USGS warns of gnathostomiasis risk in raw or undercooked Asian swamp eels
In a new study, published ahead of print in the journal, Emerging Infectious Diseases Wednesday, the U.S. Geological Survey (USGS) has found the parasitic worm, Gnathostoma species in Asian swamp eels collected between 2010 and 2012 from ethnic food markets and in Florida waters where the eel species is invasive, prompting a warning to US consumers of the risk.
Credit: U.S. Geological Survey
Department of the Interior/USGS
U.S. Geological Survey/photo by Leo Nico
“Because live Asian swamp eels are commonly imported to the U.S., a person’s dietary history and not just travel history should be considered when diagnosing gnathostomiasis,” said Rebecca Cole, USGS scientist and lead author of the study.
Asian swamp eels are not native to the United States or Canada, but at least 5 separate introduced populations of Asian swamp eels (Monopterus spp.) have been established in open waters in the continental United States-Florida, Georgia and New Jersey.
During the USGS study, scientists found gnathostome worms in eels collected from markets in Manhattan, N.Y., Atlanta, Ga., and Orlando, Fla., and in wild eels caught in peninsular Florida. All of the infected eels obtained from markets were imported from Bangladesh.
In the study, USGS scientists examined 47 eels from markets and 67 wild-caught specimens. Nematodes were identified by morphologic features and ribosomal intergenic transcribed spacer–2 gene sequencing. Thirteen (27.7%) M. cuchia eels from markets were infected with 36 live G. spinigerum AL3: 21 (58.3%) in liver; 7 (19.4%) in muscle; 5 (13.8%) in gastrointestinal tract, and 3 (8.3%) in kidneys. Three (4.5%) wild-caught M. albus eels were infected with 5 G. turgidum AL3 in muscle, and 1 G. lamothei AL3 was found in a kidney (both North American spp.).
“Consumers should be aware of the risk of contracting gnathostomiasis from Asian swamp eels if they are eating raw or undercooked eels,” Cole said.
Gnathostoma spinigerum is a nematode parasite considered endemic in Thailand and also found in most Southeast Asian countries. It has also been found in the United States, Japan, Mexico and Australia, though it is rare to find it outside of the Asian continent.
The parasite infects vertebrate mammals like dogs, cats and pigs which are the definitive or final hosts for the parasite.
People typically become infected by ingesting raw or undercooked fish or poultry.
The symptoms of human gnathostomiasis are related to the migration of the immature larval stage (L3) in the subcutaneous tissue causing painful swellings.
More serious manifestations are typically the result of larval migration to the central nervous system (CNS) causing eosinophilic meningitis.
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