What causes wns in bats

What is White-Nose Syndrome (WNS)?

White-Nose Syndrome (WNS) is a devastating disease affecting bat populations, particularly in North America. It is characterized by a distinctive white, powdery fungus that grows on the muzzle, ears, and wing membranes of infected bats. This fungal growth is the most visible sign of the disease, hence its name. WNS is highly contagious and has led to unprecedented mortality rates in many bat species, raising significant conservation concerns.

The Culprit: *Pseudogymnoascus destructans* (Pd)

The causative agent of WNS is a fungus identified as *Pseudogymnoascus destructans*, often abbreviated as Pd. This fungus is believed to have originated in Europe and was first detected in North America in a cave near Albany, New York, in 2006. Pd is a psychrophile, meaning it thrives in cold temperatures, typically between 41-57 degrees Fahrenheit (5-14 degrees Celsius). This makes hibernation sites such as caves and abandoned mines ideal environments for its proliferation.

How Pd Affects Bats

During hibernation, bats significantly lower their body temperature and metabolic rate. This period of vulnerability is when Pd can take hold. The fungus invades the skin of hibernating bats, causing inflammation and tissue damage. This invasion disrupts the bats' normal physiological processes in several critical ways:

• Immune System Disruption: The presence of Pd triggers an abnormal immune response in bats. Instead of effectively fighting off the fungus, the immune system's reaction itself can cause significant damage to the skin and underlying tissues.
• Dehydration: The fungal growth damages the skin, increasing water loss. Bats, especially during hibernation when they are trying to conserve energy and water, become severely dehydrated.
• Electrolyte Imbalance: Skin damage can also lead to the loss of essential electrolytes, further compromising the bat's health.
• Disruption of Hibernation: The irritation and discomfort caused by the fungal growth can force bats to arouse from hibernation more frequently. Each arousal requires a significant expenditure of stored body fat and energy. Since bats rely on these reserves to survive the winter, frequent arousals deplete them much faster than normal.
• Starvation: With depleted energy reserves and no food available during winter, bats succumb to starvation as they cannot sustain the increased metabolic demands caused by repeated arousals.

Transmission and Spread

The Pd fungus spreads primarily through direct contact between bats. Bats can contract the fungus from other infected bats in hibernation sites. It can also spread through contact with contaminated surfaces within caves, mines, or other roosting areas, including clothing and gear of humans who visit these sites. While Pd is not known to be harmful to humans, humans can inadvertently carry fungal spores from one location to another, thus aiding in its spread. This is why it is crucial for spelunkers, researchers, and anyone entering bat habitats to follow strict decontamination protocols.

Impact on Bat Populations

The impact of WNS on bat populations has been catastrophic. In some areas and for certain species, mortality rates have exceeded 90%. Species like the little brown bat (*Myotis lucifugus*), once one of the most common bats in North America, have experienced dramatic population declines. The loss of these bats has significant ecological consequences, as bats are crucial predators of insects, including agricultural pests and disease-carrying mosquitoes. This ecological imbalance can lead to increased pest damage in agriculture and potentially higher rates of insect-borne diseases. The economic impact is also considerable, given the value of bats' pest control services to agriculture and forestry.

Conservation and Research Efforts

Scientists and conservationists are actively working to understand WNS and develop strategies to mitigate its impact. Research focuses on identifying factors that contribute to bat survival, developing potential treatments for infected bats, and exploring ways to manage the Pd fungus in hibernation sites. Efforts also include monitoring bat populations, educating the public about the disease and its spread, and implementing measures to prevent human-assisted transmission. While a cure has not yet been found, ongoing research offers hope for the long-term survival of bat populations affected by this devastating disease.