Viral haemorrhagic septicaemia (VHS) is one of the most important viral diseases in rainbow trout that has caused great losses to Iranian rainbow trout aquaculture industry in the last 3 years. Therefore, rapid and reliable diagnosis of VHS virus infections is of great importance. An enzyme linked immunosorbent assay (ELISA) method was performed to study serum antibodies against viral haemorrhagic septicaemia virus (VHSV) using recombinant fragments of their N protein. For this purpose, the virus was first isolated from an infected farm. A part of the nucleocapsid (1-505 bp) gene was amplified by RT-PCR using specific primers. The amplified fragment was ligated to pMALc2x vector and transferred to DH5α strain of Escherichia coli. Then, recombinant plasmids were tested for protein expression in E. coli Rosetta strain. SDS-PAGE analysis indicated the production of a recombinant protein with an expected molecular weight of 61 KDa. Analysis of trout serum samples from seven previously infected farms and two VHS free farms showed that the designed ELISA method was effective in diagnosing the infected fish. The results revealed that the developed serological assay using designed ELISA based on recombinant protein (N) has the potential to be used in monitoring studies and to determine the prevalence of VHS in rainbow trout farms. The present data allow evaluating the levels of nonneutralizing antibodies without crude virus preparations.

Background: Lead (Pb) is an important metal used in industries, mining and agriculture. It is equally important to the aquatic ecosystems and has negative impact on the health of aquatic organisms. Methods: The LC50 of lead toxicity at varying salinities was first determined for 96 hours. Then juvenile fish were transferred to tanks individually and were exposed to 0, 15, 30, 60 and 120 mg/l of Pb at varying salt concentration of 0, 0.1, 0.2 or 0.4 g/l. The blood samples were taken after the 4th day and the hematological parameters were evaluated. Results: Red Blood Cells (RBC) and White Blood Cells (WBC) were decreased in almost all lead treated groups. The Hb levels decreased consistent with increasing lead concentrations (P<0.05). The mean corpuscular volume, hemoglobin and the concentration were not affected by the lead concentrations compared to those for the control group. The WBC and RBC counts showed an inverse correlation with the lead concentrations in the Pb-exposed fish. A direct correlation was also observed in the lead concentration and the heterophile rate (P<0.05). Conclusion: The results showed that salinity did not affect the hematological parameters, but the LC50 values decreased with increasing salinity.

Background: Herbicides are widely used in agriculture to kill a large variety of unwanted weeds. However, the application in water ecosystems may pose harmful impacts on the health of aquatic organisms. We studied the acute toxicity of four major types of herbicides on the survival of adult shrimp, Artemia franciscana (AF). Methods: The brine shrimp, AF, was hatched from the commercially encysted dry eggs. The acute toxicity (LC50; 48 hr) of four herbicides, paraquat; 2,4-dichlorophenoxy acetic acid (2,4-DCPA); trifluralin; and glyphosate, was examined by a standard method. We exposed the shrimps to sequentially rising concentrations of each herbicide in triplicate. The mortalities were recorded at 12, 24, 36, and 48 hours after exposure and the LC50 was calculated, using a Probit software. Results: This study demonstrated that the acute toxicity of these herbicides was significantly different in adult shrimp AF. The lethal concentrations (LC50) of Paraquat, 2,4-DCPA, trifluralin and glyphosate against the shrimp were 2.701, 14.475, 0.446 and 17.431 mg/l, respectively. Trifluralin and paraquat caused the highest lethality at lower LC50 concentration compared to the other two herbicides. Conclusion: The results demonstrated that increasing herbicides concentration or duration of exposure raised the mortality rate of AF’s.