Eslami et al.: Infection of Anisakids Larvae in Long Tail Tuna… Introduction Aseveral species of marine fish nisakis larvae were reported from throughout the world. The adult worms live in the intestine of marine mam- mals and fish. The small 3rd stage larvae are found encapsulated or free in abdominal cavity and other organs. The larvae will mi- grate to abdominal muscle if the fish are not quickly eviscerated. Consumption of raw, salted, smoked, fermented or undercooked fish could produces human anisakiasis. Although 3rd stage larvae have been reported from several species of fish from south Cas- pian Sea(1-3), north Persian Gulf (4-6) and from abdominal cavity muscles of tuna fish (Euthynus sp.) from Persian Gulf and pike- perch (Lucioperca lucioperca) from Caspian Sea (5), no human anisakiasis is yet re- ported from Iran. Since the first case report in the Netherland in 1960(7), several cases have been reported throughout 27 countries including Japan until 1998 (8). In Japan, the annual incidence has been estimated as 2000-3000 (9). The induced clinical symp- toms are due to physical effects of larval in- vasion into the mucosa of stomach or be- cause of hypersensitivity to the larval secre- tions (10). The aim of this paper was to study the preva- lence and intensity of anisakids larvae in the long tail tuna fish captured from Iranian shores of Persian Gulf. Materials and Methods One hundred long tail tuna fish (Thannus tonggol) caught from waters of north parts of Persian Gulf were purchased from local fish market in Bandar -Abbas in Hormozgan 97 Province, south of Iran, and examined for the presence of anisakid nematodes. The fish were examined within 24 hours of being caught. Each fish was eviscerated and ab- dominal cavity and different viscera were washed under running water into a 100 mesh sieve to remove adhering larvae. Then skin, abdominal cavity, stomach sub serous tis- sues, the contents of stomach and intestine and sliced livers, spleens and gonads were searched for anisakids larvae through naked eyes and under dissecting microscope. Meanwhile, 20 grams of muscles taken from around the body cavity of each fish were di- gested in artificial gastric juice and exam- ined under dissecting microscope. All col- lected larvae were preserved in 70% alcohol containing 5% glycerin and cleared in lacto- phenol for identification using Chai et al. key (11). Results Eighty nine percent of examined fish har- bored anisakids larvae in different organs, the results of which are summarized in Table 1. A total 367 larvae were collected from in- fected fish. The data in Table 1 would indi- cate that stomach sub serous tissues (Fig. 1) were the most and intestine the least infected organs. The high rate of prevalence and low intensity may indicate that the anisakids lar- vae are dispersed within their hosts. Mean- while two fish (2%) harbored a low number of Raphidascaris sp. (ranged 1-2) in the in- testine and Anisakis sp. in body cavity. No larva was found in the digested muscles.