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U.S. Department of Health and Human Services

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BBB - Eustrongylides sp.

Bad Bug Book:
Foodborne Pathogenic Microorganisms and Natural Toxins Handbook
Eustrongylides sp.

A new version of the Bad Bug Book was released in 2012, below is a previous version.


1. Name of the Organism:

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.

2. Nature of Acute Disease:

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.

3. Nature of Disease:

One live larva can cause an infection.

4. Diagnosis of Human Illness:

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.

5. Associated Foods:

Fish from fresh, brackish or salt water.

6. Relative Frequency of Disease:

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

7. Course of Disease and Complications:

Septicemia, which is due to the perforated digestive tract.

8. Target Populations:

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

9. Food Analysis:

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

10. Selected Outbreaks:

There have been no major outbreaks.

For more information on recent outbreaks see the Morbidity and Mortality Weekly Reports from CDC.

11. Education and Background Resources:

Literature references can be found at the links below.

Loci index for genome Nematoda (Roundworm family)

Available from the GenBank Taxonomy database, which contains the names of all organisms that are represented in the genetic databases with at least one nucleotide or protein sequence.

12. Molecular Structural Data:

None currently available.

13. FDA Regulations or Activity:

FDA has no specific regulation or activity regarding these worms; however, as pathogens, no live Eustrongylides sp. should be present in fish consumed raw or semiraw.