April 26, 2011
Q&A: Animal Testing of Shellfish Toxins
Q: What is the purpose of testing shellfish for toxins?
A: Foods of animal origin are prone to contamination by bacteria and other hazardous substances. This is particularly true in the case of oysters, scallops and other shellfish, which readily accumulate toxic compounds when feeding that can severely affect the health of consumers.
Q: Are there different types of shellfish toxins?
A: There are many different shellfish toxins; however, those of particular human health concern are the diarrhetic (causing diarrhea), amnesiac (causing short-term memory loss), and paralytic (causing paralysis and even death).
Q: How is the testing of shellfish regulated in different parts of the world?
A: In the European Union, conditions for the marketing of live shellfish, including requirements to test for the presence of toxins and other biological contaminants, are specified in a number of separate directives and regulations. These require independent member state laboratories to regularly test shellfish beds for the presence of toxins, and establish upper limits on contamination for sale of live shellfish. In New Zealand, The New Zealand Biotoxin Monitoring Programme of the New Zealand Food Safety Authority (NZFSA) combines regular shellfish testing with setting upper limits of contamination and lays down the regulations for testing requirements. In the U.S., the primary agency responsible for seafood safety and marine biotoxins is the Food and Drug Administration (FDA). In the area of domestic food safety, cooperative programmes between the FDA and individual states exist. The National Shellfish Sanitation Programme provides guidelines for these cooperative agreements.
Q: What tests are carried out to detect shellfish toxins?
A: The mouse/rat bioassay has historically been considered the “gold standard” for detecting shellfish toxins. The method involves injecting shellfish extract into the abdomen of mice/rats and then timing how long it takes for them to die. The death of two-thirds or more of the animals within 24 hours is believed to indicate the presence of a toxin. Animals in these tests often exhibit signs of severe pain, distress and trauma—without pain relief—before they die. Regulations in New Zealand and Germany also permit the use of non-animal methods, once they have been specifically validated for a particular class of toxin. However, in the event of discrepancies between the results obtained by the use of different methods, most regulations state that results of the mouse bioassay should be treated as definitive.
Q: Are the current animal tests accurate in detecting shellfish contamination?
A: Just as animal use in other areas of toxicology suffers from serious limitations, so too does the mouse/rat bioassay. Although this test is said to be sensitive to a broad range of toxins, there are a number of toxin types that it consistently fails to detect, which raises doubt as to whether food safety is truly assured. In addition, results of replicate mouse tests have been found to be highly variable between laboratories. The limitations of the mouse/rat bioassay include an inability to reveal the exact toxins in the extract; the assay is affected by the animals’ gender, age, and strain; it is time-consuming; and animals often die for reasons other than toxin poisoning. In fact, the mouse bioassay has been described more than once in the scientific literature as “impossible to validate.”
Since 2009, the European Food Safety Authority (EFSA) has produced Scientific Opinions [PDF] on the suitability of the mouse/rat bioassay for the various known shellfish toxins. Experts have concluded that the tests “have shortcomings” and are “inappropriate” for assessing the majority of toxins.
Q: What are some practical alternatives to animal testing?
A: Today, as analytical chemistry approaches have become the default throughout Europe and New Zealand for detecting amnesic shellfish toxins (although regulations allow use of “any other recognised method,” which could include animal tests). In the case of paralytic shellfish toxins, similar approaches, including the so-called “Lawrence method,” have been endorsed as scientifically valid and been taken up under EU regulations. (However, the use of the mouse bioassay is still required if the non-animal results are challenged.) With regard to diarrhetic shellfish toxins, the mouse bioassay continues to be the default method in the EU and elsewhere. Yet in the opinion [PDF] of the German Federal Institute for Risk Assessment, “the physico-chemical analytical procedures have proved to be superior to the Mouse-Bioassay and to represent the more appropriate methods for safeguarding consumer protection.”
Q: What is HSI doing to spare animals from use in shellfish toxin testing?
A: Often, there can be an unnecessary delay of many months or even years from the time an alternative test method is developed to when it can actually be used in the lab to start replacing animals. HSI scientists and policy experts are working to reduce this time delay so that animal use in shellfish toxin testing can be reduced and replaced more quickly. HSI is lobbying hard in the E to guarantee the current regulations are revised to ensure non-animal techniques are employed for shellfish toxicity testing.