By 2001 some 20 ranches reported cases across six states (Colorado, Kansas, Montana, Nebraska, Oklahoma and South Dakota) and one other Canadian province (Alberta).
By 2001 some 20 ranches reported cases across six states (Colorado, Kansas, Montana, Nebraska, Oklahoma and South Dakota) and one other Canadian province (Alberta).
2001年，约有20座牧场传出病例，跨越美国六个州（科罗拉多、堪萨斯、蒙大拿、内布拉斯加、俄克拉荷马与南达科他）及加拿大一省（亚伯达）。