Suckling mice (C57BL/6), 2 to 3 days old and weighing 3 to 4 g, were maintained by Bio-pharmacy, Jinyu Group Co., Ltd. Male and female guinea pigs weighing 250 to 300 g and large white swine, Vet. Res. (2010) 41:30 2-to 3-months-old and weighing 40 to 50 kg, were used to perform viral challenge. All of the animals were housed in disease-secure isolation facilities in an FMDV-free area, and had no previous FMD contact as confirmed by the absence of detectable anti-FMDV antibodies in their sera.