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

BVDVs have been detected in Japan since 1969. After the designation of BVD as a notifiable disease in 1998, the numbers of BVD diagnosed cases stabilized between 100 and 200 animals per year [19] . According to the results of the latest survey on PI animals in dairy farms in Japan, the proportion of farms with PI animals and that of cattle diagnosed as PI animals were 7.6% (95% confidence limits [CI]: 3.1-16.4%) and 0.12% (95% CI: 0.05-0.25%), respectively [19] . The majority of dairy cattle in Japan are raised in Hokkaido Prefecture, which is an island located in the northern part of Japan. As dairy husbandry is one of the main industries in the eastern part of Hokkaido, some husbandry communities have implemented independent control measures for BVD virus infection in cattle. In Betsukai Town, Nemuro District, mass vaccination using a combination of inactivated and attenuated vaccines and screening tests using bulk tank milk followed by individual serum tests have been implemented since 2006 [18] . These independent but well-designed control measures reduced the numbers of PI detected by active surveillance from 21 in 2006 to 2 in 2012 [29] . As a result of these intensive control measures, the risk of BVDV infection in this area was reduced dramatically; however, the sustainability of these control measures should be a focus so as to prevent the BVDV endemic in this area.