Roundworm infection of the turkey intestine
Roundworm infection of the turkey intestine is an infestation of the intestine by nematodes, which are thread-like unsegmented worms. The most common species are Ascaridia dissimilis, which lives in the small intestine, and Heterakis gallin...
What is it?
Roundworm infection of the turkey intestine is an infestation of the intestine by nematodes, which are thread-like unsegmented worms.
The most common species are Ascaridia dissimilis, which lives in the small intestine, and Heterakis gallinarum, found in the caeca (small pouches located at the junction between the small intestine and the large intestine).
These parasites are widespread in turkey flocks, especially when birds have access to outdoor range or when shed hygiene is poor.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
In heavily infested young poults, marked stunted growth and weight loss are seen despite appetite being maintained initially, followed later by reduced feed intake.
The plumage becomes dull and rough, the birds appear depressed, less active, huddled together and cold-sensitive.
Diarrhoea or soft stools may develop, sometimes with visible worms in the droppings.
The abdomen may appear slightly distended in heavily parasitised birds.
In severe infestations, pale mucous membranes may indicate anaemia, and intestinal obstruction from a mass of worms is possible though rare.
In adults, infection is often subtle or asymptomatic, but still results in reduced flock performance (slower growth, uneven batch development).
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The condition is caused by intestinal nematodes, mainly Ascaridia dissimilis (small intestine) and Heterakis gallinarum (caeca), sometimes accompanied by other roundworms depending on the region.
These parasites have a direct life cycle: the turkey becomes infected by swallowing eggs present in the environment (contaminated soil, litter, water or feed) or, in the case of Heterakis, sometimes by eating an earthworm that has itself ingested eggs (optional intermediate host).
The eggs of these worms are highly resistant and can survive for long periods in litter or outdoor soil, which explains the persistence of contamination from one batch of birds to the next.
Young poults a few weeks to a few months of age are most susceptible, with more marked clinical signs than in adults.
Access to outdoor range, especially if used continuously without rest or rotation, favours accumulation of eggs in the soil.
High stocking density, damp litter that is seldom changed, and poor cleaning between batches increase the risk of infestation.
Mixed rearing with chickens on the same range can also promote spread of Heterakis gallinarum, which is very common in poultry in general.
A weakened general condition (other disease, nutritional deficiency, stress) makes birds more vulnerable to the clinical effects of parasitism.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian suspects gastrointestinal parasitism when observing stunted growth, weight loss or declining performance in the flock, particularly in young poults with access to outdoor range.
Confirmatory diagnosis relies on faecal analysis (coproscopy), which allows detection and counting of worm eggs, and post-mortem examination of one or more birds, which allows direct visualisation of worms in the intestine or caeca.
These examinations also allow identification of the parasite species involved and assessment of the extent of infestation in the group.
Treatment
Treatment is based on administration of antiparasitic agents (dewormers) effective against nematodes, prescribed and dosed by the veterinarian according to the weight of the birds and the farm situation.
Treatment of the entire flock is generally necessary, combined with thorough cleaning of the environment to prevent reinfestation.
Nutritional support (quality feed, vitamin supplementation) may be offered to weakened birds to promote recovery.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention relies on good management of building hygiene and litter: regular cleaning, disinfection and renewal of litter between flocks.
On outdoor ranges, rotating grazing areas and allowing soil rest reduce the burden of parasite eggs in the environment.
A preventive deworming program (antiparasitic treatment), established with the veterinarian, can be put in place according to the risk level of the farm.
Regular monitoring through faecal analysis (coproscopy) allows tracking of the infestation level in the flock and adjustment of measures before significant clinical signs appear.
Avoiding prolonged housing of multiple generations of birds on the same range also limits the risk of recontamination.
Possible complications
Massive untreated infestation can result in persistent stunted growth, mortality in the youngest or weakest birds, and exceptionally intestinal obstruction from worm accumulation.
Heterakis gallinarum also acts as a vector for a protozoan responsible for histomoniasis ("blackhead disease"), a potentially serious condition, particularly in turkeys, which are especially susceptible to this co-infection.
When to see a veterinarian
Stunted growth or unexplained weight loss in young poults, especially those with access to outdoor range.
Persistent diarrhoea or visible worms in droppings.
Dull plumage, lethargy or reduced activity affecting several birds in the group.
Unusual mortality or marked variation in growth rate across the flock.
Prognosis
The prognosis is generally good when infestation is detected and treated early, with growth recovery following treatment.
It becomes more guarded in young poults with heavy parasitism, particularly if complications such as histomoniasis develop or significant general weakness is present.
Without treatment, persistent infestation causes lasting harm to flock performance and health.
Frequently asked questions
Are roundworms from turkeys transmissible to humans?
No, Ascaridia dissimilis and Heterakis gallinarum are parasites specific to birds and are not transmitted to humans.
How does a turkey catch roundworms?
By ingesting parasite eggs present in bedding, soil in the run, contaminated water or feed, or sometimes by eating an earthworm carrying eggs.
Can an infested turkey poult recover completely?
Yes, with appropriate antiparasitic treatment prescribed by the veterinarian and improved environmental hygiene, most subjects recover well.
Why are turkeys particularly affected by this parasitism?
Turkeys, especially young ones, are susceptible to roundworms, and Heterakis gallinarum can additionally transmit histomoniasis to them, a disease to which this species is very sensitive.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
WOAH — Organisation mondiale de la santé animale (ex-OIE)
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 03 September 2026
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