In my last post on bats, I talked about how these animals can spread dangerous diseases among humans. This post is also about diseases, but the victims in this story are the bats. Millions of bats.
A fungus called Pseudogymnoascus destructans got its scientific name in 2009, and the word destructans was chosen for the species name because the English translation of the word is destroying. It is the fungus that is destroying bats in North America. People also use its abbreviated name: Pd.
Pd is a white fungus that loves the cold. It grows well between 4°C and 20°C, and it cannot grow above 20°C, which means that winter is its favorite season. The other important fact about this fungus is that it lives on bat bodies. Specifically, it lives on the hairless parts of a bat: the wings, the ears, and the muzzle (or the nose). Because of its white color, a bat infected with this fungus has a white nose, which gives the name of the disease: the white-nose syndrome.
A bat infected with white-nose syndrome. The powder-like white fungus is visible on the nose, ears, and wings.
Image source: pixabay
Since the first cases of white-nose syndrome were observed in New York State in 2006, the fungus has spread to 31 states in the US and 5 provinces in Canada, and has killed at least 6 million bats, sometimes killing more than 90% of the population in a colony. The syndrome has been confirmed in at least 9 species and there are several more species that have tested positive for the fungus, some of which are endangered and threatened species. Several species have been projected to go extinct soon.
The fungus invades the hairless bat skin and breaks down the skin as well as the underlying tissue. The bats infected with it are constantly woken up from their hibernation, which leads to a waste of their valuable energy and ultimately leads to their death.
First, let us remember the fact that Pd can thrive only in cold temperatures. And when it comes to fighting the cold, bat species are of two types: migrating and hibernating. A migrating bat will move to a warm place in the winter and thus save itself from the deadly fungus as well as from the cold.
But in the case of a hibernating bat, while it is in its deep sleep inside a cold, dark cave, the fungus slowly grows in its body. A hibernating bat runs all its life processes in slow motion: its body temperature is lowered, its rate of breathing is slower, and the overall metabolic processes slow down to conserve energy. This is important because food is scarce during the wintertime, and maintaining the summertime temperature and metabolic rates is costly in terms of energy. The energy needs are being fulfilled by burning the stored fat, and the best strategy is to make it last as long as possible.
But if a bat has the white-nose syndrome, the fungus won’t let it sleep. While a healthy hibernating bat does wake up a few times through the winter, the fungus makes these conscious intervals much more frequent. When the bat wakes up often because of the disease, its fat reserve gets used up quickly because of the need for extra energy. And there are no insects to eat in the cold. The fungus also grows into the wings causing a serious disruption to the water and electrolytic balance of the body.
Imagine starving to death while a plant grows into your muscles and wakes you up from a life-saving sleep.
Some bats that survive the winter hibernation have been known to die later in the spring when their immune system gets activated and attacks the fungus and their own tissues that are intermingled with the parasite.
Nothing effective on a large scale has been found yet.
But there are scientists working on several projects to learn more about the disease. Among other things, they are studying how bats in Europe seem to be more resistant to the disease.
A bacteria-based treatment was tested successfully in 2015, but the researchers quoted in the article say that much more testing and work from different aspects is required, for example to decontaminate caves where the bats hibernate. A researcher in Wisconsin is working on using ultra-violet light to control the fungus.
The fungus has been known to spread among bats, and also from humans to bats. Human health problems because of the fungus have not been reported although thousands of people have visited caves with infected bats and possibly come in contact with the bats.
While we do not get the disease that is killing the bats, it should be a matter of concern for us because it is the worst animal epidemic in years and the ecological balance that the flying mammals help to maintain is threatened. The disruption of the pest-controlling function of the bats will be the most observable effect since the insect-eating, hibernating bats (not the fruit eating or migrating bats) are the victims of this disease.
If you want to know more about how you can help to save the bats, you can read more on whitenosesyndrome.org.
Links to references and image sources are provided in the text.
