Molecular genetic evidence for polyandry in Ascaris suum

Zhou, Chunhua; Yuan, Keng; Tang, Xiaoli; Hu, Ningyan; Peng, Weidong

doi:10.1007/s00436-010-2116-3

Cited by 22 publications

(13 citation statements)

References 38 publications

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“…Low nucleotide diversity was observed in B. schroederi and this revealed a relative lack of genetic variation across the ascaridoid, regardless of geographical origin and population size. Interestingly, similar findings were also described for other Ascaris species, including Ascaris galli [ 50 ], Ascaris suum [ 60 , 61 ] and Parascaris equorum [ 51 ]. Together, these results implied that low level of diversity may be a common feature of ascaridoid nematodes.…”

Section: Discussionsupporting

confidence: 82%

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing

Xie

Zhou²,

Zhang

et al. 2014

Parasites Vectors

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BackgroundInfection with the parasitic nematode, Baylisascaris schroederi (Ascaridida: Nematoda), is one of the most important causes of death in giant pandas, and was responsible for half of deaths between 2001 and 2005. Mitochondrial (mt) DNA sequences of parasites can unveil their genetic diversity and depict their likely dynamic evolution and therefore may provide insights into parasite survival and responses to host changes, as well as parasite control.MethodsBased on previous studies, the present study further annotated the genetic variability and structure of B. schroederi populations by combining two different mtDNA markers, ATPase subunit 6 (atp6) and cytochrome c oxidase subunit I (cox1). Both sequences were completely amplified and genetically analyzed among 57 B. schroederi isolates, which were individually collected from ten geographical regions located in three important giant panda habitats in China (Minshan, Qionglai and Qinling mountain ranges).ResultsFor the DNA dataset, we identified 20 haplotypes of atp6, 24 haplotypes of cox1, and 39 haplotypes of atp6 + cox1. Further haplotype network and phylogenetic analyses demonstrated that B. schroederi populations were predominantly driven by three common haplotypes, atp6 A1, cox1 C10, and atp6 + cox1 H11. However, due to low rates of gene differentiation between the three populations, both the atp6 and cox1 genes appeared not to be significantly associated with geographical divisions. In addition, high gene flow was detected among the B. schroederi populations, consistent with previous studies, suggesting that this parasite may be essentially homogenous across endemic areas. Finally, neutrality tests and mismatch analysis indicated that B. schroederi had undergone earlier demographic expansion.ConclusionsThese results confirmed that B. schroederi populations do not follow a pattern of isolation by distance, further revealing the possible existence of physical connections before geographic separation. This study should also contribute to an improved understanding of the population genetics and evolutionary biology of B. schroederi and assist in the control of baylisascariasis in giant pandas.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-014-0606-3) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 82%

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing

Xie

Zhou²,

Zhang

et al. 2014

Parasites Vectors

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“…More recently, Zhou et al . utilized multilocus microsatellite genotyping to disapprove the former hypothesis by demonstrating that pig Ascaris can indeed serve as an important source of human Ascaris even in China, areas where the two coexist, similar to what we have observed in Papua [21]. …”

Section: Discussionmentioning

confidence: 70%

Reducing zoonotic and internal parasite burdens in pigs using a pig confinement system

Agustina¹,

Swacita²,

Oka³

et al. 2017

Vet World

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Aim:This study was designed to validate the effectiveness of the pig confinement system (PCS) in reducing the prevalence of zoonotic and internal parasite burdens in pigs.Materials and Methods:Ten PCS households were selected together with 10 households practising traditional scavenging systems. Five pigs were monitored per household every 3 months for 15 months and blood and feces collected. Pigs received a single dose of oxfendazole at 30 mg/kg at baseline. Qualitative fecal examinations for intestinal parasite stages were performed, and serum was tested for antibodies to cysticercus of Taenia solium, Trichinella spp., and Toxoplasma gondii.Results:Based on fecal examination, the prevalence of pigs positive for parasite eggs was reduced in PCS pigs over consecutive samplings (Ascaris suum [14.3% to 0%], Trichuris suis [46.9% to 8.3%], Strongyle-type eggs [81.6% to 8.3%], Physocephalus spp. [6.1% to 0%], and Metastrongylus apri [20.8% to 0%]) compared with increases in the number of pigs positive for parasite eggs in non-PCS pigs (T. suis [20-61.5%], Strongyle-type [60.4-80.8%], Physocephalus spp. [8.3-15.4%], and M. apri [20.8-34.6%]) and little change in pigs positive for A. suum (18.8-19.2%). While the prevalence of pigs with antibodies against to cysticerci of T. solium reduced in PCS pigs from 18% to 14%, the prevalence in non-PCS pigs increased from 42% to 52%. Antibodies to Trichinella were not detected, but the prevalence of T. gondii antibodies increased from 6% to 10% in PCS pigs and from 7% to 24% in non-PCS pigs.Conclusion:These data demonstrate the potential of a PCS to reduce the prevalence of pigs infected with zoonotic and internal parasites and thus the risk to human and pig health.

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“…The relatively high frequency of polyandrous pairings would substantially increase the diversity of genotypes found among the progeny, as more possible pairs of haplotypes would be generated. This feature of H. contortus biology is likely to play a significant role in generating and maintaining the high levels of genetic diversity characterised in laboratory [63] and field [67, 68] isolates of this parasite and is also relevant to other parasitic nematode species where polyandry has been reported [69-71].…”

Section: Discussionmentioning

confidence: 99%

A genome resequencing-based genetic map reveals the recombination landscape of an outbred parasitic nematode in the presence of polyploidy and polyandry

Doyle

Laing

Bartley

et al. 2017

Preprint

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The parasitic nematode Haemonchus contortus is an economically and clinically important pathogen of small ruminants, and a model system for understanding the mechanisms and evolution of traits such as anthelmintic resistance. Anthelmintic resistance is widespread and is a major threat to the sustainability of livestock agriculture globally; however, little is known about the genome architecture and parameters such as recombination that will ultimately influence the rate at which resistance may evolve and spread. Here we performed a genetic cross between two divergent strains of H. contortus, and subsequently used whole-genome re-sequencing of a female worm and her brood to identify the distribution of genome-wide variation that characterises these strains. Using a novel bioinformatic approach to identify variants that segregate as expected in a pseudo-testcross, we characterised linkage groups and estimated genetic distances between markers to generate a chromosome-scale F1 genetic map composed of 1,618 SNPs. We exploited this map to reveal the recombination landscape, the first for any parasitic helminth species, demonstrating extensive variation in recombination rate within and between chromosomes. Analyses of these data also revealed the extent of polyandry, whereby at least eight males were found to have contributed to the genetic variation of the progeny analysed. Triploid offspring were also identified, which we hypothesise are the result of nondisjunction during female meiosis or polyspermy. These results expand our knowledge of the genetics of parasitic helminths and the unusual life-history of H. contortus, and will enable more precise characterisation of the evolution and inheritance of genetic traits such as anthelmintic resistance. This study also demonstrates the feasibility of whole-genome resequencing data to directly construct a genetic map in a single generation cross from a non-inbred non-model organism with a complex lifecycle.Author summaryRecombination is a key genetic process, responsible for the generation of novel genotypes and subsequent phenotypic variation as a result of crossing over between homologous chromosomes. Populations of strongylid nematodes, such as the gastrointestinal parasites that infect livestock and humans, are genetically very diverse, but little is known about patterns of recombination across the genome and how this may contribute to the genetics and evolution of these pathogens. In this study, we performed a genetic cross to quantify recombination in the barber’s pole worm, Haemonchus contortus, an important parasite of sheep and goats. The reproductive traits of this worm make standard genetic crosses challenging, but by generating whole-genome sequence data from a female worm and her offspring, we identified genetic variants that act as though they come from a single mating cross, allowing the use of standard statistical approaches to build a genetic map and explore the distribution and rates of recombination throughout the genome. A number of genetic signatures associated with H. contortus life history traits were revealed in this analysis: we extend our understanding of multiple paternity (polyandry) in this species, and provide evidence and explanation for sporadic increases in chromosome complements (polyploidy) among the progeny. The resulting genetic map will aid in population genomic studies in general and enhance ongoing efforts to understand the genetic basis of resistance to the drugs used to control these worms, as well as for related species that infect humans throughout the world.

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Molecular genetic evidence for polyandry in Ascaris suum

Cited by 22 publications

References 38 publications

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing

Reducing zoonotic and internal parasite burdens in pigs using a pig confinement system

A genome resequencing-based genetic map reveals the recombination landscape of an outbred parasitic nematode in the presence of polyploidy and polyandry

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