Roundworm infection of the pelican (gastrointestinal parasitism)
Roundworm infection of the pelican is an infestation of the digestive tract by parasitic nematodes, often ascarids or related worms. These parasites live in the stomach, proventriculus, or intestines of the bird. They feed at the bird's exp...
What is it?
Roundworm infection of the pelican is an infestation of the digestive tract by parasitic nematodes, often ascarids or related worms. These parasites live in the stomach, proventriculus, or intestines of the bird. They feed at the bird's expense and can cause serious illness in young pelicans or weakened birds when present in large numbers. This condition primarily affects pelicans in captivity, such as those in zoos, wildlife rehabilitation centers, or water basins where the parasite life cycle can easily complete.
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 are often subtle at first, making early detection difficult. Progressive weight loss may be seen despite maintained appetite, or conversely, frank loss of appetite can occur. The plumage becomes dull and less waterproof. Digestive problems appear: soft stools or diarrhea, sometimes vomiting of undigested food. Whole worms may be visible in regurgitations or droppings. In young birds, growth retardation is common. In severe cases, the bird becomes lethargic, remains prostrate, and may show abdominal tenderness.
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 gastrointestinal nematodes, particularly worms related to ascarids (genus Contracaecum and related types) that naturally infest fish-eating birds such as pelicans. Pelicans become infected mainly by swallowing fish or other aquatic prey carrying infective larvae. Some parasites have an indirect life cycle involving an aquatic intermediate host (small crustacean) followed by a fish that serves as a transport host.
Young pelicans with less developed immunity are more susceptible to heavy worm infestation.
Captivity with repeated access to the same fishing pools promotes the buildup of infective larvae in the environment.
General weakness, stress, or concurrent illness in the bird increases susceptibility to parasitism.
Feeding on uncontrolled fish from wild sources raises the risk of exposure.
Transmission
Transmission occurs through ingestion of fish or aquatic prey containing infective roundworm larvae. There is no direct transmission from one pelican to another through simple contact. Contaminated water basins or bodies of water with infected fish maintain the parasitic cycle within a colony.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is based on microscopic examination of droppings to identify worm eggs through fecal flotation.
In some cases, direct observation of worms that are coughed up or expelled confirms the infestation.
Endoscopy or imaging studies may be considered by a specialist veterinarian if there is doubt or severe disease.
Blood work can help assess the overall impact on the bird's health status.
Treatment
Treatment uses broad-spectrum antiparasitic drugs prescribed and tailored by a veterinarian with expertise in exotic or aquatic animals.
Supportive care may be given for dehydration or weakness, including fluid therapy and nutritional supplementation.
Post-treatment follow-up with fecal examination confirms the effectiveness of the protocol.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention relies on regular parasitological examination of droppings, particularly in captive birds or those in care facilities.
Water quality management and cleaning of pools reduce the load of infective larvae in the environment.
Controlling the origin of fish given as food, if the bird is fed in captivity, limits the introduction of parasites.
A preventive deworming program can be established by the veterinarian based on the context of the facility or center.
Possible complications
An untreated heavy infestation can lead to digestive blockage, perforation of the stomach or intestinal wall, and severe decline in overall condition.
In young birds, lasting growth retardation is possible.
Chronic malnutrition weakens the bird against other infectious diseases.
When to see a veterinarian
The bird loses weight despite eating normally.
Worms are visible in the droppings or regurgitated material.
The bird shows persistent diarrhea or repeated vomiting.
A young pelican displays clear growth lag compared to others.
The bird becomes listless, remains inactive, or refuses to eat.
Prognosis
The outlook is generally good when roundworm infestation is detected early and treated appropriately.
It becomes more guarded in cases of heavy parasite burden, digestive complications, or in a pelican already weakened by other conditions.
Regular monitoring helps prevent severe disease.
Frequently asked questions
Is pelican parasitism transmissible to humans?
No, these roundworms are specific to fish-eating birds and are not transmitted to humans under normal conditions.
How does a pelican catch these worms?
By eating fish or other aquatic prey carrying infesting larvae of the parasite.
Can you see worms with the naked eye?
Yes, in some cases entire worms can be visible in the droppings or regurgitations of the infested bird.
Should all captive pelicans be systematically dewormed?
This depends on the context: a veterinarian specializing in this field assesses the need for a deworming program based on fecal analysis results and breeding conditions.
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 30 October 2026
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