Molecular characterization of ascaridoid parasites from captive wild carnivores in China using ribosomal and mitochondrial sequences

Abstract

Background: Despite the public health importance of toxocariasis/toxascariasis, only a few species of these ascaridoid parasites from wild canine and feline carnivores have been studied at the molecular level so far. Poor understanding of diversity, host distribution and the potential (zoonotic) transmission of the ascaridoid species among wild animals negatively affects their surveillance and control in natural settings. In this study, we updated previous knowledge by profiling the genetic diversity and phylogenetic relationships of ascaridoid species among eleven wild canine and feline animals on the basis of a combined analysis of the ribosomal internal transcribed spacer region (ITS) gene and the partial mitochondrial cytochrome c oxidase subunit 2 (cox2) and NADH dehydrogenase subunit 1 (nad1) genes. Results: In total, three genetically distinct ascaridoid lineages were determined to be present among these wild carnivores sampled, including Toxocara canis in Alopex lagopus and Vulpes vulpes, Toxocara cati in Felis chaus, Prionailurus bengalensis and Catopuma temmincki and Toxascaris leonina in Canis lupus, Panthera tigris altaica, Panthera tigris amoyensis, Panthera tigris tigris, Panthera leo and Lynx lynx. Furthermore, it was evident that T. leonina lineage split into three well-supported subclades depending on their host species, i.e. wild felids, dogs and wolves and foxes, based on integrated genetic and phylogenetic evidence, supporting that a complex of T. leonina other than one species infecting these hosts. Conclusions: These results provide new molecular insights into classification, phylogenetic relationships and epidemiological importance of ascaridoids from wild canids and felids and also highlight the complex of the taxonomy and genetics of Toxascaris in their wild and domestic carnivorous hosts.

What lies behind the curtain: Cryptic diversity in helminth parasites of human and veterinary importance

“…leonina from dogs and wolves clustered together (Kimura 2-parameter (K2P) barcode gap distance > 1.7%), while those from wild felids (K2P barcode gap distance of 3%) and red foxes (K2P barcode gap distance of 6.58%) formed two separate groups, suggesting the existence of three cryptic species within the complex. Interestingly, this research also pointed out that gene flow among wild felid isolates could be low ( Fogt-Wyrwas et al., 2019 ) as supported by complete sequences and partial cox 2 and nad 1 analyses ( Xie et al., 2020 ).…”

“…Several molecular studies have demonstrated the presence of cryptic species among Ta. leonina isolates, with apparent species delimitation according to host ( Song et al., 2015 ; Li et al., 2018 ; Fogt-Wyrwas et al., 2019 ; Jin et al., 2019 ; Xie et al., 2020 ). In a preliminary study, cox 1 was employed to determine the genetic relationship between Ta.…”

The complete mitogenome ofToxascaris leoninafrom the Siberian tiger (Panthera tigris altaica)

“…The solid black diamond represents the species in this study. Fogt-Wyrwas et al 2019;Xie et al 2020), suggesting at least two distinct subclades of T. leonina infecting these hosts and supporting that T. leonina represents a species complex. Furthermore, four T. leonina isolates of grouped together, regardless of isolate origins and hosts, and were more closely related to other species from the family Ascarididae than species of families Toxocaridae, Anisakidae, and Ascaridiidae, demonstrating phylogenetic stability of these paraphyletic groups characterized in this study.…”

“…Moreover, increased epidemiological evidences suggest that T. leonina is emerging as an underestimated zoonotic agent because of close relationships between humans and their pets (e.g. dogs and cats) and increased interactions between people and wildlife hosts in zoos (Robertson and Thompson 2002;Li et al 2007;Li et al 2008;Okulewicz et al 2012;Xie et al 2020). Such situations highlight the significance and necessity for diagnosis and identification of T. leonina.…”

“…Such situations highlight the significance and necessity for diagnosis and identification of T. leonina. Unfortunately, current diagnosis and identification of this parasite still rely on morphological characteristics, host sources and geographical distributions although these criteria are not always sufficient to distinguish the morphologically similar species (Gasser 2006;Chen et al 2012;Fogt-Wyrwas et al 2019;Xie et al 2020). Under such context, obtaining a more efficient approach to identify T. leonina infections has become urgent for clinical diagnosis and epidemiological investigation, and achieving this goal is foreseeable only through utilization of molecular methodologies.…”