Syngamus trachea

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Syngamus trachea
Kingdom Animalia
Phylum Nematoda
Class Secernentea
Order Strongylida
Super-family Strongyloidea
Family Syngamidae
Genus Syngamus
Species S. trachea

Also known as: Syngamus parvis — Syngamus gracilis — Gapeworm


S. trachea is a nematode of the superfamily Strongyloidea, and is found worldwide. It commonly affects the lungs of many game birds within the UK.


Chickens, turkeys, pigeons and game birds.


The female is deep red in colour, and the male is white. They are permanently copulating forming a Y shape. The worms have large buccal capsules.

Life Cycle

L1-L3 develops in the egg. Infection may be via ingestion of L3 in the egg, or a hatched L3, or ingestion of a paratenic host, most commonly the earthworm and the slug.

The L3 penetrate the intestine and then enter the lungs. The L3 then undergo two further moults, and copulation occurs in the trachea a few days later.

The prepatent period of S. trachea is between 16 and 20 days.

Clinical Signs

The parasite causes laboured breathing, and 'gaping': affected birds stretch out their necks, open their mouths and gasp for air producing a hissing noise as they do so. Severe infestation may obstruct the tracheal lumen resulting in suffocation.

Other clinical signs include: coughing, weakness, emaciation and shaking of the head.

Adult birds are usually less affected and may only show an occasional cough or even no obvious clinical signs.


Diagnosis is usually made on the basis of clinical signs.

On post mortem: small nodules and adult worms can be found in the trachea of infected birds.

Faecal smears can also be performed, which may reveal characteristic bioperculate eggs.

Differential diasnoses:


Treatment and Control

Medication licensed in the UK and effective against Syngamus include anthelmintics of the benzimidazole group and nitroxynil. The benzimidazoles are best administered in the feed, nitroxynil is given in drinking water. Caution must be exercised in using nitroxynil which may result in toxicity, kidney damage and egg production problems; it is not recommended for use in birds over 17 weeks old.

Infection can be prevented by raising birds on wire so they do not come into contact with the eggs or intermediate hosts.

Birds raised on the ground are always at risk. They can be treated prophylactically with an anthelmintic. Since wild birds can also carry the parasite, efforts should be made to prevent their faeces from falling on the ground where poultry is being raised.


Herenda, D. (1996) Poultry diseases and meat hygiene Wiley-Blackwell

Shapiro, L. (2005) Pathology and parasitology for veterinary technicians Cengage Learning

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