Gapeworm in Poultry
Gapeworms, Syngamus trachea, are parasitic nematodes that invade the respiratory tracts of many species of birds, including domestic poultry. They survive by attaching to the mucosal linings in the trachea and, to some extent, the bronchial passages. During post-mortem examinations, gapeworms can also be found in the lung tissue. These parasites infect all gallinaceous bird species, including chickens, turkeys, peafowl, pheasants, and grouse. They also infect ducks and geese. Gapeworms have been found in many bird species, including magpies, jays, meadowlarks, seagulls, starlings, crows, myna birds, finches, and even whooping cranes. Wild birds and infected domestic poultry can be carriers that spread the parasite. Because of the wide range of bird species these worms can infect, transmission between species is often a problem.
While gapeworms can be found in all poultry species, they’re extremely problematic when they become established in young pheasants, turkey poults, and other juvenile fowl. Any infestation of gapeworms can be fatal, but mortality is often highest in young birds. Mortality losses of 25 precent are not uncommon. Infected fowl of any age, may exhibit poor health and impaired growth rates due to the toll the parasitic worms take.
The name gapeworm (or gape worm) was coined because of an infected bird’s tendency to “gape” or gasp for air, due to the blockage the worms make in the trachea and airways. Other common names for this parasite include “red worm” and “forked worm.” Like most nematodes, this parasitic worm has distinct male and female sex differentiation. Female worms are dark red, while the males are lighter red. The red color is a result of ingested blood. The term “forked worm” comes from the forked or Y-shape the organisms make when male and female worms are copulating. Male worms are approximately 1/4 inch long and attach to the host by permanently burying their head into the respiratory tract tissues. Female worms, up to 1-1/2 inches in length, attach to the tracheal wall beside a male worm and copulation begins. Conjoined, copulating worms can be found in the trachea and bronchial passages during the necropsy of infected fowl.
When a female gapeworm lays her eggs in the trachea of an infected fowl, the eggs can either be coughed up and disgorged orally, or swallowed. Eventually, the bird defecates the swallowed eggs. The gapeworm eggs soon hatch into pre-parasitic larvae and can be ingested by other birds while they’re foraging. Birds can also contract gapeworms by consuming infected carrier hosts. Carrier hosts include earthworms, common garden snails, and insects. These hosts become infected by ingesting the gapeworm eggs and larvae while they’re foraging for their food. Gapeworm larvae can remain viable for up to three years in the muscular tissues of an earthworm.
After a bird consumes the gapeworm larvae, the larvae penetrate the intestinal walls. From there, they migrate to the lungs and develop into adult worms before moving into the bronchial passages and trachea. Once in the trachea, they attach to its mucosal lining.
If a gapeworm outbreak occurs in areas where fowl are free-ranging, rotating out of those areas becomes necessary. Recommended time ranges for this are at least six months, with a year or more optimal. Sometimes, if an infestation has been severe, the soil in contaminated areas has to be treated as a last resort to eradicate both larvae and infected carrier hosts in the area. The University of Maine’s Cooperative Extension Service recommends moving chicken tractors (portable poultry pens) often to avoid bare and muddy ground which gives birds easier access to gapeworm larvae and eggs, as well as earthworms or other invertebrates that might be carrying them.
Gapeworms cause damage to their hosts in several ways. Once the larvae and adults invade the birds’ lungs, they often cause pneumonia and mucosal build-up in the lungs. As the adults attach to the trachea and bronchial passages, lesions form where they attach. Bronchitis and hemorrhagic tracheitis are often the end results. Voluminous production of mucous occurs. Secondary infections are also common. As the worms grow, they begin to restrict airflow and breathing. As breathing becomes harder, the birds stick their necks out, open their beaks, and gasp or “gape” to get air. This condition is often referred to as “The Gapes.” The mucosal buildup forms plugs, which further block the airways. Birds of any age can suffocate from these blockages. However, loss through suffocation and asphyxiation are significantly higher in younger birds because of narrower airways. Blood loss from the attached adult worms leaves many birds weak and emaciated. The lesions caused by the larvae burrowing through intestinal walls can also cause pathways for secondary infections.
Symptoms of Gapeworm in Chickens
Signs and symptoms of gapeworm infestations include infected birds gasping or “gaping” for air. Gurgling or rattling sounds may be heard coming from the trachea. Infected birds may shake their heads as they try to dislodge the worms. Birds with only minor parasitic buildup may show few symptoms. If gapeworm infestation becomes severe, infected birds are often found lethargic on roosts or the ground, with ruffled feathers, eyes closed, and heads drawn back against the body. They will gasp and stick out their necks as they attempt to breathe. Death is often the result in these cases.
Parasitic control begins with monitoring flocks for signs of illness or infestation. If flocks free-range, keeping birds out of contaminated areas is important. Fowl showing signs of infection should be isolated and treated to prevent the spread to the rest of the flock.
Ideally, runs and housing should have wire mesh or hardware cloth with very small openings to keep wild birds from entering. A solid covering or roof on outdoor runs and yards will keep wild birds from dropping feces into the poultry yard. Regular removal of old litter and manure is essential to control the spread of gapeworms and other parasites.
Gapeworms are a serious parasite and obtaining input and treatment from a licensed veterinarian may be worth the expense, to protect a flock from a catastrophic outbreak. Keeping the premises clean, avoiding overcrowding, and practicing basic biosecurity measures, such as keeping wild birds out of pens and runs, are basic steps that all poultry owners can take to reduce the risk of their flocks contracting gapeworms and other parasites.
The MSD Veterinary Manual, which is readily available online (MSDVetManual.com), is a resource that’s accessible to lay persons and professionals alike. It’s updated every two years and lists treatments and medications legally authorized for gapeworm control as of the date of last publication. Federal regulations often change on medications, including veterinary drugs. The Chicken Health Handbook by Gail Damerow is another resource many poultry owners rely on.
Doug Ottinger lives, works, and writes from his small hobby farm in northwest Minnesota. His educational background is in agriculture with an emphasis in poultry and avian science.
Originally published in the August/September 2024 issue of Backyard Poultry and regularly vetted for accuracy.
