الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 235 |  |  |
| | | from | 235 | | |
Abstract
The present investigation was carried out to clarify the following points:
prevalence of different parasites infecting some freshwater fish at Qena governorate including seasonal and monthly dynamics of the infection Morphological description of the recovered parasites.Egypt’s aquaculture production is by far the largest of any African country and places it 11th in terms of global production. The aquaculture sector makes a significant contribution to income, employment creation and food security in the country, all of which are national priority areas given low per capita income levels, rising population, worsening food security indicators, and official unemployment levels which have remained at around 10% for the last ten years (Macfadyen, et al. 2011).Fish is a good source of high quantity animal protein, minerals, vitamins particularly vitamin A and D from fatty fish species as well as thiamine (B1), riboflavin (B2) and niacin important for human health and growth, worldwide.
Furthermore, fish is important to man as a good source of protein in man’s diet and as a vector of some human disease pathogens. One of the scientific importances of identifying a fish properly is to tell to some reliable extent the health condition of the fish, and certain parasitic infections present with some symptoms that bear on the external treatment of the fish. All species of fish are vulnerable to various parasitic infections depending on the species of fish and the type of stream inhabitedHowever, fish like any other animals could be infected by several kinds of pathogens including parasitic one, about 80% of fish diseases are parasitic especially in warm water fish (Eissa, 2002Fish parasitology is an important field in aquatic sciences as fish parasites are a group of organisms that often produce disease condition in fish thereby increasing their susceptibility to other diseases, causing nutritive devaluation of fish and fish loss.
Fish parasites and diseases constitute one of the most important problems confronting the fishery biologist today( Ravichandran et al. 2007). Pathological conditions resulting from parasites and diseases assume high magnitude of epidemics under crowded and other unnatural conditions (Ravichandran et al., 2010).The need to assess the parasitic infection arises because the fish suffering from parasitic infections resulted into severe damage to fisheries industry and for successful prevention and elimination of such infections, it is extremely important to achieve early and correct diagnosis (Ahmed, 1994).
The major parasitic groups found in freshwater fishes are helminthes (trematodes, cestodes, nematodes and acanthocephalans), protozoan, hirudineans and crustaceans (Tonguthai, 1997; Schmidt and Roberts, 2004).Gut helminthes, such as trematodes, cestodes, nematodes don’t induce severe damage to the vertebrate gastrointestinal tract (Dezfuli, et. al, 2003), unless they are found in large numbers, when they induce growth retardation (Tonguthai, 1997) or mechanical blockage at the gut lumen. However, some acanthocephalan genera penetrate thorough the intestinal wall and provoideextensive damage to the gastrointestinal tract (Dezfuli, et. al, 1998, 2002). Additionally, the larval stages of some trematodes (metacercariae) infect gills and may disrupt the respiration leading to high mortalities (Tonguthai, 1997).Although nematodes may be important pathogens of fish, of greater concern is usually their roles in transmitting parasites to man, who become accidental hosts. The most common of these fish-born zoonotic diseases is anisakiasis, caused by larval Anisakid nematodes that cause invasive gastrointestinal anisakiasis in human (Lymbery and Cheah, 2007Parasitic infections, especially ectoparasites from monogenetic flukes and protozoa are the most dangerous groups affecting skin and gills that induces slimness of the skin, irritation, destruction of gills, anorexia and impaired breathing (Lom, 1995). The synergistic action of the parasites may cause mortalities (Osman, 2001).Monogeneans are mostly ectoparasitic helminthes with direct life cycle and they are typically parasitize the gills and skin of fish; have a series of hooks that attach to the fish causing irritation, excessive mucus production (Reed et al.2003) and are generally host specific (Buchmann and Bresciani, 2006Parasitic crustaceans are invariably ectoparasitic on fish and have a direct life cycle, often with a considerable period of time spent off the host. Parasiticstages are usually blood feeders on gills, skin or fins of the host and in large numbers can have serious pathogenic effects (Lester and Hayward, 2006).Moreover, parasites may also regulate host population dynamics; their resistance to other stress factors; susceptibility to predation and influence community structure (Woo, 1995)