The prevalence of proliferative kidney disease from the kidney and muscle of rainbow and brown trout in Aragón (Spain).

The prevalence and parasite density of PKX (the unknown myxosporean that causes proliferative kidney disease [PKD] of salmonids) were investigated in eight fishfarms in Aragón, Spain. Tissue sections stained with the biotynilated lectin GS-I revealed the presence of this protozoan in only one of the farms. In rainbow trout, the renal prevalence and parasite density peaked in July, but in brown trout the maximum renal prevalence and maximum renal parasite density were reached in May and in July, respectively. In rainbow trout, after the acute phase of the disease, the number of PKX decreases in the kidney but increases in the muscle. In this species of fish, the prevalence and parasite density are much higher in the muscles than in the kidney in October.