Gastrointestinal parasitism of the owl (roundworms)
Gastrointestinal parasitism by roundworms (nematodes) is a common condition in little owls, both in the wild and in captivity or in care centers. These parasites live in the digestive tract of the bird, particularly in the stomach, gizzard...
What is it?
Gastrointestinal parasitism by roundworms (nematodes) is a common condition in little owls, both in the wild and in captivity or in care centers. These parasites live in the digestive tract of the bird, particularly in the stomach, gizzard or intestine, and feed at the expense of their host. Several species of nematodes may be involved, some being quite specific to nocturnal birds of prey.
The infestation is often silent in a healthy bird, but it becomes problematic when the parasite load is high or when the bird is already weakened, for example a young one, an injured one or an animal stressed after capture.
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:
The signs are often subtle at first. We can observe a progressive weight loss despite a preserved appetite, or on the contrary a clear drop in appetite.
Digestive disorders are possible: abnormally soft stools, regurgitation, or sometimes the presence of worms visible in the droppings or regurgitation.
The bird becomes depressed, less lively, with dull and poorly maintained plumage. In severe infestations, especially in young owls, growth retardation or marked weight loss may occur, with a risk of anemia and mortality if nothing is done.
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 nematodes can parasitize the digestive tract of nocturnal birds of prey, including worms belonging to the families close to Capillaria, Porrocaecum or Synhimantus depending on the region. These worms lay eggs which are eliminated in the droppings, which contaminate the environment.
Transmission most often occurs by ingestion of prey (insects, small rodents, earthworms) which play the role of intermediate hosts or vectors, or by direct ingestion of eggs present on the ground, perches or soiled food.
Young, recently weaned owls are more vulnerable because their immune system is still immature.
Weakened, injured, or recently collected birds in a care center present an increased risk, as do individuals living in environments with a high density of contaminated insects or rodents.
Promiscuity in convalescent aviaries, insufficient hygiene of enclosures, and the stress linked to captivity also promote an increase in the parasitic load.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The diagnosis is mainly based on a parasitological examination of the droppings carried out by a veterinarian, making it possible to identify the worm eggs under a microscope. In certain cases, an endoscopy or post-mortem autopsy can directly reveal the presence of adult worms.
The veterinarian also assesses the general condition of the bird, its weight and its hydration before deciding on the course of action to take.
Treatment
Treatment is based on the administration of antiparasitics from the broad-spectrum dewormer family, adapted to the species and prescribed only by a veterinarian experienced in wildlife or avian medicine. Nutritional support and rehydration may be necessary in addition, particularly in very weakened birds.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
In care centers or in captivity, regular cleaning of aviaries and feeders limits contamination of the environment by parasite eggs.
A veterinary check upon entry into the care center, with parasitological examination of the droppings, makes it possible to detect an infestation before it worsens.
Avoiding an overdensity of birds in the same space and ensuring good quality food also helps to strengthen the animal's natural resistance.
Possible complications
A massive untreated infestation can lead to anemia, severe weight loss and digestive obstruction in extreme cases.
In young birds or birds already weakened by an injury, digestive parasitism can considerably worsen the prognosis and promote other opportunistic infections.
When to see a veterinarian
The bird visibly loses weight despite normal food intake.
Worms are visible in droppings or regurgitation.
The bird becomes unusually despondent or listless.
The plumage becomes dull and poorly maintained without apparent cause.
A young bird shows obvious growth retardation.
Prognosis
The prognosis is generally favorable if the infestation is detected and treated at an early stage, particularly in a care center where regular monitoring is possible.
The prognosis becomes more guarded in very young birds, injured or carrying a very high parasitic load, where the risk of complications is greater.
Frequently asked questions
Can a wild owl live normally with roundworms?
Yes, a low level of infestation is often well tolerated by a healthy wild bird. The problem mainly occurs when the parasite load increases or the bird is already weakened.
How does an owl get these worms?
Most often by eating contaminated prey, such as certain insects or small rodents, or by accidentally ingesting parasite eggs present in the environment.
Can you deworm an owl yourself?
No, self-medication should be avoided. Only a competent wildlife veterinarian can assess the need for treatment and choose a product adapted to this protected species.
Is this parasitism dangerous for humans or other animals?
Owl digestive nematodes are not considered transmissible to humans under usual handling conditions.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 30 October 2026
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