الفهرس 
Abstract
TilapiaOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
The present study was carried out to compare different helminthes load in wild and cultured Oreochromis niloticus (Nile tilapia) in Assuit, Egypt. Two hundred and eighty- eight fish (12 wild fish/ month and 12 cultured fish/ month) of differentsexesandlengthswererandomlycollectedfromtheRiverNileatdifferent localitiesofAssiutcityduringthevariousseasonsoverayearstartedfromDecember 2013 until November 2014. Clinical and postmortem investigation of the examined infected fish revealed non-specific clinical signs as enlarged hemorrhagic stomach, intestinal intussusception as well as congestion or paleness of the intestine. Isolated parasites were identified belonging to two phyla; phylum platyhelminthes and phylum acanthocephala. They were identified as Enterogyrus cichlidarium (Monogenoidea: Ancyrocephalidae) from the stomach, encysted metacercariae (EMC)ofdigenetictrematodesfrombothstomachandintestine,andAcanthocentius tilapiae (Acanthocephala: Quadrigyrdae) from the intestineonly.
The infection rates E. cichlidarum throughout the year were 43.75% and 47.91% in wild and cultured Nile tilapia, respectively. The highest infection rates were in February and March, 2014. Parasite intensity varied from 1-14 specimens per fish in wild O. niloticus and from 1-22 specimens per fish in cultured ones. The greatestmeanintensitywas5.16inwildfishinNovember,2013while,itwas6.5in
culturedfishinDecember,2014.Infectionratesofculturedmalesweresignificantly higher than that of wild males. The infection rates increased significantly with the increase in the fish host age in cultured fish. The infected stomach with the E. cichlidarum showed marked congestion and inflammatory cellreaction.
Encysted metacercaria (EMC) were isolated from the stomach and theintestine ofbothwildandculturedO.niloticus.NomacroscopicEMCwasdetectedfromboth stomach and intestine of the examined fish. The EMC was round to oval double- walled cyst free or attached to the gastrointestinal wall. The total rates of infection were (5.90%). The highest infection rates were in the summer season. Predilection sitesofEMCwereintheintestinebutwithnosignificantdifference,whencompared with the stomach. The infections were found only in cultured males, but not the females. Infection rates were increased with the host age with no significant differences among the age groups. The infected O. niloticus intestine showed necrotic enteritis with local aggregation of lymphoid cell reaction aroundEMC.
Acanthogyrus (Acanthosentius) tilapiae Baylis, 1948 (Acanthocephala: Quadrigyrdae) is the only acanthocephalan parasite isolated from the intestine of both wild and cultured O. niloticus. The overall total infection rates with A. tilapiae was 12.5% with a mean intensity of 4.70 in the wild fish, and infection rate of 13.19%andameanintensityof2.68intheculturedones.Thehighestinfectionrate
was recorded in the winter (36.1% in wild and 33.3% in cultured one). The parasite was found mainly in the anterior two-thirds of the intestine with the lowest number of the parasite in the posterior third. O. niloticus males were insignificantly more infected than the females in both wild and cultured fish. There was a positive relationshipbetweenfishageandA.tilapiaeinfectionratewhereolderfishwerethe highest infection rates. Parasitic enteritis, lytic necrosis in the intestinal mucosa which associated with esinophilic cell reaction of the infectedintestine.
Overall, the total parasitic infection rates and mean intensities were highest in case of E. cichlidarum, followed by A. tilapiae and finally EMC infections with significant differences in both wild and cultured fish. The total infection rates with gastrointestinal helminthes were 62.5% in wild and 67.4% in cultured O. niloticus. Single infection rates with one species of GIT helminthes were highest (88.8%) in the winter in both wild and cultured fishes. When single and mixed infection rates were compared, high significances were obtained in both wild and cultured fishes. In wild fish, the total parasitic infection rates of females were significantly higher thaninthemalesbutinculturedfish,themaleswereinsignificantlyhigherinfections than the females. As well, no significances were reported to gastrointestinal helminthes of both two males and two females in wild and cultured fish. Positive correlation between host age using fish standard length and the total parasitic infection rates with intestinal helminthes wasobserved.