Comparative evaluation of experimental challenge by intraperitoneal injection and cohabitation of Atlantic salmon (Salmo salar L) after vaccination against Piscirickettsia salmonis (EM90‐like)

• Published in: Journal of fish diseases 2019-12, Vol.42 (12), p.1713-1730
• Main Authors: Meza, Karla, Inami, Makoto, Dalum, Alf S., Lund, Hege, Bjelland, Ane M., Sørum, Henning, Løvoll, Marie
• Format: Article
• Language: English
• Subjects: Animals; Aquaculture; Atlantic salmon; Bacterial Load; Bacterial Vaccines - therapeutic use; CD8 antigen; Cell-mediated immunity; challenge model; Cohabitation; Comparative analysis; Comparative studies; Disease control; Fish; Fish Diseases - microbiology; Fish Diseases - prevention & control; Freshwater fishes; Gene expression; Immunity; Injection; Injections, Intraperitoneal; intraperitoneal injection; Lymphocytes; Lymphocytes T; Marine fishes; Performance evaluation; Piscirickettsia; Piscirickettsia salmonis; Piscirickettsiaceae Infections - prevention & control; Piscirickettsiaceae Infections - veterinary; Salmo salar; Salmo salar - microbiology; Salmon; Survival; Vaccination; Vaccination - methods; Vaccination - veterinary; Vaccine efficacy; Vaccines
• ISSN: 0140-7775; 1365-2761
• DOI: 10.1111/jfd.13091

The Chilean aquaculture has been challenged for years by piscirickettsiosis. A common prophylactic measurement to try to reduce the impact from this disease is vaccination, but the development of vaccines that induce satisfactory protection of the fish in the field has so far not been successful. Experimental challenge models are used to test vaccine efficacy. The aim of this study was to evaluate the performance of experimental vaccines after challenge by the two most widely used challenge routes, intraperitoneal injection and cohabitation. A total of 1,120 Atlantic salmon were vaccinated with non‐commercial experimental vaccines with increasing amounts of an inactivated Piscirickettsia salmonis EM90‐like isolate. Differences in mortality, macroscopic and microscopic pathological changes, bacterial load and immune gene expression were compared after challenge by different routes. The results revealed a similar progression of the diseases after challenge by both routes and no gross differences reflecting the efficacy of the vaccines could be identified. The analysis of the immune genes suggests a possible suppression of the cellular immunity by CD8 T cell and with this stimulation of bacterial survival and replication. Comparative studies of experimental challenge models are valuable with regard to identifying the best model to mimic real‐life conditions and vaccines’ performance.