White-nose syndrome
White-nose syndrome is a disease caused by a fungus that grows on a bat's skin during hibernation. It affects the muzzle, ears, and wings, where it forms a characteristic whitish deposit. This disease has decimated entire bat populations in...
What is it?
White-nose syndrome is a disease caused by a fungus that grows on a bat's skin during hibernation. It affects the muzzle, ears, and wings, where it forms a characteristic whitish deposit. This disease has decimated entire bat populations in North America and is now a concern in Europe, where the greater horseshoe bat can carry the fungus. The cold conditions of hibernation caves and shelters are essential for this fungus to develop.
Key point
This disease has caused mass mortality in several bat species in North America and represents a major wildlife conservation concern.
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:
A white fuzzy deposit or coating appears on the muzzle, ears, and sometimes the wing membranes of the sleeping bat.
Wing skin may show small lesions, holes, or damaged texture once the bat wakes.
Infected bats wake abnormally often during winter, causing them to burn through their fat reserves too quickly.
They may be seen flying in broad daylight in winter, leaving their hibernation shelter, or gathering near the entrance—highly unusual behavior for this season.
The animal loses considerable weight and may be found dead inside or near the hibernation site.
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 caused by a filamentous fungus, Pseudogymnoascus destructans, which develops only in cold, humid conditions like those found in caves and cavities where bats hibernate. This fungus invades the skin, particularly in areas with little fur such as the muzzle and wings.
Hibernation in dense colonies within humid and cool caves promotes transmission between individuals.
The fungus persists in cave environments from year to year, which exposes the same sites repeatedly over successive seasons.
European bat species, including the Greater horseshoe bat, appear to have developed a degree of historical tolerance to the fungus, in contrast to North American species where mortality rates are very high.
Human disturbance of hibernation sites can increase stress and cause premature arousals in the animals.
Transmission
The fungus spreads mainly through direct contact between bats during group hibernation. It can also spread through spores in cave dust and walls, and may potentially be carried unintentionally by humans on clothing or caving equipment that has contacted an infected site.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is made by a veterinarian or wildlife specialist, usually in liaison with specialized laboratories. It is based on observation of the characteristic white deposit, confirmed by laboratory analysis to verify the presence of the fungus Pseudogymnoascus destructans, using microscopy or molecular biology techniques.
Treatment
No validated antifungal treatment applicable under natural conditions exists for treating affected wild bats. Care of isolated animals in wildlife rehabilitation centers may include supportive care and, in some experimental cases, topical antifungal treatments, always determined by a veterinarian specializing in wildlife medicine.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention relies mainly on limiting disturbance to natural bat hibernation sites, particularly during winter.
Cleaning and decontamination of caving equipment between visits to different caves reduce the risk of spreading the fungus from one site to another.
Regular monitoring of colonies by specialized associations enables early detection of the disease at a new location.
No vaccine or large-scale preventive treatment suitable for wild populations currently exists.
Possible complications
Depletion of fat reserves during winter can lead to death from starvation before the arrival of spring.
Skin lesions on the wings can impair flight and thermoregulation even after hibernation ends.
At the population level, the disease can cause local collapse of colony numbers.
When to see a veterinarian
Unusual white deposit noticed on the muzzle or wings of a bat.
Bat flying during daytime in winter months.
Discovery of multiple dead or severely weakened bats near a hibernation site.
Bats clustered unusually at the entrance of a cave during winter.
Prognosis
The individual prognosis is guarded once clinical signs are well established, particularly in cases of significant weight loss. In the Greater Horseshoe Bat and other European species, observed mortality appears overall lower than in certain North American species, suggesting better tolerance, but long-term follow-up studies remain necessary.
Frequently asked questions
Is white-nose syndrome dangerous to humans or domestic animals?
No, this fungus is specific to hibernating bats and is not known to infect humans or domestic animals.
Can you help an injured bat found in the wild?
Never handle a wild bat yourself. It is recommended to contact a wildlife protection association or a specialized care center.
Why does this disease worry specialists so much?
Because it has caused the collapse of entire bat populations in North America, and bats play an important ecological role, particularly in regulating insects.
How to avoid spreading the fungus between two caves?
By carefully cleaning and disinfecting all caving equipment before visiting a new site, and by respecting local recommendations regarding the closure of certain sensitive sites.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
CDC — Centers for Disease Control and Prevention
Content reviewed by the TunisieVet editorial team · Updated 01 September 2026
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