Abstract
A normal peripheral lymphocyte count was obtained on the basis of age in a herd of 185 healthy cows of the indigenous Japanese Black breed screened by physical checkup, blood examinations, serum biochemical tests, and bovine leukemia virus-serum antibody test. With normal values and the Bendixen index as references, diagnostic criteria were determined for preleukemic Japanese Black cattle. In them, the lymphocyte count was judged from three rounds of tests performed at intervals of at least three months. Examined cattle were classified into negative (Group 1, 83.4%), suspicious (Group 2, 13.0%), and persistent lymphocytosis (Group 3, 3.6%) groups. The results obtained indicated that the positive rate was lower than in one test of a grouping (expressed in roman numerals). However, evaluation of persistent lymphocytosis was more reliable. Within the same year in which the lymphocyte counts were obtained, two of the seven cattle diagnosed in Group 3, and one of the twenty-tive diagnosed in Group 2 two years later suffered from leukemia. The cattle were assigned to one of the three groupings by two or three testings in each round. Only one case was classified as Group III every time. Rather than serving simply as a part of early preventive measures to remove preleukemic cattle from the herd, this lymphocyte count test is considered to be a significant index of pathological conditions in the leukemic state and a forewarning of its onset.
