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Gapeworm Infection

Other Names: Syngamiasis, Red Worm, Forked Worm

The gapeworm, Syngamus trachea, is a parasitic nematode found in the trachea of domestic and wild birds worldwide. S. trachea are tiny, bright red (caused by ingestion of the host's blood), worms that have a 'y'-shaped appearance (which are actually two worms, the male and female---that are joined together, with the male acting as an anchor for the female). These worms attach themselves to the mucosa of the chicken's trachea, where they feed on blood. This results in the development of lymphoid nodules, catarrhal tracheitis and occasional secondary lobar pneumonia. If enough worms are present, they can cause partial to complete obstruction of the trachea.

Female S. trachea lay their eggs in the bird's trachea, which hatch and are either coughed up or swallowed by the bird, later defecated out into the environment.

Life cycle
Chickens become infected with S. trachea by accidentally eating the larvae that has contaminated the surrounding environment, feed, or water through the presence of feces from an infected bird. Many wild bird species can be infected with S. trachea, which will shed the larvae in their feces. Chickens can also become infected indirectly, by eating earthworms, snails or slugs that are infected.
Regardless of how, once chickens ingest the larvae, they will migrate through the gastrointestinal system until they reach the trachea, where they reproduce, lay eggs, feed on blood, and live. The eggs are either coughed up or swallowed by the chicken. When swallowed, they will get passed along with the feces, further contaminating the environment with more eggs for other flock members---or even the same bird to ingest and accumulate more worms or infect others. The prepatent period is between 17 to 20 days.

Clinical signs
Affected chickens are often observed stretching their necks out, while opening their mouths and gasping or gaping for air. The gaping is caused by the presence of multiple worms in the trachea, causing a partial to complete block in airflow. Without treatment, if birds are heavily infested, they often die from suffocation.

Small chicken breeds, such as bantams and younger chickens are more severely affected by gapeworms. This is related to the size of the chicken's trachea, as when there is a larger amount of space available for the worms to attach onto, the less likely they will cause a blockage in the airflow for the chicken not to be able to breath.

Clinical Signs

Emitting a grunting sound
Difficulty breathing
Head shaking
Reduced feed intake
Unthrifty appearance


  • History
  • Clinical signs
  • Physical exam
  • Fecal flotation
  • Necropsy

Reported Cases

  • Case 1: Gapeworm infection in a Macaw An adult, 900g female Ara ararauna from a project for the rehabilitation of the Brazilian fauna was kept in a collective nursery together with 12 specimens of the same species. Their diet was composed of typical fruits of the region, which were offered twice a day, and water ad libitum. The macaws had no previous history of anthelmintic treatment. The specimen evaluated presented progressive weight loss, constant sneezing, and reduced appetite for seven days. During physical examination the animal presented apathy, lethargy, spiked feathers, body condition score of 1/4, frequent sneezing, and inspiratory dyspnea. After this examination, the bird died, and the necropsy was performed. The postmortem findings were pale periocular, oral, and cloacal mucosae, cachexia, and presence of parasites of round shape, reddish color, with length of approximately 0.5 cm, in the proximal portion of the trachea. Another parasite with the same characteristics, but smaller in size, showing Y shape was found in the body. The trachea also showed colorless mucus and petechial hemorrhages in the proximal and middle portions of the mucosa. These parasites were subjected to morphological analysis in the Laboratory of Microscopy of the University Center of Triângulo and were identified as Syngamus trachea. Ref


Albendazole (Valbazen)Given to each bird orally. Measure out ¼ mL (per bantam) or ½ mL (per regular-sized breed). Repeat in 2 weeks.G Damerow
Safeguard 10% Liquid Dewormer for GoatsFenbendazole is used off-label in poultry. Add to the flock's drinking water source at a rate of 3 mL per gallon of water, for 3 days. Repeat every 3 weeks.G Damerow
Panacur or Safeguard Equine Dewormer 25 g Paste 10%Fenbendazole is used off-label in poultry. Given individually to each chicken orally, squeezed out in a pea-size portion and placed inside their mouth. Repeat every 3 weeks.G Damerow
(1% Ivermectin) Injectable for Cattle and SwineIvermectin is used off-label in poultry. The drug is given to each chicken orally or added to the flock’s water source.

If given by mouth - 0.25 mL per large size, 0.1 mL per bantam size.

If added to flock water source- 4 mL per gallon of water. Made fresh daily for 2 days.
G Damerow
Pour-on for Cattle and Swine (5 mg/mL Ivermectin)Ivermectin is used off-label in poultry. Should not be given internally to the bird. Should be used only externally.

Apply to each chicken topically - Use an eye dropper to apply to the skin at the back of the bird’s neck. Bantam size birds should get 3 drops, normal-sized 4-5 drops, and large breeds 6 drops. Repeat in 2 weeks.
G Damerow
Levamisole Soluble Drench Powder (46.8g)Levamisole is used off label in poultry. It's added to the flock’s water source.

Note- Chickens who are severely debilitated should not receive this medication, because it will impact their ability to fight infections.

Add to the flock’s drinking water source - at a rate of 10 mL per gallon of water for only 1 day. Repeat in 7 days, and again in 7 days after that.
G Damerow



  • Tilling the soil in the pens at the end of the growing season helps to reduce the residual infection.
  • Treating the soil to eliminate earthworms, snails and slugs
  • Rotating areas used for poultry confinement

Scientific References

Good Overviews

Age Range

Young birds are more seriously and more frequently affected by gapeworms

Risk Factors

  • Crowding of birds
  • Unsanitary living conditions
  • Small chicken breeds, such as bantams and younger chickens
  • Ingestion of earthworms, slugs, or snails.