The Status of VNN (Viral Nervous Necrosis)-lnfected Grouper Fish Tissue with Chlorella vulgaris Extract as Anti-Virus Candidate

Abstract

To date, the most common problem in Grouper fish cultivation is VNN (Viral Nervous Necrosis) virus attack. Visual and histological observations on the fish behavior can be done to diagnose the presence of VNN. Chlorella vulgaris is believed to be one of the natural alternative ingredients that have the potential to be a VNN anti-virus. The purpose of this study is to determine the potential use of C. vulgaris extract as a candidate for VNN antivirus by conducting histological observations on the organ tissue of Grouper fish. The method used in this study was a qualitative approach with histopathological techniques examining the fish organs such as brain, kidney and eyes from each treated fish. The clinical symptom observation was carried out for 14 days. Then, the harvested organs were brought for tissue preparation and observed again with a light microscope. In this case, the histopathological changes can be assessed using a semiquantitative scoring method. The results reveal that the Grouper fish had several symptoms such as darkening body-color, abdominal bloating, abnormal swimming behavior, and decreased appetite. It is also found that there was a change in the histological picture between the infected fish without treatment and the infected fish with the administration of C. vulgaris extract. There were a number of lesions such as vacuolization, hemorrhagic, hypertrophy, and necrosis in the kidney, eye, and brain of the infected fish. Of all the treatments given, treatment (D) shows a little damage to the fish kidney, eye, and brain respectively by 26.7%, 33.3% and 33.3%. Therefore, it can be said that the administration of C. vulgaris as an alternative feed and antivirus candidate can be used as a natural immune-stimulant to enhance the immune system of Grouper fish.