Tape worms or Cestodes consist of several species and are not often seen but the most troublesome one is the small tape worm, Davainia Proglottina which may accumulate in large numbers in the duodenum.
The large tape worm is called Raillientina.
The Davainea or small tape worms have an indirect life cycle, infecting the chicken through eating slugs and snails containing the cysticeroids (immature parasites).They are considered to be the most pathogenic of all tape worms.They are made up of up to nine segments with 80-90 small hooks arranged in rows on the head. Tape worms are uncommon in barn or cage kept hens because they dont come into contact with the intermediate hosts.
Symptoms include: diarrhoea and wasting. On examination of a dead bird there may be some thickening of the intestines and signs of bleeding. The worms are only 1.5-4mm long which makes them difficult to see.
These large tape worms are pale yellow, segmented, flat worms and vary in shape nd are able to shrink and expand and separate into segments. they remain in the host for life if they are not passed out in the droppings.