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The importance of worming chickens

All animals are susceptible to worms. Hens are no different. Don’t be lulled into thinking that your hens don’t have visitors just because you haven’t seen any in their droppings. In fact, if you actually see worms in their excreta, it means that your hen has a heavy worm burden. Worms lay thousands of eggs every day that are not always visible and left untreated they can play havoc with your flock. We give you the lowdown on what to look out for and how to tackle these sneaky little parasites, so your hens stay happy and healthy.

How do worms affect my chickens?

Firstly, if you suspect that your hens have worms, don’t worry – it’s normal for animals to pick them up and straightforward to treat. Worms are parasites that live inside your hens’ guts and zap them of vital nutrients and some types of worms can cause them discomfort. Worms can impact your hen’s immune system, damage the lining of the gut, and have an effect on the ability your hen has to absorb nutrients. Their egg production might drop, and hens can lose weight and condition.  In extreme cases, worm infestation can lead to malnourishment and infection.

Types of worm


Ascaridia (roundworm) is the largest (up to 7cm long), inhabiting the small intestine. It burrows into the gut and large burdens may cause a blockage, resulting in damage, inflammation and a reduction in the absorption of nutrients. This leads to weight loss, diarrhoea, fewer eggs and anaemia if left untreated. These worms are very common.


Capillaria (hairworm), the smallest worm (pictured above), about 1.5mm, can be particularly damaging and commonly colonise in the crop. These worms use earthworms in part of their life cycle. Hairworms typically cause diarrhoea, anaemia, weight loss, loss of appetite and the hens can look depressed and dull.

Heterakis gallinarum

Heterakis gallinarum, or the caecal worm, is found in the caecum of hens. The worm is relatively harmless; however, it can carry ‘blackhead’, another parasite, which normally affects turkeys but can occasionally affect chickens. Blackhead burrows into the caeca, leading to inflammation and yellow droppings. The parasite migrates to the liver causing damage which can result in death. Unfortunately, there is no specific licensed treatment for blackhead, so worming is the preventative option.

Syngamus trachea

Syngamus trachea, the gapeworm, lives in the trachea (windpipe) causing gasping and head shaking. Because of the clinical signs, gape worms are the most commonly thought of worms affecting hens. However, they are quite rare and the cause is usually respiratory disease.


Tapeworms rarely affect hens; if you do suspect them consult your vet. It is easy to assume your flock have worms, so one way to check is to get the hens’ droppings tested. This avoids over-worming and will advise you of the species present.

How do worms affect my chickens?

There are a few signs that may indicate your birds have a parasite infestation, so keep an eye out for the following:

  • Slow growth
  • Reduced appetite and weight loss
  • Ruffled feathers and a droopy appearance
  • Pale comb
  • Greenish faeces

Please consult your veterinarian with any concerns regarding your hens’ health.

How do worms spread?

Worms are primarily transmitted through poultry droppings. As we all know, hens aren’t all that picky about where they do their business and other members of the flock are apt to peck, tread in and spread droppings without a second thought. The ingested worms then set up camp in another hen’s gut and the cycle begins again. This is known as a direct life cycle. Worms can also be transferred via and indirect life cycle, in which they are picked up by snails, slugs and earthworms – in other words all of the tasty morsels that our hens love to eat! In this way, they are still transferred into your hens’ guts and the same issues occur – it really is a case of ‘you are what you eat’!

Will I need to worm my hens when I bring them home on collection day?

This is a common question we are asked at Hen Central. If you are adopting ex-commercial caged hens there is no need to worm immediately. Hens that have been caged and not in contact with the ground are unlikely to have worms. Barn or free–range hens are in contact with the ground and therefore may have the opportunity to pick up worms – we do recommend seeking advice with worming through your veterinarian.

hen being treated by a vet

How can you ensure your hens are worm free?

Its best practice to clean out the coop during worming and use a disinfectant that destroys worm eggs. Keep the coop as dry and mud free as possible and change bedding regularly. If your hens are confined to a run, it helps to reduce worm burdens by moving the run regularly or changing the surface material every so often. For further advice and information, contact your vet or call our Hen Helpline on 01884 860086.

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