Food allergen transfer up the food chain: from animal feeds to consumer

There is already evidence that simply avoiding triggers may not be enough to prevent allergic reaction in sensitized individuals; allergic reactions are still possible when eating meat from animals raised on animal feeds containing the allergens¹. Does this mean that the potential allergens end up in meat for the final consumer? In some cases – yes, it appears so, as shown by Fӕste et al. (2015) in their paper investigating parasitic fish larva proteins transfer to final product².

Searching for studies that showed survival of food allergens and pathogens such as prions remaining viable following food preparation and digestion, the research team found that zebrafish are often used as models in this work. Using these as the model, the research team investigated whether anisakid proteins could transfer from feed into fish meat destined for the table.

They examined transfer of proteins from Anisakis simplex, a common parasitic nematode found in fish that causes allergic reaction in some human consumers. In addition to direct infestation problems known as anisakiasis, which causes immunoglobulin E release in response to parasitic larvae burrowing within the gastrointestinal walls, ingestion of A. simplex proteins can provoke an allergic reaction in sensitized individuals. Furthermore, fishmeal is a common feed ingredient for both commercial farmed fish and poultry feeds meaning that A. simplex proteins could be found in that feed.

The researchers took young adult zebrafish and fed them commercial fish food spiked with freeze-dried and heat-treated A. simplex larvae. A control group consumed larvae-free feed. At days 3, 7 and 14, the researchers killed the fish, removed the visceral organs then prepared extracts from the remaining skeletal tissues. After trypsin digestion, they examined the peptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using an LTQ-Orbitrap XL mass spectrometer (Thermo Scientific). They analyzed the feed and tissue preparations for anisakid hemoglobin proteins that are unique to the species and show know similarity to fish proteins.

In addition to proteomic analysis, Fӕste et al. confirmed A. simplex proteins in both fish food and flesh by immunoassay – enzyme linked immunosorbent assay (ELISA) and gel electrophoresis followed by immunostaining, each using specific antibodies raised in patients showing allergy to A. simplex ingestion. The researchers also examined feed and fish tissues for parasite presence with real-time polymerase chain reaction (RT-PCR).

Following these tests, the researchers found the parasitic nematode proteins only in the food preparations spiked artificially with the larvae. Furthermore, when they analyzed the zebrafish tissues, the assays showed anisakid proteins present only after 14 days of feeding, with none found in the control groups. The team also found that ELISA was not sensitive enough to detect the low levels of larval protein in the zebrafish even at day 14.

Although spiking levels in feed was far higher than seen in commercial food production practice, Fӕste et al. feel that their initial studies show “proof of principle” that low levels of allergenic anisakid peptides could transfer from animal feed into meat destined for the consumer. They suggest that further studies involving longer term feeding in a range of food species are needed to further elucidate the relevance of these study results to the consumer and food producers. They also note that these trials should also be performed for feed ingredient alternatives such as legumes, since they also contain potential allergens.

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References

1. Armentia, A.et al. (2006) “Anisakis simplex allergy after eating chicken meat“, Journal of Investigative Allergology and Clinincal Immunology (pp.258–63)

2. Fæste, C.K. et al. (2015) “Fish feed as source of potentially allergenic peptides from the fish parasite Anisakis simplex (s.l.)“, Animal Feed Science and Technology (pp.52–61)