Diagnostic investigation of avian reovirus field variants circulating in broiler chickens in Pennsylvania of United States between 2017 and 2022

Avian reovirus (ARV) has been continuously affecting the poultry industry in Pennsylvania (PA) in recent years. This report provides our diagnostic investigation on monitoring ARV field variants from broiler chickens in Pennsylvania. Genomic characterization findings of 72 ARV field isolates obtained from broiler cases during the last 6 years indicated that six distinct cluster variant strains (genotype I-VI), which were genetically diverse and distant from the vaccine and vaccine-related field strains, continuously circulated in PA poultry. Most of the variants clustered within genotype V (24/72, 33.3%), followed by genotype II (16/72, 22.2%), genotype IV (13/72, 18.1%), genotype III (13/72, 18.1%), genotype VI (05/72, 6.94%), and genotype I (1/72, 1.38%). The amino acid identity between 72 field variants and the vaccine strains (1133, 1733, 2408, 2177) varied from 45.3% to 99.7%, while the difference in amino acid counts ranged from 1–164. Among the field variants, the amino acid identity and count difference ranged from 43.3% to 100% and 0 to 170, respectively. Variants within genotype V had maximum amino acid identity (94.7–100%), whereas none of the variants within genotypes II and VI were alike. These findings indicate the continuing occurrence of multiple ARV genotypes in the environment.

近年来，禽呼肠孤病毒（Avian reovirus, ARV）持续影响美国宾夕法尼亚州（Pennsylvania, PA）的家禽养殖业。本报告针对宾夕法尼亚州肉鸡源禽呼肠孤病毒野外毒株的监测工作展开诊断调查。对过去6年间从肉鸡临床病例中分离得到的72株禽呼肠孤病毒野外分离株进行基因组特征解析后发现，共存在6种独立聚类的变异毒株（基因型I至VI）；这些毒株与疫苗株及疫苗相关野外毒株遗传多样性显著、亲缘关系疏远，并持续在宾夕法尼亚州的家禽种群中循环传播。其中，基因型V包含的毒株数量最多，共计24株，占比33.3%；其次依次为基因型II（16株，22.2%）、基因型IV（13株，18.1%）、基因型III（13株，18.1%）、基因型VI（5株，6.94%）以及基因型I（1株，1.38%）。72株野外变异株与疫苗株（1133、1733、2408、2177）之间的氨基酸序列一致性介于45.3%至99.7%之间，氨基酸残基数量差异范围为1至164个。在野外变异株内部，氨基酸序列一致性范围为43.3%至100%，氨基酸残基数量差异范围为0至170个。基因型V内的变异株之间氨基酸序列一致性最高，为94.7%至100%；而基因型II与基因型VI内的变异株之间无同源性一致的毒株。上述研究结果表明，宾夕法尼亚州家禽环境中持续存在多种禽呼肠孤病毒基因型。