STX1A and Bovine mastitis: Studies in Iran indicated that genes encoding Shiga-toxins (stx1 and stx2) were the most prevalent virulence factors that were isolated from the clinical bovine mastitis cases 77.8% and 13.9%, respectively [25]; 64.1% and 12.8% isolates had stx2 and both stx1-stx2, respectively [12], 31% isolates contained stx1 in New Zealand [62].