Crow gastrointestinal parasitism (roundworms)
Crow gastrointestinal parasitism refers to the infestation of the digestive tract by roundworms (nematodes), internal parasites that live in the stomach or intestine of the bird. In the crow (Corvus corax), an omnivorous and opportunistic b...
What is it?
Crow gastrointestinal parasitism refers to the infestation of the digestive tract by roundworms (nematodes), internal parasites that live in the stomach or intestine of the bird. In the crow (Corvus corax), an omnivorous and opportunistic bird that often searches the ground, carrion and waste, this type of parasitism is common, particularly in young individuals or weakened birds. Most healthy adult crows tolerate a moderate parasite load without visible signs, but a heavy infestation can cause the bird to become truly exhausted.
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 and may go unnoticed. We frequently observe progressive weight loss despite a preserved appetite, or on the contrary a drop in appetite. The plumage becomes dull and less neat, the bird appears tired, less active, sometimes prostrate on a branch or on the ground. Digestive problems are possible: abnormally soft or diarrheal stools, sometimes colored or containing threadlike elements which correspond to expelled adult worms. In young crows (nestlings or juveniles), growth retardation and a distended belly (bloat) may appear. In severe forms, dehydration and a state of marked depression set in.
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 can colonize the digestive tract of corvids, including roundworms and other intestinal or gastric roundworms. These parasites lay eggs passed in the feces of the infested bird; these eggs become infective in the environment after a certain time, or pass through an intermediate host (insect, earthworm) depending on the species of parasite. The crow becomes contaminated by ingesting eggs present on the ground, in contaminated water, or by consuming prey (insects, small invertebrates, carrion) carrying infective larvae.
Young age is a major risk factor, with nestlings and juveniles still having immature immunity. Promiscuity in a nest or in a wild bird care center, feeding on the ground in areas soiled by droppings, access to landfills or carrion, and a weakened general condition (injury, concomitant illness, stress) favor the establishment and worsening of the infestation. A humid and warm environment also promotes the survival of eggs and larvae in the environment.
Transmission
Transmission occurs mainly by the fecal-oral route: ingestion of infective eggs present in the environment contaminated by droppings, or consumption of prey (insects, earthworms) serving as intermediate hosts carrying larvae.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian makes the diagnosis by a coproscopic examination, that is to say a microscopic analysis of a sample of droppings in search of worm eggs. This examination may require several samples because egg excretion is sometimes irregular. A complete clinical examination assesses the general condition, weight, hydration and condition of the plumage. In some cases, further identification of the type of parasite can be carried out in a specialized laboratory.
Treatment
Treatment is based on the administration of a broad-spectrum antiparasitic agent active against nematodes, prescribed and dosed exclusively by a veterinarian competent in avian medicine or wildlife. Nutritional support and rehydration may be necessary if marked weakening occurs. Cleaning the holding environment is an integral part of treatment to avoid immediate reinfestation.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is mainly based on good environmental hygiene when the bird is in captivity or in a care center: regular cleaning of floors and feeders, rapid elimination of droppings, avoidance of stagnation of dirty water. For a crow collected or kept under authorization, regular parasitological checks of stools make it possible to detect an infestation before the appearance of clinical signs. In nature, there is no direct means of prevention, the parasitic cycle being part of the ecosystem.
Possible complications
A massive, untreated infestation can lead to intestinal obstruction from worm buildup, severe malnutrition, anemia, and general weakening that makes the bird more vulnerable to other infections or predation. In young people, lasting growth retardation is possible.
When to see a veterinarian
Unexplained progressive weight loss in a detained or monitored crow
Presence of visible worms in the droppings
Persistent diarrhea or abnormal stools
Marked depression, dull plumage and prostrate bird
Distended or bloated belly in a young crow
Signs of dehydration (sunken eyes, weakness)
Prognosis
The prognosis is generally good when the infestation is detected early and treated by a veterinarian, with full recovery within a few weeks. On the other hand, a massive infestation discovered late, especially in a young bird already weakened, can be life-threatening in the absence of rapid treatment.
Frequently asked questions
Can a wild crow carrying worms transmit the disease to humans?
Corvid intestinal nematodes are generally specific to birds and are not transmitted to humans. However, it is still recommended to wash your hands after any contact with wild bird droppings, as a general hygiene measure.
How does a crow become infested with roundworms?
It becomes infected by ingesting eggs present in soil or water contaminated by contaminated droppings, or by consuming prey such as insects or earthworms carrying infective larvae.
Should we systematically treat all crows in a care center against worms?
It depends on the coproscopic analysis results. Systematic treatment without diagnosis is not recommended; it is the veterinarian who decides according to the parasitic load observed.
Should a healthy wild adult crow be concerned if it has worms?
A low to moderate parasite load is often well tolerated by a healthy adult and does not always require intervention. Vigilance is especially required in the event of visible clinical signs.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 29 September 2026
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