Gastrointestinal parasitism in Hawaiian geese (roundworms)
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in Hawaiian geese, a small waterfowl species native to Hawaii, often raised in captivity or part of conservation reintroduction programs. Worms ranging from...
What is it?
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in Hawaiian geese, a small waterfowl species native to Hawaii, often raised in captivity or part of conservation reintroduction programs.
Worms ranging from several millimetres to a few centimetres long settle in the intestine, and sometimes also in the gizzard or oesophagus depending on the species involved.
They live at the bird's expense, feeding on its blood or digestive contents, which gradually weakens the animal.
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:
Early signs are often subtle, especially in adults, which makes the disease difficult to detect without examination.
In young Hawaiian geese, growth retardation, ruffled feathers and lethargy are frequently observed.
Diarrhoea or abnormal droppings may develop, sometimes accompanied by loss of appetite.
The bird loses weight gradually despite apparently normal feeding, and becomes more lethargic than its companions.
In heavy infestations, the abdomen may appear swollen or tender, and dehydration sets in.
Severe cases, particularly in young chicks, can lead to marked weakness or even death if left untreated.
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 nematodes (roundworms) that parasitise the digestive tract of waterfowl, particularly genera such as Amidostomum (gizzard worm) or other intestinal nematodes common in anatids (the family of ducks, geese and geese).
Eggs of these parasites are shed in the droppings of infested birds and contaminate soil, water or vegetation.
Other birds become infested by ingesting these eggs or larvae while feeding or drinking contaminated water.
Some parasite life cycles involve an intermediate host, such as an earthworm or mollusc, which facilitates transmission.
Young birds are more susceptible as their immune system is still immature.
Crowding in conservation pens or aviaries increases risk, as does damp, muddy or poorly drained ground.
Overcrowding, poor park hygiene and stress from transport or breeding weaken the birds' natural defences.
Hawaiian geese living in semi-freedom or reintroduced into the wild may also be exposed to areas already contaminated by other wild birds.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian first reviews the bird's history: origin, living conditions, age, and observed signs.
Definitive diagnosis is based on microscopic examination of droppings to identify roundworm eggs.
A full physical examination assesses the bird's general condition, hydration, and weight.
In some cases, necropsy or additional tests may be needed to pinpoint the exact parasite involved, especially in conservation program settings.
Treatment
Treatment involves giving antiparasitic drugs specific to roundworms, prescribed and dosed by a veterinarian based on the identified parasite and the bird's condition.
Nutritional support and rehydration may be added in weakened birds.
Environmental improvements—cleaning, disinfection, and humidity management—always accompany medication 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
Good drainage of enclosures and regular cleaning of living areas limit the buildup of parasite eggs in the environment.
Pasture rotation, when feasible, allows the soil to rest and reduces parasite load.
Access to clean, non-stagnant water and careful management of bird density are important measures.
Regular parasitological examination of droppings by a veterinarian helps detect infestation before severe symptoms appear and allows antiparasitic treatments to be given at the right time.
Possible complications
Untreated heavy infestation can cause severe weight loss, significant dehydration, and stunted growth in young birds.
In severe cases, particularly in chicks or already weakened birds, the outcome may be fatal.
Chronic infestation also leaves the bird vulnerable to other infectious diseases.
When to see a veterinarian
The bird has persistent diarrhea or abnormal droppings.
It is losing weight or appetite with no obvious cause.
A young bird shows poor growth or dull, ruffled feathers.
The bird appears depressed, lethargic, or less active than usual.
The belly seems bloated or tender to touch.
Prognosis
The outlook is generally good when the disease is detected early and treated promptly with veterinary follow-up and environmental improvement.
It becomes more guarded for heavy infestations, especially in young birds or already weakened individuals, where delayed treatment can compromise survival.
Frequently asked questions
Can the Hawaiian goose transmit these worms to humans?
No, gastrointestinal nematodes in barnacle geese are not considered transmissible to humans. The risk primarily concerns other birds.
How do you know if a bird is infested without visible symptoms?
Only a fecal analysis performed by a veterinarian can detect parasite eggs, even in the absence of obvious clinical signs.
Should all birds in a group be treated if only one is infested?
This decision is up to the veterinarian, who assesses the risk of contamination to the herd based on living conditions and test results.
Is a well-maintained enclosure sufficient to prevent parasitism?
Good maintenance greatly reduces the risk but does not eliminate it completely, especially in cases of contact with wild birds or a damp environment.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 03 September 2026
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