The occurrence and significance of triploidy in the liver fluke,<i>Fasciola hepatica</i>

Fletcher, Hugh; Hoey, Elizabeth M.; Orr, Nick; Trudgett, Alan; Fairweather, Ian; Robinson, Mark W.

doi:10.1017/s003118200300427x

Cited by 55 publications

(37 citation statements)

References 13 publications

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“…Furthermore, some liver fluke isolates have been shown to be triploid, which provides further options for genetic recombination and increased diversity (Fletcher et al, 2004). These parasites, therefore, appear to have the potential for high rates of true genetic change (microevolution).…”

Section: Genetic Adaptationmentioning

confidence: 99%

Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions

Dijk

Sargison

Kenyon

et al. 2010

Animal

206

123

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In the UK, recent mean temperatures have consistently increased by between 18C and 48C compared to the 30-year monthly averages. Furthermore, all available predictive models for the UK indicate that the climate is likely to change further and feature more extreme weather events and a trend towards wetter, milder winters and hotter, drier summers. These changes will alter the prevalence of endemic diseases spatially and/or temporally and impact on animal health and welfare. Most notable among these endemic parasites are the helminths, which have been shown to be very strongly influenced by both the shortterm weather and climate through effects on their free-living larval stages on pasture. In this review, we examine recent trends in prevalence and epidemiology of key helminth species and consider whether these could be climate-related. We identify likely effects of temperature and rainfall on the free-living stages and some key parasite traits likely to determine parasite abundance under changed climatic conditions. We find clear evidence that climate change, especially elevated temperature, has already changed the overall abundance, seasonality and spatial spread of endemic helminths in the UK. We explore some confounders and alternative explanations for the observed patterns. Finally, we explore the implications of these findings for policy makers and the livestock industry and make some recommendations for future research priorities.

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Section: Genetic Adaptationmentioning

confidence: 99%

Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions

Dijk

Sargison

Kenyon

et al. 2010

Animal

206

123

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“…probably arises repeatedly and occasionally in various regions by a variety of mechanisms and facultative gynogenesis is thus widespread in Fasciola. Local populations could be outbreeding and diverse, or clonal with few genotypes present (Fletcher et al, 2004). A rather broad genetic diversity among geographically distinct Fasciola populations was also discussed by Semyenova et al (2006) and Dreyfuss & Rondelaud (2008).…”

Section: Discussionmentioning

confidence: 77%

“…Moriyama et al, 1979;Sakaguchi, 1980;Terasaki et al, 1998Terasaki et al, , 2000Itagaki et al, 2009;Srimuzipo et al, 2000;Ichikawa & Itagaki, 2010). Additionally, triploid F. hepatica has been found in Britain and Ireland (Fletcher et al, 2004). Recent molecular studies have suggested that the origin of Asian triploids may be hybridization between F. hepatica and F. gigantica (Itagaki & Tsutsumi, 1998;Agatsuma et al, 2000;Lin et al, 2007;Itagaki et al, 2009;Peng et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Recent molecular studies have suggested that the origin of Asian triploids may be hybridization between F. hepatica and F. gigantica (Itagaki & Tsutsumi, 1998;Agatsuma et al, 2000;Lin et al, 2007;Itagaki et al, 2009;Peng et al, 2009). Moreover, Terasaki et al (2000), Fletcher et al (2004) and Dreyfuss & Rondelaud (2008) suggest that triploidy in Fasciola spp. probably arises repeatedly and occasionally in various regions by a variety of mechanisms and facultative gynogenesis is thus widespread in Fasciola.…”

Section: Discussionmentioning

confidence: 99%

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A description of karyotype of the giant liver fluke Fascioloides magna (Trematoda, Platyhelminthes) and a review of Fasciolidae cytogenetics

Reblánová

Špakulová

Orosová³

et al. 2010

Helminthologia

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69 SummaryThe study describes a karyotype of a common parasite of cervids, the giant liver fluke, Fascioloides magna (Trematoda, Platyhelminthes). The chromosome set of F. magna comprises 11 pairs of chromosomes, all classified as subtelocentric except for the submeta-metacentric pair No. 8 and the submetacentric pair No. 10 (2n = 22, n = 1sm + 1sm-m + 9st). The first longest pair is 4.65 μm long and the length decreases continuously to the 1.92 μm length of the last pair No. 11. No distinct secondary constriction has been observed in mitotic preparations. Fluorescent DAPIstaining reveals distinct heterochromatin bands on all 11 chromosome pairs in the centromeric regions; another DAPI-positive bands are localized at the end of the long arms of chromosomes No. 5 and the last less distinct signals appear interstitially on the long arms of the pair No. 6. Synchronous meiotic divisions of 8-spermatocyte groups have been observed during spermatogenesis, similarly with a development of spermatocytes in other trematodes. In the first two stages of heterotypic spermatocyte division, 11 bivalents (n = 11) are regularly observed, confirming the diploid number of 22 elements. Furthermore, the present analysis summarises and discusses available cytogenetic data on Fasciolidae flukes suitable for future studies on taxonomy or phylogenetic interrelationships within the family.

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“…T he study of karyotypes from F. hepatica samples identified triploid azoospermic flukes, which then induced asexual reproduction (Fletcher et al, 2004). This type of reproduction is frequent in Asia among diploid or triploid flukes, suggesting that parthenogenesis is widely present in Fasciola.…”

Section: Ploidia Of Flukesmentioning

confidence: 98%

Biodiversity of flukes

Dreyfuss

Rondelaud

2008

Parasite

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Summary :As many others parasites, speciation of flukes depends on the genetic characteristics and on ploidia. Ploidia of flukes can be different in a same species. In Asia, diploid, triploid and hybrid (2n/3n) populations are encountered. The comparison of morphological parameters between diploid and triploid flukes showed that they were morphologically different. Nevertheless, a genetic relationship between parthenogenetic organisms would exist regardless of their ploidia. In the Fasciola genus, the main consequence of the high level of diversity is the frequent probability of development of resistance to anthelmintics and fast adaptation to climatic changes. In the Paragonimus genus, diversity can enhance different forms of pathogenicity, can also be related to the species of intermediate hosts, and to the definitive host. The strain of flukes plays a part in the visceral localization of P. westermani adults. DIFFICULTY OF SPECIATION IN MEDICAL PARASITOLOGYPLOIDIA P arasitology is a biological field in which taxonomy often still uses morphological and Linnean criteria. The limits of the Linnean descriptive methods were reached many decades ago: the dilemma Entamoeba histolytica/E. dispar is a demonstrative example. Similarly, the infra-specific relationships between biogeography of parasites and their biological characteristics (rhythm, pathology, reservoirs) were used to organize the taxonomy of genetically different parasitic populations (Wuchereria bancrofti, for instance). Genetic diversity cannot yet be evaluated by easy and low cost methods. The results of the biological diagnosis of parasitic diseases tend to be less precise, and decrease at the genus level (E. histolytica/E. dispar), or even the family (Opisthorchiidae, Ancylostomatidae, Paragonimidae). Protozoa are parasites for which genetic diversity can be evaluated quite easily. Helminths, particularly Digenea, cannot be analyzed easily, because many species have a variable ploidia, which modifies their morphology and DNA size. A comparative morphometric study, by light microscopy, of eggs and adults from three populations with different sizes of Fasciola gigantica, and the morphology of adults, under scanning electron microscopy, showed variations in the sizes of eggs and adults, whereas the surface was similar using electronic morphology (Srimuzipo et al., 2000). The observations on mitotic metaphase chromosomes revealed a diploid type (2n = 20) in all three size-races. The speciation of Digenea can no longer be evaluated by simple morpholo-

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The occurrence and significance of triploidy in the liver fluke,Fasciola hepatica

Cited by 55 publications

References 13 publications

Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions

Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions

A description of karyotype of the giant liver fluke Fascioloides magna (Trematoda, Platyhelminthes) and a review of Fasciolidae cytogenetics

Biodiversity of flukes

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