Abstract
Background Gyrodactylus salaris is a monogenean, which has collapsed tens of wild Atlantic salmon populations. One of the means of preventing the spread of the parasite is the disinfection of the fishing equipment, which is used in the rivers having susceptible salmon populations. Little is known about the dosage of disinfectants against G. salaris. There are not standards for the testing of disinfectants against multicellular parasites. The present investigation developed a method to test disinfectants and examined the effectiveness of heated water and a commercially available disinfectant (Virkon S) in killing G. salaris. Individual G. salaris worms were followed under the microscope during treatment with heated water or Virkon S disinfectant blend. The logarithm of the time needed to kill the parasite was used as a dependent variable in linear regression. The upper 99.98 % prediction line for the dependent variable was used to obtain a value resembling the time needed for a 4 log reduction of the microbial pathogen, which is commonly used as a criterion for disinfectants. Also 6 log reduction was applied.ResultsExposure to a relatively low temperature was found to kill the parasite. Even 5–50 min treatment (=10–100 times the 99.98 % upper prediction value) with heated water at 40 °C might be used. This would enable the utilisation of hot tap water in the disinfection of fishing gear. The present practice of 1 % Virkon S for 15 min was also found to kill the parasite.ConclusionsThe follow-up of single parasites of a test population and the use of the calculated upper predictive line in the regression analysis offers a method to analyse the effects of disinfectants on parasites like G. salaris. The results of our tests give possibilities for using disinfection methods, which may be more acceptable by the fishermen than the present ones.
Highlights
Gyrodactylus salaris is a monogenean, which has collapsed tens of wild Atlantic salmon populations
Gyrodactylus salaris Malmberg 1957 was first identified on farmed Atlantic salmon (Salmo salar L.) at a fish farm in the Baltic Sea catchment area [1]
The risk of the spread of G. salaris by fishing equipment was not regarded very big [12], have national authorities in Finland, the United Kingdom and Norway provided guidelines or legal regulations on the disinfection of fishing equipment in order to prevent the spread of G. salaris to water systems free of the parasite [13,14,15]
Summary
Gyrodactylus salaris is a monogenean, which has collapsed tens of wild Atlantic salmon populations. Measures to prevent the spread of the parasite include prohibition of the transport of live fish to rivers containing wild Atlantic salmon unless the source of the fish is known to be free of G. salaris [9], barriers to stop fish migration upstream from infected river areas to the risk of the spread of G. salaris by fishing equipment was not regarded very big [12], have national authorities in Finland, the United Kingdom and Norway provided guidelines or legal regulations on the disinfection of fishing equipment in order to prevent the spread of G. salaris to water systems free of the parasite [13,14,15].
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