Department of Animal Medicine, Production and Health (MAPS), University of Padova, 35020 Legnaro, Italy.
Department of Birds and Rabbits Medicine, Faculty of Veterinary Medicine, University of Sadat City, Menoufia 32958, Egypt.
Viruses. 2023 Dec 7;15(12):2388. doi: 10.3390/v15122388.
Infectious bursal disease (IBD) is an immunosuppressive disease causing significant damage to the poultry industry worldwide. Its etiological agent is infectious bursal disease virus (IBDV), a highly resistant RNA virus whose genetic variability considerably affects disease manifestation, diagnosis and control, primarily pursued by vaccination. In Egypt, very virulent strains (genotype A3B2), responsible for typical IBD signs and lesions and high mortality, have historically prevailed. The present molecular survey, however, suggests that a major epidemiological shift might be occurring in the country. Out of twenty-four samples collected in twelve governorates in 2022-2023, seven tested positive for IBDV. Two of them were A3B2 strains related to other very virulent Egyptian isolates, whereas the remaining five were novel variant IBDVs (A2dB1b), reported for the first time outside of Eastern and Southern Asia. This emerging genotype spawned a large-scale epidemic in China during the 2010s, characterized by subclinical IBD with severe bursal atrophy and immunosuppression. Its spread to Egypt is even more alarming considering that, contrary to circulating IBDVs, the protection conferred by available commercial vaccines appears suboptimal. These findings are therefore crucial for guiding monitoring and control efforts and helping to track the spread of novel variant IBDVs, possibly limiting their impact.
传染性腔上囊炎病（IBD）是一种免疫抑制性疾病，对全球家禽业造成了重大损害。其病原体是传染性腔上囊炎病毒（IBDV），一种高度抗性的 RNA 病毒，其遗传变异性极大地影响了疾病的表现、诊断和控制，主要通过疫苗接种来实现。在埃及，非常强毒力的毒株（基因型 A3B2）曾占主导地位，这些毒株导致典型的 IBD 症状和病变，死亡率很高。然而，目前的分子调查表明，该国可能正在发生重大的流行病学转变。在 2022 年至 2023 年期间，从埃及 12 个省采集的 24 个样本中，有 7 个样本 IBDV 检测呈阳性。其中 2 个是与其他非常强毒力的埃及分离株相关的 A3B2 株，而其余 5 个是新型变异 IBDV（A2dB1b），这是首次在东亚和南亚以外地区报告。这种新兴的基因型在 2010 年代在中国引发了一场大规模的疫情，其特征是亚临床 IBD 伴有严重的腔上囊萎缩和免疫抑制。更令人担忧的是，它传播到埃及，因为与循环的 IBDV 不同，现有商业疫苗提供的保护似乎并不理想。因此，这些发现对于指导监测和控制工作、帮助跟踪新型变异 IBDV 的传播并可能限制其影响至关重要。
