There are many types of worm which can infect poultry, although not all types lead to problems.
Roundworms are not a major cause of disease, but can damage the intestinal lining and cause a decrease in egg production.
Capillaria contorta and capillaria annulta are hair-like worms found in the crop and oesophagus. They can be seen with the naked eye, burying their heads in the lining of the mouth, crop and oesophagus, causing inflammation and reducing the contractile ability of the affected parts of the gastro-intestinal system. This then in turn leads to weight loss and poor appetite.
Tetrameres develop as larvae in grasshoppers, beetles and small crustaceans (eg woodlice), before infected poultry when eaten. The females suck blood across the lining of the stomach, causing anaemia. These worms usually affect young chickens.
Treatment for all types of worms is through the use of a well-established worming product. Many keepers choose to worm their stock prophylactically twice a year. Please ask for advice about suitable products.