A gapeworm (''Syngamus trachea''), also known as a red worm and forked worm, is a
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
nematode worm that infects the
trachea
The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
s of certain
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s. 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
The turkey is a large bird in the genus ''Meleagris'', native to North America. There are two extant turkey species: the wild turkey (''Meleagris gallopavo'') of eastern and central North America and the ocellated turkey (''Meleagris ocellat ...
.
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
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s,
snail
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...
s (''
Planorbarius corneus
''Planorbarius corneus'', common name the great ramshorn, is a relatively large species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails, or planorbids, which all have ...
'', ''
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
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesis ...
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
encyst
A microbial cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist or rarely an invertebrate animal, that helps the organism to survive in unfavorable environmental conditions. It can be thought of as a state of ...
ed 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
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...
) hosts. Larvae have been shown to remain viable for more than three years encapsulated in earthworm
muscles
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of musc ...
. Other invertebrates may also serve as paratenic hosts, including terrestrial
snails
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...
and
slugs
Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a sma ...
.
The parasitic phase involves substantial migration in the
definitive host
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...
to reach the predilection site. Young birds are most severely affected with migration of larvae and adults through the
lungs
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side ...
causing a severe
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...
.
Lymphoid nodules form at the point of attachment of the worms in the
bronchi
A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...
and trachea. Adult worms also appear to feed on blood. Worms in the bronchi and trachea provoke a
hemorrhagic
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
tracheitis
Tracheitis is an inflammation of the trachea.
Although the trachea is usually considered part of the lower respiratory tract, in ICD-10 tracheitis is classified under "acute upper respiratory infections".
Symptoms
* Increasing deep or barking cr ...
and
bronchitis
Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
, forming large quantities of
mucus
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
, plugging the air passages and, in severe cases, causing
asphyxiation
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that ca ...
.
Pheasants appear to be particularly susceptible to infections resulting in
mortality rates
Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...
as high as 25% during outbreaks. The rapidly growing worms soon obstruct the
lumen of the trachea, causing suffocation. Turkey poults, baby chicks and pheasant chicks are most susceptible to infection. Turkey poults usually develop gapeworm signs earlier and begin to die sooner after infection than young chickens.
Lesions
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals.
Types
There is no designated classifi ...
are usually found in the trachea of turkeys and pheasants but seldom if ever in the tracheas of young chickens and
guinea fowl
Guineafowl (; sometimes called "pet speckled hens" or "original fowl") are birds of the family Numididae in the order Galliformes. They are endemic to Africa and rank among the oldest of the gallinaceous birds. Phylogenetically, they branched o ...
.
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 bird
Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are ofte ...
s 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
reservoir hosts may include pheasants,
ruffed grouse
The ruffed grouse (''Bonasa umbellus'') is a medium-sized grouse occurring in forests from the Appalachian Mountains across Canada to Alaska. It is the most widely distributed game bird in North America. It is non-migratory. It is the only specie ...
,
partridges
A partridge is a medium-sized galliform bird in any of several genera, with a wide native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They are sometimes grouped in the Perdic ...
,
wild turkey
The wild turkey (''Meleagris gallopavo'') is an upland ground bird native to North America, one of two extant species of turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic turkey, which was originally d ...
s,
magpies
Magpies are birds of the Corvidae family. Like other members of their family, they are widely considered to be intelligent creatures. The Eurasian magpie, for instance, is thought to rank among the world's most intelligent creatures, and is one ...
,
meadowlarks,
American robins,
grackle
Grackles is the common name of any of 11 passerine birds (10 extant and one extinct) native to North and South America. They belong to various genera in the icterid family. In all the species with this name, adult males have black or mostly blac ...
s,
jays
A jay is a member of a number of species of medium-sized, usually colorful and noisy, passerine birds in the Crow family, Corvidae. The evolutionary relationships between the jays and the magpies are rather complex. For example, the Eurasian m ...
,
jackdaw
Jackdaws are two species of bird in the genus ''Coloeus'' closely related to, but generally smaller than, the crows and ravens (''Corvus''). ''Coloeus'' is sometimes treated as a subgenus of ''Corvus'', including by the IUCN.Madge & Burn (1994) ...
s,
rook
Rook (''Corvus frugilegus'') is a bird of the corvid family. Rook or rooks may also refer to:
Games
*Rook (chess), a piece in chess
*Rook (card game), a trick-taking card game
Military
* Sukhoi Su-25 or Rook, a close air support aircraft
* USS ...
s,
starling
Starlings are small to medium-sized passerine birds in the family Sturnidae. The Sturnidae are named for the genus '' Sturnus'', which in turn comes from the Latin word for starling, ''sturnus''. Many Asian species, particularly the larger ones, ...
s and
crow
A crow is a bird of the genus '' Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientifica ...
s.
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
emaciation
Emaciation is defined as the state of extreme thinness from absence of body fat and muscle wasting usually resulting from malnutrition.
Characteristics
In humans, the physical appearance of emaciation includes thinned limbs, pronounced and protrud ...
, usually spending much of their time with eyes closed and head drawn back against the body. An infected bird may give its head a
convulsive
A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is sometimes used as a s ...
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
Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...
. At this stage, death is the usual outcome. Adult birds are usually less severely affected and may only show an occasional
cough
A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ph ...
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
An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death or to evaluate any di ...
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
A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...
is extensively irritated and
inflamed
Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecu ...
. 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
Range may refer to:
Geography
* Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra)
** Mountain range, a group of mountains bordered by lowlands
* Range, a term used to i ...
. Confinement rearing of
broilers/pullet
The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adul ...
s 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
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
and breaking the life cycle rather than
chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
. Confinement rearing on
litter
Litter consists of waste products that have been discarded incorrectly, without consent, at an unsuitable location. Litter can also be used as a verb; to litter means to drop and leave objects, often man-made, such as aluminum cans, paper cups ...
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
beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s, 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
Carbaryl (1-naphthyl methylcarbamate) is a chemical in the carbamate family used chiefly as an insecticide. It is a white crystalline solid previously sold under the brand name Sevin, which was a trademark of the Bayer Company. The Sevin trademark ...
,
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
Flubendazole
Flubendazole is an anthelmintic. Its brand name is Flutelmium which is a paste manufactured by Janssen Pharmaceutica N.V. used by veterinarians for protection against internal parasites and worms in dogs and cats. Other brand names are Flubenol, ...
(Flubenvet) is the only licensed
anthelmintic
Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may ...
for use in poultry and game birds. Continuous medication of pen-reared birds has been recommended, but is not economical and increases the possibility of drug resistance. Several other compounds have been shown effective against ''S. trachea'' under experimental conditions. Methyl 5-benzoyl-2-benzimidazole was 100% efficacious when fed
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
Levamisole, sold under the brand name Ergamisol among others, is a medication used to treat parasitic worm infections, specifically ascariasis and hookworm infections. It is taken by mouth.
Side effects may include abdominal pain, vomiting, ...
(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
Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the tapeworm genus '' Taenia'' (but not effective against '' Dipylidium caninum'', a comm ...
(Panacur) at 20 mg/kg for 3–4 days is also effective.
Ivermectin
Ivermectin (, '' EYE-vər-MEK-tin'') is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, today it is used to treat i ...
injections may be effective in treating resistant strains.
Sources
# https://web.archive.org/web/20100703145151/http://cal.vet.upenn.edu/projects/merial/Strongls/strong_4.htm
# https://web.archive.org/web/20110717194656/http://www.vetsweb.com/diseases/syngamus-trachea-d75.html#effects
{{Taxonbar, from=Q5266533
Strongylida
Poultry diseases
Veterinary helminthology
Parasites of birds
Nematodes described in 1811