Anisakiasis

Abstract

Adult stages of Anisakis simplex or Pseudoterranova decipiens live in the stomach of marine mammals. Eggs produced by adult females are passed in the faeces. First-stage larvae are formed when in the water. The larvae moult to become second-stage larvae, which then hatch from the eggs and become free-swimming. The larvae released from the eggs are ingested by crustaceans and then develop into third-stage larvae. The crustaceans are eaten by fish and squid, where the larvae migrate from the intestine to the peritoneal cavity and grow up to 3 cm in length. When the host dies, larvae migrate to the muscle tissues and are transferred from the fish to the predator. When fish or squid containing third-stage larvae are ingested by marine mammals, the larvae develop into adult worms. The adult females produce eggs that are shed by marine mammals. Humans become infected by eating raw or undercooked infected marine fish. After ingestion, the larvae penetrate the stomach (less often the intestine), causing the symptoms of anisakiasis.