The number of bovine leukemia cases has increased continuously over recent years, with over 1,700 cases identified in 2010. The majority of these are believed to be enzootic bovine leucosis (EBL) caused by bovine leukemia virus (BLV). Here we report the result of a nationwide serological survey of both dairy and beef breeding-cattle, conducted over the fiscal years of 2009 and 2010, respectively. A total of 11113 dairy and 9722 beef breeding-cattle sampled from 587 and 558 farms, respectively; of these 40.9% and 28.7%, respectively, were found to be serologically positive according to the commercial indirect ELISA. The observed seroprevalence of the dairy and beef cattle were ten and four times higher, respectively, than those in previous surveys in the early 1980s. In addition, both dairy and beef cattle in western and southern parts of Japan showed a higher seroprevalence compared to those in other regions. Furthermore, at less than one year of age, 21.0% and 13.7% of dairy and beef cattle, respectively, were serologically positive, and these percentages increased with age. Our results reveal the current dissemination of BLV among the cattle population of Japan for the first time in 30 years. Increased seroprevalence may reflect changes in the environment surrounding the Japanese livestock farming system and in herd management practices. These findings provide animal health authorities with valuable information for considering further control measures against EBL.
(Viral Disease and Epidemiology Research Division)
References:
Murakami K. et al. (2013) J. Vet. Med. Sci. 75(8):1123-1126
