Infectious bursal disease virus (IBDV) is an economically relevant and widespread pathogen that produces immunosuppression in young chickens. IBDV is genetically classified into seven genogroups (G1-G7), where the traditional classic, variant and very virulent strains correspond to G1, G2 and G3, respectively. The G4 strains, also known as 'distinct' (dIBDV), have recently acquired increased relevance because of their prevalence and notorious impair to the poultry industry in South America. Here, worldwide dIBDV strains were studied using phylogenetic and phylodynamic approaches. The phylogenetic analyses performed using partial and complete sequences of both viral segments (A and B) consistently clustered the dIBDV strains in a monophyletic group. The analyses of the VP5, polyprotein and VP1 coding regions identified amino acid residues that act as markers for the identification of the entire dIBDV group or different sub-populations. The phylodynamic analyses performed using the hypervariable region of VP2 indicated that the dIBDV strains emerged in the early 1930s in Eastern Europe, shortly after the emergence of classic strains (1927) and before variant (1949) and very virulent strains (1967). The analysis of the migration routes indicated that after its emergence, the dIBDV strains spread to Eastern Asia around 1959, to Brazil around 1963, and to Argentina around 1990. These inter-continental migrations resulted in three sub-populations that are currently represented by strains from (a) Brazil, (b) Eastern Asia and Canada, and (c) Eastern Europe, Argentina and Uruguay. Taken together, our results highlight the complex evolutionary history of IBDV and the importance of new phylodynamic data to unravel and nearly follow the different evolutionary pathways taken by this important poultry pathogen.

中文翻译：

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传染性法氏囊病病毒的祖传世系的起源和全球传播。

传染性法氏囊病病毒（IBDV）是一种与经济相关且广泛存在的病原体，可在雏鸡中产生免疫抑制作用。IBDV在基因上分为七个基因组（G1-G7），其中传统的经典，变异和极强毒株分别对应于G1，G2和G3。G4品系，也称为“独特”（dIBDV），由于它们的流行和对南美洲家禽业的臭名昭著的危害，最近已变得越来越重要。在这里，使用系统发育和系统动力学方法对全世界的dIBDV菌株进行了研究。使用两个病毒片段（A和B）的部分和完整序列进行的系统发育分析一致地将dIBDV菌株聚集在一个单系统组中。VP5的分析，多蛋白和VP1编码区鉴定出氨基酸残基，这些氨基酸残基可作为鉴定整个dIBDV组或不同亚群的标记。使用VP2的高变区进行的系统动力学分析表明，dIBDV菌株于1930年代初在东欧出现，在经典菌株（1927）出现后不久，在变种（1949）和高毒力菌株（1967）出现之后不久。对迁徙路线的分析表明，dIBDV菌株出现后，在1959年左右扩散到东亚，在1963年左右扩散到巴西，再到1990年左右扩散到阿根廷。这些洲际迁移导致目前以菌株为代表的三个亚种群来自（a）巴西，（b）东亚和加拿大，以及（c）东欧，阿根廷和乌拉圭。在一起