The first record of Ascocotyle (Phagicola) longa (Digenea: Heterophyidae) metacercariae as the fish-borne zoonotic trematode in Chelon auratus and Chelon saliens (Pisces: Mugilidae) around the cage culture in the Caspian Sea, Iran.

As a matter of fact, there has not been any reportage of the parasite of Ascocotyle (Phagicola) longa Ransom, 1920 from the Caspian Sea, Iran. During two years, April 2017 until 2018, 158 specimens of mullet fish, Chelon auratus and Chelon saliens (Risso, 1810) were collected and carefully examined considering the standard parasitological methods. Interestingly, the metacercaria was found in the stomach and intestine of the mullets. Morphological and morphometric analyses indicated that this parasite species belongs to Ascoctyle (Phagicola) longa. Overall infection mean intensity (52.1±128.3), mean abundance (14.8±71.9) and prevalence (28.5%) were calculated in mullets. Differences in the infection level of Ascocotyle (Phagicola) longa in relation to fish species, location and sampling years are determined and discussed. So that the mean intensity of this parasite is significantly different in the two locations of Anzali and Kiashahr (X2=13.35, df=1, p=0.00<0.05) and the mean intensity between mullet species (X2=5.49, df=1, p=0.019<0.05) is significantly different. In fact, A. (Phagicola) longa is a widespread and rife fishborne zoonotic parasite and also one of the most notable agents of human heterophyosis observed in the Caspian Sea.