Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, Benha University, Benha, Egypt.
Central Laboratory for Evaluation of Veterinary Biologics, Cairo, Egypt.
Avian Pathol. 2023 Oct;52(5):351-361. doi: 10.1080/03079457.2023.2236994. Epub 2023 Jul 26.
Avian influenza H9N2 is one of the most commonly circulating viruses in numerous Egyptian poultry farms. The Asian lineage H9N2 exhibits an immunosuppressive effect, and its pathogenicity is amplified when it co-infects with other pathogens, especially with the immunosuppressive infectious bursal disease virus (IBDV), resulting in increased mortality rates. Both vaccines and field infection can exacerbate the pathogenicity of H9N2, particularly in the bursa of Fabricius, causing more significant lymphoid depletion. To comprehend the impact of the IBD vaccine on the viral and pathogenic effect of H9N2 infection in specific pathogen-free chicks (SPF), the experiment was designed as four groups; group 1 served as the negative control, group 2 received (228E) IBD vaccine, group 3 was challenged with H9N2, and group-4 was vaccinated by the IBD vaccine then challenged with H9N2. The clinical signs, relative immune organs weights and histopathological lesion scores were recorded. The tracheal and cloacal H9N2 viral shedding were also measured. Group 4 exhibited a significant decrease ( ≤ 0.05) in the relative bursal weight and an increase in the bursal lesion score when compared with groups 1 and 3 at 4 and 8 days post-challenge (dpc). The tracheal lesion score of group-4 recorded a significant increase when compared with groups 1 and 3. The renal lesion score of group 4 achieved a significant increase when compared with 1 and 3 at 8 dpc. Also, group 4 recorded a significant increase in H9N2 shedding in comparison with groups 1 and 3. Consequently, our study concluded that routine vaccination with the IBD intermediate plus vaccine exacerbates the silent infection of H9N2 resulting in outbreaks.
禽流感 H9N2 是埃及众多家禽养殖场中最常见的病毒之一。亚洲谱系 H9N2 具有免疫抑制作用，当其与其他病原体（特别是具有免疫抑制性的传染性法氏囊病病毒 [IBDV]）共同感染时，其致病性会增强，导致死亡率增加。疫苗接种和田间感染都可使 H9N2 的致病性加剧，特别是在法氏囊，导致更多的淋巴组织耗竭。为了了解 IBD 疫苗对无特定病原体小鸡（SPF）中 H9N2 感染的病毒和致病性的影响，实验设计了四个组；第 1 组作为阴性对照，第 2 组接种（228E）IBD 疫苗，第 3 组受到 H9N2 攻击，第 4 组先接种 IBD 疫苗，然后再受到 H9N2 攻击。记录临床症状、相对免疫器官重量和组织病理学病变评分。还测量了气管和泄殖腔的 H9N2 病毒脱落量。第 4 组在攻毒后第 4 天和第 8 天，与第 1 组和第 3 组相比，相对法氏囊重量显著下降（≤0.05），法氏囊病变评分增加。第 4 组的气管病变评分与第 1 组和第 3 组相比显著增加。第 4 组的肾脏病变评分在第 8 天攻毒时与第 1 组和第 3 组相比显著增加。此外，与第 1 组和第 3 组相比，第 4 组的 H9N2 脱落量显著增加。因此，我们的研究得出结论，常规接种 IBD 中程加疫苗会加剧 H9N2 的隐性感染，导致暴发。
