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Breeding systems in Echinococcus granulosus (Cestoda; Taeniidae): selfing or outcrossing?

Published online by Cambridge University Press:  01 January 1999

K. L. HAAG ,
A. M. ARAÚJO ,
B. GOTTSTEIN ,
M. SILES-LUCAS ,
R. C. A. THOMPSON  and
A. ZAHA
K. L. HAAG
Affiliation:
Departamento de Genética, Universidade Federal do Rio Grande do Sul, Caixa Postal 15053, Porto Alegre, 91501-970, Brazil
A. M. ARAÚJO
Affiliation:
Departamento de Genética, Universidade Federal do Rio Grande do Sul, Caixa Postal 15053, Porto Alegre, 91501-970, Brazil
B. GOTTSTEIN
Affiliation:
Institute of Parasitology, University of Berne, Laengass Strasse 122, PO Box 8466, Berne, CH-3001, Switzerland
M. SILES-LUCAS
Affiliation:
Institute of Parasitology, University of Berne, Laengass Strasse 122, PO Box 8466, Berne, CH-3001, Switzerland
R. C. A. THOMPSON
Affiliation:
World Health Organization Collaborating Centre for the Molecular Epidemiology of Parasitic Infections, Division of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia
A. ZAHA
Affiliation:
Departamento de Biotecnologia, Universidade Federal do Rio Grande do Sul, Caixa Postal 15005, Porto Alegre, 91501-970, Brazil
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Abstract

We used the PCR–SSCP method followed by sequencing in order to assess the genetic variability of coding and non- coding parts of the genome of Echinococcus granulosus (Cestoda; Taeniidae) and to test whether or not the parasite populations are mainly self-fertilizing. For this, we analysed a sample of 110 E. granulosus metacestode isolates collected from different geographical regions (Southern Brazil, Europe and Australia) and from different intermediate hosts (ovine, bovine, human, macropod, swine and equine). Using appropriate controls, we were able to identify 4 strains in that sample (sheep, cattle, pig and horse strains). The high degree of genetic differentiation between strains, but not within, and the monomorphism found in most loci (EgAg4, EgActII, EgHbx2 and EgAg6 – non-coding – EgAgB/1 and EgND1 – coding) indicated that they are largely selfed. On the other hand, outcrossing was also shown to occur, since 5 potential hybrid genotypes between cattle and sheep strains were found in populations of Southern Brazil, but absent in other geographical areas. We suggest that both processes are adaptive. The article also reports, for the first time, the occurrence of the E. granulosus cattle strain in South America.

Keywords

Echinococcus granulosusSSCPstraingenetic variabilityselfing
Type
Research Article
Information
Parasitology , Volume 118 , Issue 1 , January 1999 , pp. 63 - 71
Copyright
1999 Cambridge University Press

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