parasitic disease Nightjar

Gastrointestinal parasitism in nightjars (roundworms)

Gastrointestinal parasitism caused by roundworms (nematodes) is common in nightjars, wild insectivorous birds that are sometimes admitted to wildlife rehabilitation centres or kept in controlled captivity. These worms live in the bird's sto...

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

These worms live in the bird's stomach, intestines, or crop. They feed on the digestive tissues or food eaten by the bird.

A light infection often goes unnoticed. A heavy infection can seriously weaken the animal, especially if it is already in poor health, injured, or very young.

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:

Diarrhea Weight loss Loss of appetite Reduction Bloating Soft stools Visible worms in stools Stunted growth Dull coat Vomiting Fatigue

Signs may not be obvious at first.

Gradual weight loss despite maintained appetite can occur, or conversely, a marked loss of appetite may develop.

Abnormal droppings—loose or discoloured—are possible. In some cases, worms are visible directly in the faeces.

The bird may appear weak, less active, with dull and fluffed plumage (the typical hunched posture of a sick bird).

In young birds, slow growth or delayed feather development may appear.

In severe cases, abdominal bloating or vomiting or regurgitation may sometimes be observed.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

Various species of nematodes (roundworms) can colonise the digestive tract of nightjars, including ascarids and digestive capillaries, as is common in many wild insectivorous birds.

The bird becomes infected by ingesting parasite eggs or larvae present in the environment, or by eating insects that carry larval forms of the parasite (intermediate hosts).

Young, weak, injured, or stressed birds are more susceptible. Housing in captivity with poorly cleaned ground or aviaries encourages accumulation of parasite eggs in the environment. Poor diet lacking varied insects, or repeated use of the same farmed prey, can also promote transmission in rehabilitation centers. Overcrowding in recovery aviaries increases the risk of cross-contamination between birds.

Transmission

Transmission occurs through ingestion of parasite eggs or larvae present in a contaminated environment, or through eating insects harbouring larval forms (intermediate hosts). Direct transmission between birds sharing a poorly maintained space is also possible.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

The veterinarian or wildlife care specialist typically performs fecal analysis (fecal flotation) under a microscope to look for parasite eggs. A thorough clinical examination assesses the bird's general condition, weight, and hydration status. In some cases, additional testing is needed to rule out other causes of weight loss or diarrhea.

Treatment

Treatment relies on administering an antiparasitic medication suitable for birds, prescribed and dosed only by a veterinarian experienced in wildlife medicine. Nutritional support and rehydration are often provided if the bird is weakened. Weight monitoring and fecal rechecks after treatment verify treatment effectiveness.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Regular cleaning and disinfection of floors and recovery aviaries limit parasite egg accumulation. Avoiding prolonged contact between multiple birds in a confined, uncleaned space reduces transmission risk. Veterinary screening on admission to a care facility, including fecal examination, allows detection of infestation before it worsens. A varied, quality diet suited to an insectivore supports the bird's natural defenses.

Possible complications

Untreated heavy infestation can cause dehydration, severe weakness, and marked weight loss, compromising survival chances or release potential for a wild bird. It can also favor secondary infections by weakening the body's defenses.

When to see a veterinarian

The bird is losing weight or refusing food. Worms are visible in the droppings. Droppings become abnormal or very frequent. The bird appears depressed with ruffled feathers and shows no normal reaction to approach. A young nightjar fails to gain weight normally.

Prognosis

The outlook is generally good if the infestation is detected early and treated by a qualified veterinary professional.

It becomes more guarded in a bird that is already weakened, injured, or very young, where parasitism may worsen an already fragile condition.

Frequently asked questions

Can a wild nightjar catch worms without being in captivity?

Yes. Gastrointestinal parasitism also exists in the wild. It becomes especially problematic when the bird is already weakened or stressed, which reduces its ability to tolerate the parasite.

Can you give an over-the-counter antiparasitic without veterinary advice?

No. Nightjars are protected wild birds that are sensitive to disturbance. Improper dosing can be toxic. Only a veterinarian or an authorized wildlife rehabilitation center should intervene.

How do we know if a collected nightjar has worms?

Only a professional analysis of droppings can confirm it with certainty. The visible signs (weight loss, weakness) are not specific to this disease.

Is this disease transmissible to humans or to other animals?

Digestive roundworms in wild birds are generally not transmissible to humans. The risk of contamination is mainly between birds sharing the same uncleaned space.