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Roundworm Infection

Other Names: Ascaridiosis, Ascarid Infection

The large roundworm, Ascaridia galli is the most common intestinal parasite found in backyard and free range chicken flocks worldwide. It is a yellowish white, thick worm which can grow up to 115 mm (4.5 inches) in length. It lives freely inside the chicken's small intestine. There, it reproduces and lays eggs, which are passed out of the chicken in their feces. Occasionally, adult worms will migrate into other parts of the chicken's body, such as the cloaca, oviduct, body cavity, esophagus, crop, or gizzard. When in the oviduct, they can sometimes get trapped inside a newly formed egg.

The impact roundworms have on the chicken depends on several factors:
  • Age: Chickens older than 3 months of age have considerably more resistance to infection with A. galli than younger birds.
  • Body Size: Heavier chicken breeds are more resistant compared to lighter breeds. Lighter birds tend to have higher worm burdens and more severe infection intensity.
  • Overall Health Status: Healthy chickens with a good immune system tend to be more resistant to A. galli.
  • Diet: Chickens receiving balanced diets high in vitamins A and B (complex) increase their resistance to A. galli.
In severe infections where chickens have large numbers of A. galli present, it can lead to partial to complete intestinal blockage. Failure to control roundworm infections can compromise the bird's health by increasing susceptibility to other diseases in highly infected birds.

How do chickens get roundworms?

A. galli has a direct life cycle. This means that chickens are infected by eating A. galli eggs, that are passed out of another chicken in their feces, contaminating the surrounding environment, feed, or water source. When another chicken ingests the infective A. galli eggs, they hatch in their proventriculus or the small intestine. It will take 28-30 days for A. galli to mature into adults. The pre-patent period (when birds start shedding the worm eggs in their feces) after infection is 5-8 weeks.
Ascaridia galli life cycle in chickens
Since A. galli eggs are very resistant, they can survive outside in the soil for extended periods of time. In deep litter systems, A. galli eggs can remain infective for years. Under optimum conditions of temperature and moisture (which is 25° C (77°F)), A. galli eggs can survive in the environment for up to 8 months (160 weeks), and become infective after passing through feces in 1-28 days. 2 to 3% of A. galli eggs remained viable and infective for up to 2 yr in the pasture. A. galli eggs can hatch anywhere between 17.5°C (63.5° F) to 34°C (93.2°F).

Clinical Signs of Roundworms in Chickens

Clinical signs of roundworms in chickens will vary depending on the severity of the infection. The symptoms will be more severe in younger chickens, less than 3 months of age. Signs of roundworm infection in chickens typically include paleness (of the face, comb and wattles), ruffled feathers, altered hormone levels, weight loss with a prominent keel and reduced body fat, decreased appetite, depression, and diarrhea with increased white urates. Birds will also have a decreased activity level and spend less time pecking at the ground. Hens may spend more time in nests, not associated with broodiness. There may be more frequent bullying among flock members.

Clinical Signs

Undigested feed in feces
Reduced appetite
Atrophy of breast muscle and decreased body fat
Decreased growth/weight loss
Diarrhea with increased white urates
Pale comb/wattles
Delayed crop emptying
Reduced number of droppings
Worms found in feces or eggs


  • History
  • Clinical signs
  • Fecal exam
  • Necropsy

Reported Cases

  • Case 1: Intestinal obstruction due to Ascaridia galli in a Broiler chickens Commercial broiler chickens raised on helminthic medication-free feed were diagnosed with a severe disease caused by Ascaridia galli, characterized by intestinal hemorrhage and obstruction. A. galli was identified based on the morphological features of the nematode. Broilers were raised for a longer period (63 days) for weight recovery, grouped as stunted (n=500), had low body score and had fetid diarrhea. Broilers were described with chronic fluid fetid diarrhea and showed low body score for the age, with prominent carina (sternum), as a result of reduced pectoral mass. Enlarged intestines with gas accumulations were seen at necropsy, where Ascaridia galli concentrated, mostly at the cranial part of the jejunum, causing obstruction and mucosal congestion. The duodenum-jejunum segment was the most severely affected with obstruction and had localized accumulation of gas. The intestinal mucosa was severely congested with petechial and suffusive hemorrhages. The outbreak resulted in morbidity of about 10% and mortality of up to 4% and was associated to the absence of preventive medication and slack biosecurity. Ref

  • Case 2: Ascaridiasis in a Racing pigeon Ascaridiasis was found in one adult and one juvenile racing pigeon submitted from a flock of approximately 20 birds with history of weight loss of approximately 2-week-duration. On gross examination both birds were thin and the small intestines were markedly dilated and impacted by numerous ascarids (roundworms). The owner had not treated the flock for parasites in over a year and treatment resolved the weight loss issue. Ref


Albendazole (Valbazen)Albendazole is a benzimidazole anthelmintic which is used off-label in poultry. The drug is given to each bird orally. Measure out ¼ mL (per bantam) or ½ mL (per regular-sized breed). Repeat in 2 weeks.G Damerow
Safe-guard AquaSol for ChickensAdded to the drinking water at a daily dose of 1 mg/kg BW (0.454 mg/lb) for 5 consecutive days. Each mL of Safe-Guard AquaSol contains 200 mg of fenbendazole.Per Manufacturer instructions.
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 in 10 days.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 in 10 days.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 two consecutive 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.
G Damerow
Piperazine (Wazine)Piperazine is the only FDA approved dewormer for use in laying hens in the United States. It is only effective against the adult large roundworm, not the eggs. It can be given orally by mouth in each bird, or added to the flock’s water source.

If given by mouth - 50 mg/bird (if younger than 6 weeks of age), otherwise 100 mg/bird (if older than 6 weeks of age), or according to the manufacturer label. Repeat in 7-10 days.

If added to flock water source - 3 mL per gallon of water, or in accordance with the manufacturer’s label. Repeat in 7-10 days.
G Damerow
Citrus peel ethanolic extractGiven as a feed additive at a rate of 600-1200 mg/kg for 14 daysA Abdelqader et al., 2012
Garlic (Allicin)2.5 mg/bird
Drinking water - 1.5 mg/L of water daily for 5 days
F Velkers et al., 2011
Turmeric (Curcuma longa)200-600 mg/kgAlrubaie Al, 2015
Papaya (Carica papaya) seed extract20 ml/kg feed; 1 mg per chicken for 5 daysFeroza et al., 2017; Dakpogan et al., 2017
Papaya (Carica papaya) seed powder6 g/kg body weight; 300 mg/day per birdOzaraga et al., 2017; Ameen et al., 2012
Diatomaceous earthAdded as 2% of overall dietD Bennett; R Isabirye et al., 2019
Pumpkin seeds1 g/kg BWT Feitosa et al., 2013



  • Maintaining good sanitary practices; since the eggs take 10 to 12 days to become infective once shed in droppings, if the droppings are removed then it reduces the chances birds accidentally consume them.
  • Occasionally providing apple cider vinegar in drinking water (20ml/L of water), however only should be used in non-galvanized drinkers.
  • If the birds are confined to a pen outside, rotate access to different areas regularly (once a weed) to minimize build up of worm populations
  • Discourage birds from eating off of the ground - Elevate feeder and waterer to discourage fecal contamination and clean and disinfect equipment daily.
  • Segregate birds by age groups, with particular care applied to sanitation of young birds
  • Chickens should receive a diet which includes supplementation with vitamin A and B complex vitamins. Lack of these vitamins makes the birds more susceptible to worm infections
  • Conduct routine fecal tests

Scientific References

Good Overviews

Age Range

Young chicks less than 12 weeks old are more susceptible. Chickens build a resistance with age.

Risk Factors

  • Keeping birds confined in one area on a continuous basis without rotating pasture lots.
  • Feeding birds kitchen scraps
  • Smaller birds, due to their body weight differences
  • Unbalanced diet
  • Use of a deep-litter bedding system