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News Article

Sea lice override the protective effects of vaccines in Atlantic salmon

Coinfection may explain the reduced efficacy of vaccines in sea cages

A study published in Scientific Reports suggests that the ability of vaccinated fish to modulate a bacterial infection during coinfection with sea lice is strongly diminished, impeding fish recovery from infection.

The study was compiled by researchers at the University of Waterloo, the Pontifical Catholic University of Valparaiso and Chile’s University of Valparaiso. They tested the efficacy of the vaccine for the bacterial pathogen Piscirickettsia salmonis by comparing the reaction of vaccinated and non-vaccinated Atlantic salmon when exposed to the sea louse Caligus rogercresseyi in the laboratory.

They found that although the number of bacteria living inside the fish was much lower in vaccinated fish, they showed many more signs of infection and a higher death rate compared with the unvaccinated group upon exposure to the sea lice.

The study concluded that once vaccinated, the salmon was unable to fight off multiple diseases at once. The study shows that a parasite in fish can override the protective effects of a vaccine for another disease.

The experience of salmon farmers in Chile supports this finding, where salmon are raised largely in open cages off the coast, exposing them to variety of pathogens, the most common of which is sea lice.

The researchers say this highlights the need for veterinary pharmaceutical companies to change how they design and test vaccines in the first place, recognizing how different fish immune systems are from the current human model.

“Fish have a limited number of resources to respond to an illness so their immune system makes choices — when they’re infected by sea lice, for example, the fish’s immune system is suddenly geared to respond to that specific threat, leaving them totally exposed to other threats like P. salmonis,” said Brian Dixon, a professor in biology at the University of Waterloo and a Canada Research Chair in Fish and Environmental Immunology. “It’s like sending ambulances out to all emergencies when in fact some of those emergencies need firefighters.”

Read article: Coinfection takes its toll: Sea lice override the protective effects of vaccination against a bacterial pathogen in Atlantic salmon by Carolina Figueroa, Paulina Bustos, Débora Torrealba, Brian Dixon, Carlos Soto, Pablo Conejeros & José A. Gallardo published in Scientific Reports (2017) 7, Article number: 17817, doi: 10.1038/s41598-017-18180-6

Article details

  • Date
  • 01 February 2018
  • Source
  • University of Waterloo
  • Subject(s)
  • Aquaculture