Ascaridia galli

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Ascaridia galli is a nematode parasite that causes ascariasis, or worm infection, in poultry.

Life cycle Eggs have thick, albuminous shell that are resistant to desiccation and persist for a long time in the environment. Larvae do not hatch but moult inside the eggs until it reaches the L3 stage. This can take about two weeks but the period depends on other factors such as weather condition. The infective eggs are ingested by a chicken where it reaches the small intestine and hatches. Temperature, carbon dioxide levels and pH are thought to be triggering factors that signal the larvae to hatch from its egg. The larvae then burrows into the mucosal lining of the small intestine where it undergoes two additional moults. It is this phase of their lifecycle where these worms causes the most damage to their host. They then re-enter the small intestine and develop into adults where they live their lives out feeding on gut content and making a vast amount of eggs that would then be excreted by a host and free to continue their lifecycle. If the animal is able to mount an immune respond to the larvae, i.e. from pre-exposure, the larvae do not develop into adults but hides in the mucosa of the small intestine. This is common for infection of older birds. Transport host such as earthworm is thought to play a role in transmission of Ascaridia galli and hence, free range birds tend to have a higher risk of infection.