Prophylactic effect of levamisole on rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri

Alteration in the relative percentage of survival (RPS) rate of rainbow trout (Oncorhynchus mykiss) exposed to 5, 10 and 25�g ml-1 levamisole for 2 h against Yersinia ruckeri was investigated. The average weight of the 120 fish used in this study was 6.3g. Upon challenge with a virulent strain, the relative survival percentage of respectively 83.3 percent, 86.7 percent and 76.6 percent was recorded. The results suggest that the application of levamisole in fish farms could increase resistance to infection of fish and offer economic benefits.

Efecto in vitro del suero de la trucha arco iris, oncorhynchus mykiss, sobre metacercarias del género tylodelphys trematoda displostomatidae / The in vitro effect of rainbow trout, oncorhynchus mykiss, serum in tylodelphys sp trematoda displostomatidae metacercariae

Here, it has been described that normal fresh sera from rainbow trout (oncorhynchus mykiss) were able to Iyse Tylodlphys sp. metacercariae isolated form Galaxias maculatus (Jenyns, 1842) (Teleostei, Galaxiidae) brain. This effect was time dependent, and progressively increased since 1 h up to 18 h incubation. There were oscillations in the ability of different sera samples to lyse these parasites. Similar values were achieved with other salmonid sera, and also with normal human sera pool. The lytic activity was abolished by heat-inactivated sera, by zymosan treatment and by incubation in the presence of EDTA. However, the mean values obtained in the presence of EGTA-Mg++ did not significantly differ from those found with sera as a source of complement. The results of this study suggested the role of complement alternative pathway on Tylodephys sp. in vitro lysis, under our experimental conditions

Indirect enzyme-linked immunosorbent assay (ELISA) for monitoring antibodies in rainbow trout Oncorhynchus mykiss.

An indirect enzyme-linked immunosorbent assay (ELISA) has been described to detect and measure the antibodies in O. mykiss against a lambda bacteriophage antigen (strain c1187 Sam7). Antibodies were first detected six days after the first intraperitoneal injection and by day 21 all fish were positive. Maximum mean titres were detected on day 30 (3 days after the second injection). The mean titre declined by day 33 which was 6 days after second injection and remained constant from day 39 to day 45. The results suggest that immune response in a rainbow trout occurred faster and the fish were able to mount a very good response to viruses.