Eustrongylides sp.

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 flamingos.

How does infection occur?

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.

How is an infection diagnosed?

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.

What foods may contain eustrongylides?

Eustrongylides may be found in fish from fresh, brackish or salt water.

How common is the infection?

The disease is extremely rare; there have been only five cases reported in the U.S.

What complications may occur?

Septicemia, which is due to the perforated digestive tract.

Who is susceptible to infection?

Those consuming whole minnows are at greatest risk. One case was reported from the consumption of sashimi.

How is food analyzed for eustrongylides?

These large worms may be seen without magnification in the flesh of fish and are normally very active after death of the fish.