The report, published in the online journal Science Advances on Wednesday, December 20, suggests that given the scope of the snake fungal disease caused by Ophidiomyces ophiodiicola, future surveys should operate under the assumption that all species harbor the pathogen.
“This really is the worst-case scenario,” said lead author Frank Burbrink, an associate curator at the American Museum of Natural History. “Our study suggests that first responders shouldn’t just be looking for certain types of snakes that have this disease, but at the whole community. All snakes could become infected, or already are infected.”
First report in June 2017
The fungal disease in snakes was first identified in 2009 and put in the genus, Chrysosporium. However, in 2013, after DNA sequencing revealed the fungus to be a separate species, the genus Ophidiomyces was created to accommodate the new fungus. A study reported on in early June this year showed zero occurrences of the fungus from 1880 all the way through to 1999, based on examinations of specimens in museums.
Matt Allender at the University of Illinois in Urbana said he and his team of researchers found that in the year 2000, they began to see the fungal disease reappearing, with the BBC reporting this suggests some sort of event occurred at the turn of the century that led to a relatively innocuous soil fungus turning into a deadly pathogen.
Some 30 snake species in 15 U.S. states and in Canada have been hit by the fungal infection, although rattlesnakes seem to have been hit hardest. The disease manifests itself as a minor skin irritation at first and as the snake’s immune system kicks in, within a few days the skin at the infection site begins to thicken and die-off.
This die-off creates a thick yellow crust that often breaks off, exposing raw flesh that allows the fungus to spread. When the infection reaches the head of the snake, it can interfere with the snake’s eyes or sense of smell, leaving the animal unable to hunt and prone to death by starvation. The mortality rate is 90 percent.
Second report in late June 2017
In late June of this year, the Zoological Society of London (ZSL) published their findings on snake fungal disease (SFD) in Europe. Lead author and wildlife veterinarian Dr. Lydia Franklinos said: “Our team at ZSL found evidence of SFD in grass snakes (Natrix natrix) from the UK and a single dice snake (Natrix tessellata) from the Czech Republic.”
What stands out about this investigation is that the fungus strains from Europe are different to those previously identified in North America, based on using real-time polymerase chain reaction (PCR) testing in 26 (8.6 percent) of the specimens. This was taken to mean the disease could have been present below the radar in European snakes for some time.
The European strain of O. ophiodiicola grew more slowly than the North American strain when cultured in the laboratory. And a phylogenetic analysis of isolates indicated the O. ophiodiicola strain in European snakes was in a distinctly different clade from North American isolates.
A clade is defined as a group of organisms all coming from a common ancestor. So while the disease is similar, somewhere in the very distant past, there had to be a common organism that somehow, over the evolutionary process, evolved into the different branches of the “tree of life.”
The latest study is disheartening
According to the latest report, the researchers used several novel methods, taking into account evolutionary history, physical traits and ecology of known infected species and the regions where they were found. All the data was examined using a neural network to search for associations that could be used to predict which species might be vulnerable to the virus.
Specifically, the team found that all 98 groups of snakes in the eastern U.S. could be susceptible. Their findings also indicate that the epidemic could extend across the globe.
“The data for our model may not be perfect, but it will tell you if there’s even a weak association between a characteristic – for example, eating a certain type of animal or living in a particular environment – and the potential to get this disease,” Burbrink said. “And in this study, our model found no association other than ‘you are a snake’.”
“Scientists have learned a lot about research and monitoring needs from 25 years of studying the effects of chytrid fungi on amphibians, and those lessons tell us that prevention is the best policy,” said Karen Lips, a professor of biology at the University of Maryland, College Park.
It should be noted that the paper also discusses the evolutionary history of the pathogen, which in itself has not been examined. The paper suggests that three main groups of Ophidiomyces exist, two sister clades in wild snakes in Europe and North America and one deeper clade represented by an isolate from a captive snake in the United Kingdom.
The bottom line? There is a real possibility the disease is more widespread than we first assumed, and as more studies are conducted, we may find a reduction in populations uniformly across taxa with different ecologies, physiologies, demographics, and migration rates, and that is bad news for the environment.
