Article ID: 15-0007
A cohort study was conducted to evaluate the risk of bovine leukemia virus (BLV) transmission to uninfected cattle by adjacent infected cattle in six dairy farms. Animals were initially tested in 2010–2011 using a commercial ELISA kit. Uninfected cattle were repeatedly tested every four to six months until fall of 2012. The Cox proportional hazard model with frailty showed that uninfected cattle neighboring to infected cattle (n=53) had a significant higher risk of seroconversion than those without any infected neighbors (n=81) (hazard ratio: 12.4, P=0.001), implying that neighboring infected cattle were a significant risk factor for BLV transmission. This finding provides scientific support for animal health authorities and farmers to segregate infected cattle on farms to prevent spread of BLV.