Lymphosarcoma with plasmacytoid differentiation in a scarlet macaw (Ara macao)

A lymphosarcoma in a scarlet macaw (Ara macao) affecting periocular structures is described. Microscopically and ultrastructurally, many of the lymphoid cells had plasmacytoid features. Polymerase chain reaction amplification failed to detect exogenous avian retrovirus RAV-1 in the neoplastic mass.

Cutaneous leishmaniasis in two horses

This report contains the clinical, histologic, immunohistochemical, and electron microscopic findings in two cases of equine cutaneous leishmaniasis. Nodular, sometimes crusty or ulcerated lesions were confined to the pinna and adjacent neck in both animals. The dermal inflammatory infiltrate was lymphohistiocytic in horse No. 1 and pyogranulomatous with formation of tuberculoid granulomas in horse No. 2. Numerous Leishmania organisms were found within macrophages in both animals. There was moderate to intense and specific reaction by immunoperoxidase using a polyclonal antiserum against Leishmania in both horses. Leishmania amastigotes were also revealed by electron microscopy. This is the first report of equine cutaneous leishmaniasis recognized in North America and Puerto Rico. Leishmaniasis should be considered in the differential diagnosis of cutaneous nodular diseases in the horse.

Evaluation of laboratory tests for confirming the diagnosis of encephalitic listeriosis in ruminants

Retrospective analysis of 93 bovine, ovine, and caprine cases diagnosed as listerial encephalitis revealed positive bacterial isolations in only 63% of 59 cases in which bacterial culture was attempted. Only 42% of 41 attempted bovine brain cultures were successful, compared with 67% from 6 sheep brains and 92% from 12 goat brains. Gram stains and Listeria-specific immunohistochemistry were evaluated as tools for verifying the presence of bacteria or listerial antigens in 38 animals. Sixteen of 17 animals in this group with positive bacterial isolations were immunochemically positive for listerial antigens (including 5/6 cattle), but Gram stains detected only 9/17 positive animals (including 1/6 cattle). Antigen was also detected in 15 of 21 animals (including 5/9 cattle) with unsuccessful or unattempted bacterial isolations. Of all 38 animals, the histologic diagnosis could be verified in 82% by immunohistochemistry, compared to 47% verified by Gram stains. Immunohistochemical testing was especially beneficial in locating antigen in lesions with few bacteria or bacterial antigens and is a rapid method of confirming the diagnosis of encephalitic listeriosis where inappropriate material is submitted for bacterial isolation or in culture-negative cases.

Comparison of argyrophilic nucleolar organizer regions (AgNORs) and mitotic index in distinguishing benign from malignant canine smooth muscle tumors and in separating inflammatory hyperplasia from neoplastic lesions of the urinary bladder mucosa

Staining for argyrophilic nucleolar organizer regions (AgNORs) has proven useful in differentiating recurrent or malignant neoplasms from less aggressive or benign ones. We applied this stain to benign and malignant smooth muscle tumors and to hyperplastic and carcinomatous lesions in the urinary bladder of dogs in an effort to determine its utility in diagnostic situations. The stain was simply performed, and the results were repeatable for different staining intervals and between staining batches. For smooth muscle tumors, enumeration of AgNORs in 100 nuclei was about as efficient as mitotic index in correctly categorizing histologically benign and malignant neoplasms. The mean number of AgNORs/100 nuclei for leiomyomas was significantly less than that obtained for leiomyosarcomas and significantly greater than that obtained for normal smooth muscle. Counts for smooth muscle tumors correlated with the mitotic indexes. Counts by an individual observer were repeated without introducing significant variation, but there was variability between observers, particularly in AgNOR counts for leiomyosarcomas. AgNORs were not useful in separating hyperplastic or polypoid cystitis from transitional cell carcinoma, misclassifying both. Mean AgNOR counts for these 2 conditions did not differ at the 5% level of significance; mitotic index was more efficient at separating the 2 conditions. There was no correlation between mitotic index and AgNOR in urinary tract mucosal specimens. This easily prepared stain may be useful in separating benign and malignant smooth muscle tumors, although AgNORs were less contributory to diagnosing mucosal lesions of the urinary bladder of dogs.

Pathological findings in a cat with cryptococcosis and feline immunodeficiency virus infection

This report describes the gross, histopathological, immunocytochemical and electron microscopic findings in a cat with systemic cryptococcosis and feline immunodeficiency virus (FIV) infection. Lymphadenopathy and cloudiness of leptomeninges were the major gross findings. Numerous cryptococcal yeasts were found in lymph nodes, brain, and lung, and were less common in the kidney and the eye. The inflammatory reaction varied in intensity and cell type (mononuclear through granulomatous) depending on the organ involved. Yeasts were mainly within phagocytes as revealed by electron microscopy. Some inflammatory cells were immunocytochemically-stained with anti-CD3 antibodies.

Reactivity of polyclonal human CD3 antiserum in lymphoid tissues of cattle, sheep, goats, rats and mice

Polyclonal rabbit antiserum to human T-cell CD3 was used to study its reactivity in lymphoid tissues (lymph nodes, spleen, aggregated lymphoid follicles [Peyer's patches], thymus) of several animal species (cattle, sheep, goats, rats, and mice). Using a peroxidase-antiperoxidase technique on formalin-fixed and paraffin-embedded tissues, immunoreactive cells were detected in T cell-dependent areas of the lymphoid tissues. Reactivity was high in all species tested, but mouse tissues had reduced reactivity, compared with the other species. To obtain a reaction, it was necessary to digest tissues with pronase before application of the immunocytochemical technique. Our results indicate that CD3 antiserum may specifically recognize T-lymphoid cells as it does in human lymphoid tissues and can be used as a marker to study physiologic and pathologic conditions of the lymphoid system of these species.