The invention is directed to isolated Tilapia Lake Virus or TiLV, and isolated nucleic acids sequences and polypeptides thereof. The invention also relates to probes and primers, and to antibodies against antigens from TiLV, and use of these reagents for detecting the presence or absence of TiLV in an animal. The invention also relates to iRNAs which target nucleic acid sequences of TiLV. The invention is also related to immunogenic compositions, including antibodies and vaccines, for inducing an immune response against TiLV in an animal. The invention is also related to gene constructs and cells comprising TiLV and isolated nucleic acids sequences and polypeptides thereof for use in developing prophylactic and therapeutic agents.