Organ Abdominal cavity Stomach sub serous tissues Intestinal contents Stomach contents Liver Spleen Testicles Infected (No.) 10 80 1 2 4 2 3 Fig. 1: 3rd stage larvae of Anisakis spp. on the viscera of tuna fish (Authors preparation) 1-42 1-5 1 2-6 2-6 1-5 1-10 Mean No. lar- vae 8 3 1 4 4 3 5 Iranian J Parasitol: Vol. 6, No.3, 2011, pp.96-100 Table 1: Prevalence and intensity of Anisakis sp. in 100 long tail tuna fish from north Persian Gulf, Iran Infected (%) Range Discussion Since anisakids are not host specific at the larval stage, they may be found in a wide range of different available host species, and this may result in a high probability of trans- mission (12, 13). In Iran, several species of fish from Caspian Sea (1, 2, 3, 5) and Per- sian Gulf (5, 6, 14) as well as lagoons of Khuzestan (4) have been reported to be in- fected with Anisakis sp. It seems likely that Anisakis is prevalent among tuna fish in the world (15).The prevalence rate of anisakiasis in long tail tuna fish in the present study was very high (89%), and the highest rate reported from fish in Iran. Meanwhile it is in harmony with other species of tuna fish, e.g. Euthynus sp. (79%) (5), other species of fish of Persian Gulf e.g. Epinephlus tauvina (14), other workers on tropical fish, (67-100 %) (16), and Norwegian herring (17) (98-100%). Low intensity of anisakiasis in this study and 10 80 1 2 4 2 3 98