Gastric anisakiasis

Japanese: 胃アニサキス症 - いアニサキスしょう（英語表記）Gastric anisakiasis

What is the disease?

This is a disease that develops by eating fish (such as mackerel, Alaska pollock, horse mackerel, and Japanese flying squid) that are infested with the larvae of Anisakis species (such as Anisakis and Pseudoterranova).

These parasites live in marine mammals (such as dolphins). Toothed cetaceans ( Whale-like ) and seals. pinniped ( Come and visit ) )of Definitive host ( Swishing ) The parasite resides in the stomachs of these animals as a parasite. The parasite eggs are then excreted into seawater, where they develop into second-stage larvae, which are then eaten by marine crustaceans such as krill, the first intermediate host, and are then eaten by approximately 200 species of secondary hosts (second intermediate hosts) such as marine fish and squid in the food chain. Humans become infected by eating these fish.

When infected Anisakis larvae penetrate the stomach mucosa, the disease is called gastric anisakiasis.

How symptoms manifest

Within a few hours after ingestion, symptoms such as sudden upper abdominal pain and vomiting appear. The abdominal pain is thought to be due to allergic symptoms rather than mechanical irritation caused by the larvae penetrating the gastric mucosa. In rare cases, the patient may fall into anaphylactic shock (a life-threatening condition that affects the whole body, such as sudden difficulty in breathing and a drop in blood pressure).

Testing and diagnosis

It can be easily diagnosed by checking whether fresh fish was eaten within a few days of the onset of symptoms, and by specifically checking for the parasite by gastrointestinal endoscopy. In many cases, a swelling where the parasite has penetrated the mucous membrane can be confirmed.

Treatment methods

If the parasite is confirmed by gastroscopy, it will be removed on the spot. Even if it is not confirmed, if the patient has eaten fresh squid and this disease is strongly suspected, symptoms will improve with the administration of anticholinergic drugs, antihistamines, and steroid drugs, and the prognosis will be good.

What to do if you notice an illness

If you suddenly experience abdominal pain or vomiting after eating fresh fish, do not panic and visit a medical facility that can perform an endoscopic examination. If you cannot visit a medical facility immediately, such as at night, you may visit the next day, depending on the severity of your symptoms.

Humans are not suitable hosts for Anisakis. Therefore, they do not develop into adults in the human digestive tract, but anisakiasis is an important parasitic disease because of the various symptoms it causes. It is a disease closely related to the Japanese food culture, which favors fresh seafood, and the most common sources of infection are marinated mackerel and squid.

Hajime Kuwayama

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　アニサキス類（アニサキス、シュードテラノーバなど）の幼虫が寄生した魚類（マサバ、スケソウダラ、マアジ、スルメイカなど）を食べることによって発症する病気です。

　これら寄生虫は、海の哺乳動物（イルカなどの歯鯨類(はくじらるい)やアザラシなどの鰭脚類(ききゃくるい)）を終宿主(しゅうしゅくしゅ)として、これらの動物の胃に寄生しています。そして、海水中に虫卵が排出され、海水中で第2期幼虫にまで発育し、第1中間宿主のオキアミなどの海産甲殻類に捕食され、その後、海水魚やイカなど約200種類もの2次宿主（第2中間宿主）に食物連鎖として食べられます。これらの魚類をヒトが食べて感染します。

　感染したアニサキス類の幼虫が、胃の粘膜へ入り込んで発症する場合を胃アニサキス症といいます。