A total of 100Tilapiafish samples were collected from brackish water (n=50) and fresh water (n=50) resources, Northern Egypt, and examined for heterophyid encysted metacercariae (EMC) during the period from August 2007 to July 2008. The overall prevalence of infection was 32%;
22 % for brackish water fish and 42% for fresh water fish. Significant differences in parasite occurrence among body regions were found, with muscles of the tail and caudal third being highly affected (93.4%) followed by middle third and anterior third (75%), while the head region had the lowest infection (21.9%). The prevalence was highest in summer season (46.4%) followed by spring (37.5%) and autumn (27.3%), and was lowest in winter (15.4%). The prevalence of infection decreased as fish size increased. Adult heterophyids, Heterophyes heterophyes, Heterophyes aequalis, Pygidiopsis genata, Haplorchis yokogawai, and Ascocotyle (Phagicola) ascolonga were recovered from EMC-feed puppies. Eggs of heterophyid type were detected in 10 out of 75 human stool specimens from local residents. An association exists between being a female (odd ratio [OR] 1.59 and 95% confidence interval [CI] 0.42–6.04), a fisherman (OR 1.39 [95% CI 0.26–7.48]), a housewife (OR 1.24 [95% CI 0.29–6.28]), 15–45 years old (OR 2.22 [95% CI 0.58–8.53]), or aged 5–14 years (OR 1.29 [95% CI 0.30– 5.58]) and heterophyid infection. Measures should be implemented to reduce the risk of transmission of heterophyids to human and fish-eating animals.