In the present study, the effects of Chlorella vulgaris on blood and immunological parameters of Caspian salmon (Salmo trutta caspius) before and after exposure to Viral Nervous Necrosis (VNN) virus were examined. In this regard, four treatments in triplicate were chosen. Groups included one control and 3treatments (T1, T2 and T3). Fish in control group, T1, T2 and T3 were fed diets supplemented with 0, 1×108, 2×107 and 3×106 chlorella/450 g of food respectively, for sixty days. In addition, a virus supernatant was prepared from infected wild golden grey mullet (Liza auratus) and used for virus challenge ofS. trutta caspius. Virus was injected intraperitoneally and blood samples were collected before and 14 days after the challenge. Immunological (IgM, C3, C4, total protein, respiratory burst, albumin and lysozyme) and changes in blood parameters (RBC, WBC, Htc, Hb, MCH, MCHC and MCV) were also measured. Results showed thatC. vulgaris could act as a natural immunestimulant. Also, the alteration trend in hematological and immunological parameters showed that experimental fish could be considered to be resistant to VNN virus after exposure and fish treated withC. vulgaris were more resistant in comparison to those in the control group. The dose used in T1 (1×108 chlorella/450 g food) was the most effective approach with significant differences.

Keywords:Chlorella vulgaris, Blood parameters, Immunological parameters,Salmo truttacaspious, Viral Nervous Necrosis virus