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Gapeworm – a Common Parasite of Birds Kept in Outdoor Aviaries

GapewormsGapeworms are parasitic nematodes (Syngamus trachea) that colonize the tracheal walls (please see photo) of a wide variety of wild, domestic and pet birds.  These pests present somewhat of a dilemma, as they are associated with birds kept outdoors and/or those feeding on wild-caught invertebrates – two otherwise healthful aspects of bird-keeping!


Gapeworms derive their common name from the symptoms they cause – open-mouthed gaping for air.  As they grow in size and numbers, Gapeworms irritate the bird’s trachea and literally block air from entering.  Other symptoms can include wheezing, coughing and noisy breathing.

While suffocation can occur, more commonly afflicted birds cease feeding and lose weight, after which they are attacked by faster-acting ailments such as pneumonia.

Fortunately, a Gapeworm infection is treatable if caught in its early to middle stages.

Gapeworm Life Cycle

Gapeworms require 2 hosts – an invertebrate and a bird – in order to complete their lifecycle.  Common invertebrate hosts include earthworms, snails and certain insects, all of which are favored as food by the birds most typically infected – pheasants, quails, peafowl, guinea fowl and domestic poultry.  Canaries and other Finches housed in outdoor aviaries are also at risk.  Parrots are less commonly parasitized by Gapeworms, most likely because few species consume insects (infection can also occur by direct consumption of Gapeworm eggs and larvae).

A related Nematode, Cyathostoma bronchialis, attacks ducks and geese.

Gapeworms in Zoo Collections

Red Crowned CraneWhile working in zoos, I and my co-workers looked upon Gapeworms almost as a “necessary evil”.  Since it was not possible to eradicate the parasite from huge outdoor enclosures or earth-bottomed indoor exhibits, we kept a close eye on birds for any sign of respiratory irregularity (as must be done even if Gapeworms are not a concern).

Outdoors, birds in our collection consumed large quantities of earthworms, insects and other potential Gapeworm hosts…food items whose nutritional value outweighed, I believe, the parasite risk.  Interestingly, peafowl, cranes and others that roamed the grounds almost at will (please see photo) were not often afflicted by Gapeworms.

A Live Insect Alternative

Pet-keepers seeking to add variety to the diets of their insectivorous birds, but concerned about Gapeworm, would do well to consider using canned invertebrates.

Further Reading

A wide variety of other nematodes and cestodes parasitize pet and domestic birds; hopefully this list will not keep you up nights!



Red Crowned Crane images referenced from wikipedia and originally posted by Robin Chen



  1. avatar

    You never mention how to treat gapeworm.

  2. avatar

    Hello, Frank Indiviglio here.

    Thanks for your interest. Ivermectin, Flubenvet and several other medications are used to treat gapeworm. Experienced poultry breeders use some of these medications routinely, but the average pet owner should seek veterinary advice.

    Please let me know if you need any further information.

    Best regards, Frank Indiviglio.

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I believe that I was born with an intense interest in animals, as neither I nor any of my family can recall a time when I was not fascinated by creatures large and small. One might imagine this to be an unfortunate set of circumstances for a person born and raised in the Bronx, but, in actuality, quite the opposite was true. Most importantly, my family encouraged both my interest and the extensive menagerie that sprung from it. My mother and grandmother somehow found ways to cope with the skunks, flying squirrels, octopus, caimans and countless other odd creatures that routinely arrived un-announced at our front door. Assisting in hand-feeding hatchling praying mantises and in eradicating hoards of mosquitoes (I once thought I had discovered “fresh-water brine shrimp” and stocked my tanks with thousands of mosquito larvae!) became second nature to them. My mother went on to become a serious naturalist, and has helped thousands learn about wildlife in her 16 years as a volunteer at the Bronx Zoo. My grandfather actively conspired in my zoo-buildings efforts, regularly appearing with chipmunks, boa constrictors, turtles rescued from the Fulton Fish Market and, especially, unusual marine creatures. It was his passion for seahorses that led me to write a book about them years later. Thank you very much, for a complete biography of my experience click here.
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