Worm parasites in poultry

On commercial poultry farms, fowls are rarely troubled by worm parasites because of the housing, husbandry and cleaning methods used. However, in flocks housed in free range systems where poultry regularly scratch and peck at the soil, worms can parasitise chickens and affect their health.

The most common parasitic worms that may cause problems in poultry are:

  • roundworms
  • hairworms
  • tapeworms
  • caecal worms.

Scientific name

Roundworm: Ascaridia galli
Hairworm: Capillaria spp.
Caecal worm: Heterakis gallinarum


Earthworms, flies, slugs, snails and beetles may be carriers of parasitic worms that affect poultry.

Life cycle

Birds become infected by picking up worm eggs from the litter, soil or droppings. Once in the gut, the eggs hatch and mature. The eggs of the worms are excreted in the birds' droppings and the cycle starts again.

Some worms require a host to complete their life cycle and poultry must ingest the affected host to be become infected by the parasite.

Different worms usually infect various parts of the intestine:

  • Hairworms are found in the oesophagus, the crop or the upper part of the small intestine.
  • Tapeworms attach to the wall of the upper and middle thirds of the small intestine.
  • Roundworms are found in the small intestine.
  • Caecal worms are found in the blind end of the caeca.

Affected animals

  • poultry
  • chickens

Clinical signs

Birds carrying worms show similar signs, including:

  • slow growth
  • reduced appetite and weight loss
  • ruffled feathers, droopiness and an unthrifty look
  • diarrhoea
  • reduced egg production
  • pale comb.

In severe cases, worms can be detected in the droppings of birds.


The greatest impacts in a worm infestation are reduced feed efficiency and egg quality. In severe infestations, death may occur. Occasionally worms are found inside the chicken egg.

Caecal worms can harbour the disease organism that causes blackhead. Chickens can be resistant to blackhead, however turkeys are quite vulnerable.

How it is spread

Worms are usually transmitted from bird to bird through the faecal oral route. This is where worm eggs are excreted in droppings and then ingested by birds that scratch and peck at the soil, litter or droppings. Ingestion of infected earthworms, bugs and other secondary hosts can also spread parasitic worms.

Risk period

Eggs excreted into the environment require warm and moist conditions to become infective. The summer months are often the time when worm problems are most prevalent due to the climatic conditions that favour their growth.


Wet areas encourage worm growth so have good drainage on the range area to limit water from pooling and puddling.

Treat with anti-parasitic drugs, usually added to the water. Check veterinary advice and follow manufacturer's directions, including any withholding periods where eggs and meat should not be consumed.

Regularly clean poultry housing, including their feeders and drinkers and remove any build-up of faecal material.

Using a combination of these methods will help to achieve the best results.