A gapeworm (Syngamus trachea), also known as a red worm and forked worm, is a parasitic nematode worm that infects the tracheas of certain birds. The resulting disease, known as "gape"  occurs when the worms clog and obstruct the airway. The worms are also known as "red worms" or "forked worms" due to their red color and the permanent procreative conjunction of males and females. Gapeworms are common in young, domesticated chickens and turkeys. When the female gapeworm lays her eggs in the trachea of an infected bird, the eggs are coughed up, swallowed, then defecated. Birds are infected with the parasite when they consume the eggs found in the feces, or by consuming a transport host such as earthworms, snails (Planorbarius corneus, Bithynia tentaculata and others)

Morphology
Males and females are joined together in a state of permanent copulation forming, a Y shape (forked worms). They are also known as the red worms because of their color. Females (up to 20mm long) are much longer than males (up to 6mm long). The life cycle of the gapeworm is peculiar in that transmission from bird to bird may be successfully accomplished either directly (by ingesting embryonated eggs or infective larvae) or indirectly (by ingestion of earthworms containing free or encysted gapeworm larvae they had obtained by feeding on contaminated soil). Life cycle and pathogenesis
In the preparasitic phase, third stage infective larvae (L3) develop inside the eggs at which time they may hatch. Earthworms serve as transport (paratenic) hosts.
Severely affected birds, particularly young ones, will deteriorate rapidly; they stop drinking and become anorexic. At this stage, death is the usual outcome. Adult birds are usually less severely affected and may only show an occasional cough or even no obvious clinical signs. Diagnosis
A diagnosis is usually made on the basis of the classical clinical signs of  "gaping". Subclinical infections with few worms may be confirmed at necropsy by finding copulating worms in the trachea and also by finding the characteristic eggs in the feces of infected birds. Examination of the tracheas of infected birds shows that the mucous membrane is extensively irritated and inflamed. Coughing is apparently the result of this irritation to the mucous lining. Control and treatment
Prevention
In the artificial rearing of pheasants, gapes are a serious menace. Confinement rearing of young birds has reduced the problem in chickens compared to a few years ago. However, this parasite continues to present an occasional problem with turkeys raised on range. Confinement rearing of broilers/pullets and caging of laying hens, have significantly influenced the quantity and variety of nematode infections in poultry. For most nematodes, control measures consist of sanitation and breaking the life cycle rather than chemotherapy. Confinement rearing on litter largely prevents infections with nematodes using intermediate hosts such as earthworms or grasshoppers, which are not normally found in poultry houses. Conversely, nematodes with direct life cycles or those that utilize intermediate hosts such as beetles, which are common in poultry houses, may prosper.