II, and 12 of 44 (27.3%) were grade III. The recurrences followed a similar pattern: 4 of 16 (25%) were grade I, 8 of 16 (50%) were grade II, and 4 of 16 (25%) were grade III. A positive correlation was found between the presence of neoplastic multinucleated giant cells and tumor grade. These cells were present in 9 of 12 (75%) of grade III and none of the grade I tumors. Prominent peritumoral lymphoid aggregates or follicles were present in 59% of the tumors, and many contained high proportions of T lymphocytes, varying from 19 to 87%. All fibrosarcomas were immunoreactive for vimentin and 28 of 44 (64%) were reactive for alpha-smooth muscle actin. The actin-positive cells were either part of the tumor or formed a capsule around tumor nodules. The peripheral vascularity was significantly higher than the central vascular density but no difference was found in tumor cell proliferation rates between the two areas. Centrally located, fluid-filled micro- or macrocavitations were frequently observed in the large vaccine sarcomas and probably formed secondary to rapid tumor growth and central necrosis.

No abstract

Bovine papillomaviral DNA was detected in essentially all sarcoids examined. There appears to be regional variation in the prevalence of viral types in these tumors. The fact that we detected viral DNA in normal skin samples from horses with sarcoids suggests the possibility of a latent viral phase. Viral latency may be 1 explanation for the high rate of recurrence following surgical excision of sarcoids.

Twenty feline vaccine-associated sarcomas were examined by transmission electron microscopy. Tumors contained pleomorphic spindle cells, histiocytoid cells, and giant cells. Most tumors contained myofibroblasts, which had morphologic features similar to those of fibroblasts. These cells were further distinguished by subplasmalemmal dense plaques and thin cytoplasmic actin myofilaments organized as elongated bundles concentrated at irregular intervals forming characteristic dense bodies. Intracellular crystalline particulate material was found in 5 of the 20 tumors. Energy dispersive X-ray spectroscopy was used to identify the crystalline material within one tumor as aluminum-based. One tumor from a feline leukemia virus-infected cat contained budding and immature retroviral particles.

Purpose: Measles virus (MV) causes the regression of human lymphoma xenografts. The purpose of this study was to determine if canine lymphoid cells could be infected in vitro with MV or canine distemper virus (CDV, the canine Morbillivirus equivalent of MV) and determine if in vitro viral infection leads to apoptotic cell death. Experimental Design: Reverse transcriptase-PCR was used to examine the expression of both signal lymphocyte activation molecule (CD150) and membrane cofactor molecule (CD46) mRNA. An attenuated CDV expressing enhanced green fluorescent protein was used to infect canine cells in vitro. Both flow cytometry and reverse transcriptase-PCR was used to document CDV infection. Cell death was examined using a propidium iodide staining assay and Annexin V binding. Results: Canine lymphoid cell lines and neoplastic B and T lymphocytes collected from dogs with spontaneous lymphoma expressed the Morbillivirus receptor CD150 mRNA. In contrast, only neoplastic lymphocytes expressed detectable levels of CD46 mRNA. Although MV did not infect canine cells, CDV efficiently infected between 40% and 70% of all three canine lymphoid lines tested. More importantly, CDV infected 50% to 90% of neoplastic lymphocytes isolated from dogs with both B and T cell lymphoma. Apoptosis of CDV-infected cell lines was documented. Conclusions: Attenuated CDV may be a useful treatment for canine lymphoma. As such, dogs with lymphoma may represent a biologically relevant large animal model to investigate the feasibility, safety, and efficacy of Morbillivirus therapy in a clinical setting with findings that may have direct applicability in the treatment of human non-Hodgkin's lymphoma.

Abstract.Intestinal colonization with toxigenic strains of Clostridium difficile was documented in 9 of 10 horses with acute onset diarrhea in a veterinary medical teaching hospital, whereas a similar isolate was detected in only 1 of 23 other horses without diarrhea in the hospital. One horse with diarrhea was infected simultaneously with both C. difficile and Salmonella krefeld. Clostridium difficile was detected by fecal culture on selective medium, confirmed with a latex particle agglutination test, and identified as toxigenic by polymerase chain reaction amplification of toxin A and toxin B gene sequences. Using an arbitrarily-primed polymerase chain reaction, 6 distinct C. difficile isolates were detected in the feces of the 9 affected horses at the time of the outbreak of diarrhea.Although species of the genus Clostridium, particMaterials and methods ularly C. perfringens, are known causes for enterocolitis in neonatal foals, the role of C. difficile as an enteroAnimals. In the spring of 1993, 10 adult horses developed pathogen in the adult horse is largely unknown. Intesdiarrhea in a 2-day period in the large animal clinic of the tinal colonization with C. difficile has been described University of California Veterinary Medical Teaching Hospital. The affected horses had been hospitalized for periods in the horse, 12 and there are reports of C. difficile in-of time ranging from 0 to 22 days, and 7 of the 10 horses fection in neonatal foals with associated necrotizing enterocolitis 7-9 and in an adult horse with typhlocolitis. 15 Despite the relative paucity of information regarding intestinal colonization of horses with C. difficile, the organism is a common nosocomial pathogen in human patients and causes pseudomembranous colitis associated with antibiotic therapy. 10,18 Several studies have confirmed the presence of C. difficile in animals in veterinary practices and teaching hospitals, although those reports were limited to examinations of small animals. 2,3,13,22 We recently dehad been in the hospital for 4 days or longer. All of the horses were receiving 1 or more antibiotics (ampicillin, 6 horses; gentamicin, 8 horses; ceftiofur, 1 horse; trimethoprim-sulfamethoxazole, 1 horse), and all but 2 of the horses were hospitalized for colic or diarrhea. Four of these horses had had celiotomies during their treatment for colic. Of the two horses without colic, one had uterine torsion and another was undergoing treatment for a subepiglottic mass. Affected horses were located in 4 separated areas (different buildings) of the hospital at the time of fecal sampling. There were 23 other horses without diarrhea in the hospital at this time.Laboratory methods. Specimens of the diarrheal feces were tected C. difficile in small animal patients in our teaching hospital, and although both toxigenic and nontoxigenic isolates were detected, the association between intestinal colonization and clinical signs was not clear. 20In the present study, we present evidence of colonization of adult horses with toxigenic strains...

This study documented that activation and expression of the E5 gene is evident in sarcoids obtained from horses. These data support the conclusion that infection with bovine papillomavirus is important in the initiation or progression of sarcoids in horses. Treatment strategies designed to increase immune recognition of virally infected cells are warranted.

No abstract