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Snowy Owl Roundworms
Roundworms are intestinal parasites (nematodes) that can infest the snowy owl, a nocturnal bird of prey native to arctic regions but sometimes held in captivity, notably in animal parks or falconry centers.\n\nThese parasites live in the di...
What is it?
Roundworms are intestinal parasites (nematodes) that can infest the snowy owl, a nocturnal bird of prey native to arctic regions but sometimes held in captivity, notably in animal parks or falconry centers.\n\nThese parasites live in the digestive tract of the bird, mainly in the intestine, and feed on food ingested by their host. In a healthy bird with a low parasite load, the infestation may remain discreet. But in a young owl, a weakened or heavily infested bird, roundworms can cause significant digestive problems and stunted growth.\n\nThis parasitosis is common in captive raptors, particularly when the hygiene of the aviary or the management of prey (rodents, birds) is not optimal.
Roundworm infestation may go unnoticed if it is mild. In more severe cases, we observe a loss of appetite or, on the contrary, an increased appetite without corresponding weight gain, progressive weight loss, soft or abnormal stools, sometimes vomiting of undigested food.\n\nThe plumage can become dull and less silky. In young owls, growth retardation is possible. In some cases, segments of worms or entire worms are visible in the droppings.\n\nA heavily parasitized bird becomes sluggish, less lively, with a reduction in its flight and hunting activity. Dehydration may occur if diarrhea persists.
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:
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) mainly belonging to the genera Capillaria, Porrocaecum or Serratospiculum, found in raptors. These worms colonize the digestive tract or, for certain species, other organs such as the respiratory tract.\n\nInfestation most often occurs by ingestion of eggs or larvae present in the environment, in contaminated water, or by consumption of prey (rodents, birds) themselves carrying parasitic larvae. Some worms have a direct cycle, others require an intermediate host such as an insect or earthworm.
Young owls are more vulnerable due to their still immature immune system.\n\nA poorly maintained aviary, with accumulation of droppings and humidity, promotes the survival of parasitic eggs and larvae in the environment.\n\nA diet based on wild prey or uncontrolled rodents increases the risk of contamination.\n\nA bird that is stressed, immunocompromised or carrying another disease is more susceptible to an infestation severe.\n\nPromiscuity with other infested birds in a park or care center promotes transmission.
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 based on a parasitological examination of the droppings (coproscopy) allowing the search for roundworm eggs under a microscope. A complete clinical examination of the bird is also carried out to assess its general condition, weight and hydration.\n\nIn certain cases, an endoscopy or additional examinations may be necessary to directly visualize the parasites, particularly when they lodge in deep organs such as the air sacs.
Treatment
Treatment is based on the administration of antiparasitics (wormers) suitable for birds, prescribed and dosed only by a veterinarian specializing in exotic animals or raptors.\n\nSupportive treatment may be associated in the event of dehydration or general weakening, including rehydration and nutritional support.\n\nFollow-up parasitological checks are generally carried out after treatment to verify effectiveness and the absence of reinfestation.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Rigorous management of aviary hygiene is essential: regular cleaning, removal of droppings, disinfection of surfaces and water points.\n\nIt is recommended to control the origin of the prey given to the bird and to avoid uncontrolled wild rodents.\n\nParasitological examinations of stools carried out regularly by a veterinarian make it possible to detect an infestation before the appearance of symptoms.\n\nA preventive dewormer may be recommended by the veterinarian depending on the context breeding or keeping, particularly for birds in intensive captivity.
Possible complications
A massive, untreated infestation can lead to intestinal obstruction, severe malnutrition and general weakening of the bird.\n\nIn young people, lasting growth retardation is possible. A chronic infestation weakens the immune system and makes the bird more vulnerable to other infections.\n\nIn severe cases, particularly in already weakened raptors, the outcome can be fatal.
When to see a veterinarian
Abnormal, soft stools or those containing visible worms.\nProgressive weight loss despite a preserved or increased appetite.\nDull plumage and loss of liveliness in a young or adult owl.\nRetarded growth in a young bird.\nRepeated vomiting or marked depression.
Prognosis
The prognosis is generally good when the infestation is detected and treated early, with complete recovery after appropriate deworming.\n\nIn the event of severe infestation or late diagnosis, particularly in a young bird or an already weakened individual, the prognosis becomes more guarded due to the risk of digestive complications and malnutrition.
Frequently asked questions
Are owl roundworms transmissible to humans?
No, intestinal nematodes specific to raptors such as the snowy owl are not considered transmissible to humans under usual conditions of detention.
How does a snowy owl get roundworms?
Most often by ingesting eggs or larvae present in the contaminated environment, or by consuming prey such as rodents themselves carrying parasitic larvae.
Can a owl without symptoms carry roundworms?
Yes, a light infestation can remain silent. This is why regular parasitological checks are recommended even in the absence of visible signs.
Can dewormer be given without veterinary advice?
No, the administration of an antiparasitic to a raptor must always be supervised by a veterinarian, because the dosage and molecule must be adapted to the species and the condition of the bird.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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