Anisakis

• Anisakis


  Nematode parasite of whales, dolphins, porpoises, walruses, seals, sea lions, and other deep-marine mammals

  
• Infective species

  • Anisakis simplex
  • Pseudoterranova decipiens
• Related species

  • Contracaecum species
  • Hysterothylacium species
• Definitive Hosts

  • Whales
  • Dolphins
  • Porpoises
  • Walruses
  • Seals
  • Sea lions
  • and other deep-marine mammals

  
• Intermediate Hosts

  • Crustacean Hosts
• Paratenic Hosts

  • Squid
  • Fish

  
• Accidental Hosts

  • Humans
• Anisakis are accidental parasites to humans

  
• Epidemiology

  • Not a very common infection
  • Reported all over the world usually, coastal population
  • Their livelihood and lifestyle are also a factor
  • Consumption of raw or inadequately cooked fish

  
• Regions where Anisakis is common

  • Asia: Japan, Korea
  • Europe: Netherlands, France, Germany, Italy, Spain, UK
  • North and South America
• Adult Anisakis

  • Embedded in gastric wall of marine mammal host
  • Females are larger than males
• Ova

  Discharge of unembryonated ova into the sea, needs water for further embryonation

  
• Larva development

  1. First Stage Larva: Developed inside the ovum

  2. Second Stage Larva: Hatched from ova, free-swimming, ingested by crustaceans

  3. Third Stage Larva: Develops inside crustaceans, eaten by paratenic hosts

  
• Third Stage Larva (L3)

  • Milky white in color
  • Measures about 19-36 mm
  • Type I Larvae: Long stomach, blunt tail with mucron
  • Type II Larvae: Short stomach, blunt tail

  
• Lifecycle

  1. Adults copulate in marine mammals, female sheds unembryonated ova

  2. Ova undergo embryonation in water, hatch into free-swimming second stage larva

  3. Second stage larva eaten by crustacean intermediate hosts, develop into third stage larva

  4. Third stage larva eaten by paratenic hosts like predator fish or humans

  5. In human hosts, third stage larva develops into fourth and fifth stage larva

  
• Hosts


  • Definitive hosts: Dolphins and other marine mammals
  • Intermediate hosts: Crustaceans
  • Paratenic hosts: Predator fish
  • Accidental hosts: Humans

  
• Infective stage

  Third stage larva

  
• Anisakiasis / Anisakidosis

  Larval infections in the stomach (does not grow into adults in humans, only L4-L5)

  
• Pathogenesis and Clinical Manifestations

  • Eosinophilic gastroenteritis
  • Eosinophilic granulomatous response in the intestine mimicking acute appendicitis
  • Ectopic Anisakidosis: Oropharynx, esophagus, colon
  • Tingling Throat Syndrome: Manifestation due to larvae invading the oropharynx
• Diagnosis

  • Definitive: Direct visualization of Third Stage Larva via Upper Gastrointestinal Endoscopy
  • Serology: ELISA

  
• Treatment

  • Definitive: Mechanical removal of larvae
  • Steroids for allergic reaction
  • Possible drug: Albendazole

  
• Erythema and granuloma are caused by the immune response of the body against the L3
• Prevention and Control

  • Thorough cooking of food
  • Blast freezing: -35*C for 15 hours or -20*C for 7 days
  • Raising awareness to producers and consumers