Gastrointestinal parasitism in domestic ducks (roundworms)
Gastrointestinal parasitism caused by roundworms is a very common condition in domestic ducks raised outdoors or on wet pasture. Nematode worms settle in the duck's intestine, stomach, or esophagus and feed at the bird's expense. The main...
What is it?
Gastrointestinal parasitism caused by roundworms is a very common condition in domestic ducks raised outdoors or on wet pasture.
Nematode worms settle in the duck's intestine, stomach, or esophagus and feed at the bird's expense. The main culprits in ducks are Amidostomum anseris (muscular stomach worm), Capillaria species (capillary worms of the esophagus and intestine), and Heterakis gallinarum (caecal worm).
This parasitic disease primarily affects young ducklings, which are more vulnerable, but can also affect adults, particularly when they live in groups on the same water source or pasture for several years.
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:
Signs vary depending on the intensity of infestation and the bird's age.
In ducklings, marked growth retardation, dull and ruffled plumage, and general weakness are often observed. The most severely affected young ducks may show diarrhea, sometimes tinged with mucus.
In adults, infestation is often more subtle: decreased appetite, progressive weight loss despite apparently normal feeding, and less lustrous plumage.
In severe cases, especially with Amidostomum anseris which damages the muscular stomach wall, frank depression may be seen, along with crop or abdominal distension and dehydration. Worms may sometimes be visible in the droppings.
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 disease is caused by the presence of nematodes (roundworms) in the digestive tract. Ducks become infected by ingesting the eggs of these worms present in water, mud, grass, or soil contaminated by droppings from parasitized birds.
Some worms, such as Heterakis gallinarum, can also be transmitted through earthworms that serve as intermediate hosts. A duck foraging in wet soil easily ingests infective larvae this way.
Several factors increase the risk: raising ducks on wet pasture or stagnant water sources used for a long time without rotation, high stocking density, mixing ducks of different ages, poor hygiene of ponds and watering troughs, and muddy ground favoring the survival of eggs and larvae.
Young ducklings a few weeks to a few months old are particularly vulnerable because their immune system is still immature.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Your veterinarian suspects gastrointestinal parasitism based on clinical signs and rearing conditions (wet pasture, young animals, flock history).
Diagnosis is confirmed by laboratory examination of droppings, called faecal testing, which allows the veterinarian to detect and count worm eggs. In some cases, post-mortem examination of a deceased animal may be performed to directly observe worms in the digestive tract and confirm the species involved.
Treatment
Treatment involves administering a broad-spectrum antiparasitic effective against roundworms, prescribed by your veterinarian according to the worm species identified and the age of the animals.
Alongside medication, supportive measures can be helpful in weakened animals: improved nutrition, access to clean water, stress reduction. Cleaning and sanitation of the living environment should accompany any treatment to prevent rapid reinfection.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is based primarily on managing pasture and living conditions. It is recommended to rotate ducks across several paddocks to allow the ground to rest, to avoid overcrowding, and to clean water sources and drinkers regularly.
Soil sanitation (draining stagnant muddy areas) reduces the survival of worm eggs in the environment. Separating young ducklings from adults, who can be carriers without visible signs, also reduces the risk of contamination.
A regular worming programme, established with your veterinarian based on your flock's situation, complements these hygiene measures.
Possible complications
Severe untreated infestation can lead to permanent stunted growth in young ducks, chronic weight loss, and general weakness that makes ducks more susceptible to other diseases, particularly respiratory or digestive conditions.
In the most severe cases, particularly with worms that damage the stomach or intestinal wall, death may occur, especially in very young or weakened ducklings.
When to see a veterinarian
A duckling or duck is losing weight despite eating normally.
Plumage becomes dull and ruffled with no other apparent cause.
Worms are visible in the droppings.
Diarrhoea persists in several animals in the group.
Ducklings show stunted growth compared to their age-matched companions.
One or more animals in the group are lethargic, weak, or refuse to move.
Prognosis
The prognosis is generally good if parasitism is detected and treated early, with gradual return to normal body condition after worming and pasture sanitation.
Conversely, in cases of severe untreated infestation, particularly in young ducklings, the prognosis becomes more guarded with a risk of death and lasting effects on growth.
Frequently asked questions
Are duck worms dangerous to humans?
No, gastrointestinal nematodes in ducks are bird-specific and do not transmit to humans.
How often should you deworm your ducks?
There is no universal frequency: it depends on the rearing system, animal density and the level of contamination in the pasture. The veterinarian can establish a tailored programme after a faecal examination.
Can an adult duck that appears to be in good health carry worms?
Yes, an adult can harbour worms without showing obvious signs, while still contaminating the environment and posing a risk to more vulnerable young ducklings.
Is simple pool cleaning enough to eliminate the risk?
Cleaning helps but is generally not enough on its own: worm eggs can survive for a long time in mud and damp soil, which is why it is important to combine sanitation, pasture rotation, and worming.
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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