Potential reverse spillover of infectious bursal disease virus at the interface of commercial poultry and wild birds

Abstract

Recently, multiple spillover events between domesticated poultry and wild birds have been reported for several avian viruses. This phenomenon highlights the importance of the livestock-wildlife interface in the possible emergence of novel viruses. The aim of the current study was to investigate the potential spillover and epidemiological links of infectious bursal disease virus (IBDV) between wild birds and domestic poultry. To this end, twenty-eight cloacal swabs were collected from four species of free-living Egyptian wild birds (i.e. mallard duck, bean goose, white-fronted goose and black-billed magpie). Genetic and phylogenetic analysis of three positive isolates revealed that the IBDV/USC-1/2019 strain clustered with previously reported very virulent IBDV (vvIBDV) Egyptian isolates. Interestingly, two other wild bird-origin isolates (i.e. IBDV/USC-2/2019 and IBDV/USC-3/2019) grouped with a vaccine strain that is being used in commercial poultry. In conclusion, our results revealed the molecular detection of vaccine and vvIBDV-like strains in Egyptian wild birds and highlighted the potential role of wild birds in IBDV epidemiology in disease-endemic regions.

Keywords: Evolution; Poultry; Spill over; Viruses.

Fig. 1

Phylogenetic analysis of studied isolates and their clustering patterns with representative IBDVs. Full length VP2 gene based phylogenetic analysis of three wild-bird origin IBDV isolates with representative strains of currently circulating IBDVs in Egypt. One of the reported isolates clustered within vvIBDVs with close relationship with the previously characterized strains from commercial poultry while the other one clustered vaccine strains. The reported isolated marked with red colour

Fig. 2

Pairwise identity, localization of specific mutations in the VP2 protein of the newly identified vvIBDV strain and IBDVs selective pressure. The pairwise identities plot of VP2 gene for a Egypt-USC-IBD-1-2019 compared to vvIBDVs and b Egypt-USC-IBD-2-2019 and Egypt-USC-IBD-3-2019 compared to IBDV vaccine-like strains aligned by ClustalW and displayed by Sequence Demarcation Tool (SDT) software. c Cumulative behaviour of the average synonymous and non-synonymous substitutions moving codon by codon across VP2 gene. d 3D structure template for IBDV isolate IBDV/USC-3/2019 showed the localization of specific mutations in the VP2 protein for IBDV isolate IBDV/USC-1/2019. The 3D was visualized by PyMOL software