Abstract:

To investigate the infection of BEFV and the genetic diversity of its prevalent strain G gene in a dairy farming community in Dali Prefecture,Yunnan Province.It designed and synthesized two pairs of specific amplified G genes for 10 suspected cases in dairy cattle breeding community of Dali Prefecture,with reference to the G gene sequence of bovine ephemeral fever virus in GenBank,sequenced and completed sequence analysis.At the same time,60 serum samples were collected for antibody detection.The results showed that 6 out of 10 whole blood samples of cattle suspected of BEF were positive for BEFV nucleic acid.The G gene of four bovine ephemeral fever virus Yunnan epidemic strains was amplified and sequenced by removing the repetitive sequence.The total sequence length was 1 872 bp,encoding 623 aa.The nucleotide sequence homology among the four strains was 99.7%-99.9%.Phylogenetic analysis showed that the four strains were grouped together with Asian strains and were a small branch alone.It had the closest relationship with TH-NP0065 strain isolated from Thailand in 2017 and Chinese strain.Compared with the amino acid homology of the vaccine strain JB76H in China,seven amino acid mutation sites were found:K⁵³ → N⁵³,K⁶² → R⁶²,P¹⁸³ → S¹⁸³,G²⁶³ → E²⁶³,K⁴⁶¹ → E⁴⁶¹,K⁴⁵⁷ → R⁴⁵⁷,I⁴⁷⁵ → M⁴⁷⁵.Except the neutralizing antigen site G1,mutation sites were present in G2,G3 and G4.According to the results of antibody test kit,19 samples with antibody concentration≥52.5 ng/L critical value were found,with a positive rate of 31.67%.In conclusion,BEFV infection was present in this dairy farming community and there were multi-locus variants in the G gene of the prevalent strain.

Key words: Bovine ephemeral fever virus, Yunnan prevalence strain, G gene, Sequence analysis