CRYPTOSPORIDIUM AND OTHER ZOONOTIC PARASITES IN OREOCHROMIS NILOTICUS IN ASSIUT GOVERNORATE

摘要

This study was carried out on 120 Oreochromis niloticus fish (60 wild and 60 cultured). The fish were randomly collected, from different areas of Assiut Govemorate as well as from some fish farms. They were used to investigate the prevalence of Cryptosporidium and other zoonotic parasites in O. niloticus. Examination of gills, muscles and the contents of the gastrointestinal tract revealed highest parasitic infestation rate (80 %) in wild compared to (55 %) in cultured O. niloticus. The prevalence ofthe isolated parasites in wild and cultured O. niloticus was as follows: Cryptosporidium spp. 15.0 % and 23.3% respectively; Acanthocephela (Acanthocentius tilapae) 8.3 % and 9.2% respectively; microscopic encysted metacercariae 88.3% and 26.7 % respectively while macroscopic encysted metacercariae detected only in wild O. mloiicus 40%. Killing factors (temperatures, solutions and processing methods) were studied on encysted metacercariae (EMC) in 0.niloticus killing criteria followed the movability index (MI) from 1.000 within 24 hoiu’s. Muscle pieces containing viable EMC were incubated in different concentrations of NaCI, acetic acid or commercial vinegar at room temperature. The MI was <1 (killing effect) within I. 2 hours for 30% and 20% ofNaClrespectively and1,6 andl2 hours for 5, 2.5 and 1.25%of acetic acid, respectively while commercial vinegar has MI > 1 (no killing effect) at 5%.Storage afO. niloticus at (- lOX^) resulted in killing die EMC after 12 hours of storage while storage at 5 *Cfor 24 hours has nokilling effect. Dry salting of O. niloticus could kill the EMC within one hour of saltcontact, while marination in 5 % acetic acid for one minute resulted in eradication ofEMC after 2 hours of treatment with barely detected acetic acid odor and significant reduction in muscle pH (P < 0.05.).