Rattlesnakes face increased risk of deadly infections

A deadly combination of fungal, parasitic and bacterial infections could push certain species of snakes toward extinction, according to new research from the University of Georgia.

The study found that some pathogens are more prevalent across snake species than previously thought. Certain native snake species, such as pygmy rattlesnakes, are at risk for serious illness and death.

Snakes play a key role in the environment. They serve as both predators and prey, helping to maintain environmental balance and biodiversity. But they aren’t always seen in the most positive light, particularly the venomous ones.

“We often fear what we do not understand. Rattlesnakes are dangerous, as are many wild animals, but it is critical for the public to be educated on their value in our ecosystems and to learn how to safely coexist, ” said Corinna Hazelrig, corresponding author of the study and a doctoral graduate from the UGA College of Veterinary Medicine and the Southeastern Cooperative Wildlife Disease Study. Hazelrig is currently pursuing her Doctor of Veterinary Medicine degree. “Rattlesnakes deserve to live peacefully and unharmed as any animal does.”

Disease risk for snakes varies by state, species

The researchers swabbed and analyzed more than 500 snakes from Georgia, Florida and South Carolina over four years. The researchers tested individuals from 29 species for seven pathogens, including those that can cause skin, gastrointestinal and respiratory diseases. Some were more harmful than others.

Previous research cited Ophidiomyces ophidiicola as the cause for Snake Fungal Disease, a highly contagious skin infection that is sometimes fatal. The present study found that the fungus disproportionately affects pygmy rattlesnakes, with more than one in three rattlers testing positive.

This is concerning for the pygmy’s future, as the fungus has already been linked to localized population crashes in other rattlesnake relatives like the endangered eastern massasauga rattlesnake.

“A snake can carry a pathogen and still appear completely healthy. What matters is understanding what pushes infection into something deadly,” Hazelrig said.

"We often fear what we do not understand … but it is critical for the public to be educated on their value in our ecosystems and to learn how to safely coexist."

Corinna Hazelrig, College of Veterinary Medicine

Pygmy rattlesnakes were also more likely to test positive for Raillietiella orientalis, otherwise known as snake lungworm. This is possibly because of the snakes’ consumption of lizards and frogs, which play a role in the parasite’s life cycle and pass the infection to snakes.

The researchers found Ophidiomyces ophidiicola was more prevalent in Georgia snakes while snake lungworm only infected Florida snakes. This discrepancy is likely due to climate and landscape differences that allow fungal infections to thrive in Georgia. Meanwhile, the lungworm was probably introduced to Florida species through the invasive Burmese python.

“Life and death for wildlife like snakes is not so simple,” said senior author Dr. Nicole Nemeth, head of UGA’s Southeastern Cooperative Wildlife Disease Study’s research and diagnostic service and a professor in the College of Veterinary Medicine’s department of pathology. “Any group or regional population of snakes is likely to be already under some level of stress, so they are primed for that fungus or bacteria to take advantage of them and become a full-blown infection.”

2 of every 5 snakes tested positive for multiple pathogens

All native snakes face risks from these infections, the researchers said. But increases in co-infections are particularly pressing.

More than 40% of the reptiles in the study tested positive for multiple pathogens, with salmonella found in over half of the snakes. Just one of these infections can compromise a snake’s immune system, making it more vulnerable to additional, potentially deadly infections.

The present study was the first to identify Mycoplasma spp. in free ranging snakes. The antibiotic-resistant bacteria can cause severe upper respiratory tract diseases in a variety of reptiles. While infection with Mycoplasma spp. can cause clinical signs like pneumonia in snakes, it frequently presents as secondary infection alongside other pathogens.

Snakes infected by fungal pathogens like Ophidiomyces ophidiicola became malnourished and experienced skin lesions and deformities of the face. Some native snakes lost up to a quarter of their body mass in a single month, leading to death.

“Most snakes carrying salmonella appeared completely healthy, but the snakes with Ophidiomyces ophidiicola and the lung parasite were more likely to be emaciated and show visible clinical abnormalities,” Hazelrig said. “Co-infections further contributed to increased prevalence of disease.”

Disease spillover may endanger threatened native species

As with many wildlife diseases, the researchers are concerned about the risks of spillover.

The more these pathogens move through wild snake species, the more likely it is that the diseases can trickle into species that are already in jeopardy.

The snake lungworm parasite, for example, doesn’t pose much risk to its original host, the Burmese python.

But native snakes don’t have the python’s protective mechanisms.

“When people first thought about Burmese pythons being invasive to Florida, I think everyone was focused on the snake itself. But it likely has brought so much more with it,” Hazelrig said.

"Understanding … pathogens is one piece of the puzzle toward understanding and better conserving snakes, as well as all of the resources they and other wildlife need to survive."

Dr. Nicole Nemeth, College of Veterinary Medicine

One in five reptiles worldwide are facing extinction. Understanding infections is the next step in preventing a massive snake die-off, the researchers said.

“Snakes are a critical wildlife group due to their ecological importance as predators and prey,” Nemeth said. “Understanding the prevalence and distribution of targeted pathogens is one piece of the puzzle toward understanding and better conserving snakes, as well as all of the resources they and other wildlife need to survive.”

Published in Frontiers in Veterinary Science, the study was funded by the Morris Animal Foundation. It was co-authored by researchers from UGA’s Warnell School of Forestry and Natural Resources and the Center for the Ecology of Infectious Diseases. Additional co-authors come from Stetson University, University of Central Florida, University of Florida and the University of Arkansas.

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