In this study, histopathology of tissues of different cultured fishes (Cyprinus carpio, Clarias gariepinus, Oreochromis aureus, Sarotherodon galilaeus and Tilapia zillii) due to different helminthes had been investigated. Obviously, the
direct effect of helminth parasites mainly depend on their attachment organs.Herein, helminthes belong to monogenean, digenean, cestode, nematode and acanthocephalan parasites, were identified as Cichlidogyrus halli typicus,
Dactylogyrus afrobarbae, Orientocreadium batrachoides, Polyonchobothrium clarias, Paracamallanus cyathopharynx, Procamallanus laevichonchus and Acanthosentis tilapiae respectively. Severe damage occurred to the gill tissue
due to the monogeneans opithohaptor. Limited lesions to the infected tissue of the fish host due to the nematodes were induced at the attachment site by the parasite buccal capsule. Deep penetration of intestinal tissue of the fish infested
with the cestode Polyonchobothrium clarias was occurred due to the parasitic scolex. The digenean Orientocreadium batrachoides induced damage by its sucker at the attachment site to the infected epithelia of the host tissue as well.
The acanthocephalan parasite Acanthosentis tilapiae caused severe rupture of the infected tissue by its proboscis hooks at the attachment site. Moreover, it may lead to complete decompose to intestinal tissue of the host. It is worthy to
conclude that, in cases of the intense infestation negative impact of the parasite become more dangerous.