Gnathostomatoidea Nematode: Parasite of Sillago sihama Forsskal, 1775, Sillaginidae, and Argyrops spinifer Forsskal, 1775, King soldier bream, in the Iraqi Marine Water Fishes, with Notes on Clinical Pathology and Feeding Habits of Infection

Background: The present finding describes third-stage larvae (L3) nematode (Gnathostomatidae) cysts parasitizing the intestinal serosa of the digestive tract of Sillago sihama (Forsskal, 1775) and Argyrops spinifer (Forsskal, 1775, King soldier bream) fishes collected from the Arabian Gulf. Objective: Two species of Gnathostomatidae are recorded, Gnathostoma sp and Gnathostoma binucleatum Almeyda-Artigas, 1991. The gross clinical pathology examination showed extensive damage to the host intestinal tissue, including epithelial necrosis, hemorrhaging, worm encapsulation, and the presence of live larvae encysted and adult in skeletal muscles of fishes causing lesions including mild hyperplasia of fibrous connective tissue around the parasite. The cross examination of fish intestines revealed food items containing parts of the animal body, appendages, Chela, and parts of the carapace of crustaceans. Most food items found in all months also including annelids (polychaetes) in high percentage in November Volume of food items were related to fish size. Juveniles appear to feed mainly on crustaceans and the adults mainly feed on crustaceans, molluscs, polychaetes, echinoderms, and teleosts, among other items. The summer was apparently not the season of parasite infection. The prevalence of infection with Gnathostoma binucleatum was low (6 of 57 fish), whereas the prevalence of infection with Gnathostoma sp. was 3 of 57 fish. These findings of Gnathostomatids represent new records of these parasites in Arabian Gulf fishes. More study needed to recognize on the larval stage parasite infection and their clinic pathology to provide a basic understanding of the general principles of the pathogenesis and pathology of Gnathostomiasis, and the relationship between fish length, food items and infection.