Development of a polymerase chain reaction diagnostic assay for Ceratomyxa shasta, a myxosporean parasite of salmonid fish.

A diagnostic procedure based on the polymerase chain reaction (PCR) was developed for the myxosporean parasite Ceratomyxa shasta. Three sets of oligonucleotide primers were designed to specifically amplify C. shasta ribosomal RNA genes and several parameters of the assay were tested and optimised. A simple protocol for the processing of fish tissue samples was also developed. In a single round, 20 microliters volume reaction the optimised procedure allows the detection of 50 fg of purified C. shasta genomic DNA, or 0.01 spore from a seeded fish intestine sample. This protocol is considerably faster, cheaper and more reliable than any previous diagnostic procedure for a myxosporean parasite, and can be an invaluable tool for the monitoring of early and/or subclinical C. shasta infections in wild and cultured salmon populations.