Distribution Status of Hybrid Types in Large Liver Flukes, Fasciola Species (Digenea: Fasciolidae), from Ruminants and Humans in Vietnam

Abstract

The aim of this study is to delineate ‘admixed hybrid’ and ‘introgressive’ Fasciola genotypes present in the Fasciola population in Vietnam. Adult liver flukes collected from ruminants in 18 Provinces were morphologically sorted out by naked eyes for small (S), medium (M) and large (L) body shapes; and human samples (n=14) from patients. Nuclear ribosomal (rDNA) ITS1 and ITS2, and mitochondrial (mtDNA) nad1 markers were used for determination of their genetic status. Total 4,725 worm samples of ruminants were tentatively classified by their size: 6% (n=284) small (S)-, 13% (n=614) medium (M)-, and 81% (n=3,827) large (L)-forms. All the representative (n=120, as 40 each group) and 14 human specimens, possessed maternal mtDNA of only F. gigantica and none of F. hepatica. Paternally, all (100%) of the L-(n=40) and 77.5% (n=31) of the M-flukes had single F. gigantica rDNA indicating ‘pure’ F. gigantica. A majority (90%, n=36) of the S- and 15% (n=6) of the M-worms had single F. hepatica rDNA, indicating their introgressive; the rest (10%, n=4) of the S- and 7.5% (n=3) of the M-flukes had mixture of both F. gigantica and F. hepatica rDNAs, confirming their admixed hybrid genetic status. Fourteen human samples revealed 9 (64%) of pure F. gigantica, 3 (22%) of introgressive and 2 (14%) of admixed hybrid Fasciola spp. By the present study, it was confirmed that the small worms, which are morphologically identical with F. hepatica, are admixed and/or introgressive hybrids of Fasciola spp., and able to be the pathogens of human fascioliasis.

Exposing the Barcoding Void: An Integrative Approach to Study Snail-Borne Parasites in a One Health Context

“…Knowledge gaps are even greater for trematodes of wildlife, where many species lack molecular reference sequences (9,10). Additionally, hybridization between animal and human trematode species has been documented and some trematodes are of major zoonotic importance (11)(12)(13). Therefore, it is recommended to study trematodiases in a One Health framework, where human and animal trematodes are considered equally important to map their distributions, detect high-risk locations and improve disease control (14).…”

Description and phylogenetic analyses of ribosomal transcription units from species of Fasciolidae (Platyhelminthes: Digenea)

“…These included: Fasciola hepatica (isolate GL) collected from cattle in Geelong, Australia (38°9′0.0072″S; 144°21′0.0216″E), designated Fhep-GL (AU) (Le et al ., 2001); F. gigantica (isolate T4V) from cattle in Thua Thien-Hue Province, Vietnam (16°22′7.932″N; 107°37′31.584″E), designated Fgig-T4V (VN); F. gigantica (isolate NB) from cattle in Ninh Binh Province (20°15′28.764″N; 105°58′33.3732″E), designated Fgig-NB (VN); ‘hybrid’ Fasciola sp. (isolate DL11) from buffalo in Dak Lak Province (12°47′19.284″N; 108°14′23.892″E), designated Fsp-DL11 (VN) (Nguyen et al ., 2018); Fas. jacksoni (isolate Madu) from post mortem wild elephants in Maduru, Sri Lanka (7°34′33″N; 81°08′34″E), designated Fjac-Madu (LK) (Rajapakse et al ., 2019); Fa.…”

“…jacksoni was 12–14 mm (BL) × 9–12.5 mm (BW) and for the Fa. buski fluke was 41 mm (BL) × 13 mm (BW), with typical morphological features for each species/form described in previous studies (Le et al ., 2004; Lotfy et al ., 2008; Periago et al ., 2008; Nguyen et al ., 2018; Rajapakse et al ., 2019). However, the shape of the hybrid form of Fasciola sp.…”

“…The analyses of short fragments have been extensively used for molecular classification, species identification and evolutionary studies both within and between trematode families (Weider et al ., 2005; Blair, 2006). In fact, the rDNA sequences have been shown to be valuable markers in the identification of hybrids and measuring introgression between populations of sympatric fluke species (Blair, 2006; Nguyen et al ., 2018). However, until recently very few complete rDNA reference sequences for trematodes have been available which could have been used to develop and refine such molecular markers further (Weider et al ., 2005; Blair, 2006).…”

Structure and characterization of the ribosomal transcription units of small liver flukes, Opisthorchis viverrini, O. Felineus and Clonorchis sinensis

“…Một trong những dữ liệu gen học quan trọng cần xác lập, khám phá và khai thác là DNA ribosome (ribosomal DNA, rDNA) hay còn gọi là đơn vị sao chép ribosome (ribosomal transcription unit, rTU) có trong hệ gen nhân của tế bào (Blair, 2006). Chuỗi gen của rTU được tận dụng làm chỉ thị phân tử có giá trị trong giám định, phân biệt loài và xác định dòng bố (paternality) đối với các loài độc lập, hoặc loài lai ngoại loài (hybrid hoặc introgressive hybridization) hoặc lai chéo trong quần thể (Blair, 2006;Blair et al, 2016;Nguyen et al, 2018). Trong hệ gen nhân ở tế bào động vật, rDNA sắp xếp hàng trăm đơn vị nối tiếp nhau thành dãy.…”