Histogenesis of leukemic changes in cows

: A histopathologic study was carried out on lymph nodes and viscera of 98 cows and 28 heifers that responded positively in serologic examinations for leukosis. The animals did not exhibit clinical and paraclinical symptoms, neither were there found any morphologic changes characteristic of leukosis. There existed activation and proliferation of the reticuloendothelial tissue in the sinuses of the lymph nodes. The same response was shown by the endothelium of the capillaries in visceral organs. There was also metaplasia that concerned mainly the connective tissue cells of the lymph node trabeculas as well as the adventitial cells of the vascular walls. It was considered that the infection could be manifested morphologically as a reticuloendotheliosis. By its clinical course and morphologic manifestation bovine leukosis resembles some other virus diseases that have been systematized as "delayed virus infections'.