During the last decades, cases of anisakis poisoning have increased considerably among the fish-eating population. The anisakis is a parasitic worm that has a hazardous life in the sea, its life unfolds in stages, jumping from species to species. The eggs are released into the water, they hatch, and small larvae emerge from them, which are first consumed by crustaceans, whose bodies they take advantage of to encyst and wait for other predators such as fish, octopus, and squid, where they continue their development until they are consumed by marine mammals. , such as dolphins or whales in which they finish their development until they again generate eggs that are excreted to start a new life cycle.
In the midst of this wandering from one species to another, the infected fish can end up on the table of a human eater and, if the preparation for consumption is not adequate to kill the larvae, they can end up in the digestive system of the consumer to whom they cause different disorders such as abdominal pain, nausea, vomiting or can cause the typical symptoms of allergies, such as itching, skin lesions or anaphylaxis.
Recently, an international team of researchers, led by our interviewee, the Researcher of the Higher Council for Scientific Research and the Museum of Natural Sciences, Alfonso Navas Sánchez, have published a study on the genome of two Anisakis species and a hybrid of both. The study reveals that anisakis are real allergenic “bombs”.
Genetic study of Anisakis species, A. simplex sensu stricto and A. pegreffii, and of the hybrid between the two reveals that they contain numerous genetic sequences that encode proteins known to cause allergic reactions in people. To get an idea of the allergenic power of anisakis, a total of 509 allergenic compounds of food origin have currently been identified in fungi, animals and plants. Of all of them, the researchers have searched for homologues in the genetic sequences of the anisakis species analyzed in this study and have discovered protein sequences corresponding to 121 different allergens.
A total of 12 different species of anisakis are known, whose populations are located in different regions of the planet’s seas and oceans. The increasing movements of some marine mammals, such as whales, due to their difficulty in finding a mate, due to the decrease in the number of their populations, leads them to visit very distant regions, favoring their infection by different species of anisakis. When two species infect the same individual, contact between them allows hybridization and gives rise to a third class that carries its own allergens.
Alfonso Navas comments on the three existing strategies to fight against Anisakis. In the field of consumption, freezing fish in refrigerators at -20ºC for at least five days before consuming it raw, for example, to make sushi or anchovies in vinegar (some freezers do not reach that temperature, so it would be insufficient). A second protection is achieved by cooking the fish at more than 65ºC for at least half an hour. In this way the allergenic proteins are destroyed. Another measure, this one to avoid the proliferation of the parasite in the sea, consists of eliminating it in the viscera of the fish caught before being returned to the sea, in this aspect the CSIC has developed a method that makes it possible to kill the larvae in the viscera with a relatively simple treatment.
I invite you to listen to D. Alfonso Navas Sánchez, Researcher of the CSIC and the National Museum of Natural Sciences.
Llorens C, Arcos SC, Robertson L, Ramos R, Futami R, Soriano B, Ciordia S, Careche M, Gonzalez-Muñoz M, Jimenez-Ruiz Y, Carballeda-Sangiao N, I , Gift , JP Albar , M Blaxter and A Navas . Functional insights into the infective larval stage of Anisakis simplex s.s., Anisakis pegreffii and their hybrids based on gene expression patterns. BMC Genomics 19:592 DOI: 10.1186/s12864-018-4970-9
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