The Gibel carp, (Bloch), is an important freshwater farming species that grows rapidly, has a high meat yield, and wide adaptability. However, in the past decade, diseases have been a severe challenge to successful culture systems. The parasitic disease caused by causes massive deaths of the larval and adult Gibel carp every year. Establishing an efficient, sensitive, and specific detection method is of great significance for the early diagnosis and prevention of the disease. In this study, a single-tube, semi-nested polymerase chain reaction assay to detect and monitor the infection of was developed with two newly designed primer pairs, which were designed based on 18S rDNA. The specificity, sensitivity, repeatability, and applicability of the assay were evaluated. The results indicated that amplification was positive only in the Carassius auratus gibelio Bloch were all negative; the lowest detection was 4.2 copy/μL of the target gene. The clinical detection samples showed that was present in the ovaries, kidneys, and spleen of asymptomatic Gibel carp from the epizootic zone, with a positive incidence of 40%, 32%, and 8%, respectively. In conclusion, the method developed in this study is of high specificity and sensitivity, which provides a new and reliable technical means for the early diagnosis and control of .