Parasitology



Development and application of an ethically and epidemiologically advantageous assay for the multi-locus microsatellite analysis of Schistosoma mansoni


C. M. GOWER a1a2c1, J. SHRIVASTAVA a1, P. H. L. LAMBERTON a1, D. ROLLINSON a2, B. L. WEBSTER a2, A. EMERY a2, N. B. KABATEREINE a3 and J. P. WEBSTER a1
a1 Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College (St Mary's Campus), Norfolk Place, London W2 1PG, UK
a2 Wolfson Wellcome Biomedical Laboratories, Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
a3 Vector Control Division, Ministry of Health, Kampala, PO Box 1661, Uganda

Article author query
gower cm   [PubMed][Google Scholar] 
shrivastava j   [PubMed][Google Scholar] 
lamberton ph   [PubMed][Google Scholar] 
rollinson d   [PubMed][Google Scholar] 
webster bl   [PubMed][Google Scholar] 
emery a   [PubMed][Google Scholar] 
kabatereine nb   [PubMed][Google Scholar] 
webster jp   [PubMed][Google Scholar] 

Abstract

Non-availability of adult worms from living hosts remains a key problem in population genetic studies of schistosomes. Indirect sampling involving passage through laboratory animals presents significant ethical and practical drawbacks, and may result in sampling biases such as bottlenecking processes and/or host-induced selection pressures. The novel techniques reported here for sampling, storage and multi-locus microsatellite analysis of larval Schistosoma mansoni, allowing genotyping of up to 7 microsatellite loci from a single larva, circumvent these problems. The utility of these assays and the potential problems of laboratory passage, were evaluated using 7 S. mansoni population isolates collected from school-children in the Hoima district of Uganda, by comparing the associated field-collected miracidia with adult worms and miracidia obtained from a single generation in laboratory mice. Analyses of laboratory-passaged material erroneously indicated the presence of geographical structuring in the population, emphasizing the dangers of indirect sampling for population genetic studies. Bottlenecking and/or other sampling effects were demonstrated by reduced variability of adult worms compared to their parent field-collected larval samples. Patterns of heterozygote deficiency were apparent in the field-collected samples, which were not evident in laboratory-derived samples, potentially indicative of heterozygote advantage in establishment within laboratory hosts. Genetic distance between life-cycle stages in the majority of isolates revealed that adult worms and laboratory-passaged miracidia clustered together whilst segregating from field miracidia, thereby further highlighting the utility of this assay.

(Received September 28 2005)
(Revised April 27 2006)
(Revised September 18 2006)
(Revised September 21 2006)
(Accepted September 22 2006)
(Published Online November 13 2006)


Key Words: schistosome; sampling; laboratory passage; 3 Rs; bottlenecking; miracidia; cercariae; population genetics; multiplex.

Correspondence:
c1 Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College (St Mary's Campus), Norfolk Place, London W2 1PG, UK. Tel: +44 (0) 20 7594 3819. Fax: +44 (0) 207 402 3927. E-mail: c.gower@imperial.ac.uk


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