Animal and Plant Quarantine Agency, Gimcheon-si, Gyeongsangbuk-do, Korea.
Biogenoci Co., Ltd., Suwon, Gyeonggi-do, Korea.
Poult Sci. 2020 Dec;99(12):6533-6541. doi: 10.1016/j.psj.2020.09.035. Epub 2020 Sep 25.
Although it has rapidly decreased since the early 2000s, fowl typhoid still occurs in commercial layer chickens, causing a significant economic loss in Korea. There is growing concern about the emergence of new pathogenic strains of the causative agent, Salmonella Gallinarum, which is able to overcome vaccine immunity. It has also been suspected that the poultry red mite, Dermanyssus gallinae, which is commonly found in layer chicken farms, may be an important cause of the recurrence of fowl typhoid in the farms. This study was conducted to examine changes in the virulence of recent isolates of S. Gallinarum obtained from layer farms and estimate the potential of the disease transmission of D. gallinae in the farms. Clinical and environmental samples and mites collected from layer farms affected by fowl typhoid between 2013 and 2018 were tested for S. Gallinarum. The isolates were characterized by genotypic analyses and in vitro virulence assays with chicken-derived cell lines. Vaccine protection against recent isolates was examined in the chickens. A total of 45 isolates of S. Gallinarum were collected and there was no evidence of changes in their virulence. It has also been demonstrated that the S. Gallinarum 9R vaccine strain widely used in Korea is still effective in controlling fowl typhoid if the susceptibility of birds to the disease is not increased by stress. Salmonella Gallinarum isolated from the outer and inner parts of D. gallinae, environmental dust, and dead birds of the same farm showed the same or closely related genotypes. Consequently, the present study indicated that the horizontal transmission and environmental persistence of S. Gallinarum and the increased disease susceptibility of chickens in layer farms could be mediated by D. gallinae, causing persistent outbreaks of fowl typhoid.
尽管自 21 世纪初以来，禽伤寒已迅速减少，但仍在商业蛋鸡中发生，给韩国造成重大经济损失。人们越来越担心引起禽伤寒的病原体——鸡白痢沙门氏菌新的致病菌株的出现，这些新菌株能够克服疫苗的免疫。也有人怀疑在蛋鸡养殖场中普遍存在的家禽红螨——鸡皮刺螨，可能是养殖场禽伤寒复发的一个重要原因。本研究旨在检查从蛋鸡养殖场获得的最近分离的鸡白痢沙门氏菌的毒力变化，并评估鸡皮刺螨在养殖场中传播该病的潜力。对 2013 年至 2018 年间受禽伤寒影响的蛋鸡养殖场的临床和环境样本以及从养殖场采集的螨虫进行了鸡白痢沙门氏菌检测。对分离株进行了基因分析和鸡源性细胞系的体外毒力检测。对鸡进行了最近分离株疫苗保护的检测。共采集了 45 株鸡白痢沙门氏菌分离株，未发现其毒力有变化。研究还表明，如果鸡对该病的敏感性不因应激而增加，韩国广泛使用的鸡白痢沙门氏菌 9R 疫苗株仍能有效控制禽伤寒。从鸡皮刺螨的内外部分、环境灰尘和同一养殖场的死鸟中分离出的鸡白痢沙门氏菌显示出相同或密切相关的基因型。因此，本研究表明，鸡皮刺螨可介导鸡白痢沙门氏菌的水平传播和环境持久性，以及蛋鸡养殖场鸡的疾病易感性增加，从而导致禽伤寒持续爆发。
