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Efficacy study of Vaccine A and B developed against pathogen Z under co-infection / latent infection with other pathogens (L,M,N,O,P)

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Atlantic salmon vaccinated in the field/ farm encounter a complex environment different from laboratory where they may be subjected to many asymptomatic infections. Many of these latent infections are thought to cause immune suppression or immune disruption which can influnce the vaccination efficacies. It is therefore, of great significance to identify these disease factors and devise strategies to improve the efficacy of current vaccines and this in turn will improve the general health of farmed salmon and further reduce the use of antibiotics and other chemicals. Additionally, these latent infections are the target of many current vaccine development projects and this study will complement these efforts

A series of experiments are planned to identify the effects of persistent/ chronic infections in farmed Atlantic salmon on the efficacy of a new live attenuated vaccine developed against pathogen Z. A persistant infection is a subclinical development of infection and fish may not show much distress outwardly but nevertheless, can be bothersome for fish. Such persistently infected fish will be vaccinated, challenged and observed for the development of disease (against which it is being vaccinated) before termination. Alternatively, fish will be also be co-infected with these pathogens after vaccination and before challenge with pathogen Z.

The total number of fish (Atlantic salmon) to be used in this study is 5000 and salmon parrs of the avg size 10-15 g will used at the start of the study. The study can cause considerable distress to the fish and mortality is expected. The persistent infections and their immune suppression effects are difficult to replicate in a laboratory-cell culture environment but pathogen candidates chosen in this study are well researched and such information has been used to keep the experiments and number of fish to minimum. The fish involved in the experiment will be fed properly and will be housed with a favourable light regime and humane culling will be prioritised for fish observed to be under severe distress.