In Southeast Asia, swamp eels are a common source of human gnathostomiasis, a foodborne zoonosis caused by parasitic Gnathostoma larvae.
If the infected eels are eaten undercooked or raw, the parasite can cause mild to serious consequences in humans, including blindness, paralysis or even death. So researchers at the U.S. Geological Survey wanted to find out whether the live eels imported into the U.S. and sold in ethnic food markets or released into the wild are also infected.
“The reason was to examine the imported live eels both for risk to consumers but also to North American fish and wildlife,” says Rebecca Cole, lead author of the study published in the April 2014 issue of the public health journal, Emerging Infectious Diseases. The team is concerned that eels released into the wild could be introducing the parasites to native species.
They examined 47 eels from markets and found that 13 were infected in the liver, muscle, gastrointestinal tract and kidneys. Three of the 67 wild-caught eels were infected with the parasite.
Most organs are disposed of when an eel is butchered, but the risk of human infection persists if the muscle is infected. In addition, Cole says, the offal needs to be disposed of so that fish, wildlife or domestic carnivores can’t consume it and become infected themselves.
Human gnathostomiasis is rare in the U.S., so much so that “if it is diagnosed in a human, clinicians will usually write it up and submit it to a journal,” Cole says.
But “because human gnathostomiasis has been documented with increased frequency in countries where the parasite is not endemic, it is currently regarded as an emerging imported disease,” the study states.
Cole adds that it’s important for consumers to be aware that eating raw or undercooked eels – such as in sushi or sashimi — can carry a risk of infection with gnathostomes.
When diagnosing this infection, clinicians should consider their patients’ dietary history, not just travel history.
“Individuals do not have to travel to Southeast Asia to become infected with gnathostomes,” Cole says.© Food Safety News