Long-term epidemiological survey of Kudoa thyrsites (Myxozoa) in Atlantic salmon (Salmo salar L.) from commercial aquaculture farms

Kudoa thyrsites (Myxozoa) encysts within myocytes of a variety of fishes. While infected fish appear unharmed, parasite‐derived enzymes degrade the flesh post‐mortem. In regions of British Columbia (BC), Canada, up to 4–7% of fillets can be affected, thus having economic consequences and impacting t...

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Bibliographic Details
Published in:Journal of fish diseases 2016-08, Vol.39 (8), p.929-946
Main Authors: Marshall, W L, Sitjà-Bobadilla, A, Brown, H M, MacWilliam, T, Richmond, Z, Lamson, H, Morrison, D B, Afonso, L O B
Format: Article
Language:English
Subjects:
Animals
Aquaculture
British Columbia - epidemiology
Female
Fish Diseases - epidemiology
Fish Diseases - parasitology
Geography
histopathology
immunity
intensity
Kudoa thyrsites
Male
Muscles - parasitology
myoliquefaction
Myxozoa
Myxozoa - genetics
Myxozoa - physiology
Parasitemia - epidemiology
Parasitemia - parasitology
Parasitemia - veterinary
Parasitic Diseases, Animal - epidemiology
Parasitic Diseases, Animal - parasitology
Polymerase Chain Reaction - veterinary
Prevalence
pseudocysts
Salmo salar
Seasons
Thyrsites
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Summary:Kudoa thyrsites (Myxozoa) encysts within myocytes of a variety of fishes. While infected fish appear unharmed, parasite‐derived enzymes degrade the flesh post‐mortem. In regions of British Columbia (BC), Canada, up to 4–7% of fillets can be affected, thus having economic consequences and impacting the competitiveness of BC's farms. K. thyrsites was monitored in two farms having high (HP) or low (LP) historical infection prevalence. At each farm, 30 fish were sampled monthly for blood and muscle during the first year followed by nine samplings during year two. Prevalence and intensity were measured by PCR and histology of muscle samples. In parallel, fillet tests were used to quantify myoliquefaction. Infections were detected by PCR after 355 and 509 degree days at LP and HP farms, respectively. Prevalence reached 100% at the HP farm by 2265 degree days and declined during the second year, whereas it plateaued near 50% at the LP farm. Infection intensities decreased after 1 year at both farms. Blood was PCR‐positive at both farms between 778 and 1113 degree days and again after 2000 degree days. This is the first monitoring project in a production environment and compares data between farms with different prevalence.
ISSN:0140-7775
1365-2761
DOI:10.1111/jfd.12429