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Researchers investigate origins of snake fungal disease in US

Licht werpen op de gezondheid van reptielen: onderzoekers onderzoeken de oorsprong van slangenschimmelziekte in de VSPLOS Biology† Credit: University of Northern Arizona” width=”800″ height=”523″/>

A team of researchers, including NAU assistant professor Jason Ladner, conducted a genetic study on fungal disease in snakes recently published in PLOS Biology† Credit: University of Northern Arizona

Although only recently recognized as a problem in wildlife ecology, snake fungal disease (SFD) is an emerging problem in the US, with parallels to other better-known fungal diseases in the wild, such as bat white nose syndrome. SFD can be fatal to snakes and even in milder cases interferes with an animal’s ability to perform normal biological functions such as hibernation, feeding and avoiding predators.

To better understand SFD, a team of researchers, including assistant professor Jason Ladner of the Pathogen and Microbiome Institute at Northern Arizona University, conducted a genetic study of the pathogen that was recently published in PLOS Biology“The causative agent of snake fungal disease population genetics points to recent introductions into the US.”

Collaborating with study co-author Jeff Lorch of the US Geological Survey (USGS) and other scientists from the USGS, Genencor Technology Center, the University of California-Riverside, Stetson University, the Institute of Zoology, the University of Kentucky, and Holyoke Community College Ladner’s goal was to determine whether SFD originated in the US or was introduced from outside the country, which could provide a historical basis for how it originated — and ultimately inform management of the disease.

“Snake fungal disease was first recognized in the US around 2008. There was a well-studied population of rattlesnakes in Illinois that started dealing with some very serious fungal infections. People were asking, ‘Okay, what’s this thing? “What’s going on? Is this a new emerging fungal pathogen or not?” What they eventually found was that it was already almost everywhere, at least in the eastern half of the US,” Ladner said.

SFD, while seemingly not as deadly as other fungal diseases in the wild, is still a worrisome threat to animals that are an important part of the ecosystem. “We are deeply concerned not only about the effect of SFD in driving population decline, but also as a contributing factor in addition to many other threats that snakes already face, such as habitat destruction or excessive collection for the pet trade,” said Lorch.

Understanding diseases in wildlife is critical, both in the context of ecosystem health and their potential impacts on humans. “I’m very interested in disease in wildlife, in part because wildlife serves as important reservoirs for diseases that could potentially develop in humans; SARS coronavirus-2 is a good example of that. If we want to be prepared for With the next emerging infectious disease in humans, we need to better understand the pathogens currently circulating in wildlife populations that could potentially be transmitted to humans,” Ladner said.

However, the study presented unique difficulties. “For snakes, there is almost no data on long-term population trends, especially if we compare snakes to an animal like bats, which have suffered from white nose syndrome,” Lorch said. “In many states, there is historical data on bat populations because they are generally not as difficult to track as some other types of wildlife.”

Snakes, on the other hand, “are pretty secretive animals. They’re not something you’re likely to see routinely in the landscape unless you’re looking for them,” explains Lorch. Without a large amount of historical data on North American snake populations, “it makes it hard to say what snake populations were doing before SFD was noticed. Long-term trends are really hard to decipher.”

Before the study began, the team had two hypotheses about how the disease originated in the US. 100 years. The alternative hypothesis was that this pathogen has been around for a long time and is essentially native to the US; perhaps it has been here for thousands of years and evolved along with these snake populations. In the latter case, maybe it seems to pop up simply because we’re looking for it right now. Or there’s been some kind of environmental change, maybe something related to climate change, leading to an increase in the number of cases, even though this pathogen has been with this all along,” Ladner said.

To track the evolution of the disease, Ladner and Lorch created a “family tree” for strains of the fungus that causes SFD and found it in the US. “One of the ways we were able to reconstruct the history of the disease was by looking at the genetics of the pathogen to get an idea of ​​how long it’s been here and how it’s changed over time. Lorch said.

Studying the genetics of SFD gave the team a breadcrumb trail, revealing more about its history and shed light on SFD cases in the US “The reason genomic data is helpful for doing this is because every time That this fungus multiplies, grows and divides, the polymerase (the molecule that makes the new copy) sometimes makes mistakes. Those mistakes result in mutations. And then those mutations will be passed down through the generations. On to those different mutations in the population By looking at it, we can understand how long certain descendants already have an idea of ​​how the different tribes are related to each other. And that can tell us something about how long SFD has been here,” Ladner said.

After taking samples from several SFD-infested snakes, the team performed genetic sequencing on 82 strains of the fungus. This included SFD strains isolated from wild snakes in the US and Europe, as well as captive snakes from three different continents. Based on the genetic similarities and differences between the strains, the team was able to partially reconstruct the evolutionary history of this fungus. “In the US, we found that there are several divergent lines of this fungus circulating, but a lack of intermediates between these lines, which would be expected if they came from the US, so we think there are likely multiple, somewhat recent introductions of this fungus in the US, and that an unsampled population, elsewhere in the world, acted as the source,” Ladner said.

This evidence allowed the team to draw conclusions about how SFD arrived in America. “It suggests that this fungus was introduced into the United States through anthropogenic means — humans moving these snakes. The most likely culprit is the trade in captive snakes as pets: We also see the different clonal lines we see in the U.S. represented in captive snake populations,” Ladner said.

The study provides guidance for future management of SFD in the US, as well as a better understanding of how it was introduced. “If we had noticed the introduction of SFD very early, you can imagine that we are trying to stop and possibly even eradicate the spread of the disease in the US. I think that is unlikely at this point, given the widespread I think it is still useful to better understand the mechanism for the introduction of SFD, as there is still the potential for new introductions of various strains from these source populations. Knowing that this fungus has appeared several times over the past decades introduced through the captive animal trade, more restrictions and controls and animal testing in that process may be important to prevent further spread,” Ladner said.

While their work provides critical insight into SFD, its treatment and its movement in the US, both scientists emphasize the need for further research. “What I hope is that this study raises awareness of the disease. I think SFD deserves more of our attention,” Lorch said.

More needs to be done to assess the ecosystem, population and species impacts of SFD. “The broader question of ‘what will be the impact of this fungal pathogen on these snake populations?’ is a very open question and needs more research,” Ladner said.

Snake fungal disease first identified in wild British snakes

More information:
Jason T. Ladner et al, The population genetics of the causative agent of snake fungal disease indicate recent US introductions, PLOS Biology (2022). DOI: 10.1371/journal.pbio.3001676

Provided by the University of Northern Arizona

Quote: Shedding light on reptile health: Researchers investigate the origins of snake fungal disease in the US (2022, June 29) retrieved June 29, 2022 from https://phys.org/news/2022-06-reptilian-health-snake- fungal disease .html

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