Species Diversity and Geographical Distribution of Poultry Ascaridids: A Scoping Review

Poultry nematodes, particularly Ascaridid species, significantly affect avian health and productivity and are widely distributed globally. Yet despite over 80% of poultry in developing countries being raised under extensive rearing systems, knowledge on infection risks posed by different poultry nematodes remains limited. This scoping review synthesizes the knowledge based on the evaluation of existing literature, consolidating insights into the diverse Ascaridid species infecting poultry and their distribution, thereby contributing to the broader comprehension and management of avian nematodes. We found a total of 11 nematode species infecting 8 host types having median prevalence of 24% (IQR: 41.07%-12%). Ascaridia galli and Heterakis gallinarum were the cosmopolitan nematodes reported with median prevalences of 28.75% and 17.20%, respectively. These nematodes almost have a cosmopolitan distribution with a potentiality of transmission between domesticated and across wildlife-poultry pathways. However, during this scoping review, analysis verifies that six Ascaridia and five Heterakis species are present in chickens worldwide, with Africa and Asia showing a higher prevalence of infection because of adopting long-standing free-range poultry farming. The occurrence and diversity of Ascaridid infections in poultry depend on geography, host type, diagnostic methods, and rearing practices, highlighting the need for effective disease management, biosecurity, and control of anthelmintic resistance.