Gastrointestinal parasitism in avocets (roundworms)
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in wild waterbirds such as avocets. These parasites live in the bird's intestine or stomach and feed at its expense. In avocets, it is mainly waders frequen...
What is it?
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in wild waterbirds such as avocets. These parasites live in the bird's intestine or stomach and feed at its expense.
In avocets, it is mainly waders frequenting wetlands, lagoons and mudflats that are at risk, as the life cycle of these worms often involves aquatic invertebrates or crustaceans that the bird ingests while feeding.
Light infestation often goes unnoticed. Heavy parasite burden, however, can weaken the bird, especially young birds or individuals already weakened by food shortage, cold or other illness.
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 not always visible to the naked eye, especially in the wild.
Progressive weight loss may be observed despite apparently normal eating, dull and neglected plumage, reduced activity and lethargy.
Digestive problems are possible: abnormally soft or liquid droppings, sometimes discoloured, abdominal bloating.
In young avocets, heavy infestation can slow growth and make the chick more vulnerable to cold and predators.
In severe cases, dehydration and general weakness may lead to death, especially with massive infestation or associated stress (food shortage, difficult weather conditions).
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 families of nematodes (roundworms) can parasitize the digestive tract of waders such as avocets, notably worms belonging to genera commonly found in waterbirds frequenting wetland habitats.
The life cycle of many of these parasites involves an intermediate host, often a small aquatic invertebrate, a crustacean or a mollusc, which the avocet swallows while filtering mud or shallow water in search of food.
Once ingested, the larvae develop in the bird's digestive tract and become adult worms that lay eggs shed in droppings, continuing the cycle in the environment.
Young birds, which are less resistant, are more susceptible to the effects of heavy infestation.
High densities of birds at the same feeding or nesting site increase the risk of cross-contamination through the environment.
Water or mud rich in infested intermediate hosts, site pollution, or a season when natural food becomes scarce (leaving the bird weakened) all favour the disease.
Stress from captivity (wildlife care centres, animal parks) or pre-existing injury can also promote disease development.
Transmission
Indirect transmission via ingestion of intermediate hosts (small aquatic invertebrates, crustaceans) present in the mud or water of wetland areas frequented by the bird.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is mainly based on microscopic examination of droppings (faecal flotation), which allows identification of worm eggs and determines the type of parasite involved.
In some cases, post-mortem examination (necropsy) is what reveals infestation, particularly in birds found dead or severely weakened.
Assessment of the bird's overall condition (weight, body condition, hydration) completes the evaluation, especially at wildlife care centres.
Treatment
Treatment, when implemented (generally at wildlife care centres), relies on administration of antiparasitic drugs from the broad-spectrum anthelmintic family, adapted for birds.
General supportive care may be added: rehydration and nutritional supplementation to help the weakened bird recover.
Only a veterinarian or an approved wildlife care centre can decide on appropriate treatment, as wild birds require specific handling and management.
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 mainly depends on maintaining healthy, unpolluted wetland areas with good water level management and mud quality.
In captivity or at care centres, regular droppings collection, good hygiene of pools and aviaries, and avoiding overcrowding of birds limit transmission.
Regular veterinary monitoring with droppings examination (faecal flotation) allows detection of infestation before severe clinical signs appear, particularly for birds admitted to wildlife rescue centres.
Possible complications
Massive untreated infestation can lead to partial intestinal obstruction, severe malnutrition, and general weakness predisposing to secondary infections.
In young birds, sustained growth retardation may compromise survival chances during fledging and first migration.
When to see a veterinarian
An avocet found emaciated, lethargic, or unable to fly properly.
Observation of worms in the droppings of a rescued bird.
A young bird showing clear growth retardation compared to its siblings.
A rescued bird with persistent diarrhoea and dehydration.
Prognosis
The prognosis is generally good for light to moderate roundworm infections that are detected and treated promptly, particularly in a rehabilitation centre.
It becomes more guarded in cases of heavy infestation, especially if the bird is already weakened by other factors (injury, young age, difficult weather conditions).
Frequently asked questions
Is a wild avocet carrying worms necessarily sick?
No. A light parasitic load is common and generally well tolerated by a healthy bird. Only a heavy infestation or an already weakened bird presents a real risk.
Can these worms be transmitted to humans or other animals?
Gastrointestinal nematodes of avocets are specific to water birds and are not transmitted to humans or domestic animals such as dogs or cats.
What should I do if I find a weakened avocet with worms in its droppings?
You must contact a wildlife rescue center or a licensed veterinarian without attempting to treat it yourself or giving it any medication.
Does this disease affect only avocets?
No, many shorebirds and waterfowl frequenting the same habitats (mudflats, lagoons) can be affected by similar gastrointestinal parasites.
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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