Intensive fish farming and the evolution of pathogen virulence

The case of columnaris disease in Finland

K. Pulkkinen, L. R. Suomalainen, Andrew Fraser Read, D. Ebert, P. Rintamäki, E. T. Valtonen

Research output: Contribution to journalArticle

122 Citations (Scopus)

Abstract

Ecological changes affect pathogen epidemiology and evolution and may trigger the emergence of novel diseases. Aquaculture radically alters the ecology of fish and their pathogens. Here we show an increase in the occurrence of the bacterial fish disease Flavobacterium columnare in salmon fingerlings at a fish farm in northern Finland over 23 years. We hypothesize that this emergence was owing to evolutionary changes in bacterial virulence. We base this argument on several observations. First, the emergence was associated with increased severity of symptoms. Second, F. columnare strains vary in virulence, with more lethal strains inducing more severe symptoms prior to death. Third, more virulent strains have greater infectivity, higher tissue-degrading capacity and higher growth rates. Fourth, pathogen strains co-occur, so that strains compete. Fifth, F. columnare can transmit efficiently from dead fish, and maintain infectivity in sterilized water for months, strongly reducing the fitness cost of host death likely experienced by the pathogen in nature. Moreover, this saprophytic infectiousness means that chemotherapy strongly select for strains that rapidly kill their hosts: dead fish remain infectious; treated fish do not. Finally, high stocking densities of homogeneous subsets of fish greatly enhance transmission opportunities. We suggest that fish farms provide an environment that promotes the circulation of more virulent strains of F. columnare. This effect is intensified by the recent increases in summer water temperature. More generally, we predict that intensive fish farming will lead to the evolution of more virulent pathogens.

Original languageEnglish (US)
Pages (from-to)593-600
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Volume277
Issue number1681
DOIs
StatePublished - Feb 22 2010

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Flavobacterium columnare
Pathogens
fish culture
Finland
virulence
Agriculture
Fish
Virulence
Fishes
pathogen
pathogens
fish
fish farms
Fisheries
signs and symptoms (animals and humans)
infectivity
pathogenicity
death
fish diseases
Fish Diseases

All Science Journal Classification (ASJC) codes

  • Medicine(all)
  • Immunology and Microbiology(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

Cite this

Pulkkinen, K. ; Suomalainen, L. R. ; Read, Andrew Fraser ; Ebert, D. ; Rintamäki, P. ; Valtonen, E. T. / Intensive fish farming and the evolution of pathogen virulence : The case of columnaris disease in Finland. In: Proceedings of the Royal Society B: Biological Sciences. 2010 ; Vol. 277, No. 1681. pp. 593-600.
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Intensive fish farming and the evolution of pathogen virulence : The case of columnaris disease in Finland. / Pulkkinen, K.; Suomalainen, L. R.; Read, Andrew Fraser; Ebert, D.; Rintamäki, P.; Valtonen, E. T.

In: Proceedings of the Royal Society B: Biological Sciences, Vol. 277, No. 1681, 22.02.2010, p. 593-600.

Research output: Contribution to journalArticle

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