Molecular and morphological characteristics of Trichuris tenuis from South American Camelids bred in Europe

Background The intestinal nematode Trichuris tenuis Chandler, 1930 is an important parasite associated with South American Camelids (SAC). To date, the species T. tenuis has been characterized solely based on morphology. The aim of this study was to comprehensively characterize these nematodes using an integrative taxonomic approach.Methods Morphological, biometrical, and molecular analyses of T. tenuis specimens collected from alpacas (Lama pacos), llamas (Lama glama), and guanacos (Lama guanicoe) were performed. A total of 58 nematodes originating from three European farms and one zoo (located in Czech Republic and Italy) were subjected to morphological and biometric evaluation. For original DNA analysis, three markers were selected: a partial sequence of the nuclear 18S rRNA (18S) gene, both nuclear internal transcribed spacer regions (ITSs; encompassing a partial sequence of the 18S rRNA gene, ITS1, 5.8S, ITS2, and a partial sequence of the 28S rRNA gene), and a partial mitochondrial gene encoding cytochrome c oxidase subunit 1 (COI).Results Males exhibited an extremely long cloaca with a complex, unique course, as well as a long, slender spicule, measuring 4.7-5.6 mm. Additionally, the junction between the ejaculatory duct and the vas efferens formed a distinct muscular constriction. Females exhibited an uneverted aspinous vulva and a highly convoluted vagina containing a unique egg chamber. A subset of adult worms was characterized using three molecular markers, which yielded 30 unique sequences: two variants for 18S, 14 variants for the ITS regions, and 13 variants for COI. Phylogenetic trees constructed for all DNA markers placed T. tenuis close to a well-defined clade of trichurid species parasitic to domestic ruminants.Conclusion Integrative morphological, molecular, and phylogenetic analysis indicated that this species is both morphologically and molecularly distinct from its congeners. Furthermore, the evidence suggests that it exclusively infects SACs and potentially other camelids within captive populations worldwide. Similar integrative approaches are necessary for the taxonomic revision of the genus Trichuris and should be applied more frequently in future taxonomic research.