Abstract
The circulation in Europe of novel reassortant strains of infectious bursal disease virus (IBDV), containing a unique genetic background composition, represents a serious problem for animal health. Since the emergence of this novel IBDV mosaic was first described in Poland, this scenario has become particularly attractive to uncover the evolutionary forces driving the genetic diversity of IBDV populations. This study additionally addressed the phenotypic characterization of these emergent strains, as well as the main features affecting the viral fitness during the competition process of IBDV lineages in the field. Our results showed how different evolutionary mechanisms modulate the genetic diversity of co-existent IBDV lineages, leading to the error catastrophe effect, Muller ratchet effect, or prevalence, depending on their genetic compositions. We also determined that the action of the positive selection pressure, depending on the genomic segment on which it is acting, can drive two main phenotypes for IBDV: immune-escaping strains from the selection on segment A or strains with functional advantages from the selection on segment B. This last group seems to possess an increased fitness landscape in the viral quasispecies composition, presenting better adaptability to dissimilar environmental conditions and likely becoming the dominant population. The reassortant strains also exhibited a lower mortality rate compared with the well-known vvIBDV strains, which can facilitate their spreading.
Highlights
The analysis of the deduced amino acid sequences of all Polish Infectious bursal disease virus (IBDV) strains revealed the presence of four residues within the hypervariable region of VP2 (HVR), which are characteristic of very virulent strains (G3a, 222 A, 256 I, 294 I, 299 S)
All Polish IBDV strains from the A1 lineage presented a 270 T, which is considered a signature of antigenic variants or classical
The current study provides novel and significant insights into the emergence, diversification, and phylodynamic process of IBDV
Summary
Infectious bursal disease virus (IBDV) is the typical member of the Birnaviridae family, genus Avibirnavirus [1], and is recognized as the causative agent of an immunosuppressive disorder known as Gumboro disease or infectious bursal disease (IBD) [2]. IBDV has the capacity to replicate into B-lymphocytes [3], leading to its depletion in the bursa of Fabricius and resulting in a prolonged immunosuppression [4]. IBDV impacts the poultry industry, causing either direct economic losses due to the mortality in the flocks or indirectly by the burden generated by the immunosuppression in the animals affected, which facilitates the infections with secondary pathogens [5], increases in the feed–conversion ratios [6], and decreases the effectiveness of the vaccines [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
