Studies on the Prevailing Parasitic Diseases in Some Marine Fishes

Abstract

This study has been applied on 200 marine fish (100 Dicentrarchus labrax and 100 Scomberomorus commerson) that randomly collected from Ismailia Provinces. No pathognomonic clinical abnormalities were recorded, however some infested fish showed hemorrhagic areas on gill cover, abdomen and on the bases of fins with presence of one or more isopoda with excessive mucus secretions. The postmortem findings were Marbling of the gills with excessive mucus secretion, sticking of the gill tips and greyish coloration. In some cases, liver was pale with peticheal haemorrhage, Stomach and intestine showed congestion, enlargement, thickening and inflammation of their walls. The total prevalence of parasitic infestation among examined fishes was 59%. The highest percentage was in Scomberomorous commerson (88%) followed by D. labrax (29%). The identified parasites were monogenetic trematodes (55%), Acanthocephalan (1.5%),) and Nematodes (3% (.The total seasonal prevalence of the detected parasites was the highest in summer (66%) and the lowest in autumn (48%). The relationship between length and parasitic prevalence was recorded. Molecular detection of Diplectanidae family using conventional PCR technique was evaluated using a DNA mixture prepared from the target pathogens. It was conducted using two universal primers for Trematode (ITS-2), which yielded amplification products of 539 bp. As expected, a PCR product of predicted size (539 bp) was generated in all examined samples and was finally identified as Diplectanum species. Histopathological changes of the naturally infestedfish with various parasites were recorded.