Worms living inside the intestines of chickens fall mainly into four categories.

Roundworms (ascarids), usually 5 to 7 cm (2-3 inches) long
Hairworms (capillaria), only measure 1-1,5 cm long
Caecal worms (heterakis), usually 1,5 cm long
Tape worms, usually 7-10 cm long, consisting of several small segments

Clinical signs

Mature roundworms are not a major cause of the disease, but the larvae can damage the intestinal lining, causing enteritis, anaemia, decreased egg production and at times eggs with pale yolks.

Capillaria cause more damage to the intestinal lining and can cause enteritis and anaemia with decreased egg production and the appearance of pale egg yolks ("platinum yolks").

Caecal worms are found in the caeca and do not cause serious damage, except that their eggs can transmit blackhead, mainly in turkeys (see blackhead).

Tapeworms are infrequently found and do not cause serious damage, except that they use the nutrients of the host chicken.

Diagnosis

Examination of the intestinal contents will reveal roundworms, caecal worms, and tape worms without difficulty. Capillaria can usually be found when intestinal contents are washed through a fine mesh sieve.

Treatment and control

Roundworms and caecal worm infections can be treated with piperazine. Piperazine is not effective against tape worms and capillaria for which other anthelmintics are required.