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Abstract
The present study was carried out on 280 infected freshwater fish (176 O.niloticus, 56 C.gariepinus, 32 C.carpio and 16 M.cephalus) in addition to representative water and ration samples collected from 11 private farms at different localities in Kafr El-Sheikh governorate and at different seasons examined mycologically, pond water temperature, pH value, Total Bacterial Count (T.B.C.) and Total Coliform Count (T.C.C.) were detected, the results revealed that
A total of 2040 mycotic isolates were recovered from the examined fish.
The isolated fungi belonged to 10 genra: Aspergillus, Paecilomyces, Fusarium, Ichthyophonus, Aphanomyces, Alternaria, Cladosporium, Helminthosporium, Nigerospora and Geotrichum moreover 4 genra of yeasts are Rhodoterulla, Candida , Cryptococcus and Torulopsis beside to the unidentified yeast.
The percentage of systemic mycotic infection was 89.61 %of O.niloticus, 87.76% of C.gariepinus, 89.28% of C.carpio and 100% of M.cephalus .
The percentage of mould isolates were 49.01%,75.44%,16.67% and 47.06% while the yeast isolates percentage were 50.99%,24.56%,83.33%and 53.94% from O.niloticus, C.gariepinus, C.carpio and M.cephalus respectively.
The identified moulds were Aspergillus niger (14.86,20.93,20 and 50%), A.flavus (9.46,13.95,20 and 0%), A.terreus (16.22,4.65,20and0%), A. fumigatus(1.35,11.64.20and0%),A.parasiticus(2.7,0.0,20and0%), Paecilomyces sp. (6.76, 4.65,0.0 and 0%), Fusarium sp. (13.51, 11.63 ,0 and 37.5%), Ichthyophonus sp (2.7, 13.95,0.0 and 0%), Aphanomyces sp. (6.76, 2.33,0 and0%), Alternaria sp (6.76, 9.3 ,0 and 0%), Cladosporium sp. (10.81, 4.65 ,0 and 0%), Helminthosporium sp.,(1.35, 4.65 ,0 and 0%), Nigrospora sp.(1.35, 4.65 ,0 and 0%) and Geotrichum sp. (5.41, 9.3 ,0 and 10%)from O.niloticus, C.gariepinus, C.carpio and M.cephalus respectively.
The identified yeast isolates were, Rhodoterulla sp. (18.18,14.29,28 and 22.22%) , Candida sp. (3.89,7.14,4 and 0%), Cryptococcus sp. (2.59,21.43,32 and 0%) and Torulopsis sp.(10.38,0,4 and 0%) from O.niloticus, C.gariepinus, C.carpio and M.cephalus respectively.
The most favorable season for systemic fungi isolation was spring followed by fall, summer and winter .spring was the most favorable season for fungi isolation from all examined fish species except for O.niloticus fall was the most favorable season.
Intestine ,gills, liver, heart, kidneys and spleen were the predominant organs for isolation of (A.niger, A.terreus, Paecilomyces and Ichthyophonus species),(A.flavus and Geotrichum species),( Fusarium and unidentified yeasts species),(Aphanomyces species),( Helminthoporium and Cryptococcus species) and Nigrospora species respectively.
Kidneys (32 isolates), intestines (80 isolates), liver (72 isolates) and kidneys (112 isolates) were the most mycologically affected organs during winter, spring, summer and fall respectively from Oreochromis niloticus while kidneys (16 isolates ), intestines (72 isolates ) and gills (24 isolates )were the target organs for fungal isolation during winter, spring and summer seasons respectively from Clarias gariepinus moreover Liver and spleen (16 isolates), liver and spleen (32 isolates) and kidneys (16 isolates) were the most mycologically affected organs from Cyprinus carpio during winter, spring and summer respectively in addition kidneys (16 isolates) and liver with kidneys (16 isolates) were the most mycologically affected organs during spring and summer respectively in naturally systemic mycologically affected Mugil cephalus.
A.flavus, A.niger, A.terreus, unidentified yeasts and Rhodoterulla sp. were isolated from both representative pond water and ration samples but A.parasiticus and Fusarium sp.were isolated only from water samples and A.fumigatus, Candida sp. and Cryptococcus sp. was isolated only from ration samples of examined fish farms.
Pond water temperature ranged from 10-35oc while pH value ranged from 6.9-8.6.
T.B.C. ranged from 3.5 x104 -9 x105 cfu / ml and T.C.C. ranged from
10 - 4x103cfu/100ml.
The pathogenicity test carried out on 97 apparently healthy O.niloticus
60+5 g/fish were infected orally with 0.2 ml of spores suspension of 2.3 x105 and 1.4 x107 of A.terreus and Paecilomyces sp. respectively and fed on commercial ration contaminated by the corresponding mould and resulted in 6.66% and 30% mortalities respectively.
The effect of Aspergillus terreus and Paecilomyces species on the immunity of experimentally infected fish against virulent strain of A.hyDROPhila after vaccination by I/M injection with A.hyDROPhila bacterin revealed to
Decreasing in the total serum protein, serum albumin, serum globulin, RLP and the antibody titer moreover increasing the A/G ratio were the characteristic picture in both of vaccinated Aspergillus terreus and Paecilomyces sp.
The histapathological finding of experimentally infected O.niloticus with A.terreus and Paecilomyes sp.revealed to sever pathological changes in all of the examined tissues and the fine fungal hyphae for both moulds were detected in all of the examined tissues but no granulomatus reaction were detected in any examined tissues for both of the examined strains.