Characterisation of Ascaris from human and pighosts by nuclear ribosomal DNA sequencesfn1fn1Note: Nucleotide sequence data reported in this paperare available in the embl, GenBankTM and DDJBdatabases under the accession numbersAJ000894–AJ000896, AJ001506, AJ001507 andY09491.

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Using a single-strand conformation polymorphism-based approach, we investigated nucleotide variation in part of the first internal transcribed spacer (pITS-1) of nuclear ribosomal DNA within and among a large number of Ascaris individuals from humans and pigs from six endemic regions in China, and examined the frequency of the different genotypes of Ascaris in relation to host species and geographical origin. Five different SSCP genotypes (G1-G5) were recorded for human Ascaris (n = 486), of which three (genotypes G1-G3) were detected for pig Ascaris (n = 329). Of the five Ascaris genotypes detected, genotype G1 predominantly infected humans (approximately 63-74%) whereas genotype G3 infected mainly pigs (approximately 79-86%), indicating that each of these genotypes has a particular host affiliation. In contrast, the frequencies of the other three genotypes was substantially lower for each of the two host species. The findings also suggested that the rate of cross infection of Ascaris between humans and pigs is relatively low and that gene flow between the predominant genotypes is limited, consistent with previous proposals for endemic regions in other countries. While the nature and extent of nucleotide variation in the pITS-1 (and the proposal of host affiliated Ascaris populations) may relate to "introgression" or "lineage sorting and retention of ancentral polymorphism", other explanations are possible. Evidence of multiple pITS-1 sequence types in some Ascaris individuals representing particular genotypes (e.g., G2 and G5) may suggest hybridization between human- and pig-affiliated Ascaris. This aspect and the species status of Ascaris (from each host species) warrant future experimental testing, employing the pig/Ascaris model and the present electrophoretic approach.*

Section: Resultsmentioning

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Section: Enzymatic Amplificationmentioning

confidence: 99%

Section: Enzymatic Amplificationmentioning

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Section: Selective Dna Sequencingmentioning

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Section: Introductionmentioning

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See 3 more Smart Citations

Molecular epidemiological investigation of Ascaris genotypes in China based on single‐strand conformation polymorphism analysis of ribosomal DNA

Peng¹,

Yuan²,

Zhou³

et al. 2003

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Mutation scanning for sequence variation in three mitochondrial DNA regions for members of theContracaecum osculatum (Nematoda: Ascaridoidea) complex

Hu¹,

D’Amelio²,

Zhu³

et al. 2001

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Anisakid nematodes of seals from different geographical origins, previously identified by multilocus enzyme electrophoresis as Contracaecum osculatum A (CoA), C. osculatum B (CoB), C. osculatum C (CoC), C. osculatum D (CoD), C. osculatum E (CoE) and C. osculatum baicalensis (Cob), were characterised genetically using a mutation scanning approach, in order to define genetic markers for their specific identification and differentiation. Three mitochondrial DNA (mtDNA) regions, namely cytochrome c oxidase subunit I (COI), and the small and large subunits of rRNA (ssrRNA and IsrRNA, respectively) were amplified separately from individual nematodes by polymerase chain reaction (PCR), analysed by single-strand conformation polymorphism (SSCP), and samples displaying sequence variability were subjected to sequencing. Forty-six haplotypes were defined for 62-66 individuals (representing the six members of C. osculatum). All taxa except CoD and CoE could be identified, or delineated from one another, by nucleotide differences in the COI, ssrRNA and/or IsrRNA sequences. For all three mtDNA regions, 4 (10.5%), 7 (18.4%), 15 (39.5%) and 11 (28.9%) of 38 nucleotide positions were considered diagnostic (fixed) and could thus unequivocally delineate CoA, CoB, CoC and Cob. The lack of an unequivocal nucleotide difference in any of the three mtDNA sequences between CoD and CoE was in accordance with previous ribosomal DNA sequence data but inconsistent with multilocus enzyme electrophoretic data. Using all fixed nucleotide positions, CoA, CoD/E and CoB were genetically more similar to Cob than each was to CoC, similar to previous findings. In spite of not being able to distinguish among all six taxa of C. osculatum, the present study demonstrated clearly the usefulness and attributes of the mutation scanning approach for investigating population genetic structures of species of parasitic nematodes.

Mutation scanning-coupled analysis of haplotypic variability in mitochondrial DNA regions reveals low gene flow between human and porcineAscaris in endemic regions of China

Peng

Yuan

et al. 2005

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Haplotypic variation within and among the Ascaris populations representing six provinces in China was investigated. Mitochondrial DNA regions in the cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes were amplified by PCR from total genomic DNA samples (n > 720) from Ascaris individuals from humans and pigs, and subjected to mutation scanning and subsequent selective sequencing. For the cox1, ten different electrophoretic profiles were recorded for human Ascaris, and the same number for pig Ascaris, one of them being common to both host species. For the nad1, 11 different profiles were detected for human Ascaris, and 15 for pig Ascaris. Having defined all haplotypes (20 for pcox1 and 26 for pnad1) by sequencing, their frequencies were estimated in each of the two host species and each of the six provinces. For each mitochondrial region, the frequency of the different haplotypes varied considerably, depending on host species and geographical origin. Analysis of the sequence data (representing all haplotypes for each mitochondrial locus) by F-statistics indicated restricted gene flow between human Ascaris and pig Ascaris, and supported the conclusions from previous molecular epidemiological investigations that pigs are not a significant source of Ascaris infection in humans in endemic regions.