Trypanoxyuris atelis and T. atelophora (Nematoda: Oxyuridae) in wild spider monkeys (Ateles geoffroyi) in tropical rain forest in Mexico: Morphological and molecular evidence

Molecular data aids pinworm diagnosis in night monkeys (Aotus spp., Primates: Aotidae) with the resurrection of a Trypanoxyuris species (Nematoda: Oxyuridae)

Neotropical primates (Platyrrhines) are commonly parasitized by pinworm nematodes of the genus Trypanoxyuris Vevers, 1923. The taxonomic identity of Trypanoxyuris sampled in night monkeys (Aotus Iliger) has been rather controversial. Two species have been described, namely T. microon (Linstow, 1907) and T. interlabiata (Sandosham, 1950). The latter was synonymized with T. microon considering that the observed morphological differences corresponded to different developmental stages of the nematode rather than to differences between both species. Here, we used an integrative taxonomy approach, based on morphological and molecular data along with host identity, in order to assess the validity of both species. Our results evidenced that these different morphotypes correspond to different and reciprocally monophyletic groups; thus, we propose the resurrection of T. interlabiata. We redescribe both pinworm species using specimens sampled in Aotus monkeys from Colombia and discuss the advantages of combining molecular and morphological data to uncover pinworm diversity, and to understand the potential forces determining the diversification process in pinworms from platyrrhine primates.

Morphology, genetic characterization and molecular phylogeny of pinworm Skrjabinema longicaudatum n. sp. (Oxyurida: Oxyuridae) from the endangered Tibetan antelope Pantholops hodgsonii (Abel) (Artiodactyla: Bovidae)

BACKGROUND

The Tibetan antelope Pantholops hodgsonii (Abel) (Artiodactyla: Bovidae) is an endangered species of mammal endemic to the Qinghai-Tibetan Plateau. Parasites and parasitic diseases are considered to be important threats in the conservation of the Tibetan antelope. However, our present knowledge of the composition of the parasites of the Tibetan antelope remains limited.

METHODS

Large numbers of nematode parasites were collected from a dead Tibetan antelope. The morphology of these nematode specimens was observed using light and scanning electron microscopy. The nuclear and mitochondrial DNA sequences, i.e. small subunit ribosomal DNA (18S), large subunit ribosomal DNA (28S), internal transcribed spacer (ITS) and cytochrome c oxidase subunit 1 (cox1), were amplified and sequenced for molecular identification. Moreover, phylogenetic analyses were performed using maximum likelihood (ML) inference based on 28S and 18S + 28S + cox1 sequence data, respectively, in order to clarify the systematic status of these nematodes.

RESULTS

Integrated morphological and genetic evidence reveals these nematode specimens to be a new species of pinworm Skrjabinema longicaudatum (Oxyurida: Oxyuridae). There was no intraspecific nucleotide variation between different individuals of S. longicaudatum n. sp. in the partial 18S, 28S, ITS and cox1 sequences. However, a high level of nucleotide divergence was revealed between the new species and its congeners in 28S (8.36%) and ITS (20.3-23.7%) regions, respectively. Molecular phylogenetic results suggest that the genus Skrjabinema should belong to the subfamily Oxyurinae (Oxyuroidea: Oxyuridae), instead of the subfamily Syphaciidae or Skrjabinemiinae in the traditional classification, as it formed a sister relationship to the genus Oxyuris.

CONCLUSIONS

A new species of pinworm Skrjabinema longicaudatum n. sp. (Oxyurida: Oxyuridae) is described. Skrjabinema longicaudatum n. sp. represents the first species of Oxyurida (pinworm) and the fourth nematode species reported from the Tibetan antelope. Our results contribute to the knowledge of the species diversity of parasites from the Tibetan antelope, and clarify the systematic position of the genus Skrjabinema.

Pinworms of the red howler monkey (Alouatta seniculus) in Colombia: Gathering the pieces of the pinworm-primate puzzle

Pinworms of primates are believed to be highly host specific parasites, forming co-evolutionary associations with their hosts. In order to assess the strength and reach of such evolutionary links, we need to have a broad understanding of the pinworm diversity associated with primates. Here, we employed an integrative taxonomic approach to assess pinworm diversity in red howler monkeys in Colombia. Molecular and morphological evidence validate the presence of at least four different species of Trypanoxyuris occurring in red howler monkeys: T. minutus, a widely distributed species, and three new species, T. seunimiii n. sp., T. kemuimae n. sp. and T. kotudoi n. sp. The mitochondrial COI gene and the 28S ribosomal gene were used for phylogenetic assessments through Bayesian inference. The three new species were morphologically distinct and formed reciprocally monophyletic lineages. Further molecular lineage subdivision in T. minutus and T. kotudoi n. sp. without morphological correspondence, suggests the potential scenario for the existence of cryptic species. Phylogenetic relationships imply that the different species of Trypanoxyuris occurring in each howler monkey species were acquired through independent colonization events. On-going efforts to uncover pinworm diversity will allow us to test the degree of host specificity and the co-phylogenetic hypothesis, as well as to further unravel the primate-pinworm evolutionary history puzzle.

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Three new species of pinworms from red howler monkeys are described.

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Phylogenetic analysis suggests the potential existence of cryptic species.

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Our results agree with pinworms of primates as highly host specific parasites.

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Trypanoxyuris species occurring in each howler species are not closely related.

Prevalence, Morphological and Molecular Phylogenetic Analyses of the Rabbit Pinworm, Passalurus ambiguus Rudolphi 1819, in the Domestic Rabbits Oryctolagus cuniculus

INTRODUCTION

Passalurus ambiguus, a pinworm nematode parasite, infects domestic and wild rabbits, hares, and rodents worldwide.

MATERIALS AND METHODS

The current parasitological study was performed during January-December 2016, to investigate helminth parasites infecting the domestic rabbit species Oryctolagus cuniculus at the Department of Animal Production, Faculty of Agriculture, Cairo University, Cairo, Egypt.

RESULTS

Of the twenty rabbit specimens examined for gastrointestinal nematodes, 75% were infected with adult oxyurid species, which were morphologically characterized using light and scanning electron microscopy studies. The oxyurid species had a triangular mouth opening surrounded by simple lips with four cephalic papillae and a pair of lateral amphidial pores with three teeth-like structures, an esophagus divided into a cylindrical corpus and globular bulb supported internally with tri-radiate valvular apparatus, and four caudal papillae distributed on the posterior end of males with a single short protruding spicule and ovijector apparatus opening ventrally by the vulva, surrounded by protruded lips in female worms. The species were compared morphometrically with other Passalurus species described previously; light differences were found in different body part sizes. Molecular characterization based on 18 small subunit (SSU) rDNA sequences showed ~ 85% similarity with other Chromadorea species. A preliminary genetic comparison between the 18S rDNA sequences of the isolated parasite and those of other oxyurid species suggested that it belonged to Passalurus ambiguus. The 18S rDNA sequence of the parasite was deposited in GenBank (accession no., MG310151.1).

CONCLUSION

The 18S rDNA gene of P. ambiguus was shown to yield a unique genetic sequence that confirms its taxonomic position within the Oxyuridae family.

Unveiling patterns of genetic variation in parasite–host associations: an example with pinworms and Neotropical primates

Patterns of genetic variation among populations can reveal the evolutionary history of species. Pinworm parasites are highly host specific and form strong co-evolutionary associations with their primate hosts. Here, we describe the genetic variation observed in four Trypanoxyuris species infecting different howler and spider monkey subspecies in Central America to determine if historical dispersal processes and speciation in the host could explain the genetic patterns observed in the parasites. Mitochondrial (cox1) and ribosomal (28S) DNA were analysed to assess genetic divergence and phylogenetic history of these parasites. Sequences of the 28S gene were identical within pinworms species regardless of host subspecies. However, phylogenetic analyses, haplotype relationships and genetic divergence with cox1 showed differentiation between pinworm populations according to host subspecies in three of the four Trypanoxyuris species analysed. Haplotype separation between host subspecies was not observed in Trypanoxyuris minutus, nor in Trypanoxyuris atelis from Ateles geoffoyi vellerosus and Ateles geoffoyi yucatanensis. Levels of genetic diversity and divergence in these parasites relate with such estimates reported for their hosts. This study shows how genetic patterns uncovered in parasitic organisms can reflect the host phylogenetic and biogeographic histories.

Lack of genetic structure in pinworm populations from New World primates in forest fragments

Microevolutionary processes in parasites are driven by factors related to parasite biology, host abundance and dispersal, and environmental conditions. Here, we test the prediction that isolation of host populations results in reduced genetic diversity and high differentiation among parasite populations. We conducted a population genetic analysis of two pinworms, Trypanoxyuris minutus and Trypanoxyuris atelis, commonly found parasitizing howler and spider monkeys in tropical rainforests across south-eastern Mexico, whose populations are currently isolated due to anthropogenic habitat loss and fragmentation. Mitochondrial DNA was employed to assess parasite genetic patterns, as well as to analyse their demography and population history. Both pinworm species showed high haplotype diversity but, unexpectedly, lower nucleotide diversity than that reported for other parasites. No genetic differentiation or population structure was detected in either pinworm species despite habitat loss, fragmentation and host isolation. Several scenarios are discussed that could help to explain the genetic panmixia found in both pinworm species, including higher than expected primate inter-fragment dispersal movements, and passive dispersal facilitating gene flow between parasite populations. The results suggest that large population sizes of parasites could be helping them to cope with the isolation and fragmentation of populations, delaying the effects of genetic drift. The present study highlights the complexity of the drivers that intervene in the evolutionary processes of parasites. Detailed genetic studies are needed, both in host and parasite populations, to assess the effects that habitat perturbation and environmental changes could have on the evolutionary dynamics of pinworms and primates.

Helminth parasites of howler and spider monkeys in Mexico: Insights into molecular diagnostic methods and their importance for zoonotic diseases and host conservation

The majority of the parasite assessments of New World primates have been conducted through the identification of the eggs found in faeces, though many species of parasites have very similar eggs, leaving uncertainty in the diagnosis. Here, we present the results of a parasite survey of the three species of primates distributed in Mexico, combining non-invasive sampling with molecular techniques via DNA extraction of the eggs found in the faeces. Mitochondrial and ribosomal DNA were employed for species identification and Bayesian phylogenetic analysis. Nine parasite taxa were found in the three primate species: the nematodes Trypanoxyuris minutus, T. multilabiatus, T. pigrae, T. atelis, T. atelophora, Strongyloides sp., unidentified Ancylostomatid, unidentified Ascarid, and the trematode Controrchis biliophilus. We were able to extract and amplify DNA from the eggs of the five species of Trypanoxyuris reported for Mexican primates, two morphologically different trematode eggs, and Strongyloides sp. Phylogenetic analysis confirmed that the two types of trematode eggs belong to Controrchis biliophilus, a member of the family Dicrocoeliidae. For Strongyloides sp., phylogenetic analysis and genetic divergence showed an association between our samples and S. fuelleborni; however, no species could be established due to the lack of more DNA sequences from Strongyloides sp. occurring in Neotropical primates. The use of molecular and phylogenetic methods could help to overcome the limitations imposed by traditional non-invasive sampling because eggs are primarily obtained from the faeces; however, its utility relies on the extant genetic library and the contributions that expand such library. The information presented here could serve as a basis for future research on primate parasitology, allowing a more accurate parasite diagnosis and a more precise evaluation of their zoonotic potential.

The complete mitochondrial genome of rabbit pinworm Passalurus ambiguus: genome characterization and phylogenetic analysis

Passalurus ambiguus (Nematda: Oxyuridae) is a common pinworm which parasitizes in the caecum and colon of rabbits. Despite its significance as a pathogen, the epidemiology, genetics, systematics, and biology of this pinworm remain poorly understood. In the present study, we sequenced the complete mitochondrial (mt) genome of P. ambiguus. The circular mt genome is 14,023 bp in size and encodes of 36 genes, including 12 protein-coding, two ribosomal RNA, and 22 transfer RNA genes. The mt gene order of P. ambiguus is the same as that of Wellcomia siamensis, but distinct from that of Enterobius vermicularis. Phylogenetic analyses based on concatenated amino acid sequences of 12 protein-coding genes by Bayesian inference (BI) showed that P. ambiguus was more closely related to W. siamensis than to E. vermicularis. This mt genome provides novel genetic markers for studying the molecular epidemiology, population genetics, systematics of pinworm of animals and humans, and should have implications for the diagnosis, prevention, and control of passaluriasis in rabbits and other animals.