Histopathology and Immunology of Rainbow Trout Fed with Levamisole

Aims: The use of immune stimulants to prevent diseases and increase the resistance of aquatic animals to stress has been rising. The aim of the present study was examining the histopathology and immunology of rainbow trout (Oncorhynchus mykiss) Fed with Levamisole.
In this experimental research, 1000 fish were divided in 5 treatments and fed on diet supplemented with levamisole at 0 (control), 100, 250, 500, and 1000mg/kg-1 diet for 45 days. Then, the fish were fed on a diet without levamisole and increased density twice for the following 15 days. Blood samples were collected from all treatments on days 15, 30, 45 and 60 to evaluate the total immunoglobulin and lysozyme activity of serum. At the end of the trial, 15 fish from each treatment (each replicate 5 fish) were randomly selected and tissue samples of gill, kidney, and liver were evaluated. The data were analyzed by SPSS 15 software, using one way ANOVA and Duncan test.
Findings: Treatment fed with 1000mg levamisole on day 30 and 60 had the highest total serum immunoglobulin and had the highest lysozyme activity in comparison to other treatments on 15, 30, and 60 days. The least amount of tissue damage was observed in gills, kidneys, and liver in 1000mg levamisole.
A total of 1000mg/kg-1 levamisole of rainbow trout diet causes the least amount of damage to the gill, kidneys, and liver tissues, as well as the increase of total immunoglobulin and lysozyme activity of serum.