Phylogenetic relationships of Habronema microstoma and Habronema muscae (Spirurida: Habronematidae) within the order Spirurida inferred using mitochondrial cytochrome c oxidase subunit 1 (cox1) gene analysis

First report of Metathelazia capsulata in red foxes (Vulpes vulpes) in Europe and new contributions to its identification

Metathelazia capsulata is a lungworm that inhabit in the bronchi and bronchioles from mammal carnivore species, which life cycle is unknown. M. capsulata-like spirurid nematodes were isolated at necropsy from the respiratory tract of red foxes (Vulpes vulpes) from the Region of Murcia (SE Spain). The main objective of this study was to describe in detail the morphometric features of these nematodes, as well as to report some molecular markers. The principal morphometric difference compared to previous M. capsulata descriptions was the shorter total length for both males and females (6.6 mm and 7.4 mm, respectively). In addition, the mean values of buccal cavity depth and distance between the excretory pore and the anterior end of the nematode were also lower than those previously reported. On the other hand, sequence data of the mitochondrial (COI) and nuclear (rDNA) genes of M. capsulata were described, being the first time that molecular markers are reported for the genus Metathelazia and also for the entire family Pneumospiruridae. Based on data available from GenBank, these results indicate that M. capsulata sequences are closely related to the family Rhabdochonidae, which is assumed to belong to superfamily Thelazioidea, a superfamily including the family Pneumospiruridae, but also suggest the distant relations with the family Thelaziidae. This is the first time that M. capsulata is reported in red fox from Europe. This study provides valuable information for future phylogenetic studies on Metathelazia spp. nematodes and, in general, on species of the family Pneumospiruridae.

Morphological and genetic characterization of Pterygodermatites (Paucipectines) zygodontomis (Nematoda: Rictulariidae) from Necromys lasiurus (Rodentia: Sigmodontinae) from Uberlândia, Brazil

Pterygodermatites (Paucipectines) zygodontomis, a nematode parasite of the small intestine of the rodent Necromys lasiurus, from Uberlândia, Minas Gerais state, Brazil, was analysed by light and scanning electron microscopy. Additionally, phylogenies were inferred from the mitochondrially encoded cytochrome c oxidase I gene (MT-CO1). Details of the helminth surface, such as the oral aperture, cephalic papillae, papillae in the posterior region of the body and longitudinal cuticular elements represented by spine-like projections and fans are presented, adding new taxonomic details. Molecular phylogenetic analysis, based on the MT-CO1, demonstrated that P. (P.) zygodontomis and Pterygodermatites (Paucipectines) jaegerskioldi form a unique evolutionary unit in accordance with the subgenus Paucipectines and corroborated their occurrence in cricetid and didelphid hosts.

Morphological and molecular identification of Habronema spp. (Nematoda: Habronematidae) from donkeys in Xinjiang, China, and notes on the taxonomical status of Habronema majus (Creplin, 1849) and H. microstoma (Schneider, 1866)

Habronematid nematodes were collected from the stomachs of donkeys, Equus asinus L., in the Tarim Basin, Xinjiang, China. After examination by light and scanning electron microscopy, Habronema muscae (Carter, 1861) and H. majus (Creplin, 1849) were identified. The morphology of our specimens representing H. muscae (Carter, 1861) agreed well with previous redescriptions in the shape of the lateral lips, origin of the lateral alae, ratio of left and right spicules, and number and arrangement of caudal papillae. However, H. majus (Creplin, 1849) differs from H. microstoma (Schneider, 1866) in the arrangement of the caudal papillae in the male. Moreover, molecular analysis also showed interspecific differences of 26.2-28.2% in ITS2 and 8.6-8.9% in cox1 between H. majus and H. microstoma, a divergence much higher than the known intraspecific variation of Habronema spp. (6.6-8.7% in ITS2; 0.2-2.2% in cox1). The results indicate that both H. microstoma (Schneider, 1866) and H. majus (Creplin, 1849) are valid species.

The complete mitochondrial genome of the gullet worm Gongylonema pulchrum: gene content, arrangement, composition and phylogenetic implications

Background

Gongylonema pulchrum (Nematoda: Gongylonematidae), a thread-like spirurid gullet worm, infects a range of mammalian definitive hosts, including cattle, pigs, equines, goats, primates and humans, and can cause gongylonemiasis.

Methods

In the present study, the complete mitochondrial (mt) genome of G. pulchrum was obtained using Long-range PCR and subsequent primer walking. The phylogenetic position of G. pulchrum within the Spiruromorpha was established using Bayesian analyses of the protein-coding genes at the amino acid level.

Results

The length of this AT-rich (75.94%) mt genome is 13,798 bp. It contains 12 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes and one non-coding region. The gene arrangement is the same as those of Thelazia callipaeda (Thelaziidae) and Setaria digitata (Onchocercidae), but distinct from that of Heliconema longissimum (Physalopteridae). Phylogenetic analyses, based on the concatenated amino acid sequence data for all 12 protein-coding genes using Bayesian inference (BI) method, showed that G. pulchrum (Gongylonematidae) was more closely related to Spirocerca lupi (Spiruroidea) than other members of the infraorder Spiruromorpha.

Conclusions

The present study represents the first mt genome sequence for the family Gongylonematidae, which provides the opportunity to develop novel genetic markers for studies of epidemiology, population genetics and systematics of this nematode of human and animal health significance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0697-5) contains supplementary material, which is available to authorized users.

Characterization of the complete mitochondrial genome of Spirocerca lupi: sequence, gene organization and phylogenetic implications

Background

Spirocerca lupi is a life-threating parasitic nematode of dogs that has a cosmopolitan distribution but is most prevalent in tropical and subtropical countries. Despite its veterinary importance in canids, the epidemiology, molecular ecology and population genetics of this parasite still remain unexplored.

Methods

The complete mitochondrial (mt) genome of S. lupi was amplified in four overlapping long fragments using primers designed based on partial cox1, rrnS, cox2 and nad2 sequences. Phylogenetic re-construction of 13 spirurid species (including S. lupi) was carried out using Bayesian inference (BI) based on concatenated amino acid sequence datasets.

Results

The complete mt genome sequence of S. lupi is 13,780 bp in length, including 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lacks the atp8 gene. The gene arrangement is identical to that of Thelazia callipaeda (Thelaziidae) and Setaria digitata (Onchocercidae), but distinct from that of Dracunculus medinensis (Dracunculidae) and Heliconema longissimum (Physalopteridae). All genes are transcribed in the same direction and have a nucleotide composition high in A and T. The content of A + T is 73.73% for S. lupi, in accordance with mt genomes of other spirurid nematodes sequenced to date. Phylogenetic analyses using concatenated amino acid sequences of the 12 protein-coding genes by BI showed that the S. lupi (Thelaziidae) is closely related to the families Setariidae and Onchocercidae.

Conclusions

The present study determined the complete mt genome sequence of S. lupi. These new mt genome dataset should provide novel mtDNA markers for studying the molecular epidemiology and population genetics of this parasite, and should have implications for the molecular diagnosis, prevention and control of spirocercosis in dogs and other canids.

Mitochondrial genome of the eyeworm, Thelazia callipaeda (Nematoda: Spirurida), as the first representative from the family Thelaziidae

Human thelaziosis is an underestimated parasitic disease caused by Thelazia species (Spirurida: Thelaziidae). The oriental eyeworm, Thelazia callipaeda, infects a range of mammalian definitive hosts, including canids, felids and humans. Although this zoonotic parasite is of socio-economic significance in Asian countries, its genetics, epidemiology and biology are poorly understood. Mitochondrial (mt) DNA is known to provide useful genetic markers to underpin fundamental investigations, but no mt genome had been characterized for any members of the family Thelaziidae. In the present study, we sequenced and characterized the mt genome of T. callipaeda. This AT-rich (74.6%) mt genome (13,668 bp) is circular and contains 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lacks an atp8 gene. All protein-coding genes are transcribed in the same direction; the gene order is the same as those of Dirofilaria immitis and Setaria digitata (Onchocercidae), but distinct from Dracunculus medinensis (Dracunculidae) and Heliconema longissimum (Physalopteridae). Phylogenetic analyses of the concatenated amino acid sequence data for all 12 protein-coding genes by Bayesian inference (BI) showed that T. callipaeda (Thelaziidae) is related to the family Onchocercidae. This is the first mt genome of any member of the family Thelaziidae and should represent a new source of genetic markers for studying the epidemiology, ecology, population genetics and systematics of this parasite of humans and other mammals.

Human thelaziosis is an underestimated parasitic disease caused by the eyeworm Thelazia callipaeda (Spirurida: Thelaziidae). Although this parasite is of significance in humans in many Asian countries, its genetics, epidemiology and biology are poorly understood. Mitochondrial (mt) DNA can provide useful genetic markers for fundamental investigations, but no mt genome had been characterized for any members of the family Thelaziidae. In this study, we sequenced and characterized the mt genome of T. callipaeda. This circular mt genome is 13,668 bp long and contains 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lacks an atp8 gene. Phylogenetic analyses of the concatenated amino acid sequence data for all 12 protein-coding genes by Bayesian inference showed that T. callipaeda is closely related to the family Onchocercidae, consistent with previous study. This is the first mt genome of any member of the family Thelaziidae, and represents a new source of genetic markers for studies of the epidemiology, ecology, population genetics and systematics of this parasite of human and animal health significance.

Phylogeography of Ascaris lumbricoides and A. suum from China

In order to obtain further understanding of genetic structure and evolutionary relationship of Ascaris from humans and pigs, phylogeography study on 12 populations from six endemic regions in China was conducted using mitochondrial DNA markers (cytochrome c oxidase subunit 1 (COX1) and NAD1) and the software programs of DnaSP 5.0, Arlequin 3.0, MEGA 4.0, and NETWORK 4.5.1.6. Results showed that (a) genetic diversity of Ascaris varied with hosts and locations, but no distinct geographical distribution pattern was found, (b) a higher level of genetic diversity and differentiation was found in pig-derived populations in contrast to human-derived ones, and in populations of human-derived Ascaris from the southern regions in comparison to that from the middle and northern locations, but similar geographical difference was not observed within pig-derived populations, (c) historical population expanding was detected from a large part of human-derived Ascaris populations but not in pig-derived Ascaris, (d) a high level of gene flow was detected between human- and pig-derived Ascaris and also among human-derived populations, and (e) network analysis from haplotype of COX1 indicated an ancestral haplotype from human-derived Ascaris. In conclusion, the present study revealed new information on Ascaris on the aspects of genetic diversity, population differentiation and historical demographic patterns, gene flow, phylogenesis reconstruction, and haplotype network, discussed the results with historical demographic migration of humans and domestication of wild boar in China, and raised a different assumption about the evolutionary relationship of the two roundworms. This study should have certain enlightenment for the epidemiology and the evolutionary and taxonomy relationship of Ascaris from humans and pigs.

Local transmission of the eye worm Thelazia callipaeda in southern Germany

This report describes the first assumed locally transmitted case of the eye worm Thelazia callipaeda in a dog living in southern Germany. A 4-year-old male golden retriever from the town of Bühl in north eastern Baden-Württemberg, about 10 km from the German-French border, showed one sided lacrimation for over 2 weeks. Despite the application of antibiotics, there was no improvement, and the dog additionally showed blepharospasmus, epiphora and red conjunctivas. A deepened eye inspection revealed five whitish filiform parasites that were morphologically identified as T. callipaeda. The partial sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1, 605 bp) from one specimen revealed a novel haplotype, which differs by 1.3% from the only one (haplotype 1) identified in Europe so far. Since the infected dog had never been abroad with the exception of two daytrips to the close Alsace region in France, the transmission of T. callipaeda most probably was domestic. With the presence of end hosts and Phortica flies nourishing on lachrymal secretions acting as intermediate hosts and an increasing number of dogs travelling to and coming from endemic regions in the South, the establishment of T. callipaeda in large parts of Europe cannot be excluded.

Local transmission of the eye worm Thelazia callipaeda in southern Germany

This report describes the first assumed locally transmitted case of the eye worm Thelazia callipaeda in a dog living in southern Germany. A 4-year-old male golden retriever from the town of Bühl in north eastern Baden-Württemberg, about 10 km from the German-French border, showed one sided lacrimation for over 2 weeks. Despite the application of antibiotics, there was no improvement, and the dog additionally showed blepharospasmus, epiphora and red conjunctivas. A deepened eye inspection revealed five whitish filiform parasites that were morphologically identified as T. callipaeda. The partial sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1, 605 bp) from one specimen revealed a novel haplotype, which differs by 1.3% from the only one (haplotype 1) identified in Europe so far. Since the infected dog had never been abroad with the exception of two daytrips to the close Alsace region in France, the transmission of T. callipaeda most probably was domestic. With the presence of end hosts and Phortica flies nourishing on lachrymal secretions acting as intermediate hosts and an increasing number of dogs travelling to and coming from endemic regions in the South, the establishment of T. callipaeda in large parts of Europe cannot be excluded.