Sensitization to Anisakis simplex s.l. in a healthy population

Basophil Activation Test in the Diagnosis of Anisakis Allergy: An Observational Study from an Area of High Seafood Consumption in Italy

The rising popularity of undercooked or raw seafood containing larvae of the Anisakis parasite has led to issues of public health concern due to allergic manifestations. We conducted an observational study on the use of an innovative Anisakis allergy diagnostic algorithm in a convenience sample of 53 allergic outpatients recruited in Western Sicily, between April 2021 and March 2022. We included individuals with an anamnesis suggestive of IgE sensitization to Anisakis reporting clinical manifestation in the last month due to allergic reactions after eating fresh fish, or in subjects at high exposure risk with sea products while abstaining from fish ingestion, excluding those with documented fish sensitization. Outpatients were tested via Skin Prick Test, IgE-specific dosage and Basophil Activation Test (BAT). Twenty-six outpatients were diagnosed with Anisakis, while 27 with Chronic Urticaria (CU). We found a seven-fold excess risk for Anisakis (p4) positivity in the Anisakis allergic outpatients, as compared to the CU ones. BAT showed the best diagnostic accuracy (92.45%) and specificity (100%), while specific IgE to Ascaris (p1) documented the best sensitivity (92.31%) but a very low specificity (37.04%). In conclusion, our findings may represent a potentially useful contribution to the future development of updated clinical guidelines.

World-wide prevalence of Anisakis larvae in fish and its relationship to human allergic anisakiasis: a systematic review

The infective stage of Anisakidae nematodes responsible for allergic reactions in humans is found in a variety of edible fish and cephalopods. The identification of geographical regions that are high risk for infected seafood may help prevent allergic reactions in humans. Despite an abundance of published literature which has identified anisakid larvae in an array of edible seafood as well as scattered reports of human allergic anisakiasis, the relationship between the two has not been fully explored. Therefore, a systematic spatio-temporal study was conducted to determine the prevalence of Anisakis spp. in fish from January 2000 to August 2020 firstly to explore the relationship between fish infection and cases of allergic anisakiasis and secondly to use fish infection data to map potential allergic anisakiasis 'hot spots'. A systematic literature search for original English text articles was conducted through search engines, Web of Science, Scopus, PubMed, Science Direct and Google Scholar. Out of 3228 articles which describe anisakid infection in fish, 264 were used for data extraction. Of 904 articles describing allergic anisakiasis, 37 were used for data extraction. A qualitative summary of the extracted data was performed using equal interval method (ArcMap software) in order to compare the global distribution of Anisakis-infected fish. Of the 152-identified fish hosts, five families were most commonly infected with Anisakis spp. These included Lophiidae (86.9%), Trichiuridae (77.05%), Zeidae (70.9%), Merlucciidae (67.8%) and Gadidae (56.8%). The hot spot areas for allergic anisakiasis were North and northeast of Atlantic Ocean, southwest of USA, west of Mexico, south of Chile, east of Argentina, Norway, UK and west of Iceland (confidence 99%). The highest rate of allergic anisakiasis was in Portugal and Norway with the prevalence rate of 18.45-22.50%. Allergologists should consider allergic anisakiasis as a public health issue particularly in high-risk countries where high prevalences in fish have been demonstrated.

Anisakiasis and Anisakis: An underdiagnosed emerging disease and its main etiological agents

Anisakiasis or anisakiosis is a human parasitic infection caused by the third-stage larvae (L3) of nematodes of the genus Anisakis, although the term is also used in medical literature for the much less frequent (<3% of cases) infection by L3 of other genera of anisakids, particularly Pseudoterranova. These parasites have a marine lifecycle. Humans are infected by the L3 through ingesting of fish and squid, the intermediate/paratenic hosts. The live larvae generally penetrate the wall of the stomach or intestine causing, among other symptoms, intense pain or allergic symptoms. These are emerging, cosmopolite illnesses. Diagnosis and treatment is usually by endoscopy and extraction and identification of the larvae. Allergic forms are usually diagnosed by prick-test and/or allergen-specific IgE detection and treated with a suitable anti-allergy treatment. The patient is also warned against further consumption of marine fish or squid, as these may be infected with Anisakis. The most common method of prevention is thermal treatment of the entire fish or squid prior to consumption (>60 °C, >1 min or - 20 °C, >24 h). Useful measures for the control of anisakiasis would be to establish a national register of cases, to initiate educational campaigns for the general public and consciousness-raising and training campaigns for health professionals. These would be complemented by control measures for the relevant sectors of the economy: fish operators, fish farming, fishermen, fishmongers, fish industry and catering facilities. Possible genetic predisposition for allergy to Anisakis and the possible relationship between anisakiasis and cancer would also require further investigation.

Analysis of Ani s 7 and Ani s 1 allergens as biomarkers of sensitization and allergy severity in human anisakiasis

The high frequency of infection by Anisakis simplex (A. simplex) has led to an increase in IgE sensitization, turning allergy to this parasite a relevant contemporary health problem. Improving the lack of conventional diagnosis test specificity is crucial to better understand these clinical scenarios. Specific IgE (sIgE) to A. simplex extract by ImmunoCAP (Anisakis-sIgE) was determined in sera from 403 blood donors (BD) from Cantabria (North of Spain) of which 51 subjects resulted sensitized. Among these latter, 47 were asymptomatic (sABD). The values of total IgE, prick-test, Anisakis-sIgE, and sIgE to Ani s 1 (anti-rAni s 1) and Ani s 7 (anti-rAni s 7) were compared between 46 sABD and 49 A. simplex allergic patients. The IgE seroprevalence by ImmunoCAP among BD was 12.65%. Allergic patients and sABD showed significant differences in all serum biomarkers evaluated. The area under the curve was assessed for Anisakis-sIgE (0.892), sIgE-rAni s 1 (0.672) and sIgE-rAni s 7 (0.668). After a severe reaction, significantly higher levels of Anisakis-sIgE and sIgE anti-rAni s 1 were detected. Determinations of sIgE by ImmunoCAP, Ani s 1 and Ani s 7 presented different sensitization patterns between allergic and asymptomatic individuals. The Ani s 1 allergen arises as a possible biomarker to detect patients at risk of suffering severe allergic reactions.

Quantitative allergenicity risk assessment of food products containing yellow mealworm (Tenebrio molitor)

Insect-based foods are starting to enter the EU market, raising concerns about their safety. Allergic consumers might be exposed to even a greater risk, since insects have proven to trigger allergic symptoms, particularly in patients sensitised to crustaceans. Current legislation does not enforce producers to include insects in the list of allergenic ingredients. Food allergenicity risk assessment (FARA) is still at its infancy, and the debate on the need to define allergen thresholds is open. In this paper, we aimed at applying the concepts of stochastic quantitative FARA to describe present and future scenarios of exposure to foods containing Tenebrio molitor, the yellow mealworm. According to our risk characterisation, mealworm-based food products represent a major risk for individuals allergic to crustaceans to develop symptoms after the consumption of a dose lower than a serving size. Moreover, other allergic consumers might be at risk. A correct labelling of insect containing foods would help safeguarding the health of EU allergic consumers. Quantitatively assessing the risk of allergenicity provides a clear description of the problem, facilitating the decisional process of the risk manager, supporting the implementation of effective allergen management procedures and limiting the phenomenon of uninformative precautionary labelling.

Occurrence of Anisakis and Hysterothylacium larvae in commercial fish from Balearic Sea (Western Mediterranean Sea)

This study investigates the occurrence of anisakids and raphidascarids in commercial fish from Balearic Sea (Western Mediterranean). A total of 335 fish including 19 black anglerfish (Lophius budegassa), 33 white anglerfish (L. piscatorius), 129 European hake (Merluccius merluccius), 30 red mullet (Mullus barbatus), and 124 striped mullet (M. surmuletus) were examined using enzymatic digestion. A total of 948 nematode larvae were isolated (prevalence 52.53%) being the highest prevalence observed in striped mullet. Forty-six larvae were identified using molecular analyses which included PCR and sequencing of the 629-bp fragment of mitochondrial cox2 gene region. Anisakis pegreffii (80.43%), A. physeteris (8.69%), Hysterothylacium fabri (6.52%), and A. simplex (4.35%) were detected based on molecular analyses of larvae. Total nematode prevalence was positively correlated with weight, length, condition factor, and maturity stage of the host and also with fishing ground depth. Statistical differences between total nematode prevalence and geographical sector of capture were observed when fishing hauls were grouped according to the abundance of sperm whales or common bottlenose dolphins. The results also corroborate that fishing water depth may play an important role in anisakid and raphidascarid parasitization.

Anisakis sensitization in different population groups and public health impact: A systematic review

Anisakis simplex spp. sensitization rates have increased worldwide, with a significant impact on health-care systems. To date, no clear-cut diagnostic criteria and laboratory algorithm have been established, so anisakiasis still represents an under-reported health problem whose clinical manifestations, when present, mimic the much more common allergic and digestive disorders. Aim of the study was to systematically review the available literature on the prevalence of sensitization against Anisakis in the general population and in specific population groups, taking into account the impact of the different available diagnostic techniques on the epidemiological data. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, relevant papers reporting Anisakis sensitization epidemiological data were found covering a period ranging from 1996 to February 2017. Overall, 41 studies comprising 31,701 participants from eleven countries were included in the qualitative synthesis. General asymptomatic population resulted sensitized to Anisakis in 0.4 to 27.4% of cases detected by means of indirect ELISA or ImmunoCAP specific IgE detection, and between 6.6% and 19.6% of the samples by Skin prick test (SPT). Occupationally exposed workers (fishermen, fishmongers and workers of fish-processing industries) documented specific IgE between 11.7% and 50% of cases, whereas SPT positivity ranged between 8% and 46.4%. Symptomatic allergic patients to any kind of allergen were found to be positive to Anisakis specific IgE detection between 0.0% (in children with mastocytosis) to 81.3% (among adults with shellfish allergy). Results highlighted that hypersensitivity prevalence estimates varied widely according to geographical area, characteristics of the population studied, diagnostic criteria and laboratory assays. Further studies are needed to overcome the documented misdiagnosis by improving the diagnostic approach and, consequently, providing more affordable estimates in order to address public health interventions on populations at high risk of exposure to Anisakis and to tailor health services related to specific groups.

Anti-Anisakis sp. antibodies in serum of patients with sepsis and their relationship with γδ T cells and disease severity

Immunosuppression in sepsis reduces both αβ and γδ T cell subsets. Anisakis sp. is a parasitic nematode with a high prevalence in Spain. Previous contact with the parasite is related to a decrease in γδ T cells. Anti-Anisakis antibodies were measured and related to αβ and γδ T cells in 114 septic patients versus 97 healthy controls. Significant differences were seen with respect to the groups with severe sepsis and septic shock where lower anti-Anisakis levels were observed. A similar decrease appeared in the case of specific IgM with significant differences between the groups of control/uncomplicated sepsis versus severe sepsis and septic shock. These differences were also apparent in the case of specific IgA. The lowest IgE levels were detected in the septic shock group. Anti-Anisakis IgG levels significantly increased in septic shock groups compared with the controls. We observed positive correlations among anti-Anisakis IgA levels and all γδ T cell subsets. There were negative correlations among IgA levels and APACHE and SOFA indices. Greater contact with the parasite (IgG) was directly related with septic shock, inflammation and markers of sepsis severity. A lack of protection in the mucosa (IgA and γδ T cells) was associated with the disease severity.

Molecular Epidemiology of Anisakis and Anisakiasis: An Ecological and Evolutionary Road Map

This review addresses the biodiversity, biology, distribution, ecology, epidemiology, and consumer health significance of the so far known species of Anisakis, both in their natural hosts and in human accidental host populations, worldwide. These key aspects of the Anisakis species' biology are highlighted, since we consider them as main driving forces behind which most of the research in this field has been carried out over the past decade. From a public health perspective, the human disease caused by Anisakis species (anisakiasis) appears to be considerably underreported and underestimated in many countries or regions around the globe. Indeed, when considering the importance of marine fish species as part of the everyday diet in many coastal communities around the globe, there still exist significant knowledge gaps as to local epidemiological and ecological drivers of the transmission of Anisakis spp. to humans. We further identify some key knowledge gaps related to Anisakis species epidemiology in both natural and accidental hosts, to be filled in light of new 'omic' technologies yet to be fully developed. Moreover, we suggest that future Anisakis research takes a 'holistic' approach by integrating genetic, ecological, immunobiological, and environmental factors, thus allowing proper assessment of the epidemiology of Anisakis spp. in their natural hosts, in human populations, and in the marine ecosystem, in both space and time.

IgE sensitization to Anisakis pegreffii in Italy: Comparison of two methods for the diagnosis of allergic anisakiasis

IgE sensitization to Anisakis pegreffii in Italian subjects suffering from gastro-allergic anisakiasis (GAA) (N=5), or showing chronic urticaria (CU+) after fish consumption (N=100), was investigated. A control group (N=5) was also included. IgE response was analysed by immunoblotting (WB) assay, using both excretory/secretory products (ESPs) and crude extract (CE) of A. pegreffii larvae. The results were compared with those achieved by the conventional immunological method for Anisakis allergy (ie, immunoCAP). Among the 110 subjects, 28 showed IgE positivity with both WB and iCAP methods; 13 proved IgE reactivity, in WB assay, to ESP antigens of A. pegreffii, here provisionally indicated as Ani s 1-like, Ani s 7-like, Ani s 13-like; only 15 sera have shown IgE-WB reaction to Ani s 7-like and Ani s 13-like. iCAP and WB exhibited a high concordance value (κ=1.00) when iCAP value was <0.35 (negative result) and >50.0 (positive result). In the sera samples recorded as positive to Anisakis allergy, Ani s 1-like was responsible for 46.4% of the sensitivity, while Ani s 7-like and Ani s 13-like for 100%. They could be considered as major antigens in the diagnosis of allergic anisakiasis caused by A. pegreffii.

Geographic and host size variations as indicators of Anisakis pegreffii infection in European pilchard (Sardina pilchardus) from the Mediterranean Sea: Food safety implications

European pilchards are traditionally eaten marinated or salted in the Mediterranean countries often without thermal processing or gutting due to small size. Since ingestion of live third stage Anisakis larvae represents a causing agent in the onset of anisakiasis, the aim of our study was to assess prevalence and intensity of Anisakis infection in European pilchards originating from different Mediterranean regions in a three-year sampling period (2013-2015). A total of 1564 specimens of European pilchard collected from two geographically distinct sampling regions (western Mediterranean and Adriatic Sea) were examined using the UV-Press method, which utilises the fluorescence of frozen anisakids in flattened and subsequently frozen fillets and viscera. A subsample of 67 isolated larvae was identified as A. pegreffii by diagnostic allozyme markers and sequence analyses of the mtDNA cox2 locus. The overall prevalence in pilchards was 12.2% (range 0-44.9% for different sampling points) and mean intensity 1.8. More importantly, we have observed an overall larval prevalence of 1.5% in fillets. The highest prevalence (44.9%) was recorded in pilchards caught in western parts of the Mediterranean. As fish host size was a significant predictor of parasite abundance, it should be highlighted that these pilchards were also the largest (mean total length 173.2mm); on average >2cm larger than the rest of the samples. Other isolated nematode species included Hysterothylacium sp. in viscera, showing almost a double of A. pegreffii prevalence, 20.1%. In summary, our study demonstrates that the presence of A. pegreffii in European pilchards from the Mediterranean Sea is highly influenced by both geographic and host size variation. This implies that, before future risk management measures are developed, these variables should be assessed in order to minimize public health concerns.

Morphological and molecular diagnosis of Pseudoterranova decipiens (sensu stricto) (Anisakidae) in imported cod sold in Brazil

An anisakid nematode larva found in cod sold in the state of Minas Gerais, Brazil was studied by light and scanning electron microscopy and by a molecular approach. Mitochondrial cytochrome c-oxidase subunit 2 (mtDNA cox-2), 28S rRNA and ITS1, 5.8S and ITS2 regions were amplified using the polymerase chain reaction and sequenced to evaluate the phylogenetic relationships of the larva. The genetic profile confirmed that this larva belongs to the species Pseudoterranova decipiens (sensu stricto). This is the first molecular and ultrastructural study of Pseudoterranova decipiens (sensu stricto) in imported cod sold in Brazil. The health implications of these findings are discussed.

Excretory/secretory products of anisakid nematodes: biological and pathological roles

Parasites from the family Anisakidae are widely distributed in marine fish populations worldwide and mainly nematodes of the three genera Anisakis, Pseudoterranova and Contracaecum have attracted attention due to their pathogenicity in humans. Their life cycles include invertebrates and fish as intermediate or transport hosts and mammals or birds as final hosts. Human consumption of raw or underprocessed seafood containing third stage larvae of anisakid parasites may elicit a gastrointestinal disease (anisakidosis) and allergic responses. Excretory and secretory (ES) compounds produced by the parasites are assumed to be key players in clinical manifestation of the disease in humans, but the molecules are likely to play a general biological role in invertebrates and lower vertebrates as well. ES products have several functions during infection, e.g. penetration of host tissues and evasion of host immune responses, but are at the same time known to elicit immune responses (including antibody production) both in fish and mammals. ES proteins from anisakid nematodes, in particular Anisakis simplex, are currently applied for diagnostic purposes but recent evidence suggests that they also may have a therapeutic potential in immune-related diseases.

Determination of Anti-Anisakis Simplex Antibodies and Relationship with αβ and γδ Lymphocyte Subpopulations in Patients with Crohn's Disease

BACKGROUND

The etiology of Crohn's disease (CD) is still unknown although new theories are based on defects in innate immunity. We have previously shown a decrease in γδ T cells in CD patients. Previous studies have shown a high prevalence of anti-A. simplex immunoglobulins in CD patients. The diminution of γδ T cells in the peripheral blood and intestinal mucosa of CD patients may create a state of immunosuppression that would facilitate A. simplex infection.

AIMS

To study the antibody responses to Anisakis antigens in Crohn's disease patients and its relationship with αβ and γδ T cell subsets.

METHODS

We recruited 81 CD patients and 81 healthy controls. αβ and γδ T cell subsets and anti-A. simplex antibodies were measured.

RESULTS

Levels of anti-A. simplex IgG and IgM were significantly increased in CD patients. Almost 20% of CD patients were positive for IgG and IgM anti-A. simplex versus only 3.7 and 2.5%, respectively, in normal subjects. However, lower specific IgA levels were observed in the group of CD patients versus healthy subjects. We found an association between CD3 + CD8 + γδ subset and IgM anti-A. simplex levels. In ileal cases and stricturing behavior of CD, we observed the highest levels of specific antibodies with the exception of anti-A. simplex IgA.

CONCLUSIONS

The relationship of specific antibodies with a γδ T cell deficiency makes these cell candidates to play a role in the immune response against Anisakis. In addition, anti-Anisakis antibodies could be considered as markers of risk of progression in CD.

Assessing the risk of an emerging zoonosis of worldwide concern: anisakiasis

Anisakiasis is an emerging zoonosis caused by the fish parasitic nematode Anisakis. Spain appears to have the highest reported incidence in Europe and marinated anchovies are recognised as the main food vehicle. Using data on fishery landings, fish infection rates and consumption habits of the Spanish population from questionnaires, we developed a quantitative risk assessment (QRA) model for the anchovy value chain. Spaniards were estimated to consume on average 0.66 Anisakis per untreated (non-frozen) raw or marinated anchovy meal. A dose-response relationship was generated and the probability of anisakiasis was calculated to be 9.56 × 10-5 per meal, and the number of annual anisakiasis cases requiring medical attention was predicted between 7,700 and 8,320. Monte Carlo simulations estimated post-mortem migration of Anisakis from viscera to flesh increases the disease burden by >1000% whilst an education campaign to freeze anchovy before consumption may reduce cases by 80%. However, most of the questionnaire respondents who ate untreated meals knew how to prevent Anisakis infection. The QRA suggests that previously reported figures of 500 anisakiasis per year in Europe is a considerable underestimate. The QRA tool can be used by policy makers and informs industry, health professionals and consumers about this underdiagnosed zoonosis.

Anti-Anisakis sp. antibodies in serum of healthy subjects. Relationship with αβ and γδ T cells

Anisakiosis is nowadays one of the nematodoses more prevalent in Spain, with rates that oscillate between 0.43% in Galicia (N.W. Spain), and 15.7% and 22.1% in inland and southern regions, respectively. Likewise, it has been proved that Anisakis larvae have developed mechanisms to modulate the dichotomy of the host immune response for their own benefit. The experimental hypothesis of the present study was that Anisakis sp. larval products can be mediators of immune suppression and induce changes on the populations of αβ+ and γδ+ T cells. In the present study we determined the levels of anti-Anisakis antibodies in the serum of healthy people, and their relationship with the B and T cell subsets. Levels of anti-Anisakis antibodies (Ig's, IgG, IgM, IgA and IgE) were measured by ELISA, while B and T cell subsets were studied by flow cytometry. Cells were labelled with monoclonal antibodies against CD45, CD4, CD8, CD56, CD3, CD19, TCRαβ and TCRγδ. All the specific isotypes studied were negatively correlated with NKT cell rates with the exception of IgG. A previous contact with Anisakis was related to a decrease in CD56+αβ+ and all γδ+ T cell subsets. The CD3+γδ+ population was lower in the group of subjects that showed IgA anti-Anisakis. We observed an inverse correlation among αβ-γδ NKT cells and anti-Anisakis sp. antibodies. CD3+CD56+ cells showed a significant decrease in the group of anti-Anisakis positive subjects. This fact was especially significant with CD3+CD56+γδ+ cells in the case of the anti-Anisakis IgA positive group.

High prevalence of Anisakis simplex hypersensitivity and allergy in Sicily, Italy

BACKGROUND

Anisakis simplex can elicit allergic reactions when ingested in raw or marinated fish. The prevalence of A simplex hypersensitivity and allergy in Sicily (Italy), an area where the consumption of raw or marinated fish is very common, has not been investigated thus far.

OBJECTIVE

To investigate the prevalence of A simplex sensitization and its clinical relevance in a large group of unselected patients.

METHODS

All consecutive patients referred to the authors' allergy clinic during a 22 month-period were included in the study, evaluated for sensitization to A simplex and other allergens depending on their clinical history, and investigated for allergic symptoms after the ingestion of raw or marinated fish.

RESULTS

Of 3,419 patients screened, 527 (15.4%) were sensitized to A simplex and 29 of these (5.5% of sensitized patients) had a history of A simplex allergy. Approximately 30% of patients had mono-sensitization to A simplex. Co-sensitization to house dust mites or molds yielded an odds ratio of 1.98 or 3.18, respectively, for allergy to A simplex.

CONCLUSION

A high prevalence of A simplex sensitization in a large proportion of patients with mono-sensitization was found, confirming that eating habits influence sensitization to this nematode. Allergic symptoms from A simplex ingestion in raw or marinated fish were quite frequent, with symptoms ranging from oral allergy syndrome to anaphylaxis. Patients sensitized to A simplex were more prone to have allergic symptoms when they had co-sensitization to house dust mites or molds, suggesting possible cross-reactive but clinically relevant allergens between these allergenic sources.

Fishing area and fish size as risk factors of Anisakis infection in sardines (Sardina pilchardus) from Iberian waters, southwestern Europe

The sardine (Sardina pilchardus) is a fish commonly consumed and appreciated in many countries, although they are more likely to be eaten fresh in western Mediterranean countries such as Spain, Portugal, France or Italy. A molecular epidemiological survey of sardines from 5 fishing areas of the Spanish Mediterranean (Málaga, southern Spain) and Atlantic coasts (southern: Cádiz and Isla Cristina; northern: A Coruña and Ondarroa) was carried out to determine the presence of Anisakis spp. larvae. The highest prevalence of these larvae was observed in fish from A Coruña (28.3%), followed by Ondarroa (5%) and Cádiz (2.5%). No Anisakis larvae were found in fish from Málaga and Isla Cristina. Three Anisakis genotypes were identified: Anisakis simplex sensu stricto, Anisakis pegreffii and a hybrid genotype between these two species. A. pegreffii was the most prevalent species in A Coruña (71% of larvae). Only three Anisakis larvae (9% collected larvae) were located in the musculature of sardines: two were identified as A. pegreffii while the other was a hybrid genotype. Sardine infection was associated with fishing area and fish length/weight (length and weight were strongly correlated; Pearson's correlation 0.82; p<0.001). Risk factor multivariate analysis showed that the risk of infection increases 1.6 times for every additional cm in the length of the sardines from the same fishing area. Comparison of fish of equal length showed that in sardines from A Coruña the risk of parasitization is 11.5 times higher than in those from other fishing areas. Although the risk of infection by Anisakis through consumption of sardines is generally low due to the low epidemiological parameter values (prevalence 10%, mean intensity 1.7 (range 1-5) and mean abundance 0.17), as larger fish are more heavily parasitized, there is an increased risk of infection by Anisakis through consumption of large sardines which are raw or have undergone insufficient treatment (undercooked, smoked, marinated, salted, pickled, freezing,…).

Characterisation of potential novel allergens in the fish parasite Anisakis simplex

The parasitic nematode Anisakis simplex occurs in fish stocks in temperate seas. A. simplex contamination of fish products is unsavoury and a health concern considering human infection with live larvae (anisakiasis) and allergic reactions to anisakid proteins in seafood. Protein extracts of A. simplex produce complex band patterns in gel electrophoresis and IgE-immunostaining. In the present study potential allergens have been characterised using sera from A. simplex-sensitised patients and proteome data obtained by mass spectrometry. A. simplex proteins were homologous to allergens in other nematodes, insects, and shellfish indicating cross-reactivity. Characteristic marker peptides for relevant A. simplex proteins were described.

An extended study of seroprevalence of anti-Anisakis simplex IgE antibodies in Norwegian blood donors

During the last decade, cases of the fish parasite Anisakis simplex infection and allergy in human have increased in countries with high fish consumption. Our aim was to perform an extended seroprevalence study of anti-IgE antibodies against this parasite in Norway, one of the high fish-consuming countries. At the Department of Immunology and Transfusion Medicine and the Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway, two main groups of anonymized serum samples were collected; the first (n = 993) from recently recruited blood donors (designated 'BDO') and the second (n = 414) from patient with total IgE levels ≥1000 kU/l (designated 'IGE+'). The sera were analysed by the ImmunoCAP(®) method for total IgE and IgE antibodies against A. simplex, house dust mite (HDM), shrimp, cod, crab, brine shrimp and shrimp tropomyosin. The A. simplex positive sera were further tested by an enzyme-linked immunosorbent assay (ELISA) method, which uses 2 recombinant (r) major allergens, rAni s 1 and rAni s 7 as target antigens. SDS-PAGE and Western immunoblotting analyses were also performed. Whereas the prevalences by ImmunoCAP(®) were 0.4% and 16.2% in the BDO and IGE+ groups, respectively, analyses with recombinant allergens showed only 0.0% and 0.2%. Cross-reactivity and immunoblotting analyses suggested that most of the ImmunoCAP(®) positive sera were probably false-positive due to cross-sensitization to shrimp and HDM. However, positivity due to other A. simplex antigens should also be considered. Compared with other high fish-consuming countries, we observed a very low seroprevalence of anti-Anisakis IgE antibodies in a Norwegian population.

Anti-Anisakis IgE seroprevalence in the healthy Croatian coastal population and associated risk factors

BACKGROUND

The main objective of the study was to determine the degree of sensitization to Anisakis spp. antigens in healthy coastal population of Dalmatia given the high thermally unprocessed fish intake rate present in this area, suggested as a significant risk factor for anisakiasis. We performed a monocenter, cross-sectional pilot study stratified by geographic area of residence, conducted at the County secondary healthcare provider Medicine-biochemical Laboratory in Split (Croatia), from November 2010 till December 2011, on 500 unpaid volunteer subjects undergoing routine blood analysis and belonging to the south coast of the Adriatic Sea.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the IgE seroprevalence to Anisakis spp. Ani s l and Ani s 7 allergens by indirect ELISA in healthy subjects, which were selected at random in the region of Dalmatia (Southern Croatia), among islands, coastal urban and inland rural populations. In order to detect possible cross-reactivity to other human helminthes, serum samples were tested also for the presence of IgG antibodies to Ascaris lumbricoides and Toxocara canis. The overall and coastal Anisakis seroprevalences for the sampled population were 2% and 2.5%, respectively. The logistic univariate regression analysis confirmed that regarding anti-Anisakis IgE seroprevalence, raw fish intake, daily fish intake, homemade origin of fish dish and occupational contact (professional, artisanal or hobby contact with fishery or fish industry) were risk factors associated to Anisakis spp. sensitization, but neither of the variables was exclusive for a particular seropositive population. Also, a significant difference was observed between seropositive and seronegative subjects that had stated allergy or symptoms associated with allergy (atopic dermatitis, asthma or rhinitis) in their previous history.

CONCLUSIONS/SIGNIFICANCE

Being the first in Croatia, our study underlines the necessity of incorporating Anisakis spp. allergens in routine hypersensitivity testing of coastal population.

Synergism between prior Anisakis simplex infections and intake of NSAIDs, on the risk of upper digestive bleeding: a case-control study

Background

The aim of this study was to investigate the relationship between prior Anisakis infections and upper gastrointestinal bleeding (UGIB), and its interaction with non-steroidal anti-inflammatory drug (NSAID) intake.

Methods/Principal Findings

We conducted a hospital-based case-control study covering 215 UGIB cases and 650 controls. Odds ratios (ORs) with their confidence intervals (95% CIs) were calculated, as well as the ratio of the combined effects to the sum of the separate effects of Anisakis allergic sensitization and NSAIDs intake. Prior Anisakis infections were revealed by the presence of anti-Anisakis IgE antibodies specific to the recombinant Ani s 1 and Ani s 7 allergens used as the targets in indirect ELISA. Prior Anisakis infections (OR 1.74 [95% CI: 1.10 to 2.75]) and the intake of NSAIDs (OR 6.63 [95% CI: 4.21 to 10.43]) increased the risk of bleeding. Simultaneous NSAIDs intake and Anisakis allergic sensitization increased the risk of UGIB 14-fold (OR = 14.46 [95% CI: 6.08 to 34.40]). This interaction was additive, with a synergistic index of 3.01 (95% CI: 1.18–7.71).

Conclusions

Prior Anisakis infection is an independent risk factor for UGIB, and the joint effect with NSAIDs is 3 times higher than the sum of their individual effects.

Anisakiasis is a worldwide re-emerging disease produced by the consumption of raw, lightly cooked, smoked or marinated fish containing live Anisakis larvae. In acute anisakiasis, mucosal lesions generated by the larvae may provoke upper gastrointestinal bleeding (UGIB). However, the effect of past unnoticed Anisakis infections as a risk factor for UGIB, and a possible synergism with other risk factors such as NSAIDs intake, have never been investigated. In this case-control study we observed that: i) prior Anisakis infections and NSAIDs intake are two independent risk factors for UGIB, and ii) that both risk factors act synergistically to the extent that their joint effect is 3 times higher than the sum of their individual effects. We concluded that, in countries where Anisakis infections are frequent, it would be wise to determine parasite-specific IgE antibodies and to conduct a closer follow-up of patients who consume raw or lightly cooked fish and who are prescribed NSAIDs for long periods.

Anisakiasis, an underestimated infection: effect on intestinal permeability of Anisakis simplex-sensitized patients

Anisakis simplex is a parasite that, if present in uncooked and contaminated saltwater fish, can invade the human gut. Two different clinical situations are recognized: the first, known as a gastrointestinal disease, varying from an asymptomatic episode to vomiting and diarrhea, and the second, classified as an adverse reaction to food, characterized by a wide spectrum of allergic reactions like rhinitis, conjunctivitis, or even anaphylaxis causing hypotension and/or shock. The intestinal epithelium, the major defense system against external molecules, represents an open gate for toxins and allergens if its protective function is compromised. Previous data have demonstrated a strict relationship between an altered intestinal permeability (I.P.) and worsening of the clinical manifestations in patients with adverse reactions to the food. In this article we evaluated the sensitization to A. simplex among patients who referred clinical symptoms of allergy. All subjects underwent commonly used alimentary skin prick test for food allergens, to which Ani s1, an A. simplex allergen, was added. In addition, in A. simplex-sensitized subjects, I.P. was determined upon their enrolment to the study (time 0) and after 6 months of consuming a raw fish-free diet (time 6). Five hundred and forty subjects were screened, and 170 had a positive skin prick test, 87 (51.2%) of whom were positive to Ani s1. Increased I.P. was evidenced in A. simplex-sensitized subjects with worse clinical symptoms, which receded after 6 months' elimination of raw seafood. With our data we demonstrated that the alimentary habit to eat raw fish represents a high risk for the integrity of the intestinal mucosa, and we suggest that this pathological situation may constitute an ideal, under-estimated, open gate for molecules that predispose to other, more important pathologies.

Anisakid parasites of the pouting (Trisopterus luscus) from the Cantabrian Sea coast, Bay of Biscay, Spain

An epidemiological survey was undertaken of anisakids in 139 specimens (length: 13.2–24.5 cm) of pouting or bib (Trisopterus luscus) captured off the coast of northern Spain in the Cantabrian Sea. Third-stage larvae of two species of nematodes, Anisakis larvae type I and Hysterothylacium aduncum, were isolated. One adult female H. aduncum was also detected in the intestine of one pouting. Total prevalence of anisakids was 88.5%. Hysterothylacium aduncum and Anisakis showed, respectively, prevalence of 87.8% and 22.3%, mean intensity of 19.7 and 3.5, and mean abundance of 17.3 and 0.8. Analysis of infection parameters as a function of host length revealed a much higher prevalence in pouting specimens with length < 20 cm (94.4% for H. aduncum; 28.0% for Anisakis) than in those with length ≥ 20 cm (65.6% for H. aduncum; 3.1% for Anisakis). The high mean intensity of Anisakis in muscle of parasitized pouting (5.9) may pose human health risks, although these are minimized by eating only thoroughly cooked pouting, as is the custom in Spain.

Western blot antibody determination in sera from patients diagnosed with Anisakis sensitization with different antigenic fractions of Anisakis simplex purified by affinity chromatography

Using Western blot techniques, the specificities of crude and purified (PAK and PAS) Anisakis simplex antigens were compared against 24 sera from patients diagnosed with Anisakis sensitization. All patients recognized a 60 kDa protein against the A. simplex crude extract, while 37.5% and 12.5% reacted with proteins of 40 and 25 kDa, respectively, when IgG was tested. In the case of IgE determination, 41.6% of sera were negative, while 12.5% and 20.8% appeared to cross-react against Toxocara canis and Ascaris suum, respectively. When the PAK antigen (A. simplex antigen purified by means of a column of IgG anti-A. simplex) was tested, immune recognition towards the 60, 40 and 25 kDa proteins increased in 83.3%, 16.7% and 4.2%, respectively, when the Ig antibodies were tested. In the case of the PAS antigen (PAK antigen purified by means of a column of IgG anti-A. suum), the reaction against the 40 and 25 kDa proteins increased to 45.8% and 25%, respectively, when Ig antibodies were used. Finally, when the EAS antigen (eluted from the anti-A. suum column after PAK purification) was tested, 83.3% of the assayed sera reacted against the 14 kDa protein, when the Ig antibodies, IgG and IgM immunoglobulins were measured. With the IgE determination, the reactions were observed in 41.7% of patients with proteins between 60 and 35 kDa against the PAS antigen. With the EAS antigen, reactive bands of 184, 84 and 14 kDa appeared. In conclusion, in the purification process of the A. simplex larval crude extract, the proteins implicated in cross-reactions with Ascaris and Toxocara were eliminated, with an important concentration of proteins responsible for the induction of specific responses.

Anisakis simplex: the high prevalence in Madrid (Spain) and its relation with fish consumption

Anisakiosis is a nematodosis with high prevalence in Spain. In this work we (a) investigated whether a recently introduced ELISA of Anisakis simplex-specific IgE in serum suffers from cross-reactivity with other common allergens; (b) used this assay to obtain an estimate of the prevalence of A. simplex-specific IgE in the population of Madrid; and (c) related positivity to fish consumption habits. No evidence of cross-reactivity between the ELISA and other allergens was found. The prevalence of positivity was 12.4% (11.7% among healthy subjects and 16% among patients with non-digestive non-allergic pathologies). All interviewed subjects reported consumption of uncooked fish (known to be the most likely source of infection); in addition, positivity was more prevalent among subjects who habitually consumed fresh and possibly undercooked fish than among those who generally consumed frozen fish or boiled or baked fish. These results are discussed in relation to the much lower prevalence observed in Galicia (N.W. Spain).

Immune reactions and allergy in experimental anisakiasis

The third-stage larvae (L3) of the parasitic nematode, Anisakis simplex, have been implicated in the induction of hyperimmune allergic reactions in orally infected humans. In this work, we have conducted a review of an investigation into immune reactions occurring in animals experimentally infected with A. simplex L3. The patterns of serum antibody productions in the experimental animals against excretory-secretory products (ESP) of A. simplex L3 contributed to our current knowledge regarding specific humoral immune reactions in humans. In our review, we were able to determine that L3 infection of experimental animals may constitute a good model system for further exploration of immune mechanisms and allergy in anisakiasis of humans.