Gastrointestinal nematodes are re-emerging in countries where the popularity of free-range poultry production systems is increasing. Amongst all gastrointestinal nematodes, Ascaridia galli is of significant concern due to the parasite's direct life cycle and ability to survive extreme environmental conditions. In laying hens, A. galli parasites have been associated with reduced health, welfare, immunity, and egg production. Direct losses are caused by obstruction and damage of the intestinal tract in hens when high worm burdens are present. These result in reduction in egg production and body weight of infected laying hens, consequently leading to significant economic losses for farmers. Furthermore, heavy infections with A. galli may lead to increased mortality within the flock. Indirect losses are due to suppression of immune system function which can increase susceptibility to secondary infections. Infection with A. galli can also alter nutrient utilization and absorption. Levels of anti- A. galli serum and egg yolk antibodies increase following A. galli infection. Elevated antibodies can be used as an indicator of current or previous infections and therefore can be used as a diagnostic tool. The impact of A. galli on hen health and welfare manifests through the depletion of liver lipid reserves and increased use of energy reserves to mount immune responses against the parasite. This review highlights the variable effects of A. galli infection on the performance, health, egg quality, and emphasizes especially on immune responses of free-range laying hens as well as it evaluates various potential detection methods and preventive and control measures of this parasitic disease.

中文翻译：

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鸡蛔虫对蛋鸡生产性能、健康和免疫反应的影响：对老问题的新见解。

在散养家禽生产系统日益普及的国家，胃肠道线虫正在重新出现。在所有胃肠道线虫中，鸡蛔虫由于寄生虫的直接生命周期和在极端环境条件下生存的能力而备受关注。在蛋鸡中，A. galli 寄生虫与健康、福利、免疫力和产蛋量下降有关。当存在高蠕虫负荷时，母鸡的肠道阻塞和损伤会导致直接损失。这些导致受感染的蛋鸡的产蛋量和体重减少，从而导致农民遭受重大经济损失。此外，A.galli 的重度感染可能导致鸡群死亡率增加。间接损失是由于免疫系统功能受到抑制，这会增加继发感染的易感性。感染 A. galli 也会改变营养的利用和吸收。抗鸡鸡血清和蛋黄抗体的水平在鸡鸡感染后增加。升高的抗体可用作当前或以前感染的指标，因此可用作诊断工具。A. galli 对母鸡健康和福利的影响表现在肝脏脂质储备的消耗和能量储备的使用增加以产生针对寄生虫的免疫反应。这篇综述强调了 A.galli 感染对生产性能、健康、卵子质量、