Anisakis simplex

Anisakis simplex

Anisakis simplex is a parasitic nematode that causes anisakiasis, a disease contracted from the consumption of infected seafood. The lifecycle of Anisakis simplex involves several hosts, including marine mammals, which are the definitive hosts, and fish and squid, which serve as intermediate hosts. Humans become accidental hosts when they consume raw or undercooked fish containing the larvae of the parasite.

Lifecycle

The lifecycle of Anisakis simplex begins when infected marine mammals excrete the parasite's eggs into the sea through their feces. These eggs hatch into free-swimming larvae that are ingested by crustaceans, which then become the first intermediate hosts. The infected crustaceans are subsequently eaten by fish or squid, transferring the larvae into these secondary hosts. The larvae penetrate the gastrointestinal tract of the fish or squid and encyst in the tissues. When marine mammals consume these infected fish or squid, the lifecycle is completed as the larvae mature into adult worms in the mammal's digestive system.

Humans enter the lifecycle when they consume raw or undercooked fish or squid containing the larvae. Once ingested, the larvae can invade the gastrointestinal tract of humans, causing anisakiasis.

Symptoms and Diagnosis

Symptoms of anisakiasis can appear within hours of ingestion and include severe abdominal pain, nausea, vomiting, and diarrhea. In some cases, the larvae can cause an allergic reaction, leading to symptoms such as itching, rash, and anaphylaxis.

Diagnosis of anisakiasis is primarily based on the patient's history of consuming raw or undercooked fish and the presence of symptoms. Endoscopy can be used to visualize and remove the larvae from the gastrointestinal tract. In some cases, a biopsy may be necessary to confirm the diagnosis.

Prevention and Treatment

Prevention of anisakiasis involves avoiding the consumption of raw or undercooked fish and squid. Freezing fish at -20°C (-4°F) for at least 24 hours or cooking it at temperatures above 60°C (140°F) for at least one minute kills the larvae and prevents infection.

Treatment for anisakiasis typically involves the physical removal of the larvae via endoscopy. In cases where the larvae cannot be removed, medication may be prescribed to relieve symptoms. Antihistamines can help manage allergic reactions to the larvae.

Epidemiology

Anisakiasis is most commonly reported in regions where consuming raw fish is a common practice, such as in Japan, the Netherlands, and along the Pacific coast of South America. However, the popularity of dishes such as sushi and sashimi worldwide has led to an increase in cases globally.