Large Roundworm or Ascarida Galli

Large Roundworm or Ascarida Galli worms are 5 to 8cm long and live in the middle part of a bird’s intestine. Bad infestations of large roundworms in poultry usually occur when birds are kept in intensive conditions on dirty litter or in runs that have been used for many years.

Chicken RoundwormLarge roundworms can be seen with the naked eye. Infestations of roundworm occur ‘directly’ that is, by birds eating worm eggs that have been passed out in droppings. These eggs have to be infective which takes 10 days.

Once eaten, eggs hatch in the bird’s proventriculus and the larvae move on to part of the intestine called the lumen.

A week later, the larvae get into the mucosa, part of the intestine wall and start to cause damage. Occasionally, large roundworms crawl up the oviduct and can appear inside eggs which is not pleasant at all when you crack an egg open!

Large Roundworm
Roundworms inside the intestines shown after a post mortem. Photo courtesy of Elanco.

Loss of egg production and pale yolk colour and anaemia are the biggest signs of a large roundworm infection as well as a loss in weight gain for growing birds.

Birds can look depressed and eventually if the infestation is heavy, they can die as the worms will block the intestines. This can be seen clearly in the photo to the right where large roundworms can be seen in the intestine after a post-mortem examination.


As with all internal parasites, there are many treatments that will kill these worms. Worming Chickens provides some ideas for worming poultry.

Flubenvet is a licensed in feed wormer that can be used with most poultry.

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Tim Daniels

Tim is the founder of the poultrykeeper website and lives in Herefordshire, UK. He keeps Cream Legbar chickens, Silver Sebright bantams and hybrid layers for eggs, Abacot Ranger ducks, Brecon Buff geese and some quail.

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