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Summary: Polyarteritis nodosa (PAN) is a systemic vasculitis of unknown aetiology affecting small- and medium-sized arteries of multiple organ systems without involvement of pulmonary arteries. This report describes four cases of PAN in sheep from different flocks. Three of these animals displayed clinical signs of locomotor disturbance. Gross necropsy findings included bilateral nodular thickening of vessels together with thromboses and aneurysms at several locations. Microscopically, small- to medium-sized arteries of the kidneys, ovary, uterus and skin were consistently involved and other locations were affected less frequently. Arteries within the lung were normal in all animals. Vascular lesions were characterized by focal fibrinoid necrosis, rupture of the internal elastic lamina and transmural infiltration of mononuclear inflammatory cells, extending into the perivascular tissue. In the kidney, many arteries showed narrowing or occlusion of the lumen and marked fibrosis. The distribution of arterial lesions was segmental, showing alternation of affected and microscopically normal areas. Immunohistochemical studies did not identify immune complex deposition. The inflammatory infiltrates were composed of T lymphocytes and macrophages, suggesting that a cell-mediated immune response may be involved in the pathogenesis of this disease. [ABSTRACT FROM AUTHOR]

Summary: A flock of approximately 1,000 sheep were exposed intermittently to food contaminated with T-2 toxin (T-2), a potent type-A trichothecene mycotoxin produced primarily by Fusarium sporotrichioides and Fusarium poae. In the acute stage of the intoxication, affected sheep developed anorexia, decreased water consumption, ruminal atony, soft faeces and apathy. One hundred and ninety of the exposed sheep died. The main gross lesions observed in animals dying during the acute disease were rumenitis and ulcerative abomasitis, depletion of lymphocytes in lymphoid organs, necrosis of the exocrine pancreas, myocarditis and intense oedema of the skin and brain. Sheep developing the chronic stage of disease showed weight loss and reproductive inefficiency and the main pathological features observed in animals dying during this stage were gastrointestinal inflammation, myocardial fibrosis and necrotic and suppurative lesions in the oral cavity. Opportunistic infections (e.g. mycotic mastitis or parasitic pneumonia) were also identified in these animals. Increased serum concentrations of lactate dehydrogenase and creatine kinase were observed, most likely related to heart lesions. T-2 toxins were detected in all samples of the diet of these animals that were analyzed. The changes in the sheep reported here are similar to those described previously in experimental studies. Lesions observed in the present animals suggest an additional cardiotoxic effect of T-2 in sheep. [ABSTRACT FROM AUTHOR]

Summary: This study investigates the nervous form of ovine maedi-visna by histological and immunohistochemical techniques. The aim was to study the lesion types and the local cellular immune response related to each lesion type, and the possible relationship between these parameters. Thirty-four Assaf ewes were studied, 29 of which had shown nervous signs. Microscopical lesion patterns were described according to location, extent and predominance of inflammatory cell type. Immunohistochemical labelling of T cells (CD3+, CD4+, CD8+ and cells expressing the γδ form of the T-cell receptor), B cells and macrophages revealed clear differences between the lesion patterns. Two main lesion types were described. Lymphocytic lesions had areas of mild-moderate injury characterized by a predominance of infiltrating T cells. Histiocytic lesions were more severe and had extensive areas of malacia and dominant infiltration by macrophages and B cells. Each animal had a unique lesion pattern and these differences could be due to individual resistance to the progression of infection. The lymphocytic lesions appear to represent initial or latent phases of slow progression, in which the animal presents some natural resistance to the infection. The histiocytic pattern may reflect a poor immune response or a greater virulence of the viral strain. [ABSTRACT FROM AUTHOR]

Summary: Dystrophic epidermolysis bullosa (DEB) was diagnosed in five newborn Assaf lambs from a flock in which around 1–2% of the lambs were lame. Affected animals had marked erythema of the coronary band and subsequent detachment of the hooves. Blisters were present on the lips and in the oral and oesophageal mucosae. Erosions and crusts were noted in the axillary and inguinal areas. Microscopically, there was detachment of the epidermis from the dermis. The roof of these bullous spaces was formed by the intact epidermis with its basement membrane. The bullae were generally filled with pale eosinophilic proteinaceous fluid and erythrocytes. Immunohistochemical analysis revealed absence of collagen VII in the basement membrane zone. The disease in these lambs appears similar to the severe recessive form of human DEB. [Copyright &y& Elsevier]