White-nose syndrome, Tricolored bat. Photo by Karen Slote
Plants are not the only type of invasive species easily transported in our boots and clothes and cars and hair.
We carry invasive fungi around with us, too.
Image from: Cryan et al., (2010).Wing pathology of white-nose syndrome in bats suggests life-threatening disruption of physiology, BMC Biology.
White-nose syndrome, the disease known for decimating bat populations, may have been brought in this way. Pseudogymnoascus destructans or Pd was likely introduced to the United States from Europe in 2006. It’s a dangerous fungus; it grows on hibernating bats and forms a white fuzz that grows on their muzzles. It awakens them from hibernation and quickly depletes their stored fat. The fungus eats away at the wing, causing lesions and attacking the skin. If Pd causes White-nose syndrome, a 70-90% mortality rate can be anticipated. 100% fatality rates have also been reported. The Center of Biological Diversity considers it the worst wildlife disease outbreak in North America, and estimates that 6.7 million bats have died since 2006. Closing off only certain caves to human exploration has not curbed the spread. Moreover, the spores last a long time; while bats can spread it to each other and to different environments, we can also carry them around in our gear and clothing too, and cause problems even if we never come into contact with a bat: the fungus can survive on its own in caves. It hits close to home; it was first identified between Oneonta and Albany in New York State, and was identified in Western New York in the 2009-2010 hibernation period. It is currently spreading westward, with new findings identified in California over the 2018-2019 period. Few states have been spared at this point.
Check out the map here to learn more: https://www.whitenosesyndrome.org/spreadmap
Batrachochytrium dendrobatidis (Bd) or “Chytrid” is another introduced disease known to play a role in driving catastrophic declines in frog populations across the globe. Chytrid, exacerbated by climate change in some areas, is initially spread from place to place through human activity – such as the pet industry, or even shipping – when infected frogs hitch a ride in large ships that cross the sea. Chytrid spreads in pet stores in the U.S. and U.K. despite trade guidelines and research that highlights the importance of utilizing existing policy to prevent disease outbreaks. A new strain of Chytrid, Batrachochytrium salamandrivorans was discovered in 2013, which kills salamanders. It is even more deadly than Bd. It has not yet been found in the US, and thankfully new trade restrictions were implemented in January 2016 to help prevent the spread. However, these restrictions are limited to salamanders; recent studies suggest that Bsal can be vectored by imported frogs. The frogs may carry small amounts of the fungus, and not fall seriously ill; in contrast, small amounts of Bsal are lethal to salamanders.
The United States is a global hotspot for salamander biodiversity, with about 190 species, more species of salamanders than any other place on earth. The consequences of introduction of this fungal pathogen would be devastating.
Disease is complicated enough as it is. Working with wildlife complicates treatment even further. Fungicide treatments are promising, according to researchers, but we run into problems with population size; even if we sent treatment teams into as many habitats as possible – we would still be missing plenty of frogs and salamanders. And so, the disease will continue to spread. Chytrid prefers warm, but not hot water temperatures – and climate change may help the disease spread once it is in place; ironically, once water temperatures get too hot – researchers observe that it curbs itself.
Overall, this particular situation touches on not only human behavior -- but also on the illegal wildlife trade. The illegal wildlife trade is massive and spans beyond any one country. It’s a multibillion-dollar business, ranked as the 4th most lucrative illegal trade. It falls just behind drug trafficking, human trafficking, and counterfeiting. People can make a lot of money trading wildlife, and they do.
Lastly, wildlife diseases are rarely touched on by the media unless they are determined to be harmful to humans, or to domestic pets. Disease ecology and prevalence are not reported on until they become relevant. We just don’t hear about these things. The articles that spur our conversations are the ones that are most visible. The ones that are most visible aren’t necessarily the ones that are written by well-studied scientists and doctors, but the sensational ones; the ones with headlines that command attention and steer conversations in a potentially volatile way.
If the wildlife trade stems from inequities, these need to be discussed. When the world is faced with a human pandemic, we do not hesitate to provide information. And yet, if White Nose syndrome or Chytrid were to jump to the human species -- though they show no indication of doing so -- how many individuals would jump out of their seats in shock, startled, and say, “Why haven’t I heard of this before?”
Who would be to blame? How do we fix it? Why do we constantly need to utilize fear to begin these conversations?
We’ve lost our bats. We’ve lost our frogs. They are valuable for what they are; not for what they bring to humans. However, the loss of biodiversity and other life on this planet will be a huge loss for humans as well. We are all a part of nature. The damage we do to ecosystems and other life on this planet, we do to ourselves. By paying attention to our behaviour and even just cleaning our gear and washing our cars and being mindful of the pets we purchase and the places we travel, we can reduce harm. It’s up to us to share stories with each other and keep each other up to date until the media catches up, and to take responsibility for our actions. We can make a difference if we learn the facts and act on them -- before it’s too late.