Dynamics of the Emerging Genogroup of Infectious Bursal Disease Virus Infection in Broiler Farms in South Korea: A Nationwide Study

Abstract

Infectious bursal disease (IBD), caused by IBD virus (IBDV), threatens the health of the poultry industry. Recently, a subtype of genogroup (G) 2 IBDV named G2d has brought a new threat to the poultry industry. To determine the current status of IBDV prevalence in South Korea, active IBDV surveillance on 167 randomly selected broiler farms in South Korea from August 2020 to July 2021 was conducted. The bursas of Fabricius from five chickens from each farm were independently pooled and screened for IBDV using virus-specific RT-PCR. As a result, 86 farms were found to be infected with the G2d variant, 13 farms with G2b, and 2 farms with G3. Current prevalence estimation of IBDV infection in South Korea was determined as 17.8% at the animal level using pooled sampling methods. G2d IBDV was predominant compared to other genogroups, with a potentially high-risk G2d infection area in southwestern South Korea. The impact of IBDV infection on poultry productivity or Escherichia coli infection susceptibility was also confirmed. A comparative pathogenicity test indicated that G2d IBDV caused severe and persistent damage to infected chickens compared with G2b. This study highlights the importance of implementation of regular surveillance programs and poses challenges for the comprehensive prevention of IBDV infections.

Development of a Highly Efficient CRISPR/Cas9-Mediated Herpesvirus of Turkey-Based Vaccine against Novel Variant Infectious Bursal Disease Virus

“…G2 has been further geographically divided into the sub-lineages G2a, G2b, G2c, and G2d. Recently, studies have shown that G2d, the dominant genogroup, is highly prevalent in Asian countries, including China, Malaysia, Japan, and South Korea, and is a new threat to poultry farms [ 4 , 5 , 6 ]. Previous studies have shown that this new variant of IBDV could cause more severe pathological lesions than existing variant strains [ 4 ].…”

“…Recently, studies have shown that G2d, the dominant genogroup, is highly prevalent in Asian countries, including China, Malaysia, Japan, and South Korea, and is a new threat to poultry farms [ 4 , 5 , 6 ]. Previous studies have shown that this new variant of IBDV could cause more severe pathological lesions than existing variant strains [ 4 ]. In addition, current vaccines do not provide efficient protection against this novel variant; therefore, an updated antigen-matched vaccine against G2d variant IBDV is urgently needed to protect domestic poultry [ 7 ].…”

Phylogenotyping of the Vietnamese infectious bursal disease viruses according to the newly unified genotypic classification scheme

“…Korea [39], Malaysia [26], India [40], Pakistan [41,42], and Bangladesh [12,20], but it has also been observed in many European [18,43], African [44][45][46][47], and North/South American countries [16,[48][49][50]. These A3B3 genotype viruses were apparently emerged from the early reassortment of the "very virulent" segment A of the European strains around the 1980s and 1990s [51,52] and the "early-Australian" vaccine-originated segment B of the Australian IBDVs around the 1970s [8, 33,53,54].…”

The Over-40-Years-Epidemic of Infectious Bursal Disease Virus in China

“…Since 2017, nVarIBDV has been widely prevalent and has caused critical damage to major poultry breeding regions in China [ 7 , 10 , 52 ] and has also been reported in Japan [ 8 ], Korea [ 9 , 13 ], and Malaysia [ 11 , 12 ]. Atypical IBD caused by nVarIBDV pose a new threat to the poultry industry.…”

“…In China, IBD was first detected in Beijing and Guangdong in 1979 and rapidly spread to the main poultry areas of this country [ 4 , 5 , 6 ]. In recent years, the sudden prevalence of a novel variant of IBDV (nVarIBDV) in eastern Asia, including China, causing subclinical symptoms in chickens, has brought new threats and challenges to the poultry industry [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”