The E gene sequence of JE virus was amplified by semi-nested PCR. The first round of amplification , using primers: JEV 3F: TTCATAGAAGGAGCCAGTGGA and JEV 3R: TCGTTTAAACTCGCGACTGA.he gene amplification system was 25 ul, including: 2 μl of cDNA template, 12.5 μl of GoTaq ® Green Master Mix-2 × (Promega, Madison, WI), 1 μl of upstream and downstream primers at 10 umol/L, and 8.5 μl of RNase Free Water. The reaction program was: 94 ° C, 8 min for 1 cycle; 94 ° C, 1 min, 55 ° C, 1 min, 72 ° C, 1 min for 35 cycles; 72 ° C, 10 min, keep in 4 ° C. The second round of amplification sequence was 300 bp, using the first round of PCR product as a template with the forward primer JEV 3F and the reverse primer JEV 2R: TTTCCCGAAAAGTCCACATC.