Generalities:

Disease that mainly affects bovine cattle (VLB), also known as lymphosarcoma or malignant lymphoma, causes a malignant proliferation of lymphocyte-producing tissue, which is why it is considered a type of leukemia. In animals it affects the Thymus, lymph nodes and can cause skin tumors. A large percentage of cows or other species have the virus, even if they do not manifest the disease.
Recent studies suggest that the virus can be transmitted to humans and affect breast cancer. Transmission would be mainly through dairy products.