Clinical Testing Guidance for Illnesses Caused by Saltwater Harmful Algal Blooms

Key points

  • Testing may help you diagnose foodborne illnesses caused by harmful algal bloom toxins.
  • Specialized laboratories may be able to test human samples for some types of toxins.
  • If the seafood your patient ate is still available, contact FDA about testing it for toxins.
  • Report cases to your health department.
Person on a sandy beach holding out three shellfish in their hand. They have two plastic bags full of shellfish on the sand.

Testing

FDA can test seafood for toxins‎

If the seafood your patient ate is still available, contact the U.S. Food and Drug Administration (FDA) about testing it for toxins. This can help you identify the toxin causing your patient's illness and improve tracking and prevention of illnesses.
How to Report Seafood-Related Toxin Illnesses | FDA

Laboratory tests performed by specialized labs may help you diagnose the following foodborne illnesses caused by harmful algal blooms.

Neurotoxic shellfish poisoning

Consider testing for brevetoxin if your patient:

Tests

Laboratories may be able to measure brevetoxin metabolites, but not brevetoxin, in human urine using confirmatory testing by liquid chromatography-mass spectrometry (LC-MS).

Enzyme-linked immunosorbent assay (ELISA) has been used to detect brevetoxin in human serum following ingestion of contaminated shellfish.

Bioassays, ELISA, and high-performance LC-MS/mass chromatography (HPLC-MS/MC) techniques have been used to detect brevetoxin in food samples.

Ciguatera poisoning

Consider testing for ciguatoxins if your patient:

Tests

Routine laboratory test results for people with ciguatera poisoning might reflect the effects of fluid loss, such as elevated BUN and creatinine. Muscle tissue breakdown can result in mild elevation of creatinine phosphokinase (CPK) and lactate dehydrogenase (LDH).

A rapid qualitative immunoassay is available to detect ciguatoxin in fish samples.

Amnesic shellfish poisoning

Consider testing for domoic acid if your patient:

Tests

Laboratories can test human urine for domoic acid.

Laboratories can test food samples for domoic acid using bioassays, ELISA, and chromatographic techniques.

Diarrhetic shellfish poisoning

Consider testing for okadaic acid, dinophysistoxins, or pectenotoxins if your patient:

Tests

No test is available for human samples.

Biologic and HPLC tests can measure okadaic acid, dinophysistoxins, and pectenotoxins in shellfish samples.

Paralytic shellfish poisoning

Consider testing for saxitoxins or tetrodotoxin if your patient:

Tests

For tetrodotoxin, laboratories can use urine or blood clinical specimens with HPLC. Urine HPLC can be used for testing up to 5 days after exposure.

For saxitoxins, laboratories can analyze urine specimens with LC-MS, or use ELISA in whole blood sample.

Laboratories can confirm the presence of toxins in food samples using bioassay, ELISA, cell receptor assay, HPLC-FL, or LC-MS.

Azaspiracid shellfish poisoning

Consider testing for azaspiracid toxins if your patient:

Tests

Laboratories can use biologic and HPLC tests to confirm the presence of azaspiracid toxins in contaminated shellfish.

Reporting cases

Contact your local or state health department to report a harmful algal bloom-associated illness.

ICD-10-CM codes

You can use the following codes to record your diagnosis of harmful algal bloom-associated illnesses:

  • T65.82 Toxic effect harmful algae and algae toxins
  • Z77.121 Contact with and (suspected) exposure to harmful algae and algae toxins

Resources

Facts about Marine Harmful Algal Blooms for Poison Center Professionals
Learn more about exposures, symptoms, laboratory testing, and illness management.
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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID); National Center for Environmental Health