Assessment of the cost effectiveness of compulsory testing of introduced animals and bulk tank milk testing for bovine viral diarrhea in Japan

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

Bovine viral diarrhea (BVD) is a chronic disease of cattle globally distributed, caused by infection with bovine viral diarrhea virus (BVDV), and results in economic losses to the livestock industry [6, 13-15, 24, 41] . Transient infection (TI) of BVDV in adult ruminants produces subclinical or non-severe symptoms [5, 26] ; however, BVDV can be transmitted to the fetus of pregnant cattle between 30 and 120 days of gestation, thereby inducing fetal immune tolerance to BVDV and resulting in the delivery of persistently infected (PI) calves [23] . PI calves shed BVDVs through oculonasal discharge and other secretions throughout their lives, without showing any apparent clinical manifestations, except fatal mucosal disease [4, 7] . PI cattle are commonly believed to be the primary source of BVDV infection in a herd [15, 27] . Therefore, PI cattle need to be promptly detected and culled for the control of BVD [1] .