Genetic characterisation of African swine fever virus in outbreaks in Ha Nam province, Red River Delta Region of Vietnam, and activity of antimicrobial products against virus infection in contaminated feed

Abstract

<jats:title>Abstract</jats:title><jats:sec id="j_jvetres-2020-0041_s_005_w2aab3b7c43b1b6b1aab1c15b1Aa"><jats:title>Introduction</jats:title><jats:p>African swine fever (ASF) was officially reported in Vietnam in February 2019 and spread across the whole country, affecting all 63 provinces and cities.</jats:p></jats:sec><jats:sec id="j_jvetres-2020-0041_s_006_w2aab3b7c43b1b6b1aab1c15b2Aa"><jats:title>Material and Methods</jats:title><jats:p>In this study, ASF virus (ASFV) VN/Pig/HaNam/2019 (VN/Pig/HN/19) strain was isolated in primary porcine alveolar macrophage (PAM) cells from a sample originating from an outbreak farm in Vietnam’s Red River Delta region. The isolate was characterised using the haemadsorption (HAD) test, real-time PCR, and sequencing. The activity of antimicrobial feed products was evaluated <jats:italic>via</jats:italic> a contaminated ASFV feed assay.</jats:p></jats:sec><jats:sec id="j_jvetres-2020-0041_s_007_w2aab3b7c43b1b6b1aab1c15b3Aa"><jats:title>Results</jats:title><jats:p>Phylogenetic analysis of the viral p72 and EP402R genes placed VN/Pig/HN/19 in genotype II and serogroup 8 and related it closely to Eastern European and Chinese strains. Infectious titres of the virus propagated in primary PAMs were 10<jats:sup>6</jats:sup> HAD<jats:sub>50</jats:sub>/ml. Our study reports the activity against ASFV VN/Pig/HN/19 strain of antimicrobial Sal CURB RM E Liquid, F2 Dry and K2 Liquid. Our feed assay findings suggest that the antimicrobial RM E Liquid has a strong effect against ASFV replication. These results suggest that among the Sal CURB products, the antimicrobial RM E Liquid may have the most potential as a mitigant feed additive for ASFV infection. Therefore, further studies on the use of antimicrobial Sal CURB RM E Liquid <jats:italic>in vivo</jats:italic> are required.</jats:p></jats:sec><jats:sec id="j_jvetres-2020-0041_s_008_w2aab3b7c43b1b6b1aab1c15b4Aa"><jats:title>Conclusions</jats:title><jats:p>Our study demonstrates the threat of ASFV and emphasises the need to control and eradicate it in Vietnam by multiple measures.</jats:p></jats:sec>

Circulation of two different variants of intergenic region (IGR) located between the I73R and I329L genes of African swine fever virus strains in Vietnam

“…Since the first confirmed outbreak of ASFV in China in 2018, the disease has also spread to Mongolia, Vietnam, Cambodia, Hong Kong, Korea (Dem People's Rep. of), Laos, Myanmar, Philippines, Korea (Rep. of), Timor‐Leste, Indonesia, Papua New Guinea and India (Vergne et al., 2020). In Vietnam, the first ASF outbreak in Hung Yen province was confirmed by the Department of Animal Health in February 2019 (Tran, Truong, Dang, et al., 2020; Tran, Truong, Ly, et al., 2020) and an official report was submitted immediately to World Organization of Animal Health (OIE). After seven months, the disease spread to the entire country and approximately six million pigs on infected farms had been culled, suggesting the socio‐economic impact of the disease (Truong et al., 2020).…”

“…Our recent studies indicated that ASFVs circulating in the North Central region and Ha Nam province belonged to the p72 genotype II and CD2v serotype 8 (Tran, Truong, Dang, et al., 2020; Tran, Truong, Ly, et al., 2020). Further analysis of the tandem repeat sequences (TRSs) from ASFV strains in the North Central region showed that it had an IGR II variant with an additional TRS (5′‐GGAATATATA‐3′) between the I73R and I329L genes (Tran et al., 2020a; Tran, Truong, Ly, et al., 2020).…”

“…Our recent studies indicated that ASFVs circulating in the North Central region and Ha Nam province belonged to the p72 genotype II and CD2v serotype 8 (Tran, Truong, Dang, et al., 2020; Tran, Truong, Ly, et al., 2020). Further analysis of the tandem repeat sequences (TRSs) from ASFV strains in the North Central region showed that it had an IGR II variant with an additional TRS (5′‐GGAATATATA‐3′) between the I73R and I329L genes (Tran et al., 2020a; Tran, Truong, Ly, et al., 2020). In addition, the sequence analysis of TRSs, located in the central variable region ( CVR ) within the B602L gene (Gallardo et al., 2009) and in the intergenic region between the I73R and I329L genes, at the right end of the genome (Gallardo et al., 2014) is very important in distinguishing subgroups between closely related ASFVs.…”

“…In the current study, we determined the genotypes and TRSs as marker regions of ASFVs isolated from two dead pigs in the Capital Hanoi region in 2019. Conventional PCR was performed to amplify the p72 gene and the ASFV genome marker region as described previously (Li et al., 2018; Sanna et al., 2017; Tran, Truong, Dang, et al., 2020; Tran, Truong, Ly, et al., 2020). As seen in Figure 1a, ASFVs isolated in the Capital Hanoi region belong to the p72 genotype II and showed 100% nucleotide identity with all compared ASFV isolates from the North Central region and Ha Nam province, except the isolate of VN/pig/NA/1393 (Tran et al., 2020a; Tran, Truong, Ly, et al., 2020).…”

“…Conventional PCR was performed to amplify the p72 gene and the ASFV genome marker region as described previously (Li et al., 2018; Sanna et al., 2017; Tran, Truong, Dang, et al., 2020; Tran, Truong, Ly, et al., 2020). As seen in Figure 1a, ASFVs isolated in the Capital Hanoi region belong to the p72 genotype II and showed 100% nucleotide identity with all compared ASFV isolates from the North Central region and Ha Nam province, except the isolate of VN/pig/NA/1393 (Tran et al., 2020a; Tran, Truong, Ly, et al., 2020). Interestingly, the results from the TRS analysis showed two different variants, presence or absence of an additional tandem repeat sequence (GGAATATATA), located between the I73R and I329L genes of the causative ASFV strains from the Capital Hanoi region as seen in Figure 1b.…”