Reindeer nasal estrosis
Nasal estrosis is a parasitic disease caused by the larvae of a fly of the genus Cephenemyia. This fly lays its larvae directly in the nostrils of caribou or reindeer. The larvae then migrate to the animal's nasal cavities and throat where...
What is it?
Nasal estrosis is a parasitic disease caused by the larvae of a fly of the genus Cephenemyia. This fly lays its larvae directly in the nostrils of caribou or reindeer. The larvae then migrate to the animal's nasal cavities and throat where they develop for several months. It is a very widespread disease among wild or farmed caribou and reindeer in northern and Arctic regions.
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:
Infested animals often have a runny nose and repeated sneezing. They shake their heads frequently, appear embarrassed, and may emit noisy or wheezing breathing. An occasional cough is possible.
In more serious cases, the animal shows signs of difficulty breathing, unusual agitation, refusal to eat normally and progressive weight loss.
Many animals carrying only a few larvae show no visible signs.
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 due to infestation by larvae of estrid flies of the genus Cephenemyia (notably Cephenemyia trompe). The adult female, resembling a large bumblebee, deposits her live larvae directly in or near the nostrils of the caribou in flight. The larvae then ascend into the nasal cavity and pharynx, where they attach to the mucous membranes and feed on secretions and tissue debris as they develop.
Animals living in dense herds in the tundra are particularly exposed during the hot season, when adult flies are active. Young animals and those weakened by other diseases or poor nutrition tolerate a high parasitic load less well. Hot summer weather conditions favor fly activity and therefore the risk of infestation.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian suspects the disease based on typical respiratory signs and the seasonal and geographical context. Examination of the nasal cavities, sometimes using an endoscope, can reveal the presence of larvae. After an animal dies, direct inspection of the nasal passages and pharynx can easily confirm the diagnosis.
Treatment
Treatment is based on the administration of a suitable antiparasitic agent, prescribed and dosed only by a veterinarian, which eliminates the larvae present. Supportive treatment may be necessary in weakened animals, with improved diet and rest.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no easy way to prevent adult flies from laying eggs on free-ranging animals. On farms or during gatherings, a preventive antiparasitic treatment prescribed by a veterinarian may be considered before the period of fly activity. Regular monitoring of the herd makes it possible to identify the most affected animals.
Possible complications
A massive infestation can cause obstruction of the upper respiratory tract, significant inflammation of the nasal and pharyngeal mucous membranes, and promote secondary infections. In rare, serious cases, the animal's severe breathing difficulties and exhaustion can be life-threatening, especially if it is already weakened by other factors.
When to see a veterinarian
The animal has a persistent runny nose or repeated sneezing.
Noisy, wheezing, or difficult breathing is observed.
The animal shakes its head unusually and frequently.
A loss of appetite or progressive weight loss appears.
Several animals in the herd show similar signs in the summer.
Prognosis
The prognosis is generally good when the infestation is light to moderate, with most animals tolerating the presence of a few larvae well. It becomes more reserved in the event of a high parasitic load, especially in an already weakened animal, where respiratory discomfort can worsen without treatment.
Frequently asked questions
Can nasal estrosis be transmitted to humans or other pets?
No, this disease is specific to caribou and reindeer. It is not transmitted to humans or other domestic species such as dogs or cattle.
How does a caribou get this parasite?
The adult fly deposits its larvae directly into the nostrils of the flying animal, usually during the warmer months of the year, with no prolonged contact necessary.
Can an infested caribou recover on its own without treatment?
Many animals with a low larvae load show no signs and may expel mature larvae naturally. Veterinary treatment remains recommended in the event of marked clinical signs.
What time of year is the risk highest?
The risk is greatest during the warm season, when adult flies are active and lay their larvae on caribou.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 15 September 2026
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