| Abstract: | In the South-Western part of Norway, lambs of the Old Norwegian short tailed breed (Spael) and crosses with the Dala breed sometimes develop an Acute Respiratory Distress Syndrome (ARDS) shortly after they have been moved onto lush aftermath grazings from mountain pastures. This article covers the symptoms and pathoanatomical findings in lambs affected with ARDS (Table I). The lambs acquired ARDS 18-72 hours after change of pasture. Heavy dysphne, frothing at the mouth, elevated temperature (greater than 41 degrees C), tachycardia, urination and ruminal atony were striking symptoms (Table II). In the early phase of the disease the lambs were often in a tranquil state, depressed, sometimes atactic, and it seemed that they went into the overt dysphneic phase on exposure to physical stress. Morbidity was 1.4%, mortality 36%. Post mortem findings included frothy contents in the airways, heavy congestion and oedema in the lungs which also had emphysematous areas, subepicardial petechiae, varying degree of mottling of the myocardium, and also varying degree of paleness and spottyness of renal cortices. The lungs showed extensive focal alveolar and interstitial emphysema, septal congestion, alveolar oedema, partial collapse, and accumulations of polymorphonuclear leucocytes in vascular beds. Later, fibrillar material was found in the alveoli, alveolar macrophages accumulated, and interalveolar septa thickened because of increased fibromuscular tissue and mononuclear cells (Fig. 1, A-D). Alveolar epithelial hyperplasia was not seen in any stage. Four lambs were moderately infected with lungworms (D. filaria), three in the prepatent, one in the patent phase. Histopathological changes in other organs included granular degenerations of myocardial threads, and development of a glomerulonephritis and focal interstitial nephritis (Fig. 1, E-F). This disease entity (ARDS) in lambs seems to be unknown in literature. The disease is compared with other known diseases in ruminants. Etiology is so far unknown. Possibilities of sudden ruminal histamine formation coinciding with a hypersensitivity reaction is discussed. |
