DAO 63:267-271 (2005)  -  doi:10.3354/dao063267

ABSTRACT: Atlantic salmon Salmo salar skeletal muscle was examined for Kudoa thyrsites by polymerase chain reaction (PCR) and positive fish were further examined by in situ hybridization (ISH) and immunohistochemistry (IHC). The infection was detected in 42% of salmon by PCR following a 60 d exposure to infective seawater at a temperature of 10°C (= 600 degree-days, °D). The parasite was detected by ISH in skeletal and cardiac muscle but not in gill, kidney, spleen, liver, stomach, intestine, pyloric caeca and skin. None of 4 monoclonal antibodies (2F4, 4H2, 1H2, 3E8) raised against mature K. thyrsites spores reacted with the stages identified by ISH following a 600 °D exposure, but they did react with ISH-identified stages following a 1600 °D exposure. In contrast, a polyclonal antibody reacted with K. thyrsites stages in salmon with both 600 and 1600 °D exposures, suggesting that the parasite observed in 600 °D infections represents an antigenically distinct developmental stage of K. thyrsites.

KEY WORDS: Kudoa thyrsites · Myxosporea · Salmo salar · In situ hybridization · Immunohistochemistry