الفهرس 
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Abstract
This research aims to investigate role of some stressful ecological factors on cultured Nile tilapias in relation to parasitic diseases. The present study was carried on 486 of tilapia species (represented as 154 Oreochromis niloticus, 128 Oreochromis aureus, 86 Tilapia zillii and 118 Sarotherodon galilaeus) with different body weights. Also, studying some physicochemical parameters of water samples which had been taken from El- Abbassa fish production farm supplied from Ismailia canal seasonally.
The results are summarized as follow:
1- Water analysis:
• Dissolved oxygen showed the lowest concentration was 5.5±0.2 in summer, while the highest concentration was 7.4±0.4 mg/l in winter
• Secchi disk visibility recorded the lowest reading was 13.7±1.8 in summer, while the highest reading was 20.6±2.1cm in winter
• pH ranged between 8.7±0.3 in (spring and summer) and 9.1±0.4 in (autumn and winter).
• Salinity showed no significant differences for its values between the month’s samples collected in different seasons.
• Total ammonia concentrations ranged from 0.54±0.02 in autumn and 1.11±0.02 mg/l in summer. Un-ionized ammonia ranged from 0.13±0.01 in winter and 0.27±0.04 mg/l in summer.
• Nitrite concentrations ranged between 0.016±0.002 in spring and 0.033±0.002mg/l in winter. Nitrate concentrations were ranged between 0.24±0.02 in autumn and 0.64±0.03 mg/l in spring.
• Water temperature, Total hardness and Total alkalinity concentrations showed significant differences among the seasonally samples.
2- The clinical signs revealed no pathgnomic clinical abnormalities. Some infected tilapia species showed abdominal distension, hemorrhagic areas on base of abdomen and base of dorsal fins, attached external parasite (Lernaea elegans) at the gill cover, slightly unilateral exophthalmia, unilateral atrophy, whitish cloudiness and small white dots in eye.
3- The postmortem findings revealed enlargement, paleness and congestion in liver with presence of visible yellow pea-like encysted metacercariae in branchial cavity , paleness in gills with attached crustacean parasites (Lamproglena monodi) and there were congested and pale kidney with grayish encysted metacercariae varying in size.
4- The total prevalence of parasitic infection among examined tilapia species was 61.5%. The highest prevalence was found in Oreochromis aureus (69.5%) followed by O. niloticus (67.5%) then Sarotherodon galilaeus (58.5%) and Tilapia zillii (43%).
5- The identified parasites were Protozoa (Chilodonella hexasticha), Monogeneatic trematodes (cichlidogyrus tilapiae), Digenetic trematodes (Metacercaria (Diplostomum tilapiae, D. spathacaum, Clinostomum tilapiae, Euclinostomum heterostomum, Centrocestus formosanus, Haplorichis sp, Heterphyes sp, Opisthorchis felineus, Prohemostomum vivax, Unidentified metcercaria), Adult (Eumasenia egypticus)), Acanthocephala (Acanthosentis tilapiae) and Crustacea (Lernaea elegans and Lamproglena monodi).
6- The total Prevalence of protozoa infection among examined tilapia species was 1.6%. The highest prevalence was 4.7% in T. zillii and the lowest was 0% in O. niloticus.
7- The total prevalence of monogenetic trematodes was 10.7%. The highest prevalence was 12.9% in O. niloticus and the lowest was 5.8% in T. zillii.
8- The total prevalence of adult trematodes was 1.2%. The highest prevalence was 2.6% in O. niloticus and the lowest was 0% in T. zillii and S. galilee. The total prevalence of E.M.C. was 26.5%, the peak prevalence was in musculature followed by kidney in O. niloticus and T. zillii, while the peak prevalence was in kidneys followed by musculature in O. aureus and S. galilaeus
9- The total prevalence of acanthocephalans was 15.4% as it was the highest in O. niloticus (20.1%) and the lowest in T. zillii (5.8%).
10- The total prevalence of crustaceans was 5.9%. It the highest in O. niloticus (7.1%) and the lowest in S. galilaeus 5.9%.
11- The seasonal prevalence of parasitic infection in O. niloticus and O. aureus was the highest in summer (80.5, 83.3%) the lowest in autumn (56.8, 62.5%) respectively. While in T. zillii was the highest in winter (60%) and lowest in spring (5%). In S. galilaeus was the highest in spring (62.2%) and lowest in autumn (55.2%).
12- The seasonal prevalence of parasitic infection among examined tilapia species in relation to physicochemical water parameters, in spring, the most prevalent parasites were Diplostomum tilapiae, Euclinostomum heterostomum and Acanthosentis tilapiae, while, there were no protozoa and crustacean parasites. Mean physicochemical water parameters, Temp. 23.23 oC, DO 6.3mg/l, SD 16.3cm, pH 8.7, salinity 0.27‰, TAN 0.8, UIA 0.16, NO2 0.016, NO3 0.64, T.H 163.3 and T.A 337 mg/l. In summer, the most prevalent parasites were Cichlidogyrus tilapiae, Euclinostomum heterostomum, Acanthosentis tilapiae and crustacean parasites with no protozoa. Mean physicochemical water parameters, Temp. 27.8 oC, DO 5.5mg/l, SD 13.7cm, pH 8.7, salinity 0.23‰, TAN 1.1, UIA 0.27, NO2 0.022, NO3 0.51, T.H 197.3 and T.A 380 mg/l. In autumn, the most prevalent parasites were Diplostomum tilapiae, Clinostomum tilapiae, Euclinostomum heterostomum, Centrocestus formosanus, Heterphyes sp and Acanthosentis tilapiae with no protozoa and monogenea. Mean physicochemical water parameters, Temp. 22.3 oC, DO 6.5mg/l, SD 15.3cm, pH 9.1, salinity 0.23‰, TAN 0.5, UIA 0.18, NO2 0.030, NO3 0.24, T.H 240 and T.A 355 mg/l. In winter, the most prevalent parasites were Chilodonella hexasticha, Diplostomum tilapiae, D. spathacaum, Centrocestus formosanus, Haplorichis sp, Heterphyes sp and Acanthosentis tilapiae. Mean physicochemical water parameters, Temp. 15.9 oC, DO 7.4mg/l, SD 20.6cm, pH 9.1, salinity 0.27‰, TAN 0.56, UIA 0.14, NO2 0.033, NO3 0.26, T.H 253.3 and T.A 306 mg/l.
13- Seasonal prevalence of parasitic infection in O. niloticus, in spring, the highest prevalence was 29.3% for Acanthosentis tilapiae and the lowest was 0% for Chilodonella hexasticha and crustacean parasites. In summer, the highest prevalence was 34.1% for Cichlidogyrus tilapiae and the lowest was 0% for adult (Eumasenia egypticus). In autumn, the highest prevalence was 9.1, 20.5% for Euclinostomum heterostomum and Acanthosentis tilapiae and the lowest was 0% for Cichlidogyrus tilapiae, Haplorichis sp and Prohemostomum vivax. In winter, the highest prevalence was 14.3% for Diplostomum tilapiae and the lowest was 0% for fluke and Lernaea elegans.
14- Seasonal prevalence of parasitic infection in O. aureus, in spring, the highest prevalence was 31.3% for Acanthosentis tilapiae and the lowest was 0% for Chilodonella hexasticha, Haplorichis sp, Opisthorchis felineus, Eumasenia egypticus, Lernaea elegans and Lamproglena monodi. In summer, the highest prevalence was 27.8% for Cichlidogyrus tilapiae and the lowest was 0% for Chilodonella hexasticha, Clinostomum tilapiae Haplorichis sp, Opisthorchis felineus and Eumasenia egypticus. In autumn, the highest prevalence was 9.4, 12.5% for Euclinostomum heterostomum and Diplostomum tilapiae. The lowest was 0% for Chilodonella hexasticha, Clinostomum tilapiae and Lernaea elegans. In winter, the highest prevalence was 17.9%for Acanthosentis tilapiae and the lowest was 0% for Clinostomum tilapiae, Prohemostomum vivax, Eumasenia egypticus and Lernaea elegans.
15- Seasonal prevalence of parasitic infection in Tilapia zillii, in spring, the highest prevalence was 5% for Acanthosentis tilapiae and the lowest was 0% for all isolated parasites. In summer, the highest prevalence was 18.8%for Cichlidogyrus tilapiae and Lamproglena monodi. In autumn, the highest prevalence was 13.3% for Euclinostomum heterostomum. In winter the highest prevalence was 20% for Chilodonella hexasticha.
16- Seasonal prevalence of parasitic infection in S. galilee, in spring, the highest prevalence was 24.3% for Acanthosentis tilapiae, The lowest was 0% for Chilodonella hexasticha, Diplostomum spathacaum, Clinostomum tilapiae, Haplorichis sp, Opisthorchis felineus, Eumasenia egypticus (in all seasons) , Lernaea elegans (in all seasons) and Lamproglena monodi. In summer, the highest prevalence was 15.4% for Cichlidogyrus tilapiae and Acanthosentis tilapiae. In autumn, the highest prevalence was 6.9% for Diplostomum tilapiae and Euclinostomum heterostomum. In winter, the highest prevalence was 11.5% for Chilodonella hexasticha, Cichlidogyrus tilapiae and Diplostomum tilapiae.
17- A significant reduction of infected O. niloticus, O. aureus, Tilapia zillii and S. galilee than non infected in haemoglobin g/l, RBCs 106µL-1, Hamatocrit %, total plasma protein mg/dl and albumin mg/dl, a significant increase of infected than non infected in WBCs 103µL-1, blood glucose mg/l, aspartate aminotransferase (AST) U/l and alanine aminotransferase (ALT) U/l and no significant difference in total bilirobin, creatinine and uric acid mg/dl between infected and non infected O. niloticus in summer, followed by spring then winter and autumn .
18- Chilodonella hexasticha cause significant reduction of haemoglobin g/l, RBCs 106µL-1, Hamatocrit % and albumin mg/dl in infected Tilapia zillii than infected S. galilee except total plasma protein mg/dl in infected S. galilee. Significant increase of WBCs 103µL-1 in infected S. galilee, blood glucose, AST, ALT, creatinine and uric acid in infected Tilapia zillii. No significant difference in total bilirobin.
19- Cichlidogyrus tilapiae cause significant reduction of haemoglobin g/l, albumin mg/dl in infected O. niloticus and RBCs 106µL-1 in infected O. aureus. No significant difference in Hamatocrit %, total plasma protein, WBCs, blood glucose, total bilirobin, creatinine and uric acid in infected O. niloticus and infected O. aureus. Significant increase of AST and ALT in infected O. aureus
20- E.M.C. cause significant reduction of haemoglobin g/l, RBCs 106µL-1, total plasma protein mg/dl and albumin mg/dl in infected O. niloticus than infected O. aureus. Significant increase of blood glucose and ALT in infected O. aureus. No significant difference of WBCs, Hamatocrit %, AST, total bilirobin, creatinine and uric acid in infected O. niloticus and infected O. aureus.
21- Acanthosentis tilapiae cause significant reduction in haemoglobin g/l, and albumin mg/dl in infected O. niloticus than infected O. aureus and total plasma protein in infected O. aureus. Significant increase of blood glucose mg/dl and ALT U/l in infected O. aureus and AST in infected O. niloticus. No significant difference in RBCs 106µL-1, WBCs, Hamatocrit %, total bilirobin, creatinine and uric acid in infected O. niloticus and infected O. aureus.
22- Lamproglena monodi cause significant reduction of haemoglobin g/l, RBCs 106µL-1, Hamatocrit %, total plasma protein mg/dl and albumin mg/dl in infected O. niloticus than infected T. zillii. Significant increase in WBCs103µL-1, blood glucose mg/dl, AST U/l, ALT U/l, total bilirobin mg/dl and uric acid mg/dl in infected O. niloticus than infected Tilapia zillii No significant difference in creatinine in infected O. niloticus and infected T. zillii.
23- Biochemical investigation of enzyme activities in infected T. zillii by Chilodonella hexasticha, showed a significant increase except GR, MDA (liver), cytochrom oxidase and LDH (gill and liver) .In infected S. galilee by Chilodonella hexasticha, showed significant increase of all enzyme activities except GR in gills, liver and musculature in winter.
24- Biochemical investigation of enzyme activities in infected O. niloticus by Cichlidogyrus tilapiae, showed a significant increase except GR in gills, liver and musculature than caused by Lamproglena monodi in summer. Enzyme activities in infected O. niloticus by E.M.C., found the highest increase in gills infected by Centrocestus formosanus, the highest increase in liver infected by Heterphyes sp and the highest increase in musculature infected by Diplostomum tilapiae in winter.
25- Biochemical investigation of enzyme activities in infected O. aureus by Cichlidogyrus tilapiae, showed significant increase except GR in gills, liver and musculature in summer. Enzyme activities in infected O. aureus by E.M.C., found the highest increase in gills infected by Centrocestus formosanus, the highest increase in liver infected by Heterphyes sp and the highest increase in musculature infected by Diplostomum tilapiae in autumn.
26- Biochemical investigation of enzyme activities in infected O. niloticus and O. aureus by Acanthosentis tilapiae, showed ag significant increase of all enzyme activities except GR in serum in spring.