IHN is an acronym that stands for Infectious Hematopoietic Necrosis, which is a highly contagious viral disease affecting salmonid fish species. This disease is caused by the IHN virus, a member of the Rhabdovirus family. It primarily affects young fish, specifically those in their early developmental or freshwater phase, and can cause high mortality rates in affected populations.
The IHN virus is predominantly transmitted through direct contact between infected and susceptible fish, as well as through contaminated water and surfaces. The virus enters the fish's bloodstream, targeting and damaging their red blood cells and other hematopoietic tissues. This results in severe anemia, hemorrhaging, and necrosis in various organs, leading to systemic disease and often death.
Symptoms of IHN include darkening or reddening of the skin, anemia, exophthalmia (bulging eyes), hemorrhaging in the fins or internal organs, abdominal swelling, and ultimately, mortalities. Infected fish may also exhibit behavioral changes such as lethargy, loss of appetite, and erratic swimming patterns.
The presence of IHN is a significant concern in the aquaculture industry and natural fish populations, as it can cause significant economic losses and ecological disruption. Control measures for IHN focus on strict biosecurity practices, including quarantine and testing of fish stocks, water source management, disinfection protocols, and movement restrictions. Vaccination has been developed as a preventive measure against IHN in some regions.
