Rocío Callejón

Trichuris suis and Trichuris trichiura are different nematode species

In this paper, a morphological and biometrical study by optical microscopy and scanning electronic microscopy (SEM) of Trichuris suis isolated from different hosts (Sus scrofa domestica and Sus scrofa scrofa) and Trichuris trichiura isolated from chimpanzee, has been carried out. Our results demonstrate the existence of typical pericloacal papillae in both species. Biometrical parameters of T. suis and T. trichiura overlapped but males and females of T. trichiura tended to be shorter and thinner than those of T. suis. Our results suggest that T. suis and T. trichiura cannot be differentiated using standard procedures as morphological and biometrical determinations. Thus, the ITS1-5.8S-ITS2 region of the ribosomal DNA was sequenced to allow a differentiation between T. suis and T. trichiura on genetic level. The ITS1 and ITS2 sequences derived from T. trichiura eggs isolated from feces of primates (Colobus guereza kikuyensis and Nomascus gabriellae) showed clear differences to the respective sequences of T. suis derived from eggs of different porcine hosts. The 5.8S gene was similar between the two species. Sequences obtained from different populations of the same species showed no significant differences indicating that the ITS1-5.8S-ITS2 sequences reported in this study are representative for T. trichiura and T. suis, respectively. Phylogenetic relationships have been determined attending to the ITS1 and ITS2 sequences from different species of the genus Trichuris. In conclusion, T. trichiura and T. suis are considered to be closely related but genetically different species. Both species can be easily and reliably distinguished by a PCR-RFLP analysis of the ITS1 and ITS2 sequences with different restriction enzymes.

Molecular characterization and phylogeny of whipworm nematodes inferred from DNA sequences of cox1 mtDNA and 18S rDNA.

A molecular phylogenetic hypothesis is presented for the genus Trichuris based on sequence data from the mitochondrial cytochrome c oxidase 1 (cox1) and ribosomal 18S genes. The taxa consisted of different described species and several host-associated isolates (undescribed taxa) of Trichuris collected from hosts from Spain. Sequence data from mitochondrial cox1 (partial gene) and nuclear 18S near-complete gene were analyzed by maximum likelihood and Bayesian inference methods, as separate and combined datasets, to evaluate phylogenetic relationships among taxa. Phylogenetic results based on 18S ribosomal DNA (rDNA) were robust for relationships among species; cox1 sequences delimited species and revealed phylogeographic variation, but most relationships among Trichuris species were poorly resolved by mitochondrial sequences. The phylogenetic hypotheses for both genes strongly supported monophyly of Trichuris, and distinct genetic lineages corresponding to described species or nematodes associated with certain hosts were recognized based on cox1 sequences. Phylogenetic reconstructions based on concatenated sequences of the two loci, cox1 (mitochondrial DNA (mtDNA)) and 18S rDNA, were congruent with the overall topology inferred from 18S and previously published results based on internal transcribed spacer sequences. Our results demonstrate that the 18S rDNA and cox1 mtDNA genes provide resolution at different levels, but together resolve relationships among geographic populations and species in the genus Trichuris.

Molecular study on three morphotypes of Demodex mites (Acarina: Demodicidae) from dogs

Canine demodicosis is a severe and highly prevalent dermatologic disease in dogs. Pet dogs can be affected by three recognized Demodex species that can produce clinical effects. In this paper, three morphological types of Demodex mites have been isolated from Spanish dogs. A complete morphobiometrical study of each one has been carried out. Morphological and biometrical studies revealed three closely related populations with some distinctive characteristics and could be identified as Demodex canis, Demodex injai, and Demodex sp. “cornei.” Furthermore, one population of D. canis from China, different populations of Demodex folliculorum from human skin (Spain and China), D. folliculorum from human eyelashes (Spain), and Demodex brevis from human skin (China) were considered to find out the level of variation between different species and geographical origin. The aim of the present study is to assess the usefulness of mitochondrial DNA molecular markers in establishing phylogenetic relationships and resolve taxonomic questions in Demodex mites. Molecular studies based on the amplification and sequencing of the 16S rDNA and cytochrome oxidase I mitochondrial genes did not show clear differences between the three morphotypes considered. Furthermore, phylogenetic relationships in Demodex mites were analyzed. The resulting phylogenetic trees show that Demodex species from dogs were gathered together, and populations of D. folliculorum from humans appear together in a different branch; however, D. brevis from humans seemed to be more distant. Our results show that cytochrome oxidase I region is a useful tool to solve different taxonomic questions at the species and population level and to infer phylogenetic relationships in Demodex species. However, 16S mitochondrial rDNA seems a good marker for comparisons at an interspecies level, but not at a population level in this group of mites. Furthermore, from genetic distance and divergence data, we would suggest that D. canis, D. injai, and Demodex sp. cornei are polymorphisms of the same species.

Morphobiometrical and molecular study of two populations of Demodex folliculorum from humans.

A morphobiometrical and molecular study of two populations of Demodex folliculorum from humans isolated from different habitats, skin and eyelashes follicles, were carried out. Morphological and biometrical studies revealed two closely related populations with any distinctive characteristics. For molecular study, a 436-bp region of the 16S rDNA gene and a 453-bp region of the cytochrome oxidase I (COI) gene from individual mites of each population considered were sequenced. Intraindividual and interindividual sequence variation was studied in both populations. Our data show that 16S rDNA is not a useful marker to discriminate between populations; however, COI gene sequences can help to identify the two populations considered, which are morphologically very close and difficult to separate by classic methods. These results are in agreement with the morphological and biometrical differences detected between D. folliculorum from eyelashes and human skin. This study appeals for the revision of the taxonomic status of the D. folliculorum populations, as well as for the species included within genus Demodex.

16S partial gene mitochondrial DNA and internal transcribed spacers ribosomal DNA as differential markers of Trichuris discolor populations.

Comparative morphological, biometrical and molecular studies of Trichuris discolor isolated from Bos taurus from Spain and Iran was carried out. Furthermore, Trichuris ovis isolated from B. taurus and Capra hircus from Spain has been, molecularly, analyzed. Morphological studies revealed clear differences between T. ovis and T. discolor isolated from B. taurus but differences were not observed between populations of T. discolor isolated from different geographical regions. Nevertheless, the molecular studies based on the amplification and sequencing of the internal transcribed spacers 1 and 2 ribosomal DNA and 16S partial gene mitochondrial DNA showed clear differences between both populations of T. discolor from Spain and Iran suggesting two cryptic species. Phylogenetic studies corroborated these data. Thus, phylogenetic trees based on ITS1, ITS2 and 16S partial gene sequences showed that individuals of T. discolor from B. taurus from Iran clustered together and separated, with high bootstrap values, of T. discolor isolated from B. taurus from Spain, while populations of T. ovis from B. taurus and C. hircus from Spain clustered together but separated with high bootstrap values of both populations of T. discolor. Furthermore, a comparative phylogenetic study has been carried out with the ITS1and ITS2 sequences of Trichuris species from different hosts. Three clades were observed: the first clustered all the species of Trichuris parasitizing herbivores (T. discolor, T. ovis, Trichuris leporis and Trichuris skrjabini), the second clustered all the species of Trichuris parasitizing omnivores (Trichuris trichiura and Trichuris suis) and finally, the third clustered species of Trichuris parasitizing carnivores (Trichuris muris, Trichuris arvicolae and Trichuris vulpis).

Trichuris colobae n. sp. (Nematoda: Trichuridae), a new species of Trichuris from Colobus guereza kikuyensis

In the present work, a morphological and biometrical study of whipworms Trichuris Roederer, 1761 (Nematoda: Trichuridae) parasitizing Colobus guereza kikuyensis has been carried out. Biometrical and statistical data showed that the mean values of individual variables between Trichuris suis and Trichuris sp. from C. g. kikuyensis differed significantly (P < 0.001) when Student’s t test was performed: seven male variables (width of esophageal region of body, maximum width of posterior region of body, width in the place of junction of esophagus and the intestine, length of bacillary stripes, length of spicule, length of ejaculatory duct, and distance between posterior part of testis and tail end of body) and three female variables (width of posterior region of body, length of bacillary stripes, and distance of tail end of body and posterior fold of seminal receptacle). The combination of these characters permitted the discrimination of T. suis with respect to Trichuris sp. from C. g. kikuyensis, suggesting a new species of Trichuris. Furthermore, males of Trichuris sp. from C. g. kikuyensis showed a typical subterminal pericloacal papillae associated to a cluster of small papillae that were absent in males of T. suis, while females of Trichuris from Colobus appeared with a vulval region elevated/over-mounted showing a crater-like appearance. The everted vagina showed typical triangular sharp spines by optical microscopy and SEM. Thus, the existence of a new species of Trichuris parasitizing C. g. kikuyensis has been proposed.

Morphological, biometrical, and molecular characterization of Ctenocephalides felis and Ctenocephalides canis isolated from dogs from different geographical regions

In the present work, a comparative morphological, biometrical and molecular study of Ctenocephalides spp. isolated from dogs (Canis lupus familiaris) from different geographical regions (Spain, Iran, and South Africa) has been carried out. The internal transcribed spacer 1 (ITS1) sequences of Ctenocephalides felis and Ctenocephalides canis collected from dogs from different geographical regions have been determined to clarify the taxonomic status of these species and to assess intraspecific variation and interspecific sequence differences. In addition, a phylogenetic analysis based on ITS1 sequences has been performed. Four different morphological populations were observed in the individuals of C. felis collected from dogs from different geographical locations. Nevertheless, the comparative study of the ITS1 sequences of the different morphological populations observed in C. felis did not show molecular differences. The results showed clear molecular differences between C. felis and C. canis and some specific recognition sites for endonucleases were detected between both species. Thus, BfrBI and DraI sites have diagnostic value for specific determination in C. felis. The phylogenetic tree based on the ITS1 sequences of C. felis and C. canis revealed that all the populations of C. felis from different geographical regions clustered together and separated, with high bootstrap values, from C. canis. We conclude that ITS1 region is a useful tool to approach different taxonomic and phylogenetic questions in Ctenocephalides species.

Morphological and Molecular Characterization of a New Trichuris Species (Nematoda- Trichuridae), and Phylogenetic Relationships of Trichuris Species of Cricetid Rodents from Argentina

Populations of Trichuris spp. isolated from six species of sigmodontine rodents from Argentina were analyzed based on morphological characteristics and ITS2 (rDNA) region sequences. Molecular data provided an opportunity to discuss the phylogenetic relationships among the Trichuris spp. from Noth and South America (mainly from Argentina). Trichuris specimens were identified morphologically as Trichuris pardinasi, T. navonae, Trichuris sp. and Trichuris new species, described in this paper. Sequences analyzed by Maximum Parsimony, Maximum Likelihood and Bayesian inference methods showed four main clades corresponding with the four different species regardless of geographical origin and host species. These four species from sigmodontine rodents clustered together and separated from Trichuris species isolated from murine and arvicoline rodents (outgroup). Different genetic lineages observed among Trichuris species from sigmodontine rodents which supported the proposal of a new species. Moreover, host distribution showed correspondence with the different tribes within the subfamily Sigmodontinae.

Cytochrome oxidase subunit 1 and mitochondrial 16S rDNA sequences of Trichuris skrjabini (Tricocephalida: Trichuridae)

The partial mitochondrial cytochrome c-oxidase subunit 1 gene (cox 1) and partial mitochondrial 16S ribosomal DNA of Trichuris skrjabini (Baskakov 1924) isolated from Capra hircus have been amplified and sequenced. The analyses of multiple sequence alignments of mitochondrial 16S rDNA and cox 1 of T. skrjabini revealed high homology with those of Trichinella species. For the first time, the mitochondrial DNA gene sequences of one species of trichurid nematode have been cited.

How many species of whipworms do we share? Whipworms from man and other primates form two phylogenetic lineages.

Abstract: The whipworms, i.e. parasitic nematodes of the genus Trichuris Roederer, 1761, infect a variety of mammals. Apparently low diversity of primate-infecting species of Trichuris strongly contrasts with the high number of species described in other mammalian hosts. The present study addresses the diversity of whipworms in captive and free-ranging primates and humans by analysing nuclear (18S rRNA, ITS2) and mitochondrial (cox1) DNA. Phylogenetic analyses revealed that primate whipworms form two independent lineages: (i) the Trichuris trichiura (Linnaeus, 1771) clade comprised of genetically almost identical whipworms from human and other primates, which suggests the ability of T. trichiura to infect a broader range of primates; (ii) a clade containing primarily Trichuris suis Schrank, 1788, where isolates from human and various primates formed a sister group to isolates from pigs; the former isolates thus may represent of more species of Trichuris in primates including humans. The analysis of cox1 has shown the polyphyly of the genera Trichuris and Capillaria, Zeder, 1800. High sequence similarity of the T. trichiura isolates from humans and other primates suggests their zoonotic potential, although the extent of transmission between human and other non-human primates remains questionable and requires further study.