Researchers tracking Burmese pythons in the Florida Everglades noticed something unexpected over several years: many of the snakes they had fitted with transmitters stopped moving and died. The deaths occurred in clusters, and the animals showed no signs of injury, predation, or struggle. With no external cause identified, the research team, led by Dr. Michael Kirkland, brought the bodies into a laboratory for examination.

The dissection revealed that the pythons had died from a lung infection caused by a parasite native to Southeast Asia, a lungworm called Raillietina orientalis. The parasite had spread through the snakes’ respiratory systems, eventually preventing them from breathing. The pythons, which originate from the same region as the parasite, had carried it with them when they were introduced to Florida. Over time, the two species had coexisted, with the parasite typically not proving fatal to its host.

In Florida, however, the parasite has moved beyond pythons into the broader ecosystem. Researchers have found the lungworm in at least 18 species of native snakes, including rat snakes, water snakes, and rattlesnakes. Native snakes have no immunity to the parasite and often die from infections that pythons can tolerate. The parasite spreads through the food chain: eggs are shed in python waste, consumed by flies, passed to frogs, and then to snakes that eat the frogs. This cycle now operates independently of pythons, meaning the parasite would persist even if all pythons were removed from the Everglades.

Separately, genetic studies of Florida pythons have found evidence of interbreeding with Indian pythons, a closely related species. Some hybrids may carry traits that allow them to tolerate drier conditions, potentially enabling them to spread beyond the wetlands that have largely contained the python population.

Conservation efforts for the eastern indigo snake, North America’s longest native snake, have seen recent success. The species, which feeds on other snakes and is immune to pit viper venom, had largely disappeared from northern Florida. A captive breeding and release program began in 2017. In 2023, researchers documented the first wild-born indigo snakes in northern Florida in more than five decades. By 2025, over 500 indigo snakes had been released across Florida and Alabama.

The recovery of the indigo comes with an unresolved risk. The lungworm spreading through native snake populations could reach the indigo before its population becomes large enough to sustain itself. Indigos have no evolutionary exposure to the Southeast Asian parasite. It is unclear whether they would be vulnerable to it, and whether the reintroduced population could absorb such a loss.

The broader situation in the Everglades remains open-ended. Pythons are established across tens of thousands of acres and are not expected to be eradicated. The lungworm has moved permanently into native wildlife, and the long-term effects on the ecosystem are not yet known. The region has changed in ways that are unlikely to be reversed, and the eventual outcome, whether it involves a new ecological balance or continued decline, has yet to be determined.