Parasitism is quite a generalised problem as anisakis is found in the sea. It does not present a health risk providing that the fish is cooked at the right temprature or is frozen.
To prevent anisakis, order clean fish, gutted fish at our fishmongers. At home, cook it at a temperature of over 60ºC, or if you are going to eat it raw or close to raw, freeze it.
It is not possible to detect 100% of the problems despite the controls that are carried out by the Administration or by the suppliers, and despite our internal controls at our distribution platforms, Quality area or points of sale.
If you detect a reference with presence of parasitism, despite all the controls mentioned above, you can got to the store and request its replacement or return.
Ministry of Health information on anisakis: http://www.aecosan.msssi.gob.es/AECOSAN/web/para_el_consumidor/ampliacion/anisakis.htm