Pathogenic Potential of Fresh, Frozen, and Thermally Treated Anisakis spp. Type II (L3) (Nematoda: Anisakidae) after Oral Inoculation into Wistar Rats: A Histopathological Study

The third-stage (L3) larvae of Anisakis are the etiological agents of human anisakiasis caused by consumption of raw or undercooked seafood infected with anisakid nematodes. Infection with these worms is associated with abdominal pain, nausea, and diarrhea and can lead to massive infiltration of eosinophils and the formation of granulomas in the gastrointestinal tract if the larvae are not removed. Food allergy affects populations worldwide, and despite several reports on the presence of the potentially zoonotic nematodes among edible fishes in Egypt, there are few immunological and molecular studies investigating the epidemiology of these parasites. Anisakidosis, a human infection with nematodes of the family Anisakidae, is caused most commonly by Anisakis spp. In the present study, seventy specimens of the European seabass Dicentrarchus labrax commercialized in Alexandria city along the Mediterranean Sea were acquired during the period from July to December, 2015. Fish were necropsied and dissected to investigate the presence of nematode larvae. Thirty fish (42.9%) of the total were parasitized by nematode larvae which were morphologically identified as Anisakis spp. Type II (L3) according to light and scanning electron microscopy. The pathogenic potential of oral inoculation of fresh, frozen, and thermally treated larvae into Wistar rats was elucidated by histological examination of their thymus and spleen. Results obtained indicated that neither cooling nor freezing of the parasite could destroy their allergenic capacity. So, it is important to create a wider awareness of this potential risk to human health. It is becoming increasingly likely that the impact of Anisakis spp. on human health has been underestimated, and it is perhaps time to consider more sweeping measures than those currently enforced to protect the public health.