Round worms or Nematodes are the group of endo-parasites of most interest to the hen-keeper. They invade the digestive track and include Large Round worms, Capillaria, Caecal, Gizzard and Gape worms.
Hair Worms (Capillaria) which include Obsignata, Caudinflata and Contorta, are about 1-1.5cm long and very difficult to see due their hair like structure. Some follow a direct life cycle and others, an indirect life cycle by using the earth worm as an intermediate host. They can be found in the crop, oesophagus, proventriculus, small intestine or caecum.
Symptoms can include: weakness, emaciation, droopiness, pale egg yolks, blood stained diarrhoea, anaemia and sometimes death. Young birds can be worse affected. Through post mortem examination the intestines may appear inflamed and thickened and the lining may be peeling away. On close examination by separating the contents of the gut, the worms may be seen and the carcase will also look anaemic.
The Caecal worm (Heterakis gallinae) is about 1.5cm long, has a direct life cycle and lives in the caeca, two extensions from the lower end of the gut with blind endings.Although they don’t harm the hen, their eggs can carry blackhead which affects turkeys, pheasants, quail, pea and guinea fowl – so in this case the hen is the intermediate host.
There are usually no symptoms, and they do not harm the hen.
The Large Roundworm (Ascaridia Galli) is introduced into the birds when it eats embryonated eggs which are in the litter or on the land having been passed out of an infected bird via the droppings. The eggs become infective in ten to twelve days after it has been passed out of the bird. The worm can be up to 7.5cm long and is found, sometimes in large numbers, in the small intestine.