Molecular data reveal cryptic speciation and host specificity in Toxascaris leonina (Nematoda: Ascarididae)

Characterization of the complete mitochondrial genome sequence of the dog roundwormToxascaris leonina(Nematoda, Ascarididae) from China

“…The maximum-likelihood (ML) phylogeny inferred from a concatenated amino acid dataset of 12 protein-coding genes from 32 nematode parasites clearly placed T. leonina together with other species from the family Ascarididae and separated from species of the families Toxocaridae, Anisakidae, and Ascaridiidae, with high bootstrap values (Figure 1). Within the genus Toxascaris of Ascarididae, two canid-originated T. leonina (one was from China and another was from Australia) clustered together, and were phylogenetically distinctive from felid-originated T. leonina (Chinese isolate), consistent with recent molecular studies (Fogt-Wyrwas et al 2019;Jin et al 2019), supporting that T. leonina may represent a species complex. Overall, the sequenced mitochondrial genome of T. leonina in this study adds novel molecular evidence for phylogenetic and taxonomic position of this roundworm species.…”

“…Toxascaris leonina (Nematoda, Ascarididae) is a common intestinal nematode parasite of canids and felids (Okulewicz et al 2012;Fogt-Wyrwas et al 2019). Unlike other roundworms, the life cycle of T. leonina is simple and infections generally follow by oral ingestion of the infective eggs, and then the egg-hatched larvae mature in the small intestine of the definitive hosts (Sprent 1959).…”

“…Such situations highlight the significance of diagnosis and identification of T. leonina. However, current diagnosis and identification of this worm is largely based on morphology and often misdiagnosed even by experienced microscopists (Gasser 2006;Chen et al 2012;Fogt-Wyrwas et al 2019). In such context, obtaining a more efficient approach to identify T. leonina infection has become crucial for clinical diagnosis and epidemiological investigation, and achieving this goal is foreseeable only through utilization of molecular methodologies.…”

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

“…Like T. cati, the congenetic T. malaysiensis infects felids [10]. However, T. leonina is defined to infect both feline and canine species [11,12]. Humans are accidental hosts for Toxocara spp.…”

“…Traditional approaches for the specific identification of ascaridoids within the genera Toxocara and Toxascaris rely on morphological characteristics, host preference and geographical distributions. However, these criteria are not always sufficient to distinguish the closely related and/or morphologically similar ascaridoid species, particularly when the larval and egg stages are involved [1,12,13]. Moreover, the diversity patterns of life-cycles (e.g.…”