Abstract
The third larval stage (L3) of Anisakis simplex (Anisakidae) is one of the zoonotic parasitic nematodes in the musculature and visceral organs of marine fishes belonging to family Moronidae. The consumption of these high-commercial-value fish is widespread in many countries around the Mediterranean Sea including Egypt. The presence of these larvae in fish muscles poses a potential consumer hazard due to the parasite's ability to cause anisakidosis. Forty-two out of 60 (70 %) of the European seabass Dicentrarchus labrax were found to be naturally infected by L3 of A. simplex in the form of encapsulated juveniles in the fish musculature. Morphological examination of recovered parasites by light and scanning electron microscopy showed that, in general, all specimens examined closely resembled A. simplex (L3). To evaluate the allergenicity of this nematode, white blood cell count; levels of T helper 1 (Th1) [interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha)], Th2 [IL-4, IL-5, and IL-6], and Th17 [IL-17] related cytokines; total IgE and IgG antibodies; and nitric oxide (NO) were measured in the plasma of Wistar rats sensitized by oral inoculation with fresh, frozen, and heat-treated A. simplex L3 or rats intraperitoneally injected with L3 crude extract. Rats sensitized with fresh and frozen L3 larvae produced significantly higher levels of IFN-gamma, IL-5, IL-17, and total IgE as compared to control rats. Heat-treated larvae administration resulted in a significant rise of IFN-gamma, TNF-alpha, IL-5, and total IgE in comparison to control rats. Intraperitoneal sensitizations enhanced release of IFN-gamma, TNF-alpha, and total IgE. Oral sensitization led to a significant production of NO. Thereby, frozen or cooked larval L3 cannot inhibit the release of Th-related cytokines and IgE, which might impact on the overall anti-parasitic immunity.