California Animal Health and Food Safety Laboratory System, Turlock Branch, University of California, Davis, Turlock, CA 95380.
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616.
Avian Dis. 2023 Jun;67(2):212-218. doi: 10.1637/aviandiseases-D-23-00014.
False layer syndrome is a condition in which the reproductive tract of chicks is infected with infectious bronchitis virus (IBV) strains that cause permanent damage to the oviduct. These chickens subsequently develop cystic oviducts and do not lay eggs, and affected flocks fail to reach expected egg production peaks. The California Animal Health and Food Safety laboratory, Turlock Branch, received four separate case submissions from a 25-to-28-wk-old commercial ISA Brown layer flock. Birds were submitted for diagnostic evaluation due to suboptimal egg production and vent pecking. Submissions totaled 31 birds and consisted of live layers, recent mortality, and a flat of eggs. No clinical signs were observed in the submitted live birds. The most common gross findings included cystic left oviducts, signs of vent pecking, ovarian regression, and yolk coelomitis. The eggs were abnormally shaped with irregular, white, gritty deposits on the surface of the shell. Microscopically, there was atrophy of the oviducts, glandular hypoplasia, and lymphocytic salpingitis. In addition, lymphoplasmacytic tracheitis was observed, and renal tubules were dilated with multifocal areas of mineralization. IBV was identified by reverse transcription quantitative PCR from cecal tonsil tissue pools and tracheal swab pools. Sequencing of the S1 hypervariable region of IBV and whole-genome IBV sequencing were 97% homologous to the California variant CA1737/04. Definitive proof of the CA1737 strain's causing reproductive abnormalities will require challenge studies with fulfillment of Koch's postulates and evaluation of confounding and risk factors.
假层综合征是一种病症，雏鸡的生殖道感染了传染性支气管炎病毒（IBV）株，这些病毒株会对输卵管造成永久性损伤。这些鸡随后会发展出囊状输卵管，不再产蛋，受感染的鸡群无法达到预期的产蛋高峰。加利福尼亚动物健康和食品安全实验室特莱洛克分部收到了来自一个 25 到 28 周龄商业 ISA 棕色层鸡群的四起独立病例报告。由于产蛋量不佳和泄殖腔啄癖，这些鸡被提交进行诊断评估。提交的病例共有 31 只鸡，包括活鸡、近期死亡鸡和一盒鸡蛋。提交的活鸡没有观察到临床症状。最常见的大体病变包括左侧输卵管囊状、泄殖腔啄癖、卵巢退化和卵黄囊膜炎。鸡蛋形状异常，蛋壳表面有不规则的白色、沙砾状沉积物。显微镜下，输卵管萎缩，腺体发育不良，淋巴细胞性输卵管炎。此外，还观察到淋巴浆细胞性气管炎，肾小管扩张，伴有多处矿化。通过对盲肠扁桃体组织池和气管拭子池的逆转录定量 PCR，鉴定出了 IBV。IBV 的 S1 高变区和全基因组 IBV 测序与加利福尼亚变异株 CA1737/04 的同源性为 97%。CA1737 株引起生殖异常的明确证据需要通过满足科赫假设的挑战研究来证明，并评估混杂因素和风险因素。
