in Chickens: Co-Infection dynamics, effect of production, and mitigation Strategies: A review

In most countries where free-range and intensive farming are gaining importance, an increasing incidence of gastrointestinal nematodes is reported. Of all gastrointestinal nematodes, Ascaridia galli, a common gastrointestinal nematode in poultry, is a major risk to the health and performance of chickens, especially in semi-intensive and free-range systems. The complex dynamics of A. galli infections highlight that they predispose chickens to, or interact synergistically with, other pathogens, exacerbating clinical effects and compromising bird welfare. A. galli triggers innate and adaptive immune responses in the host, while chronic infections undermine the immune system and predispose the birds to secondary infections. The presence of A. galli negatively affects production traits such as growth rate, feed efficiency, and egg production, leading to significant economic losses. Some of the practices that have been mentioned to manage parasite infestation are rotational grazing, natural dewormers, improving biosecurity, tactical use of anthelmintics, and combined approaches to parasite control. Efficient and sustainable management strategies for modern poultry systems can only be achieved if we understand the multiple impacts of A. galli. This review aimed to critically assess and synthesise the latest research on A. galli co-infections in chickens, with emphasis on immunological mechanisms, effects on production, and the effectiveness of various control strategies. This review synthesises findings from peer-reviewed studies published between 2014 - 2024, identified through databases Scopus, Web of Science, Google Scholar, and ScienceDirect. This review highlights the current evidence and gaps, co-infection dynamics, the production effects, and the mitigation efforts, aims to support the development of improved, evidence-based practices for reducing the burden of helminth infections in commercial and smallholder poultry systems.