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

Abstract

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 fish and squid, the intermediate/paratenic hosts, which are either raw or have not been cooked or frozen adequately. The live larvae generally penetrate the wall of the stomach or intestine causing, amongst other symptoms, intense pain or allergic symptoms. As a result of this initial contact with live larvae the patient may become sensitized. Further contact with live or dead larvae may result in the appearance of allergic symptoms, ranging from urticaria and angioedemas to anaphylaxis, being known as allergy to Anisakis. These are emerging, cosmopolite illnesses. Diagnosis and treatment of these digestive conditions is usually by endoscopy and extraction of the larvae if easily accessible, otherwise by surgical resection with identification, usually histological, of the larvae in the tissue removed. The allergic forms are usually diagnosed by prick-test and/or allergen-specific IgE detection and treated with a suitable 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: by heat at >60 ºC, >1 min or by freezing at -20 ºC, >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.