Commercial Vaccines Do Not Confer Protection against Two Genogroups of Piscirickettsia salmonis, LF-89 and EM-90, in Atlantic Salmon

Carolina Figueroa, Débora Torrealba, Byron Morales-Lange, Luis Mercado, Brian Dixon, Pablo Conejeros, Gabriela Silva, Carlos Soto, José A. Gallardo

Research output: Contribution to journalArticlepeer-review

Abstract

In Atlantic salmon, vaccines have failed to control and prevent Piscirickettsiosis, for reasons that remain elusive. In this study, we report the efficacy of two commercial vaccines developed with the Piscirickettsia salmonis isolates AL100005 and AL 20542 against another two genogroups which are considered highly and ubiquitously prevalent in Chile: LF-89 and EM-90. Two cohabitation trials were performed to mimic field conditions and vaccine performance: (1) post-smolt fish were challenged with a single infection of LF-89, (2) adults were coinfected with EM-90, and a low level coinfection of sea lice. In the first trial, the vaccine delayed smolt mortalities by two days; however, unvaccinated and vaccinated fish did not show significant differences in survival (unvaccinated: 60.3%, vaccinated: 56.7%; p = 0.28). In the second trial, mortality started three days later for vaccinated fish than unvaccinated fish. However, unvaccinated and vaccinated fish did not show significant differences in survival (unvaccinated: 64.6%, vaccinated: 60.2%, p = 0.58). Thus, we found no evidence that the evaluated vaccines confer effective protection against the genogroups LF-89 and EM-90 of P. salmonis with estimated relative survival proportions (RPSs) of −9% and −12%, respectively. More studies are necessary to evaluate whether pathogen heterogeneity is a key determinant of the lack of vaccine efficacy against P. salmonis.

Original languageEnglish
Article number993
JournalBiology
Volume11
Issue number7
DOIs
StatePublished - Jul 2022
Externally publishedYes

Keywords

  • bacterin vaccine
  • cohabitation
  • live attenuated vaccine
  • monovalent vaccine
  • pentavalent vaccine
  • Piscirickettsiosis
  • Salmo salar
  • sea lice
  • vaccine efficacy

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