C. parvum in Melbourne's catchments: investigating prevalence and developing high-resolution molecular detection tools

The Melbourne Water Corporation has funded the University of Melbourne Veterinary School to study the prevalence of Cryptosporidium and Giardia in animals in water catchment areas of Melbourne and to establish molecular tools for the identification of the parasite to the species and strain levels. In a first epidemiological survey Cryptosporidium was found in high prevalence (17 of 24 species examined; n = 490), whereas Giardia was detected in two animals. A polymerase chain reaction (PCR)-based mutation scanning technique was established for identification of C. parvum to the strain level from oocyst isolates. This so-called single strand conformation polymorphism (SSCP) technique allows high-resolution analysis of genetic variability within and between populations of C. parvum. In a blind test, SSCP genotyping of 23 DNA samples representing C. parvum from different host and geographical regions demonstrated that the method could correctly type samples identified previously using a range of other methods, and displayed higher levels of sequence variability compared with conventional approaches. Hence, the method provides a powerful epidemiological tool for diagnosis as well as for identifying the source of waterborne outbreaks. Future molecular epidemiological surveys of cryptosporidosis/Cryptosporidium will be conducted together with Australian and European collaborators, with a particular emphasis on human cryptosporidosis.