and mortality of hosts includes the broad range of virus serotypes and strains, as well as viral loads associated with each grouping of virus. this variation affects the efficiency of horizontal transfer of the virus, with highly virulent strains more effective than variations with low virulence. additionally the stability of the virus across a range of temperature, ph and salinity and ability to infect many different hosts makes ipnv persevering both in environments and hosts. viral persistence in alternative hosts and environment across a range of conditions, creates conditions in which the virus remain a long-term threat. differences in virulence (10%-90%) of strains alongside variations in host characteristics and environmental stressors are all influential for mortality rates caused by the virus. diagnosis at present, infectious pancreatic necrosis virus has been reported in europe, north america, south america, south africa, asia, and australia, where it is a major threat to aquaculture due to its wide host range and high mortality. as such, there has been a widespread push to find an accurate and rapid technique to identify the virus. current methods of diagnosis fall into categories of clinical symptoms (described above), laboratory testing and case history. visual inspection is of most use for young salmonids but is inadequate to detect asymptomatic carriers. laboratory examinations using molecular biological processes vary but often include flow cytometry, cell culture, histology, and immunological methods. elisa is a commonly used technique as it allows for the detection of the viral antigens using infected tissue samples. however, tests like elisa and immunohistochemistry have been criticised, for the requirement of fresh samples and high viral titre needed. more recent studies have proposed the use of the more efficient and rapid rt-pcr and its variants to test for ipnv. it has also been suggested that due to a high viral load in the pectoral fins of infected fish, rt-pcr assays could be a non-lethal alternative of detection. a proposed combination of rt-pcr and flow cytometry claims to be effectual at identification the virus in titres of 1x102 and 1x103 tcid50/ml, compared to standard 1x104 tcid50/ml concentration commonly used. other modern methods for early identification have also been put forward, including biosensors and rt-lamp. treatment and control there have been a variety of attempts to reduce transmission and increase protection against infectious pancreatic necrosis virus (ipnv). selective breeding, as well as vaccination, have both been shown to be viable ways of at least reducing infection rates. horizontal transmission (transmission between individuals of the same generation) can be reduced by zoning and separation of different areas, surveillance of fish, and removing all fish affected by infectious pancreatic necrosis conditions. vertical transmission (transmission from one generation to the next) can be reduced by not using survivors of infection to breed and removing any affected individuals in the breeding stock. since infectious pancreatic necrosis virus vaccination research has begun, different types of vaccines, as well as different methods of vaccination, have been tried. broad-scale oral vaccination of young fish is likely to be the best method, as injection of hundreds of fry is impractical. however, vaccine effectiveness can be limited when young fish are vaccinated, because the fish immune system has not fully developed until after the fry stage. still, there is promising work on vaccinations. some antigens may be degraded in the digestive system after oral ingestion, presenting another potential problem. however, lactic acid bacteria can be used in a vaccine, and has been shown to significantly lower the amount of ipnv in rainbow trout populations. there is also the possibility of using virus-like particles (vlp’s) as a vaccine agent, which has been shown to have high potential. selective breeding has been massively successful in reducing mortality and spread of ipnv. in atlantic salmon, resistance has been shown to be conferred by variations in one singular gene, although since, previously-resistant fish have been infected and killed by a new ipnv strain.