Passive immunization of juvenile rainbow trout, Onchorhynchus mykiss, against vibriosis using feed or by injection

The present work was undertaken to examine the effectiveness of anti-Vibrio anguillarum IgY, obtained from chicken eggs, previously vaccinated with the killed bacteria, in prevention of vibriosis in juvenile rainbow trout Onchorhynchus mykiss using feed or by injection. Briefly, two white leghorn chickens, Gallus domesticus, (approximately one year old) were injected intramuscularly (IM) with killed V. anguillarum, the causative agent of vibriosis in salmonids. Chicken eggs collected and yolks were extracted for their antibodies. The protective efficacy of the specific, anti–vibrio IgY, was tested in Juvenile rainbow trout, O. mykiss, by feeding or intraperitonial (IP) injection. The control fish also were treated the same as the test group yet with non-specific IgY, obtained from the chickens not vaccinated with the bacteria. The results indicated that protection against induced vibriosis in the trout injected (IP) with anti-vibrio IgY was achieved, however, protection in the fish treated via oral route was minimal. To determine that protection conferred to the fish was indeed due to the specific anti-V. anguillarum IgY, in the second experiment, the extracted IgY, both from control eggs and eggs from vaccinated chickens were separately mixed with killed V. anguillarum in order to eliminate (absorb) anti-vibrio activity of IgY. Tow groups of fish then injected (IP) with absorbed either non-specific or anti-vibrio IgY. The results indicated that the protection achieved in the previous experiment was indeed due to the specific anti-vibrio IgY.