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

• Main Authors: WL Marshall, A Sitjà-Bobadilla, HM Brown, T MacWilliam, Z Richmond, H Lamson, DB Morrison, Luis Afonso
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2016
• Subjects: Fisheries sciences not elsewhere classified; Veterinary sciences not elsewhere classified; Zoology not elsewhere classified; Science & Technology; Life Sciences & Biomedicine; Fisheries; Marine & Freshwater Biology; Veterinary Sciences; histopathology; immunity; intensity; myoliquefaction; prevalence; pseudocysts; MERLUCCIUS-PRODUCTUS AYRES; GILCHRIST MYXOSPOREA; COHO SALMON; ONCORHYNCHUS-KISUTCH; PANIFORMIS KABATA; CERATOMYXA-SHASTA; CYSTEINE PROTEASE; RESERVOIR HOSTS; MUSCLE TEXTURE; PACIFIC; Centre for Integrative Ecology; School of Life and Environmental Sciences; 070404 Fish Pests and Diseases; 830102 Aquaculture Fin Fish (excl. Tuna); 3005 Fisheries sciences; British Columbia; Canada; Kabata; Pacific; Atlantic salmon; Salmo salar
• Online Access: http://hdl.handle.net/10536/DRO/DU:30081128; https://figshare.com/articles/journal_contribution/Long-term_epidemiological_survey_of_Kudoa_thyrsites_Myxozoa_in_Atlantic_salmon_Salmo_salar_L_from_commercial_aquaculture_farms/20892664

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.