Progress for control of bovine leukosis

Abstract

Bovine leukosis (the term as used will include lymphosarcoma, the related lymphocytosis, and subclinical infection with leukosis virus) has been studied intensively in recent years and a brief review for veterinarians is presented. Serological methods have now been applied to indicate and control bovine leukosis virus (BLV) infection. Since 1975, the Commission of European Communities (CEC), has sponsored international conferences annually. These have enabled coordination and exchange of current results among the concerned laboratories in Europe, as well as Canada and the United States. Emphasis has been given to the adult, sometimes called enzootic, form of bovine leukosis both because of its economic significance as the most commonly occurring, and because it is the only form with which BLV has thus far been associated. In adult lymphosarcoma there may be only scattered lymph nodes enlarged (Figure 1), but the heart, abomasum and uterus often are involved.
Three other forms are grouped with the term sporadic bovine luekosis and neither BLV or BLV antibodies can be demonstrated. The infrequent juvenile, or calf, form may be fully developed at birth or delayed until the age of about two years. Visceral organs as well as nearly all lymph nodes are usually affected. The thymic form is rare and manifested in cattle about two years old by lymphosarcoma extending from the anterior chest to the larynx. The cutaneous form is also rare. It occurs in cattle one and one-half to three years old. The scattered, discrete lesions resemble warts, but are congested and often exude serum. Lymph nodes later may become enlarged, as in the adult form. Spontaneous regression of tumors may occur in the adult, juvenile and cutaneous forms.