A weakened population is a susceptible one
In the wetlands and refuges of the American Southeast, a quiet crisis is unfolding beneath the leaf litter: wild snakes, already burdened by centuries of habitat loss and human persecution, are now carrying overlapping infections that compound one another's harm. Researchers examining more than five hundred snakes across twenty-nine species found that rattlesnakes bear a disproportionate share of this burden, their fragmented and stressed populations seemingly more vulnerable to both fungal disease and parasitic invasion. The findings remind us that the health of a species is never a single story — it is a web of pressures, histories, and ecologies that interact in ways our conservation strategies have only begun to reckon with.
- Rattlesnakes, already among the most persecuted reptiles in North America, are now testing positive for snake fungal disease at rates nearly eighteen times higher than some neighboring species.
- Nearly half of all surveyed snakes carried multiple pathogens simultaneously, and those with visible skin lesions were infected with fungal disease at fifteen times the rate of visibly healthy individuals.
- An invasive parasitic lungworm, spreading through prey like frogs and lizards, has established itself almost exclusively in rattlesnakes within the Florida sampling sites — raising alarms about what happens when invasive species like Burmese pythons move through the same territory.
- Wildlife managers who routinely translocate snakes for conservation purposes now face an urgent warning: a single screened snake carrying coinfections could introduce novel pathogens to populations that have never encountered them.
- Researchers acknowledge their sampling was geographically narrow and that the true prevalence of these pathogens is almost certainly higher than the data currently reflects, leaving the full scope of the crisis unmeasured.
Snakes across the globe are disappearing, and disease is playing a quiet but devastating role. Habitat loss dominates the headlines, but fungal, parasitic, and bacterial infections are dismantling populations from within. In the southeastern United States, researchers set out to map the full picture — and found something far more complicated than expected.
More than five hundred snakes from twenty-nine species were captured at wildlife refuges in South Carolina and Florida, tested for seven different pathogens. Nearly four in five carried at least one. Nearly half carried more than one. Salmonella appeared in sixty-three percent of snakes; a tick-borne parasite infected more than half. But the data grew more troubling when broken down by species.
Rattlesnakes stood apart. Thirty-five percent tested positive for the fungus behind snake fungal disease — compared to under six percent in most other species. Fourteen of thirty-four rattlesnakes also carried a parasitic lungworm transmitted through prey like frogs and lizards, a parasite that barely appeared in any other species sampled. Researchers suspect centuries of human persecution have left rattlesnake populations fragmented and immunologically stressed, making them far more susceptible when one infection opens the door to others. Snakes with visible skin lesions carried fungal disease at rates above thirty percent; healthy-skinned snakes, at just two percent.
Geography added another layer. The fungal disease clustered in Georgia; the lungworm appeared only in Florida. These regional patterns carry a practical warning: moving snakes between locations — a common conservation practice — risks carrying pathogens into populations that have never encountered them. Invasive species like Burmese pythons and brown anoles are known hosts for the lungworm, meaning any contact between invasive and native populations could accelerate its spread.
The study's sampling was limited to a few counties, and detecting the lungworm in live snakes is difficult enough that true prevalence is likely higher than recorded. But the core message is clear: before any snake is translocated for research or conservation, pathogen screening is no longer optional. The consequences of skipping it could ripple outward in ways we are only beginning to understand.
Snakes across the globe are disappearing, and disease is playing a quiet but devastating role in their decline. Habitat loss gets the headlines, but infections—fungal, parasitic, bacterial—are quietly dismantling populations from the inside. In the southeastern United States, researchers decided to look at the full picture of what's actually killing wild snakes, and what they found was a landscape of overlapping infections that paints a far more complicated portrait of snake health than anyone had mapped before.
Over five hundred snakes representing twenty-nine different species were captured at wildlife refuges in South Carolina and Florida, then swabbed and bled. A handful of road-killed snakes underwent full postmortem examination. The researchers were looking for seven different pathogens—fungi, parasites, bacteria—trying to understand which ones mattered most and which snakes were most at risk. What emerged from the data was striking: nearly four in five snakes carried at least one pathogen. Nearly half carried more than one. Some carried four simultaneously.
The most common infections were almost mundane in their prevalence. Salmonella showed up in sixty-three percent of snakes tested. A tick-borne parasite called Hepatozoon infected more than half. But the story shifted when researchers looked at which snakes were getting sick with which diseases. Rattlesnakes stood out. Twelve of thirty-four rattlesnakes tested positive for Ophidiomyces ophidiicola, the fungus that causes snake fungal disease—a rate of thirty-five percent. By contrast, only one in fifty-five eastern ribbon snakes and three in thirty-six ring-necked snakes carried the same infection. Rattlesnakes were also the primary hosts for Raillietiella orientalis, a parasitic lungworm that infects through prey like frogs and lizards. Fourteen of the thirty-four rattlesnakes sampled carried it. Other snake species either had it rarely or not at all.
The researchers hypothesized that rattlesnakes' vulnerability stemmed partly from their ecological position—they eat the kinds of prey that transmit these parasites—but also from something darker. Rattlesnakes have endured centuries of human persecution, killed on sight in many regions, their populations fragmented and stressed. A weakened population, the thinking goes, is a susceptible one. When an animal's immune system is already compromised by one infection, it becomes far more vulnerable to others. The data bore this out: snakes with visible skin lesions were infected with fungal disease at rates above thirty percent, compared to just two percent of snakes with healthy skin.
Geography mattered too. The fungal disease was far more common in snakes sampled in Georgia. The lungworm appeared only in Florida. These patterns suggest that different regions harbor different disease pressures, and that moving snakes from one place to another—something wildlife managers do regularly for conservation purposes—could inadvertently spread pathogens into naive populations. The researchers noted that invasive species like Burmese pythons and brown anoles are competent hosts for the lungworm, meaning they could become vectors for spreading infection to native snakes if populations ever came into contact.
The study has limitations. Sampling was concentrated in a few counties, so the results may not reflect the broader southeastern landscape. Detecting the lungworm in live snakes requires analyzing feces, and snakes can go weeks between meals, making consistent sampling difficult. The true prevalence of this parasite is almost certainly higher than the data shows. Still, the findings matter for anyone trying to conserve native snakes or manage invasive ones. Before moving snakes—whether for reintroduction, research, or any other reason—screening for these pathogens becomes essential. A single translocated snake carrying multiple infections could seed disease in a population that has never encountered it before, with consequences that ripple outward in ways we're only beginning to understand.
Citações Notáveis
When an animal has become sick from an infection their immune system is compromised which increases the risk of further disease exacerbation from other infectious agents— Dr. Corinna Mishin, University of Georgia
Certain species with poorer general population health, specifically rattlesnakes with historic and current increased risks of human persecution, are likely more susceptible to infection— Dr. Corinna Mishin
A Conversa do Hearth Outra perspectiva sobre a história
Why do rattlesnakes seem to be hit harder than other snakes in the region?
It's partly their diet. Rattlesnakes eat frogs and lizards, which carry the lungworm. But there's also the human element—they've been killed on sight for centuries. A stressed, fragmented population has a weaker immune system.
So disease is almost a symptom of a larger problem?
Exactly. The fungal disease and parasites aren't new. What's new is that rattlesnakes are in no condition to fight them off.
The study found that most snakes carry multiple infections at once. Does that change how we should think about snake health?
It changes everything. One infection weakens the immune system, making the snake vulnerable to the next one. It's not just about individual pathogens—it's about the cascade.
What happens if someone moves a sick snake to a new location?
You could introduce a pathogen to a population that's never seen it before. A native snake population with no immunity would be devastated.
Is there a way to prevent that?
Screening before translocation. Know what pathogens the snake is carrying before you move it. It's basic disease control, but it requires resources and planning that don't always happen.
What worries you most about these findings?
That we're only seeing part of the picture. The lungworm detection is probably underestimated. And we still don't fully understand how these infections interact in wild populations over time.