Larval Eustrongylides sp. are large, bright red roundworms
(nemotodes), 25-150 mm long, 2 mm in diameter. They occur in
freshwater fish, brackish water fish and in marine fish. The larvae
normally mature in wading birds such as herons, egrets, and
If the larvae are consumed in undercooked or raw fish, they can
attach to the wall of the digestive tract. In the five cases for
which clinical symptoms have been reported, the penetration into
the gut wall was accompanied by severe pain. The nematodes can
perforate the gut wall and probably other organs. Removal of the
nematodes by surgical resection or fiber optic devices with forceps
is possible if the nematodes penetrate accessible areas of the gut.
One live larva can cause an infection.
In three of the five reported cases, the worms were diagnosed by
surgical resection of the intestine. In one case, there was no
clinical data and in one other, the patient was treated medically
and recovered in 4 days.
Eustrongylides may be found in fish from fresh, brackish or salt
The disease is extremely rare; there have been only five cases
reported in the U.S.
Septicemia, which is due to the perforated digestive tract.
Those consuming whole minnows are at greatest risk. One case was
reported from the consumption of sashimi.
These large worms may be seen without magnification in the flesh
of fish and are normally very active after death of the fish.
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