Gapeworm

Gapeworm
	Gapeworms in the trachea of a common pheasant
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Chromadorea
Order:	Rhabditida
Family:	Syngamidae
Genus:	Syngamus
Species:	S. trachea
Binomial name
	Syngamus trachea; Montagu, 1811

A gapeworm (Syngamus trachea), also known as a red worm and forked worm, is a

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 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

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 (

slugs

.

The parasitic phase involves substantial migration in the

asphyxiation

.

Pheasants appear to be particularly susceptible to infections resulting in

guinea fowl

.

The male worm, in the form of lesions, remains permanently attached to the tracheal wall throughout the duration of its life. The female worms apparently detach and reattach from time to time in order to obtain a more abundant supply of food.

Epidemiology

Earthworm transport hosts are important factors in the transmission of Syngamus trachea when poultry and

game birds

are reared on soil. The longevity of L3s in earthworms (up to 3 years) is particularly important in perpetuating the infection from year to year.

Wild birds may serve as reservoirs of infection and have been implicated as the sources of infections in outbreaks on game-bird farms as well as poultry farms. Wild

jays, jackdaws, rooks, starlings and crows

.

There is also evidence to suggest that strains of Syngamus trachea from wild bird reservoir hosts may be less effective in domestic birds; if they have an earthworm transport host rather than direct infections via ingestion of L3s, or eggs containing L3s.

Clinical signs

Blockage of the bronchi and trachea with worms and mucus will cause infected birds to gasp for air. They stretch out their necks, open their mouths and gasp for air producing a hissing noise as they do so. This "gaping" posture has given rise to the common term "gapeworm" to describe Syngamus trachea.

These clinical signs first appear approximately 1–2 weeks after infection. Birds infected with gapeworms show signs of weakness and

convulsive

shake in an attempt to remove the obstruction from the trachea so that normal breathing may be resumed.

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

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

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

intermediate hosts such as beetles

, which are common in poultry houses, may prosper.

Treatment of the soil or litter to kill intermediate hosts may be beneficial. Insecticides suitable for litter treatment include carbaryl, tetrachlorvinphos (stirofos). However, treatment is usually done only between grow-outs. Extreme care should be taken to ensure that feed and water are not contaminated. Treatment of range soil to kill ova is only partially successful.

Changing litter can reduce infections, but treating floors with oil is not very effective. Raising different species or different ages of birds together or in close proximity is a dangerous procedure as regards parasitism. Adult turkeys, which are carriers of gapeworms, can transmit the disease to young chicks or pheasants, although older chickens are almost resistant to infection.

Treatment

prophylactically to turkey poults. 5-Isopropoxycarbonylamino-2-(4-thizolyl)-benzimidazole was found to be more efficacious than thiabendazole or disophenol

.

The level of control with three treatments of cambendazole on days 3–4, 6–7, and 16-17 post-infection was 94.9% in chickens and 99.1% in turkeys. Levamisole (Ergamisol), fed at a level of 0.04% for 2 days or 2 g/gal drinking water for 1 day each month, has proven effective in game birds. Fenbendazole (Panacur) at 20 mg/kg for 3–4 days is also effective. Ivermectin injections may be effective in treating resistant strains.