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Sheep myiasis
We speak of myiasis when fly larvae, maggots, develop in the skin or in a wound of a living animal. In sheep, it is one of the most frequent emergencies of the hot season. Within hours, an area of soiled wool or a small wound can turn int...
What is it?
We speak of myiasis when fly larvae, maggots, develop in the skin or in a wound of a living animal.
In sheep, it is one of the most frequent emergencies of the hot season. Within hours, an area of soiled wool or a small wound can turn into a large, deeply painful lesion.
Some flies lay eggs on damp or soiled wool; others, very present around the Mediterranean basin, deposit live larvae directly on healthy skin, at the edge of a tiny wound, around the mucous membranes, the lamb's navel or the genitals.
Key point
Myiasis is a veterinary emergency. An animal can go from a small area of soiled wool to a large, fatal lesion in one to two days of intense heat. Never postpone the examination until the next day and do not pour any household product on the wound.
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:
Agitated animal, which turns towards its side, bites itself, shakes its tail, stamps its foot, cannot sit still.
Then, conversely, an animal isolates itself, seeks shade, remains lying down, refuses to eat.
Area of damp, discolored, brownish wool, which comes off easily, with a strong and characteristic odor.
Under the wool: raw skin, wound teeming with maggots, swollen edges, discharge.
Frequent locations: hindquarters soiled by diarrhea, base of the tail, shearing wounds, castration or marking wounds, lamb's navel, rams' heads after fighting, damaged feet.
Fever, deep depression, rapid weight loss.
In advanced cases, animal lying down, in shock.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Flies are attracted to humidity, the smell of feces, blood, urine and wounds.
A fleece soiled by diarrhea, a shearing wound, recent castration, an undisinfected umbilical cord or skin damaged by scratching are enough to trigger egg-laying.
The larvae hatch quickly and feed on the tissue, making the wound larger and attracting other flies.
Some Mediterranean species do not even need an open wound: they deposit live larvae on intact skin, at the mucous membranes and moist areas, and the damage quickly becomes deep.
The toxins released by the lesion and the infection that sets in explain the general condition and possible death.
Hindquarters soiled by diarrhea, often of parasitic origin: this is the number one risk factor.
Shearing, castration, marking or dehorning wounds carried out in the middle of the hot season.
Undisinfected umbilical cord of newborn lambs.
Long, damp fleece, poorly dried after rain.
Skin diseases that cause animals to scratch, including scabies and lice.
Lameness and neglected foot sores.
Dead bodies, slaughter waste and unmanaged manure near the herd.
Spaced monitoring during periods of risk: one day without spending time in the herd is enough for a lesion to spread.
Transmission
There is no contagion from one animal to another: it is the flies which lay eggs or larvae.
However, an affected animal attracts other flies and increases the pressure on the entire flock.
The risk is greatest during the hot season, in heavy and humid weather, and around dirty areas, corpses and slaughter waste left in the open air.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The examination must be carried out on the contained animal, spreading the wool widely around the suspicious area: the visible lesion is almost always smaller than the actual lesion.
The veterinarian assesses the extent of the damage, depth, general condition, fever and dehydration.
He systematically searches for the cause that attracted the flies: diarrhea, wound, skin disease, lameness. Without this, myiasis will start again.
When faced with several cases in a herd, he examines the management of internal parasitism and animal hygiene, because this is usually where the origin of the problem is found.
Treatment
It's an emergency: the earlier the intervention, the better the chances.
The management is done with the veterinarian and combines wide mowing of the area, removal of larvae, careful cleaning of the wound and appropriate treatment: antiparasitic, local care, antibiotic in case of infection and anti-inflammatory for pain, all on prescription.
Never pour diesel, bleach, household products or homemade preparations on the wound: these practices burn the tissues, aggravate the lesion, delay healing and can kill the animal.
Don't just remove the visible maggots: those that remain deep down will restart the process within a few hours. The wound check must be repeated.
A feverish, depressed or dehydrated animal needs general support: water, shade, food, and sometimes IV fluids.
We must also treat the cause: control diarrhea, treat skin disease, manage lameness.
The withdrawal periods for meat and milk apply to all products used and must be requested from the veterinarian before any slaughter or milking.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Keeping the hindquarters clean: this starts with controlling diarrhea and therefore internal parasitism, with the veterinarian.
Clip the tail and hindquarters area before the hot season on animals at risk.
Schedule shearing, castration, marking and dehorning outside periods of high fly activity, and never during the hottest hours.
Systematically disinfect the umbilical cord of lambs at birth.
Treat and monitor any wound, even small, during the summer.
Quickly collect and dispose of carcasses and slaughter waste, manage manure, and do not leave anything to decompose near animals.
Go through the herd at least twice a day during periods of risk and remove the wool at the slightest agitated animal.
Long-acting preventive treatments exist: their benefit, timing and constraints are discussed with the veterinarian, taking into account waiting times.
Possible complications
Rapid extension of the lesion, affecting deep tissues, sometimes mucous membranes and genitals.
Bacterial infection of the wound and spread in the body.
State of shock and death within a few days in the absence of treatment.
Intense pain, refusal to eat, rapid weight loss.
In rams, damage to the genitals with consequences on reproduction.
In lambs, severe umbilical damage.
Scars, lost skins and fleeces, culled animals.
Almost certain recurrence if the initial cause, often parasitic diarrhea, is not treated.
When to see a veterinarian
You discover maggots on an animal: call the veterinarian the same day, don't wait.
An animal is agitated, chews its side or shakes its tail constantly in the middle of the hot season.
An area of wool is damp, discolored or has a bad odor.
An animal isolates itself, refuses to eat, has a fever or remains lying down.
A shearing wound, castration wound or a lamb's navel becomes dirty, swollen or smelly.
Several animals have soiled hindquarters: action must be taken before the flies take care of them.
Prognosis
A lesion caught in the first few hours generally heals well, with the wool regrowing within a few months.
Extensive, deep damage, or an animal already down and feverish, has a guarded prognosis despite treatment.
At the herd level, everything depends on controlling the causes: without controlling diarrhea, hygiene and wounds, cases repeat themselves every summer.
Frequently asked questions
Can I remove the maggots myself and wait?
Removing what you see is not enough: larvae remain deep and the lesion disappears within a few hours. The area should be mowed extensively, cleaned and treated, with repeated checking. Call the vet the same day.
Can you put gasoline or bleach on the wound?
No, never. These products burn tissue, increase pain, prevent healing and can kill the animal. They are one of the practices that most often aggravate myiasis.
Why are my sheep affected every summer?
Because the cause has not been treated. In the vast majority of cases, it is a hindquarters soiled by diarrhea of parasitic origin. Controlling internal parasitism with the veterinarian reduces the number of cases much more surely than using an insecticide.
Can these flies attack humans?
Certain species present around the Mediterranean can lay eggs in a neglected human wound, particularly in a fragile or poorly mobile person. It is not transmission by sheep: it is the same flies. Any wound must be cleaned, protected and shown to a doctor in case of abnormality.
When should you mow to limit the risk?
Before the arrival of hot weather, and avoiding periods of high fly activity for operations that create wounds. Cleaning the hindquarters of animals at risk is at least as important as general mowing.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
ANSES — Agence nationale de sécurité sanitaire (France)
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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