Reassortant strains of Infectious Bursal Disease Virus (IBDV) were detected in commercial broiler flocks in the Netherlands, Belgium, Denmark, Czech Republic and Germany and in layers and organic broilers in Sweden in the period of 2017−19. Genetic analysis, based on hypervariable region of VP2 gene showed grouping together with very virulent IBDV strains (vvIBDV, Genogroup 3), but these recent viruses formed a separate cluster, which was most closely related to Latvian IBDV strains from 2010−13. VP1 gene of these isolates was most closely related to D78 attenuated IBDV strain. The recently described reassortant IBDV strain (Bpop/03/PL) from Poland with similar genomic constellation (segment A from vvIBDV, segment B from attenuated strain) retained its pathogenicity (80 % mortality in SPF chickens). Infection with the North-West European reassortant IBDVs described in this study showed subclinical feature in the field (without complicating agents) and when tested under standardized pathogenicity test in SPF layer chickens (no mortality or clinical signs, but marked bursa atrophy was observed). Although these recent North-West European reassortant strains had all amino acid residues in their VP2 gene which are considered as markers of vvIBDV strains, they exhibited typical amino acid changes compared to vvIBDV reference strains that should contribute to the determination of pathogenicity. Diagnostic investigations indicated that co-infection with fowl adenovirus or chicken infectious anaemia virus exaggerated the outcome of the IBDV infection (10–20 % mortality). Widespread presence of this reassortant IBDV group in clinically healthy flocks draws attention to the importance of active surveillance.

在2017-19期间，在荷兰，比利时，丹麦，捷克共和国和德国的商业肉鸡群以及瑞典的蛋鸡和有机肉鸡中检出了传染性法氏囊病病毒（IBDV）的重配株。基于VP2基因高变区的遗传分析显示，它们与毒性极强的IBDV株（vvIBDV，基因组3）归为一类，但这些近期病毒形成了一个单独的簇，与2010-13年间的拉脱维亚IBDV株最密切相关。这些分离株的VP1基因与D78减毒IBDV菌株最密切相关。最近描述的来自波兰的具有相似基因组构象的重组IBDV株（Bpop / 03 / PL）（基因组星座来自vvIBDV，减毒株的区段B）保留了其致病性（SPF鸡的死亡率为80％）。本研究中所述的西北欧洲重配型IBDV的感染表现出该领域的亚临床特征（无复杂药物），并且在SPF层鸡中通过标准致病性测试进行了测试（无死亡或临床体征，但观察到明显的法氏囊萎缩）。尽管这些最近的西北欧重配株在其VP2基因中具有所有氨基酸残基，这些残基被视为vvIBDV株的标记，但与vvIBDV参考株相比，它们表现出典型的氨基酸变化，应有助于确定致病性。诊断研究表明，与禽腺病毒或鸡传染性贫血病毒的共同感染夸大了IBDV感染的结果（死亡率为10％至20％）。