In biology, resistance is specifically defined as the innate or genetic ability of an organism to prevent or fend off assaults from biological agents like pathogens, or to withstand the impact of non-biological agents such as chemicals, pesticides, salt, heavy metals, etc. The resistance exhibited by Anisakis larvae signifies their capability to persist in adverse circumstances, wich demonstrated through spontaneous movements following stimulating by bending with forceps and a needle (CODEX STAN 244, 2004; EFSA, 2010). Several authors have investigated the anti-Anisakis effects of chemical and/or biological substances (such as NaCl, vinegar, essential oils, terpenoid compounds, etc.) and adverse physical conditions like freezing, heat, pressure, and more (Giarratana et al., 2014, 2015a, 2017; Hierro et al., 2004; Pascual et al., 2010; Sánchez-Alonso et al., 2021; Šimat and Trumbić, 2019).

In recent years, eating habits in Morocco have changed considerably, under the influence of globalization, urbanization and the rise of new culinary trends. These changes include a marked increase in the consumption of raw or undercooked fish, in dishes such as ceviche, sushi, sashimi and marinated fish. While these specialties appeal for their flavor and originality, they are not without health risks, not least the potential danger of anisakiasis. This is why the search for effective solutions to eliminate Anisakis larvae in fish is very important. The use of methods and products commonly employed for their biocidal effects, such as salt, vinegar or certain spices, represents a promising avenue for limiting this risk.

Indeed, products such as chlorine dioxide has been widely used in disinfecting equipment and surfaces in food units and his efficiency against infectious agents was proved. It should be noted that under federal regulations (21 CFR Part 178), the use of sanitizing solutions containing sodium hypochlorite on food processing equipment and food contact articles is permitted under specific conditions: i) the concentration of available chlorine in sanitizing solutions used for equipment must not exceed 200 parts per million (ppm); ii) for sanitizing food contact surfaces, it is recommended to use a maximum of 15 mL of typical chlorine bleach per gallon of water (3.78 L of water); iii) equipment or articles treated with the solution must be adequately drained before being used with food (FDA, 2018).

In fact, sodium hypochlorite has a broad spectrum of activity and is effective against various infectious agents. Diluted bleach solutions are a common and cost-effective tool for disinfecting equipment and surfaces in food processing units. The action of bleach is linked to the molecule of hypochlorous acid (HOCl), which causes protein alterations, destruction of phospholipids, and the formation of chloramines that interfere with cellular metabolism. It also induces oxidative effects by causing irreversible enzymatic inactivation, as well as the degradation of lipids and fatty acids. (Estrela et al., 2002; Howell et al., 1999). In parasitology, studies have shown that bleach effective against certain nematodes (Elowni et al., 2024; Lephoto and Gray, 2022; Van Wyk, 1998). However, no works have done on the sensitivity of Anisakis larvae to bleach.

On the other hand, some products such as vinegar, salt and marinade are known for their use as antihelminthic agents in foodstuffs. Indeed, salad dressing which is typically made from oil, vinegar, salt and spices can also influence Anisakis larvae's viability. Several studies have demonstrated that salt and/or vinegar can influence the viability of Anisakis larvae (Lanfranchi and Sardella, 2010; Sánchez-Monsalvez et al., 2005; Šimat and Trumbić, 2019). Other researchers have also reported the nematicidal effects of black pepper (Nile et al., 2017). Thus, a combination of these compounds could potentially act synergistically to devitalize Anisakis larvae.

Indeed, the salting process causes structural changes in the larvae's cuticle, such as osmotic damage altering membrane permeability and causing the leakage of ions and other cellular contents (Anastasio et al., 2016). It involves placing salt crystals directly on the fish fillets to reduce the water activity of the food product, thereby inhibiting the growth of microorganisms (Abbas et al., 2009). Regarding the effect of dry salting, several studies have shown that treating fish flesh (e.g. anchovies, herring, cod, etc.) with dry salt results in the devitalization of nematode larvae within six days to three weeks (Anastasio et al., 2016; Khalil, 1969; Šimat and Trumbić, 2019; Smaldone et al., 2017). Similarly, other authors have demonstrated that the direct exposure of Anisakis larvae to dry salt inactivates them in less than 24 h (Adams and DeVlieger, 2018; Hauksson and Valdimarsson, 1997; Khalil, 1969; Lanfranchi and Sardella, 2010). In the case of brining, Šimat & Trumbić (2019) found that salt concentration affects the survival duration of parasites. Indeed, Anisakis larvae directly exposed to NaCl solutions can survive approximately 3 day at a salt concentration of 35 % and about ten days in a 5 % solution. When it comes to fish fillets, the larvae exhibited increased resistance during marination, and only dry salting was proved to be effective in destroying Anisakis spp. larvae (Anastasio et al., 2016).

Furthermore, marination which corresponds to soaking food in a seasoned liquid, often acidic, with or without cooking has multiple roles. It is not only used to enhance flavor but also to inhibit the action of bacteria and enzymes, tenderize the connective tissues, and modify the taste, texture, and structural properties of the raw material (Fernandes, 2016). This process results in a product with a distinct flavor profile and an extended shelf life. Vinegar-marinated fishes are widely popular in many countries, particularly in Asia and Western Europe. However, these methods are not sufficient to devitalisate Anisakis larvae infesting the fish. Studies have shown that treatments involving a decrease in pH, commonly used in processes like marinating fish in vinegar, do not effectively kill the larvae during storage under industrial and domestic conditions (Karl et al., 1994; Solas et al., 2009). However, Šimat and Trumbić (2019) demonstrated that alcoholic vinegar can effectively kill Anisakis larvae in less than 48 h. Additionally, Sánchez-Monsalvez et al. (2005) found that a high concentration of vinegar (12 % acetic acid w/v) combined with 6 % (w/v) salt (NaCl) can kill 100 % of Anisakis larvae in less than 24 h in herring.

In this context, we aimed at testing the resistance of Anisakis larvae to substances commonly used in industrial and domestic environments, including bleach, as disinfectant commonly used to disinfect surfaces and utensils in households and the fishing industry. As well as dry salt, salt solutions and marinades, used for fish preservation and salad dressings, with the purpose of gathering data that could assist various stakeholders in the food chain in making choices regarding the control of these infesting agents. Unfortunately, there is a lack in the study of Anisakis larvae's resistance to several components, namely chlorine and the prevalence of these larvae in fish in North Africa and especially in Morocco. In this context, we conducted the present study to contribute to the understanding of the resistance of Anisakis spp. larvae to products regularly used in moroccan industry and households. This work was the first in the world to address the resistance of Anisakis larvae to hypochlorite (bleach), and the first in Africa to have studied the resistance of this parasite to products such as salt, vinegar and salad dressing.