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Abstract
The Icthyophonosis is a dangerous disease, the consequences of which are difficult to assess for wild populations of fish. Icthyophoniasis considered as a cosmopolitan systemic granulomatus fungal disease of economic significance because epizootics have resulted in mass mortalities among a wide range of freshwater and marine fishes and distributed all over the world. therefore, it can contract Icthyophonus, and post-smolts are the most vulnerable link in this chain.
This study aimed to throw the light on the importance of I. hoferi on fresh water fish, its dangerious effect in addition to its identification and its characterization also, its isolation.
This study was carried-out on a total number of 500 Oreochromis niloticus (400 cultured and 100 wild fish) collected from different localities at Alexandria, Kafr El-Shiekh and El-Behaira. The fish were obtained from their natural sources. The samples were collected during the period from June 2007 to May 2008. The body weight of the obtained fish was ranged from 30-100 g. The fish collected from fish farms were transported alive in polyethylene bags that contained about 30%’ of its volume fish and water and the remaining volume pumped with oxygen, then sealed in a manner preventing escape of Oxygen. While the freshly dead fish were labelled and packed in a clean plastic bags put in an ice boxer and carried to the laboratory at Faculty of Vet, Med, Alexandria University. The live fish were kept in glass aquaria contained dechlorinated tap water and supplied with sufficient aerator and kept until the time of investigations. The dead fish were examined rapidly as soon as possible as they arrived to the Wetlab.
1) The experimental fish used :
A total number of 125 apparently healthy O. niloticus fish, with an average body weight
45 ± 5g, were obtained alive from (private fish farm) and transported in large tanks to the laboratory. Then kept in well prepared glass aquaria. Random sample of 5 fish were sacrificed, examined mycologically and their organs proved to be I. hoferi free. The remaining fish were grouped in aquaria and left for 7days before experiment for acclimatization .
The main immunosuppressant agent include: A synthetic corticosteroid, triamcinolone acetonide suspension (Kenacort-A)R, (Bristol-Myers Squibb Egypt Company), was used as immunosuppressant .
The characterization of I. hoferi depend on: Clinical symptoms that appeared on the fish, cultural characters on the laboratory media differential leucocytic count, PCV, Hb % , enzymatic assay, calculation of Phagocytic activity and index as well as the protein characterization..
2) The main results obtained include :
The most important symptoms showed on naturally infected Oreochromis niloticus with Ich. Hoferi shoeing deformity of vertebral column, deformities in constricted area of caudal peduncle . darkening in color, sandpaper appearance of skin, poor appetite listlessness.
The young culture of Ich. Hoferi on SDA t 10% bovin serum showing Rupture of multinucleated bodies and release of spores through extra material discharge after 9 days.but the, culture of Ich. hoferi on MEM. 10 at PH 7.0 showed hyphae with different sizes and formation of multinucleated bodies after 8 days, localization and fixation of multinucleated bodies (ameaboblast) at the end of each hyphae with rupture of some ameoboblasts, PH 3.5 showing starting of hyphal growth after 5 hours post culturing the hyphae produce many branches, extending of the hyphae to grow and increase in length after 24 hours, migration of cytoplasm to the apex of hypae after 3 days, Rounding up of the apixs of the hyphae after 7 days, finally all the hyphae rounding up to form sphericae hyphae terminal bodies after 10 days .
3) The hematological examination indicated that :
The Icth. Hoferi causes non- significant effect on differential leucocytic counts in the first period of infection and there is no effect between the treated and non-treated group on the differential leucocytic counts, but after injection of cortisone with Icth. hoferi the lymphocytic values is gradually decreased .
Also, the Monocytes and neutrophils values were lower in case of oral intubation of Icth. hoferi spores with cortisone .
The total white blood cells (WBCs%), total Red blood cells (RBSc%), hemoglobin (Hb gm %) and packed cell volume (PCV%) of Oreochromis niloticus infected with spores of Ich. hoferi showed that the WBCs values of experimental infection of Ich. hoferi spores by oral intubation accompanied with cortisone and pH at pH 7 had lowest values compared with other method of experimental groups .
Also, the RBCs and PCV values were lowest in gill sacrificate injected cortisone groups allover the period of experiment . The phagocyte activity (PA) and phagocytic index (PI) in Oreochromis niloticus experimentally infected by different means used of spores Icth. hoferi for 4th weeks after infection . Showed that both PA and PI ranked in the lowest values when cortisone is injected in all methods of experimental infections . The mean values of PA and PI were decreased gradually by increase the period of exposure in all treated groups compared with control one (without cortisone) . The liver function enzymes Serum Aspartate aminotransferase (SAST) and serum alanine aminotransferase (SALT) as well as glucose in Oreochromis niloticus experimentally infected with spores of Ich. hoferi by different means along 4th weeks after infection are presented showed that the main enzymes were increased in mean values in all experimental groups by increase the period of experimental infection in both with cortisone and without cortisone injection .