Differentiation between a pathogenic and a non-pathogenic form of Gyrodactylus safaris using PCR-RFLP

摘要

Forms of the monogenean ectoparasite Gyrodactylus salaris Malmberg (found in Norway and Sweden) are highly pathogenic to East-Atlantic salmon, Salmo salar L., colonizing rivers draining into the Atlantic. Several salmon stocks in Europe are as susceptible and vulnerable as Norwegian salmon, which is the background for implementation of countermeasures against further spreading of the parasite in Europe (Peeler 2004). Scottish, Irish and Danish salmon will allow marked parasite population increase following exposure to some of the Norwegian forms of the parasite whereas Russian, Finnish and Swedish salmon show limited susceptibility (Lindenstr0m, Sigh, Dalgaard & Buchmann 2006). Current methods for diagnosis of the species are based on light microscopic examination of parasite mounts, DNA sequencing of various genes or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) (rDNA). The PCR-RFLP method is based on differences in the DNA banding pattern obtained following PCR amplification of the internal transcribed spacer (ITS) region (1300 bp) in the parasite and subsequent digestion by specific restriction enzymes (Cunningham 1997). This will allow differentiation between different species within the genus Gyrodactylus but it can not differentiate between forms within the parasite species G. salaris. The recent discovery in Denmark of a non-pathogenic form of G. salaris has implications for management of disease-free zones in Europe (Jorgensen, Larsen, Kania, J0rgensen, Bresciani & Buchmann 2006) and the availability of a reliable diagnostic system for detection of this form is needed. The present work exploits the detection of a mutation in the ITS region of the non-pathogenic form of the parasite and the subsequent development of a PCR-RFLP method for differentiation between the pathogenic and non-pathogenic forms.