Biodiversity of flukes

Abstract

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-

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

“…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). It seems likely that divergent intraspecific lineages might differ also in their karyotypes (see discrepancies in Table 2).…”

“…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.…”

Towards the comprehension of fasciolosis (re-)emergence: an integrative overview

“…The existence of high within-population diversity translates into greater plasticity and fast adaptability to new environmental (intra or extra-hosts) variations and constraints, and thus, to higher chances of initiating and maintaining transmission, even in unusual hosts. In a worldwide scenario of fasciolosis (re-)emergence, genetically diversified parasite populations may also facilitate the appearance of resistance to anthelmintic drugs, further hindering disease control (Dreyfuss and Rondelaud, 2008).…”

Immunoblotting Identification of Diagnostic Antigens of Paragonimus westermani Type 1 for the Detection of Human Pulmonary Paragonimiasis in North East India

“…Notably, a study by Devi et al [ 19 ] identified two distinct genotypes of P. westermani from NE Indian freshwater crab, with one genotype (type 1) differing from its East Asian counterparts. This diversity can impact the disease’s behavior, underscoring the need for a nuanced understanding of host–parasite interactions, especially in terms of the antibody response [ 20 ]. For the development of an immunodiagnostic test, the use of locally available species of lung fluke, Paragonimus westermani type 1, appears to be an important source of parasitic antigens because it can easily be procured locally and developed in rodent experimental models.…”