red dots (petechiae) to large red patches. Histopathology (microscopic tissue analysis) Preliminary diagnosis involves histopathological examination, observing tissues through a microscope. Most tissue changes can be observed as minor to major necrosis (cell death) in the liver, kidneys, spleen, and skeletal muscle. The hematopoietic (blood-forming) areas of the kidney and spleen are the initial area of infection, and should show necrosis. The gill may have thickened lamellae, and the liver may have pyknotic nuclei. Skeletal muscle accumulates blood but does not suffer much damage. Virology (definitive testing) Electron microscopy can reveal the bullet-shaped rhabdovirus, but is not adequate for definitive diagnosis. The Manual or Diagnostic for Aquatic Animals, 2006, is the standard reference for definitive tests. In most cases, cell culturization is recommended for surveillance, with antibody tests and reverse transcription polymerase chain reaction (RT-PCR) and genetic sequencing and comparison for definitive confirmation and genotype classification. Virus neutralisation is another important method of diagnosis, especially for carrier fish. Prevention Thoroughly cleaning boats, trailers, nets and other equipment when traveling between different lakes and streams also helps. The only EPA-approved disinfectant proven effective against VHS is Virkon AQUATIC). Chlorine bleach kills the VHS virus, but in concentrations that are much too caustic for ordinary use. Disinfecting stations can be found at various inland lake boat launches in the Great Lakes region. Immune reactions against VHSV Fish viperin gene was identified as an interferon-stimulated gene against VHSV. Whereas, viperin produces inhibitory ddhCTP (3ʹ-deoxy-3′,4ʹdidehydro-CTP), which is an elongation inhibitor. Thereby, the VHSV RNA replication is terminated. References External links Viral Hemorrhagic Septicemia (VHS), Michigan Department of Natural Resources Great Lakes Echo: Great Lakes fish hatcheries could benefit from new test for deadly VHS virus, Sarah Coefield, June 18, 2009 Species Profile - Viral Hemorrhagic Septicemia, National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources on Viral hemorrhagic septicemia. Viral hemorrhagic septicemia virus Fish viral diseases