Page 123 - Medical Parasitology_ A Textbook ( PDFDrive )

116 10 Nematodes: Roundworms

a b

Fig. 10.23 Anisakis, (a) L3 larva, (b) Cross section of L3 larva

Pathogenesis and Clinical Features
When humans consume uncooked or improperly preserved fish containing the
infective larvae, they penetrate the gut wall leading to local inflammation and granu-
loma formation. Clinical manifestations vary depending on the site of penetration of
the intestinal wall, such as throat irritation, acute gastric (abdominal pain, nausea,
vomiting) or bowel symptoms (lower abdominal pain, diarrhoea, dysentery).
Symptoms can occur within 1 h to 2 weeks after consumption of raw or under-
cooked infected seafood.
Diagnosis
History of consuming raw marine fish shortly before the onset of symptoms should
suggest the possibility of anisakiasis.

1. Endoscopic examination
May provide visual evidence and removal of the worm for identification.
2. Molecular diagnosis
PCR on the worm specimen obtained after removal.
3. Serodiagnosis
To detect Anisakis-induced IgE. This antibody, however, lacks specificity as a
result of cross-reactivity with other nematode antigens. The serological test is
not generally available and it is of limited benefit in early diagnosis.
4. Histological examination
To demonstrate the Y-shaped lateral epidermal cords on cross section of the
worm (Fig. 10.23b).
Treatment
The preferred treatment is the extraction of the worm via endoscopy. Larvae do not
respond to anthelmintics. In cases of surgical complications, laparotomy or bowel
resection may have to be performed.

Prevention and Control
1. Proper cooking of marine fish
2. Freezing of marine fish
(Salting and marinating will not kill the parasites)