Gastrointestinal roundworm parasitism in puffins
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in puffins, pelagic seabirds that nest in colonies along Mediterranean coasts and islands, including the coasts of Tunisia. These parasites live in the stoma...
What is it?
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in puffins, pelagic seabirds that nest in colonies along Mediterranean coasts and islands, including the coasts of Tunisia. These parasites live in the stomach, proventriculus (glandular stomach), or intestines of the bird. Infection occurs mainly through eating fish or small marine invertebrates carrying infective larvae. Young puffins still in the nest are most commonly affected, as they are more vulnerable, but adults can also become infected without necessarily showing visible signs.
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 chicks, stunted growth is often observed, along with progressive weight loss and dull or ruffled feathers despite seemingly adequate feeding by the parents.
Digestive problems may develop: regurgitation, abnormal droppings, abdominal bloating. The bird becomes lethargic, less responsive, and sometimes refuses food.
In severe cases, anemia (pale mucous membranes) may develop if the parasites cause bleeding into the digestive tract. Some heavily infested birds may die before fledging, sometimes with few obvious outward signs, making detection difficult without examination.
In adults, infection is often symptomless, except when the worm burden is high or the bird is weakened by other factors (stress, food shortage, or other illness).
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Several genera of roundworms can parasitize the digestive tract of puffins, particularly those belonging to families found in fish-eating seabirds. They attach to the stomach or intestinal wall, where they feed and can cause local irritation, inflammation, or small bleeds when the worm burden is heavy.
Young age (nestlings), abundant food containing highly infested prey, breeding colony density, and any factor weakening the bird (stress, pollution, reduced food availability) favour the emergence of clinical signs.
Transmission
Infection occurs through eating marine prey (small fish, crustaceans) carrying the parasite's infective larvae. The cycle requires an intermediate marine host. There is no direct transmission between birds or to humans.
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 faecal samples (looking for worm eggs), carried out by a veterinarian or laboratory specialising in wildlife. A thorough clinical examination and sometimes endoscopy or blood analysis (checking for anaemia) complete the assessment, especially in a weakened bird.
Treatment
Treatment uses broad-spectrum antiparasitic agents active against nematodes, administered only under veterinary supervision, with monitoring of the bird's weight and general condition. Nutritional support may be necessary alongside treatment in weakened individuals.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
In the wild, prevention relies mainly on preserving the quality of the marine environment and breeding areas, limiting stress and exposure to heavy parasite loads. In care or rehabilitation centres, regular veterinary checks of admitted birds, including faecal examination, enables early detection.
Possible complications
Untreated heavy infestation can cause severe anaemia, significant growth delay in nestlings, or even death before fledging. In a weakened adult, it can worsen other health problems and reduce chances of survival at sea.
When to see a veterinarian
A puffin nestling shows visible growth delay or weight loss.\nWorms are visible in regurgitated material or droppings.\nThe bird is lethargic, stops eating, or has pale mucous membranes.\nA bird admitted to a care centre should routinely have a parasite check before release.
Prognosis
The prognosis is generally good when infestation is detected and treated before serious complications develop. It becomes guarded in very weak chicks or cases of severe anemia, where death remains possible even with treatment.
Frequently asked questions
Can roundworms from shearwaters be transmitted to humans or domestic animals?
No, these nematodes are specific to the cycle of seabirds and their prey. They pose no known risk to humans or domestic animals.
How to tell if a puffin chick is parasitized?
Only a veterinary examination, with fecal analysis, can confirm the presence of worms. Stunted growth or weight loss should raise concerns and prompt a consultation.
Should all shearwaters admitted to rehabilitation centers be systematically treated?
Parasite screening is recommended for any bird that is rescued, but treatment is only decided after the veterinarian confirms infestation, to avoid unnecessary treatment.
Is this disease common in Tunisian puffin colonies?
Gastrointestinal parasitism is commonly reported in pelagic seabirds in the Mediterranean, but its actual impact depends on each colony and requires monitoring by wildlife specialists.
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 23 August 2026
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