Antigenicity of Anisakis simplex s.s. L3 in parasitized fish after heating conditions used in the canning processing

BACKGROUND

Some technological and food processing treatments applied to parasitized fish kill the Anisakis larvae and prevent infection and sensitization of consumers. However, residual allergenic activity of parasite allergens has been shown. The aim here was to study the effect of different heat treatments used in the fish canning processing industry on the antigen recognition of Anisakis L3. Bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) were experimentally infected with live L3 Anisakis. After 48 h at 5 ± 1 °C, brine was added to the muscle, which was then canned raw (live larvae) or heated (90 °C, 30 min) (dead larvae) and treated at 113 °C for 60 min or at 115 °C for 90 min. Anisakis antigens and Ani s 4 were detected with anti-crude extract and anti-Ani s 4 antisera respectively.

RESULTS

Ani s 4 decreased in all lots, but the muscle retained part of the allergenicity irrespective of the canning method, as observed by immunohistochemistry. Dot blot analysis showed a high loss of Ani s 4 recognition after canning, but residual antigenicity was present.

CONCLUSION

The results indicate that heat treatment for sterilization under the conditions studied produces a decrease in Ani s 4 and suggest a potential exposure risk for Anisakis-sensitized patients.

Viability and antigenicity of anisakis simplex after conventional and microwave heating at fixed temperatures

Inactivation of parasites in food by microwave treatment may vary due to differences in the characteristics of microwave ovens and food properties. Microwave treatment in standard domestic ovens results in hot and cold spots, and the microwaves do not penetrate all areas of the samples depending on the thickness, which makes it difficult to compare microwave with conventional heat treatments. The viability of Anisakis simplex (isolated larvae and infected fish muscle) heated in a microwave oven with precise temperature control was compared with that of larvae heated in a water bath to investigate any additional effect of the microwaves. At a given temperature, less time was required to kill the larvae by microwaves than by heated water. Microwave treatment killed A. simplex larvae faster than did conventional cooking when the microwaves fully penetrated the samples and resulted in fewer changes in the fish muscle. However, the heat-stable allergen Ani s 4 was detected by immunohistochemistry in the fish muscle after both heat treatments, even at 70°C, suggesting that Ani s 4 allergens were released from the larvae into the surrounding tissue and that the tissues retained their allergenicity even after the larvae were killed by both heat treatments. Thus, microwave cooking will not render fish safe for individuals already sensitized to A. simplex heat-resistant allergens.

Antigenicity and viability of Anisakis larvae infesting hake heated at different time-temperature conditions

Heat treatments (40 to 94 degrees Celsius, 30 s to 60 min) were applied to different batches of Anisakis simplex L3 larvae isolated from hake ovaries and viscera to study the effect of heat on the viability of the larvae measured as mobility, emission of fluorescence under UV light, and changes in color after staining with specific dyes, and on A. simplex antigenic proteins. The aim was to determine the lowest time-temperature conditions needed to kill the larvae to avoid anisakiasis in consumers, and to evaluate whether high temperature modifies the antigenicity of A. simplex extracts. Heating at 60 degrees Celsius for 10 min (recommended by some authors) was considered unsafe, as differences in viability between batches were found, with some larvae presenting spontaneous movements in one batch. At higher temperatures (> or = 70 degrees Celsius for > or = 1 min), no movement of the larvae was observed. Antigenic protein Ani s 4 and A. simplex crude antigens were detected in the larvae heated at 94 + or - 1 degrees Celsius for 3 min. This indicates that allergic symptoms could be provoked in previously sensitized consumers, even if the larvae were killed by heat treatment.

Anisakis Simplex Antigens in Fresh and Frozen-thawed Muscle of Anchovies in Vinegar

Marinated fish treatment using low pH to enlarge the storage life of fish as in anchovies in vinegar, does not kill Anisakis simplex larvae infesting fish muscle. To kill the larvae it is compulsory in many countries to freeze fish intended to be marinated raw, which prevents the consumer to be infested with the live larvae. However, it is not known if A. simplex antigens are released to the media after freezing and vinegar processing, which may cause allergic reaction to A. simplex sensitized consumers. Anchovy fillets were artificially infested with A. simplex L3, treated with a vinegar solution and chilled stored for 10 days. Infested frozen-thawed fillets were treated and stored in the same conditions. Viability of the larvae, SEM, immunoblotting and immunohistochemistry were performed on the treated fillets before and after pepsin treatment. Viability of the larvae was detected only in the chilled fillets; however, A. simplex antigens were detected in the chilled and in the frozen-thawed fillets even after pepsin treatment. This suggests that the consumption of anchovies in vinegar may be a potential hazard when ingested by sensitized consumers, even if freezing kills the larvae.

Allergenic properties and cuticle microstructure of Anisakis simplex L3 after freezing and pepsin digestion

This article examines the viability of and the alterations to the larval cuticle and the pattern of the antigens released when live or frozen Anisakis simplex larvae were treated with acid and pepsin. The results showed that freezing did not greatly alter the larva body. If ruptures were observed, the antigen release to the incubation media was not enhanced, and most of the antigenic content was retained inside the bodies of the larvae. The immunoblotting assay demonstrated that most of the antigens released, including the allergen Ani s 4, were resistant to pepsin. Freezing killed the larvae, but their survival was not compromised by acid treatment or pepsin digestion when kept chilled. All these findings support recommendations about freezing fish for consumption raw or undercooked to prevent human infection by A. simplex larvae. However, our data show that the antigenicity of the larvae is preserved after freezing and may explain why some sensitized patients develop symptoms after ingestion of infested frozen fish.

Scanning electron microscopy of Anisakis larvae following different treatments

Ingestion of fish parasitized with Anisakis larvae can produce infestation and/or allergy in consumers. Technological and food processing treatments have been applied to parasitized fish in order to kill the larvae and avoid the infestation; however, their influence on allergenicity has not been studied. Four lots of hake (Merluccius merluccius) steaks artificially parasitized with Anisakis larvae were subjected to two storage chilling (5 degrees C +/- 1 degrees C) and freezing (-20 degrees C +/- 1 degrees C) treatments and two food processing treatments of heat (final temperature 86.3 degrees C) and microwave (final temperature 66.9 degrees C) and studied by scanning electron microscopy, environmental scanning electron microscopy (ESEM) (acid [pH = 2] and water preparations), and emission of fluorescence. Anisakis larvae were resistant to acid conditions, remaining alive after treatment. Larvae in the heat- and microwave-treated lots presented coagulated and disrupted zones in the cuticle with release of fluids. The cylindrical shape changed to a dehydrated appearance mainly observed by ESEM. Fluorescence was only noticeable in the frozen larvae. Larvae without apparent changes, together with dehydrated ones, were observed by ESEM in the frozen lot; nevertheless, no disruptions in the cuticle were perceptible. Further studies are needed in order to elucidate if the changes observed in the cuticle reduce the resistance of the parasites to the action of gastric enzymes in the gastrointestinal tract and to determine the release of allergens to the flesh by the live larvae during chilled storage of the fish.

[Results of preoperative autotransfusion with ferrous ascorbate prophylaxis in orthopedic surgery patients]

PURPOSE

Restrictive erythropoiesis caused by iron deficiency may hinder pre-deposit autotransfusion in surgical procedures. In order to evaluate the response to prophylactic ferrous ascorbate, a prospective study was conducted on patients subjected to orthopaedic surgery and autotransfusion.

PATIENTS AND METHODS

Sixty-eight patients were included in the study: hip prostheses 67%, knee prostheses 25%, other procedures 7.4%. Their mean age was 61.3 +/- 10.2 years, and there were 42% male and 57% female. A mean of 2.8 +/- 0.6 units (450 mL) of blood were drawn to each patient in a month. Starting one week before their first blood donation and up to 2 months after surgery, each patient received 99 mg elementary iron per days as oral ferrous ascorbate. Blood cell counts were done at the beginning of the programme and after the first, second, third and fourth blood withdrawal, as well as one month after finishing the treatment. A survey of iron profile including serum iron, total iron binding capacity, transferrin saturation, serum ferritin and free erythrocyte protoporphyrin was carried out at onset and end of the programme in each patient. All data were analysed with the SPSS-PC 4.0 statistical programme.

RESULTS

Haemoglobin rates decreased in every control, returning to values close to the initial ones by the end of the programme (mean figures are as follows: 14.63; 13.17; 12.70; 11.88; 14.11 g/dL); and similar changes were seen with respect to the other parameters of blood. The initial and final values for ferritin were 157.32 and 91.06 ng/mL, respectively, and no significant changes were appreciated in the other data from the iron profile, regardless of the number of blood units collected in a given case. Minor intolerance to ferrous ascorbate appeared in 11% of the patients. No significant differences with control patients were seen regarding hospitalization (16.54 vs 19.82 days) or postoperative fever (14.1% vs 17.11%).

CONCLUSIONS

As opposed to others, we feel that iron treatment should be maintained up to 2 months after surgery since better results are thus attained. Recombinant erythropoietin is more expensive a method. Ferrous ascorbate is better tolerated than ferrous sulphate plus additives.