Sheep pulmonary adenomatosis (jaagsiekte) in the United States

Morphologic features of 8 cases of sheep pulmonary adenomatosis in the United States are described. All cases were studied by light microscopy and 1 case, by electron microscopy. The common finding in all sheep was an adenoma composed of fetal type II alveolar epithelial cells. The stroma closely resembled interalveolar septa in most areas. In other areas, there was excessive collagenous or myxomatous tissue. Metastatic tumor in mediastinal lymph nodes of 2 sheep closely resembled tumor in the lung. A virus with cultural and structural characteristics like those of ovine progressive pneumonia virus was isolated from the lungs of 1 sheep, but neither virions nor viral inclusions were seen in the pulmonary parenchyma.