Strongyloides avium are a type of threadworm (or pinworm) that are found to infest the cecum of poultry. S. avium are most frequently found in tropical and subtropical regions worldwide, often in rural areas with poor sanitary conditions. Adult S. avium are very thin and small and almost appear transparent. They infest the small intestines of the birds, where they lay their eggs which are shed with the bird's feces, into the environment. They can remain infective in the environment for up to 4 months by suitable conditions, but they don't resist cold and dryness.