ABNORMAL WATER PARAMETERS AS POTENTIAL STRESS TO INDUCE TILAPIA LAKE VIRUS (TILV)

The quality of water generally refers to the component of water present at the optimum level for suitable growth of plants and animals. Mass mortality of Oreochromis niloticus was observed  in a lake in Katpadi during November 2018. To understand the situation, water samples were collected to analyze the different physical chemical and biological parameters. The comparison with the standard values revealed high level of turbidity, total dissolved solids, hardness, alkalinity and phosphate in the water. Analysis of algae showed the presence of many species including Microcystis sp. (Microcystis aeruginosa). On suspicion, the affected samples were screened for Tilapia lake virus (TiLV) and found to be positive indicating the abnormal water quality stress could be an inducer of the disease.

Aquatic organisms need a healthy environment to live and adequate nutrients for their growth. The maximum productivity can be obtained only when the physico- chemical parameters are present at the optimum levels

This study was conducted in Katpadi lake, Vellore. The water samples were collected as the standard methods of Boyd (2015). The phytoplankton analysis was carried out using the samples of 1L of water fixed in lugol-iodine solution. Parameters such as temperature, pH, electrical conductivity, dissolved oxygen and turbidity, were directly evaluated in the study area whereas other parameters were analyzed in laboratory. The algal diversity included Mougeotia, Sphaerocystis, Euglena, Pinnularia, Chrysomonads, Oscillatoria, Rhizoclonium, Tribonema, Oocystis, Phormidium, Chilomonas, Mallomonas, Tetraedron, Chlorella, Asterionella, Synedra, Stauronesis, Microcysts and Spirogyra

RNA extracted from tissues of tilapia that exhibited redness in skin, swollen eye balls and swimming abnormalities and screened for TiLV. Results showed that the samples were positive by RT-PCR analysis (Fig.1).