Sequence and PCR–RFLP analysis of the internal transcribed spacers of the rDNA repeat unit in isolates of Cryptosporidium from different hosts

U. M. MORGAN a1c1, P. DEPLAZES a2, D. A. FORBES a3, F. SPANO a4, H. HERTZBERG a2, K. D. SARGENT a1, A. ELLIOT a1 and R. C. A. THOMPSON a1
a1 World Health Organization Collaborating Centre for the Molecular Epidemiology of Parasitic Infections and State Agricultural Biotechnology Centre, Division of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia
a2 Institute of Parasitology, University of Zurich, Wintherthurerstrasse 266a, CH-8057, Zurich, Switzerland
a3 Department of Paediatrics, University of Western Australia, Princess Margaret Hospital, GPO Box D184, WA 6001, Australia
a4 Istituto di Parassitologia, Università di Roma ‘La Sapienza’, P. le A. Moro 5, 00185 Rome, Italy


The Cryptosporidium ITS1, 5·8S and ITS2 rDNA regions from a number of Cryptosporidium isolates from different hosts and geographical areas were cloned and sequenced in order to investigate the extent of sequence heterogeneity between human and cattle-derived isolates from different geographical locations and also between isolates of Cryptosporidium from different hosts such as cats, pigs, mice and a koala. Calf-derived isolates from different continents were virtually identical as were human-derived isolates from the UK and Australia. Genetic differences between Cryptosporidium isolates were extensive and were in fact greater than the level of nucleotide divergence between Toxoplasma gondii and Neospora caninum rDNA sequences. Based on the sequence information derived from this study, PCR–RFLP of the ITS1 region was undertaken in order to directly amplify and genotype Cryptosporidium isolates from different hosts. This PCR–RFLP approach can now be used for molecular epidemiology studies, circumventing the need for costly sequencing and allowing a wider range of genetically different isolates to be examined.

(Received April 1 1998)
(Revised June 10 1998)
(Accepted June 11 1998)

Key Words: Cryptosporidium; rDNA; ITS; genotypes.

c1 Corresponding author: Division of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150. Tel: +08 9360 2457. Fax: +08 9310 4144. E-mail: