Evaluation of control measures for bovine viral diarrhea implemented in Nemuro District, Hokkaido, Japan, using a scenario tree model

ISODA, Norikazu; ASANO, Akihiro; ICHIJO, Michiru; WAKAMORI, Shiho; OHNO, Hiroshi; SATO, Kazuhiko; OKAMOTO, Hirokazu; NAKAO, Shigeru; KATO, Hajime; SAITO, Kazuma; ITO, Naoki; USUI, Akira; TAKAYAMA, Hiroaki; SAKODA, Yoshihiro

The efficacies of the disease detection program under the implementation of vaccination were compared (Fig. 3) . When compared among the same monitoring test for detection, the numbers of detected and missed BVD cattle decreased with increases in the number of vaccine administrations, although the degree of decrease among vaccination programs found was small. When compared in the same vaccination program, the differences in the number of detected and missed BVD cattle between 10 and 50% were smaller under the vaccine programs incorporating a greater number of vaccine administrations. We compared the efficacies of the individual test prior to communal pasture grazing and bulk milk tests under the vaccination strategy so as to estimate which rates of use in communal pasture tests would be equally effective to the screening test using bulk tank milk. The numbers of detected cattle by the bulk tank milk tests under single-, double-and triple-administrations were almost equal to those of BVD cattle in 20, 30 and 30% use rates of communal pasture tests, respectively. In parallel, the numbers of missed cattle by the bulk tank milk tests under these three vaccination scenarios were almost equal to those of detected BVD cattle in 50, 40 and 40% use rates of communal pasture tests respectively. Considering these results together, during the early phase of the vaccination program, it was indicated that the efficacy of the communal pasture test with low use rates would be equal to that of the bulk milk tests, whereas at the later phase of the vaccination program, the efficacy of the bulk milk test would not be inferior to that of the communal pasture test with low coverage rates. We should conclude that the communal pasture test is more effective to control BVD during the early phase of a vaccination program than a screening test using bulk tank milk.