Phylogenetic analysis of the Metastrongyloidea (Nematoda: Strongylida) inferred from ribosomal RNA gene sequences

Comparative biology of parasitic nematodes in the genus Angiostrongylus and related genera

The rise to prominence of some Angiostrongylus species through associated emerging disease in humans and dogs has stimulated calls for a renewed focus on the biology of this genus and three related genera. Although significant research efforts have been made in recent years these have tended to focus on individual species and specific aspects such as diagnosis and treatment of disease or new records of occurrence and hosts. This comprehensive review takes a comparative approach, seeking commonalities and differences among species and asking such questions as: Which species belong to this and to closely related genera and how are they related? Why do only some species appear to be spreading geographically and what factors might underlie range expansion? Which animal species are involved in the life cycles as definitive, intermediate, paratenic and accidental hosts? How do parasite larvae find, infect and develop within these hosts? What are the consequences of infection for host health? How will climate change affect future spread and global health? Appreciating how species resemble and differ from each other shines a spotlight on knowledge gaps and provides provisional guidance on key species characteristics warranting detailed study. Similarities exist among species, including the basic life cycle and transmission processes, but important details such as host range, climatic requirements, migration patterns within hosts and disease mechanisms differ, with much more information available for A. cantonensis and A. vasorum than for other species. Nonetheless, comparison across Angiostrongylus reveals some common patterns. Historically narrow definitive host ranges are expanding with new knowledge, combining with very broad ranges of intermediate gastropod hosts and vertebrate and invertebrate paratenic and accidental hosts to provide the backdrop to complex interactions among climate, ecology and transmission that remain only partly understood, even for the species of dominant concern. Key outstanding questions concern larval dynamics and the potential for transmission outside trophic relations, relations between infection and disease severity in different hosts, and how global change is altering transmission beyond immediate impacts on development rate in gastropods. The concept of encounter and compatibility filters could help to explain differences in the relative importance of different gastropod species as intermediate hosts and determine the importance of host community composition and related environmental factors to transmission and range. Across the group, it remains unclear what, physiologically, immunologically or taxonomically, delimits definitive, accidental and paratenic hosts. Impacts of infection on definitive host fitness and consequences for population dynamics and transmission remain mostly unexplored across the genus. Continual updating and cross-referencing across species of Angiostrongylus and related genera is important to synthesise rapid advances in understanding of key traits and behaviours, especially in important Angiostrongylus species that are emerging causative agents of disease in humans and other animals.

Potential new species of pseudaliid lung nematode (Metastrongyloidea) from two stranded neonatal orcas (Orcinus orca) characterized by ITS-2 and COI sequences

Knowledge about parasite species of orcas, their prevalence, and impact on the health status is scarce. Only two records of lungworm infections in orca exist from male neonatal orcas stranded in Germany and Norway. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but morphological identification to species level remained impossible due to the fragile structure and ambiguous morphological features. Pseudaliid nematodes (Metastrongyloidea) are specific to the respiratory tract of toothed whales and are hypothesized to have become almost extinct in terrestrial mammals. Severe lungworm infections can cause secondary bacterial infections and bronchopneumonia and are a common cause of mortality in odontocetes. DNA isolations and subsequent sequencing of the rDNA ITS-2 and mtDNA COI revealed nucleotide differences between previously described Halocercus species from common dolphin (H. delphini) and harbor porpoises (H. invaginatus) that were comparatively analyzed, pointing toward a potentially new species of pseudaliid lungworm in orcas. New COI sequences of six additional metastrongyloid lungworms of seals and porpoises were derived to elucidate phylogenetic relationships and differences between nine species of Metastrongyloidea.

Molecular phylogeny of the Pseudaliidae (Nematoda) and the origin of associations between lungworms and marine mammals

Metastrongyloid lungworms from the family Pseudaliidae infect the lungs and cranial sinuses of cetaceans worldwide, except Stenuroides herpestis, which exhibits a striking terrestrial association with the Egyptian mongoose, Herpestes ichneumon. Previous phylogenies of the Metastrongyloidea that included some (2-7) marine species of the Pseudaliidae confirmed that these species are closely related, but also grouped species of Parafilaroides (family Filaroididae) between the members of the Pseudaliidae. In this study we extracted DNA from representatives of all six genera of the Pseudaliidae and amplified the second internal transcribed spacer (ITS2) and cytochrome c oxidase subunit I (cox1) genes in order to investigate the concept of the Pseudaliidae as a monophyletic unit. Three species of Parafilaroides were also included in the analysis. Maximum Likelihood and Bayesian Inference analyses of the concatenated genes resulted in a well-supported clade including the marine pseudaliids, S. herpestis and Parafilaroides spp. These findings validate the status of S. herpestis as a pseudaliid species and support the inclusion of Parafilaroides in the Pseudaliidae. Although males of Parafilaroides spp. lack a copulatory bursa, this trait itself is highly variable in the Pseudaliidae, which include abursate species. Furthermore, life cycles seem to be closely similar between both taxa. When all the available phylogenetic data on the Metastrongyloidea were mapped of onto a phylogeny of the Laurasiatheria, there was a strong suggestion that the Pseudaliidae may have descended from ancestors infecting terrestrial carnivores, with odontocetes being colonized in the marine realm as a result of a host-switching event from pinnipeds through shared fish prey. The origin of the association between S. herpestis and mongooses remains uncertain.

Diversity of Crenosoma species in mustelids with the first molecular characterization of C. melesi and C. petrowi

Species of genus Crenosoma have a wide distribution and are reported in Europe, the Americas, and Asia. Currently, the genus includes 14 nominal species, out of which 9 are parasitic in mustelids. Two species are mostly reported in mustelids from Europe, namely C. melesi and C. petrowi. Up to now, no genetic sequences are deposited in GenBank for any of the two. The aims of this study were to investigate the distribution, prevalence, and diversity of Crenosoma spp. infecting mustelids in Romania and to genetically characterize the species. Mustelids (n = 247) were collected over a period of 7 years from different locations in Romania and the respiratory tract was removed and examined for nematodes. Detected nematodes were morphologically identified and fragments of two genes were sequenced. Sampled mustelids included Eurasian badger, Meles meles (n = 102), Eurasian otter, Lutra lutra (n = 20), beech marten, Martes foina (n = 36), European pine marten, Martes martes (n = 5), steppe polecat, Mustela eversmanii (n = 1), European mink, Mustela lutreola (n = 1), least weasel, Mustela nivalis (n = 2), European polecat, Mustela putorius (n = 78), and marbled polecat, Vormela peregusna (n = 1). Nematodes from Eurasian badgers were morphologically identified as C. melesi (n = 13, 12.74%) and C. petrowi (n = 3, 2.94%). Nematodes from the beech martens were identified as C. petrowi (n = 6, 16.66%), C. vulpis (n = 1, 2.78%) and Crenosoma spp. (n = 3, 8.33%). Co-infections with two Crenosoma species were detected in one beech marten (C. petrowi + C. vulpis, n = 1, 2.77%) and in one European pine marten [C. petrowi + C. vulpis (n = 1, 20%)]. Two genes of Crenosoma melesi and C. petrowi were partly sequenced for the first time. We report new host-parasite associations for M. martes and C. vulpis. However, further studies are needed in order to determine the host-parasite associations and to improve the understanding of the epidemiology of Crenosoma nematodes.

PHYLOGENETIC ANALYSIS OF THE LUNGWORMS (NEMATODA: METASTRONGYLOIDEA) INFERRED USING NUCLEAR RIBOSOMAL AND MITOCHONDRIAL DNA SEQUENCES

Phylogenetic relationships among the mammal-parasitic lungworms (Metastrongyloidea) were inferred using small- and large-subunit ribosomal DNA sequences together with 12S ribosomal mtDNA sequences. Maximum parsimony and Bayesian inference methods were used from optimal alignments and those filtered for alignment ambiguity. Analysis of 30 ingroup sequences using ribosomal DNA sequences yielded a single most parsimonious tree. Monophyly of the Metastrongyloidea was supported, but there was no support for monophyly of any of the 7 families as they have been traditionally defined. Parafilaroides decorus, an abursate lungworm of pinnipeds currently classified in the Filaroididae, was nested within a clade containing members of the Pseudaliidae, parasites of cetaceans. The tree also shows clades somewhat resembling the traditional familial divisions of the Metastrongyloidea, but in all groups, paraphyletic relationships were recovered. In a combined analysis of nuclear rDNA and 12S mtDNA, maximum parsimony and Bayesian analyses showed similar patterns to those observed with only nuclear rDNA sequences. Based on the phylogeny, the respiratory tract was inferred to be the ancestral predilection site for Metastrongyloidea, with multiple evolutionary invasions of extrapulmonary sites such as sinuses, circulatory system, and meninges. Similarly, the ancestral host was inferred to be a carnivore with subsequent colonization events into marsupial, rodent, artiodactyl, pinniped, and cetacean hosts.

Angiostrongylosis in Animals and Humans in Europe

Lungworms in the genus Angiostrongylus cause disease in animals and humans. The spread of Angiostrongylus vasorum within Europe and the recent establishment of Angiostrongylus cantonensis increase the relevance of these species to veterinary and medical practitioners, and to researchers in parasitology, epidemiology, veterinary science and ecology. This review introduces the key members of the genus present in Europe and their impacts on health, and updates the current epidemiological situation. Expansion of A. vasorum from localized pockets to wide distribution across the continent has been confirmed by a rising prevalence in foxes and increasing reports of infection and disease in dogs, while the list of carnivore and mustelid definitive hosts continues to grow. The tropically distributed rat lungworm A. cantonensis, meanwhile, has been recorded on islands south of Europe, previously the Canary Islands, and now also the Balearic Islands, although so far with limited evidence of zoonotic disease. Other members of the genus, namely, A. chabaudi, A. daskalovi and A. dujardini, are native to Europe and mainly infect wildlife, with unknown consequences for populations, although spill-over can occur into domestic animals and those in zoological collections. The epidemiology of angiostrongylosis is complex, and further research is needed on parasite maintenance in sylvatic hosts, and on the roles of ecology, behaviour and genetics in disease emergence. Improved surveillance in animals and humans is also required to support risk assessments and management.

Molecular phylogenetic relationships of Metastrongylus nematodes with emphasis on specimens from domestic pigs in Vietnam

Lungworms of the genus Metastrongylus are parasitic nematodes in the respiratory tract of swine. Although they infect both wild boars and domestic pigs, studies on Metastrongylus infections in wild boars in Europe, the Americas and Africa are numerous, while those in domestic pigs are few. There are several studies analysing the molecular phylogenetic relationships of few individual Metastrongylus species with other nematode taxa, but there are no studies on the phylogenetic relationships of species within the genus Metastrongylus. In Southeast Asia, reports on swine lungworms are extremely scarce and do not include any nucleotide sequence data. Therefore, the aim of the present study is to survey Metastrongylus infection in domestic pigs raised in Dien Bien Province, Northern Vietnam, and to analyse the molecular phylogenetic relationships of Metastrongylus species. Based on morphological and molecular data, we identified two species: Metastrongylus apri and Metastrongylus pudendotectus. The prevalence of the former species was found to be significantly higher than the latter one (24.1% vs. 2.3%). We observed pigs exhibiting a coinfection with the two lungworm species or a single infection with only M. apri. However, we did not observe any pigs being infected with just M. pudendotectus. Vietnamese Metastrongylus specimens showed slight morphological and molecular differences compared to those from other countries. The molecular analyses revealed a close genetic relationship between M. apri and Metastrongylus salmi, while both these species were far distant from M. pudendotectus. The present study highlights the needs for further studies to clarify the morphological features and ecological and phylogenetic relationships of Metastrongylus species at the global scale.

Morphological and molecular evidence of Oslerus osleri (Nematoda: Filaroididae) in the Andean fox (Lycalopex culpaeus)

Oslerus osleri is a cosmopolitan filaroid nematode that parasitizes the respiratory system of domestic and wild canids. Natural infection by O. osleri is reported in the Andean fox (Lycalopex culpaeus) in this study. Nematodes, enclosed in small and compact fibrous nodules of 1 to 5 mm in diameter, were found on the surface of the trachea near the bronchial bifurcation on four Andean foxes during necropsy (one from Cuzco, Peru and three from Northwestern Patagonia in Argentina). The nematodes were identified as O. osleri by morphological and molecular methods. Ribosomal and mitochondrial DNA analyses were performed amplifying the second internal transcribed spacer region (ITS-2), the partial cytochrome c oxidase 1 (cox1), and the large subunit of nuclear ribosomal RNA (LSU rRNA) genes. Sequences of the ITS-2 and LSU rRNA had a genetic variation of 1.5% and 1.0%, respectively, with previous sequences of O. osleri registered in Genbank. This is the first amplification of the cox1 gene of O. osleri and demonstrated an identity of 92% to Perostrongylus falciformis (KY365437), and 90% to Angiostrongylus cantonensis (KY779735) and Angiostrongylus costaricensis (AP017675).

First description of a Raphidascaris species (Nematoda: Raphidascarididae) in a mudskipper Apocryptes bato (Actinopterygii: Gobiidae) from West Bengal, India

A new nematode species, Raphidascaris mundeswariensis n. sp. (Raphidascarididae), is described from male and female specimens found in the intestines of the mudskipper Apocryptes bato (Hamilton, 1822) (Gobiidae) from the Mundeswari River of West Bengal, India. This species is distinguished from its congeners by 214–255-μm-long spicules, 14 pairs of preanal papillae of two markedly different sizes, one pair of adanal papillae, six pairs of postanal papillae and the absence of lateral alae. Phylogenetic analyses using partial sequences of the 28S ribosomal RNA gene place the new species in a clade containing Raphidascaris gigi, Raphidascaris lophii, Raphidascaris longispicula and two species of Hysterothylacium. The molecular analyses also corroborate results of previous studies that have found Raphidascaris and Hysterothylacium to be paraphyletic. The finding of R. mundeswariensis in A. bato is the first Raphidascaris species described from a mudskipper anywhere.

Description of Crenosoma vismani n. sp., parasitic in the lungs of Lynx lynx (L.) (Carnivora: Felidae), with identification key to the species of the genus Crenosoma Molin, 1861 (Nematoda: Crenosomatidae)

A new species of Crenosoma Molin, 1861 is described from the lungs of the Eurasian lynx, Lynx lynx (L.) (Carnivora: Felidae). Crenosoma vismani n. sp. differs from other species of the genus in the morphology of the male copulatory organs (two ventral rays originating from a common stem; three lateral rays with common stem; gubernaculum 79-92 μm long, well developed, spoon-shaped; spicules 232-253 μm long, slightly curved, with robust dorsal appendage) and a vulva with rounded, prominent vulvar cuticular appendage is located in middle region of body in females. An analysis of the morphology and life-cycle data for Crenosoma petrowi Morozov, 1939 from Ursus americanus Pallas indicate that this nematode should be described as a new species. The validity of Crenosoma schulzi Gagarin, 1958 is resurrected. A new identification key for the species of Crenosoma is provided. Published records of the genus Crenosoma from definitive hosts and patterns of host specificity are presented. Morphological data revealed that the genus Crenosoma should contain 15 species (14 with valid names) with different host specificity, ranging from oioxenous to euryxenous. However, a review of the current genetic data indicates that the actual number of Crenosoma spp. is greater, and the host range is still unknown, even in Europe.

Surprisingly long body length of the lungworm Parafilaroides gymnurus from common seals of the Dutch North Sea

Lungworms of the genera Parafilaroides and Otostrongylus are responsible for parasitic bronchopneumonia, the foremost disease of eastern Atlantic common seals (EACS, Phoca vitulina vitulina) in the Dutch North Sea. Recently, there have been increased reports of lungworm cases and observations of unusually long Parafilaroides sp. adults in this location. The initial aim of this study was to confirm the identity of the Parafilaroides species infecting this population. Parafilaroides are usually small and delicate, making them difficult to extract from host tissue, and there is often difficulty accessing fresh specimens for morphological study. The large size of the Dutch worms and the accessibility of specimens from numerous animals enabled the description and measurement of many intact specimens (N = 64) from multiple host animals (N = 20). Species identity was confirmed by targeted sequencing of ribosomal and mitochondrial DNA amplicons from a subset of worms. Worm morphology was consistent with descriptions for P. gymnurus, but the mature females were 1.9-fold and 3.4-fold longer than those recovered from French EACS (P ≤ 0.001) and Canadian western Atlantic common seals (Phoca vitulina concolor; P ≤ 0.0001). They were also significantly longer than mature female P. gymnurus described from other seal species, with the exception of those from harp seals of Les Escoumins, Quebec. We suggest that intraspecific genetic differences in P. gymnurus and the environment within the host could contribute to the variation reported here. This study is the first to describe P. gymnurus using morphological and molecular methods and should serve as a reference for identification of the species.

Clinical crenosomosis in a black bear (Ursus americanus)

An orphaned black bear (Ursus americanus) cub, estimated to be 9 months-of-age was presented to a wildlife rehabilitation facility in December of 2016. The cub was afebrile, under-weight (6.8 kg) and had a cough condition. Centrifugal sugar fecal flotation examination failed to detect any gastrointestinal helminth or protozoan parasites, but revealed the presence of first-stage nematode larvae (L₁). Large numbers of L₁ (>8000 L₁/g) identified as Crenosoma sp. based on morphology were recovered using the Baermann technique. Three species (Crenosoma petrowi, Crenosoma potos, Crenosoma vulpis) have been reported from black bears. Based on larval length measurements (range = 253-277 μm; mean = 263 μm; n = 8), the L₁ were tentatively identified as C. petrowi. Further molecular characterization using Polymerase Chain Reaction (PCR) and DNA sequencing of the small subunit (SSU) RNA gene and two regions of the large subunit (LSU) rRNA gene did not match any submissions in GenBank, but were most similar to Crenosoma mephiditis. There is a paucity of molecular data for members of the genus Crenosoma, with only information for Crenosoma vulpis (red fox), C. mephitidis (skunks), Crenosoma striatum (hedgehog) and Crenosoma sp. (red panda) in GenBank. Molecular analysis eliminates C. vulpis as a possibility in this case but due to the lack of submissions in GenBank, the identification of the L₁ as C. petrowi based on length measurements could not be confirmed. Receiving in total, three separate courses of treatment with fenbendazole (50 mg/kg, oral, once a day for 3 days), fecal larval shedding ceased and clinical signs resolved. The black bear cub was released into the wild in June 2017. This is the first report of clinical chronic respiratory disease due to Crenosoma sp. infection in a black bear.

Annotated catalogue of species of Angiostrongylus and the related genera Gallegostrongylus, Rodentocaulus and Stefanskostrongylus (Nematoda: Metastrongyloidea, Angiostrongylidae)

This catalogue is concerned with the closely related angiostrongylid genera Angiostrongylus, Gallegostrongylus, Rodentocaulus and Stefanskostrongylus. Three species, Angiostrongylus cantonensis, A. costaricensis and A. vasorum, have attracted most attention because of their importance in human and domestic animal disease. Many of the remaining species are poorly known and the number of valid taxa is unclear. The catalogue lists all nomenclaturally available and unavailable genus-group and species-group names that have been applied to the above genera and the species included in them, indicating their current nomenclatural status and providing the rigorous nomenclatural basis for future work. The catalogue lists 14 published and nomenclaturally available genus-group names, with the above four treated as valid, the other ten being junior synonyms. There are 42 published species-group names: 36 are valid, two are junior synonyms, four are nomenclaturally unavailable. One additional species, described in Chabaudistrongylus (synonym of Angiostrongylus), is listed as incertae sedis in Angiostrongylidae. Also listed are two unpublished collection names. The catalogue provides bibliographic details for all published names, and for available names provides locations of type material, details of type localities, geographic distributions and details of type and other hosts, both definitive and intermediate, to the extent known. The catalogue is a work of nomenclature, not a revisionary taxonomic work. No new names or new combinations are proposed. The apparently new family-group synonymy of Cardionematinae with Angiostrongylidae is introduced, as are four genus-group synonymies, three with Angiostrongylus and one with Stefaskostrongylus.

Validity of genus Perostrongylus Schlegel, 1934 with new data on Perostrongylus falciformis (Schlegel, 1933) in European badgers, Meles meles (Linnaeus, 1758): distribution, life-cycle and pathology

BACKGROUND

A century of debates on the taxonomy of members of the Metastrongyloidea Molin, 1861 led to many reclassifications. Considering the inconstant genus assignation and lack of genetic data, the main aim of this study was to support the validity of the genus Perostrongylus Schlegel, 1934, previously considered a synonym of Aelurostrongylus Cameron, 1927, based on new molecular phylogenetic data and to understand its evolutionary relationships with other metastrongyloid nematodes.

RESULTS

Specimens of lungworm collected from European badgers in Germany, Romania and Bosnia and Herzegovina were morphologically and molecularly (rDNA, cox1) characterized. From a phylogenetic standpoint, Perostrongylus is grouped with high support together with the genera Filaroides van Beneden, 1858 and Parafilaroides Dougherty, 1946 and includes probably two species: Perostrongylus falciformis (Schlegel, 1933), a parasite of Meles meles in Europe and P. pridhami (Anderson, 1962), a parasite of Neovison vison in North America. Perostrongylus and Aelurostrongylus are assigned to different clades. Aelurostrongylus becomes a monotypic genus, with the only species Aelurostrongylus abstrusus (Railliet, 1898). In addition, we provide morphological and morphometric data for the first-stage (L1), second-stage (L2), and third-stage (L3) larvae of P. falciformis and describe their development in experimentally infected Cornu aspersum snails. The pathological and histopathological lesions in lungs of infected European badgers are also described. This is the first record of P. falciformis in Romania.

CONCLUSIONS

Molecular phylogenetic and morphological data support the validity of the genus Perostrongylus, most probably with two species, P. falciformis in European badgers and P. pridhami in minks in North America. The two genera clearly belong to two different clades: Perostrongylus is grouped together with the genera Filaroides and Parafilaroides (both in the family Filaroididae Schulz, 1951), whereas Aelurostrongylus belongs to a clade with no sister groups.

Hurdles in the evolutionary epidemiology of Angiostrongylus cantonensis: Pseudogenes, incongruence between taxonomy and DNA sequence variants, and cryptic lineages

Angiostrongylus cantonensis, the rat lungworm, is a zoonotic pathogen that is one of the leading causes of eosinophilic meningitis worldwide. This parasite is regarded as an emerging pathogen with a global range expansion out of southeastern Asia post-WWII. To date, molecular systematic/phylogeographic studies on A. cantonensis have mainly used two mitochondrial (mtDNA) markers, cytochrome c oxidase 1 (CO1) and cytochrome b (CYTB), where the focus has largely been descriptive in terms of reporting local patterns of haplotype variants. In order to look for more global evolutionary patterns, we herein provide a collective phylogenetic assessment using the six available whole mtDNA genome samples that have been tagged as A. cantonensis, A. malaysiensis, or A. mackerrasae along with all other GenBank CO1 and CYTB partial sequences that carry these species identifiers. The results reveal three important complications that researchers will need to be aware of, or will need to resolve, prior to conducting future molecular evolutionary studies on A. cantonensis. These three problems are (i) incongruence between taxonomic identifications and mtDNA variants (haplotypes or whole mtDNA genome samples), (ii) the presence of a CYTB mtDNA pseudogene, and (iii) the need to verify A. mackerrasae as a species along with other possible cryptic lineages, of which there is suggestive evidence (i.e., A. cantonensis could be a species complex). We provided a discussion of how these complications are hurdles to our understanding of the global epidemiology of angiostrongyliasis. We call for future studies to be more explicit in morphological traits used for identifications (e.g., provide measurements). Moreover, it will be necessary to repeat prior morphological and life-history studies while simultaneously using sequence data in order to assess possible associations between critical epidemiological data (e.g., biogeography, virulence/pathology, host species use) and specific lineages.

Varestrongylus (Nematoda: Protostrongylidae), lungworms of ungulates: a phylogenetic framework based on comparative morphology

Varestrongylus Bhalerao, 1932 comprises ten valid lungworm species infecting wild and domestic ungulates from Eurasia and North America. Here, we present a phylogenetic hypothesis for the genus based on morphological characters in a broader context for the family Protostrongylidae and discuss species relationships and aspects of character evolution. Phylogenetic analysis of 25 structural attributes, including binary and multistate characters, among the 10 species of Varestrongylus resulted in one fully resolved most parsimonious tree (61 steps; consistency index = 0.672, retention index = 0.722, and consistency index excluding uninformative characters = 0.667). Varestrongylus forms a monophyletic clade and is the sister of Pneumostrongylus, supporting recognition of the subfamily Varestrongylinae. Monophyly for Varestrongylus is diagnosed by six unequivocal synapomorphies, all associated with structural characters of the copulatory system of males. Varestrongylus pneumonicus is basal, and sister to all other species within the genus, which form two subclades. The subclade I contains V. sagittatus + V. tuvae and V. qinghaiensis + V. longispiculatus. Subclade II contains V. alpenae, V. capricola, V. capreoli, and V. eleguneniensis + V. alces. Both subclades are diagnosed by two unambiguous synapomorphies. Highlighted is the continuing importance of phylogenetic assessments based on comparative morphology as a foundation to explore the structure of the biosphere across space and time.

New information on morphology and molecular data of camallanid nematodes parasitising Xenopus laevis (Anura: Pipidae) in South Africa

Three species of nematodes from the Camallanidae that are known to infect Xenopus laevis Daudin (Anura: Pipidae) were collected from several localities across South Africa. New data on morphology, partial 28S and cox1 genes, infection levels and distribution are presented herein. The most common species, Batrachocamallanus slomei Southwell et Kirshner, 1937, from the stomach and less often oesophagus, was found in eight localities. Camallanus kaapstaadi Southwell et Kirshner, 1937, also from the oesophagus, was found in two localities and C. xenopodis Jackson et Tinsley, 1995, from the intestine, at a single locality. New localities for both C. kaapstaadi and C. xenopodis provide a geographical range extension. Males of C. xenopodis are described for the first time herein. The existence of a left spicule in the males of both the species of Camallanus Railliet and Henry, 1915 is confirmed and measurements are provided. Although C. xenopodis is distinguished from C. mazabukae Kung, 1948 in the present study, we suggest greater sampling effort in other African amphibians to confirm the species status of the latter taxon. Finally, the new molecular data showed distant relationships between collected species of Camallanus and species parasitising fish and freshwater turtles.

Redescription and first molecular characterization of the little known feline neurotropic nematode Gurltia paralysans (Nematoda: Metastrongyloidea)

Gurltia paralysans is a poorly documented metastrongyloid nematode of cats, which mainly parasitizes the veins in the spinal cord subarachnoid space and parenchyma. Parasitic paraparesis caused by G. paralysans is a lesser-known spinal cord disease affecting domestic and wild felids of South America. Regions where feline gurltiosis is endemic include the southern parts of Chile and Argentina. Intra vitam diagnosis of feline gurltiosis remains challenging and is based primarily on neurological signs and the exclusion of other ethiologies for feline myelopathies. In view of the lack of information in the literature for this neglected feline neurological parasitosis, we have undertaken a detailed redescription and molecular characterization to expand on the previously available details in the original descriptions by Wolffhügel in 1993. The specimens used in this study were collected from spinal cord lesions of gurltiosis-affected domestic cats. Female and male specimens were morphologically and morphometrically examined using light and scanning electron microscopy. Molecular characterization was performed by sequencing a partial region of the nuclear ribosomal DNA and cytochrome oxidase gene of this parasite, and phylogenetic trees were constructed from the 28S D2-D3 and ITS2 regions using the Maximum Likelihood method. Sequence matching and phylogenetic analysis with these new sequences were consistent with the morphological classification of G. paralysans being within the Metastrongyloidea superfamily, but no consistent relation to a specific metastrongyloid family. The newly developed G. paralysans-specific PCR described here not only provides a useful diagnostic tool for feline gurltiosis in domestic cats living in endemic areas, but could also be used in large-scale epidemiological surveys on the intermediate mollusk host and the final host. By combining the morphology, molecular, and phylogenetic data we have reliably identified G. paralysans and confirmed its taxonomic status within the Metastrongyloidea.

Lungworm seroprevalence in free-ranging harbour seals and molecular characterisation of marine mammal MSP

Harbour seals (Phoca vitulina) are frequently infected with the lungworms Otostrongylus circumlitus and Parafilaroides gymnurus. The infection is often accompanied by secondary bacterial infections and can cause severe bronchopneumonia and even death in affected animals. Hitherto, the detection of lungworm infections was based on post mortem investigations from animals collected within stranding networks and a valid detection method for live free-ranging harbour seals was not available. Recently, an ELISA was developed for detecting lungworm antibodies in harbour seal serum, using major sperm protein (MSP) of the bovine lungworm, Dictyocaulus viviparus as recombinant diagnostic antigen. To determine lungworm seroprevalence in free-ranging harbour seals, serum was taken from four different seal age groups (n = 313) resulting in an overall prevalence of 17.9% (18.9% of males, 16.7% of females). 0.7% of harbour seals up to six weeks of age were seropositive, as were 89% of seals between six weeks and six months, 53.6% between six and 18 months and 24.2% of seals over 18 months of age. In the 18 months and over age group, seropositive animals showed statistically significant reductions in body weight (P = 0.003) and length (P < 0.001). Sera from lungworm infected harbour seals in rehabilitation (n = 6) revealed that duration of antibody persistence may be similar to that of lungworm infected cattle, but further studies are needed to confirm this. Phylogenetic analyses of MSP sequences of different marine and terrestrial mammal parasitic nematodes revealed that lungworm MSP of the genus Dictyocaulus (superfamily Trichostrongyloidea) is more closely related to metastrongylid marine mammal lungworms than to trichostrongylid nematodes of terrestrial hosts.

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First study on lungworm seroprevalence in live free-ranging harbour seals.

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Total seroprevalence was 17.9%, but age-dependent differences were observed.

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Six weeks to six months old seals showed highest prevalences (89% positives).

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Seropositive adult seals showed significantly reduced body weight and length.

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Phylogenetic tree construction using MSP of marine and terrestrial mammal parasites.

A survey of Angiostrongylus species in definitive hosts in Queensland

Despite the recent sporadic reports of angiostrongyliasis in humans, dogs and wildlife in eastern Australia there has been no systematic study to explore the epidemiology of Angiostrongylus spp. in definitive and intermediate hosts in the region. Little is known about the epidemiology of Angiostrongylus species in the definitive host in southeast Queensland, since the only survey conducted in this region was performed in the late 1960s. In this study, free-living populations of Rattus spp. were sampled and examined for the presence of adult and larval Angiostrongylus in the lungs, and of larvae in faeces. The prevalence of infection with Angiostrongylus spp. was 16.5% in Rattus spp. trapped in urban Brisbane and surrounds. This prevalence is much higher than estimates of earlier studies. This highlights the possible risk of zoonotic infection in children, dogs and wildlife in this region and indicates the necessity for public awareness as well as more detailed epidemiological studies on this parasite in eastern Australia.

Intermediate hosts of Angiostrongylus cantonensis in Tenerife, Spain

The nematode Angiostrongylus cantonensis is the causative agent of human angiostrongyliasis, the main clinical manifestation of which is eosinophilic meningitis. Although this parasite has been found recently in its definitive rat host in Tenerife (Canary Islands, Spain), showing a widespread distribution over the north-east part of the island, there are no available data regarding which snail and/or slug species are acting as intermediate hosts on this island. Consequently, the objective of this work was to determine the possible role of three mollusc species, Plutonia lamarckii, Cornu aspersum and Theba pisana, as intermediate hosts of A. cantonensis in Tenerife. Between 2011 and 2014, 233 molluscs were collected from five biotopes where rats had been found previously to harbor either adult worms or antibodies against A. cantonensis, and the identification was carried out on the basis of morphological features and a LAMP technique. The prevalence of A. cantonensis larvae in the mollusc samples, based on morphological identification, was 19.3%, whereas 59 out of the 98 individuals (60.2%) analyzed by LAMP were positive. Positive results were obtained for the three mollusc species analyzed and two of the positive samples, both obtained from P. lamarckii, were confirmed as positive by 18S rRNA and ITS1 PCR. Sequence analysis of 18S rRNA PCR products showed 100% similarity with previously published A. cantonensis sequences. These results may be relevant from a public health point of view, since all the biotopes from which the samples were obtained were in inhabited areas or areas with human activity, but it is also important from the perspective of a possible transmission to other accidental hosts, such as dogs and horses, animals that are present in some of the areas analyzed.

Fatal Parastrongylus dujardini Infection in Captive Callitrichids

Intravascular nematodes were considered the cause of death of 14 captive callitrichids. All animals were captive born at zoos in France and died with little or no premonitory signs of disease. No consistent gross lesions were observed at necropsy, although in certain cases intracardiac adult parasites were noted. The most significant histologic findings were verminous pneumonia and pulmonary endarteritis. In all cases except one, intravascular adult nematodes were observed with eggs and larvae in the lungs. Adult nematodes were obtained from 8 animals and in all cases were identified as Parastrongylus dujardini. To the authors’ knowledge, this is the first report of intravascular angiostrongylosis with primary cardiopulmonary location in callitrichids in France.

Diverse gastropod hosts of Angiostrongylus cantonensis, the rat lungworm, globally and with a focus on the Hawaiian Islands

Eosinophilic meningitis caused by the parasitic nematode Angiostrongylus cantonensis is an emerging infectious disease with recent outbreaks primarily in tropical and subtropical locations around the world, including Hawaii. Humans contract the disease primarily through ingestion of infected gastropods, the intermediate hosts of Angiostrongylus cantonensis. Effective prevention of the disease and control of the spread of the parasite require a thorough understanding of the parasite's hosts, including their distributions, as well as the human and environmental factors that contribute to transmission. The aim of this study was to screen a large cross section of gastropod species throughout the main Hawaiian Islands to determine which act as hosts of Angiostrongylus cantonensis and to assess the parasite loads in these species. Molecular screening of 7 native and 30 non-native gastropod species revealed the presence of the parasite in 16 species (2 native, 14 non-native). Four of the species tested are newly recorded hosts, two species introduced to Hawaii (Oxychilus alliarius, Cyclotropis sp.) and two native species (Philonesia sp., Tornatellides sp.). Those species testing positive were from a wide diversity of heterobranch taxa as well as two distantly related caenogastropod taxa. Review of the global literature showed that many gastropod species from 34 additional families can also act as hosts. There was a wide range of parasite loads among and within species, with an estimated maximum of 2.8 million larvae in one individual of Laevicaulis alte. This knowledge of the intermediate host range of Angiostrongylus cantonensis and the range of parasite loads will permit more focused efforts to detect, monitor and control the most important hosts, thereby improving disease prevention in Hawaii as well as globally.

Phylogenetics and systematics of Angiostrongylus lungworms and related taxa (Nematoda: Metastrongyloidea) inferred from the nuclear small subunit (SSU) ribosomal DNA sequences

The Angiostrongylus lungworms are of public health and veterinary concern in many countries. At the family level, the Angiostrongylus lungworms have been included in the family Angiostrongylidae or the family Metastrongylidae. The present study was undertaken to determine the usefulness and suitability of the nuclear 18S (small subunit, SSU) rDNA sequences for differentiating various taxa of the genus Angiostrongylus, as well as to determine the systematics and phylogenetic relationship of Angiostrongylus species and other metastrongyloid taxa. This study revealed six 18S (SSU) haplotypes in A. cantonensis, indicating considerable genetic diversity. The uncorrected pairwise ‘p’ distances among A. cantonensis ranged from 0 to 0.86%. The 18S (SSU) rDNA sequences unequivocally distinguished the five Angiostrongylus species, confirmed the close relationship of A. cantonensis and A. malaysiensis and that of A. costaricensis and A. dujardini, and were consistent with the family status of Angiostrongylidae and Metastrongylidae. In all cases, the congeneric metastrongyloid species clustered together. There was no supporting evidence to include the genus Skrjabingylus as a member of Metastrongylidae. The genera Aelurostrongylus and Didelphostrongylus were not recovered with Angiostrongylus, indicating polyphyly of the Angiostrongylidae. Of the currently recognized families of Metastrongyloidea, only Crenosomatidae appeared to be monophyletic. In view of the unsettled questions regarding the phylogenetic relationships of various taxa of the metastrongyloid worms, further analyses using more markers and more taxa are warranted.

The mitochondrial genome of Protostrongylus rufescens - implications for population and systematic studies

Background

Protostrongylus rufescens is a metastrongyloid nematode of small ruminants, such as sheep and goats, causing protostrongylosis. In spite of its importance, the ecology and epidemiology of this parasite are not entirely understood. In addition, genetic data are scant for P. rufescens and related metastrongyloids.

Methods

The mt genome was amplified from a single adult worm of P. rufescens (from sheep) by long-PCR, sequenced using 454-technology and annotated using bioinformatic tools. Amino acid sequences inferred from individual genes of the mt genomes were concatenated and subjected to phylogenetic analysis using Bayesian inference.

Results

The circular mitochondrial genome was 13,619 bp in length and contained two ribosomal RNA, 12 protein-coding and 22 transfer RNA genes, consistent with nematodes of the order Strongylida for which mt genomes have been determined. Phylogenetic analysis of the concatenated amino acid sequence data for the 12 mt proteins showed that P. rufescens was closely related to Aelurostrongylus abstrusus, Angiostrongylus vasorum, Angiostrongylus cantonensis and Angiostrongylus costaricensis.

Conclusions

The mt genome determined herein provides a source of markers for future investigations of P. rufescens. Molecular tools, employing such mt markers, are likely to find applicability in studies of the population biology of this parasite and the systematics of lungworms.

The mitochondrial genome of Aelurostrongylus abstrusus-diagnostic, epidemiological and systematic implications

Aelurostrongylus abstrusus (Railliet, 1898) is a metastrongylid nematode of major clinical relevance in felids, causing aelurostrongylosis. In spite of its clinical importance in cats, the genetics, epidemiology and biology of this parasite are not entirely understood. mt DNA can provide markers for studies of these areas, but genetic data are scant for A. abstrusus and related lungworms. Here, the mt genome was amplified by long-range polymerase chain reaction (long-PCR) from a single male adult of A. abstrusus, sequenced using 454 technology and annotated using an established bioinformatic pipeline. This circular mt genome is 13,913 bp and contains two ribosomal RNA, 12 protein-coding and 22 transfer RNA genes, consistent with most other chromadorean nematodes. This genome should provide a source of markers for future investigations of the epidemiology and ecology of A. abstrusus. Molecular tools, employing such mt markers, are likely to find utility for explorations into the epidemiology, biology and systematics of this parasite, and the diagnosis of feline aelurostrongylosis.

Improved detection of canine Angiostrongylus vasorum infection using real-time PCR and indirect ELISA

This study reports the development of a real-time PCR assay and an indirect ELISA to improve on current detection of canine Angiostrongylus vasorum infection. A highly specific fluorescent probe-based, real-time PCR assay was developed to target the A. vasorum second internal transcribed spacer region and detected DNA in EDTA blood, lung tissue, broncho-alveolar larvage fluid, endotracheal mucus, pharyngeal swabs and faecal samples. PCR was fast (∼1 h), highly efficient when using EDTA blood samples, consistently detected a single molecule of parasite DNA and did not amplify DNA from other parasitic nematodes or definitive host species. An indirect ELISA was also developed using the soluble protein fraction from adult A. vasorum worms. Some cross-reactive antigen recognition was observed when tested against sera from dogs infected with Crenosoma vulpis (n = 8), Toxocara canis (n = 5) and Dirofilaria immitis (n = 5). This was largely overcome by setting the cut-off for a positive result at an appropriately high level. Field evaluation of the real-time PCR and ELISA was conducted by testing sera and EDTA blood from dogs with suspected A. vasorum infection (n = 148) and compared with the Baermann's larval migration test in faeces. Thirty-one dogs were positive by at least one test. Of these, 20 (65%) were detected by the Baermann method, 18 (58%) by blood PCR, 24 (77%) by ELISA and 28 (90%) by blood PCR and ELISA together. Combined testing using real-time PCR and ELISA therefore improved the detection rate of A. vasorum infection and holds promise for improved clinical diagnosis and epidemiological investigation.

Transmission of lungworms of harbour porpoises and harbour seals: molecular tools determine potential vertebrate intermediate hosts

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) from German waters are infected by six species of lungworms (Metastrongyloidea). These nematodes parasitise the respiratory tract, are pathogenic and often cause secondary bacterial infections. In spite of their clinical and epidemiological significance, the life cycle and biology of lungworms in the marine environment is still largely unknown. Regions of ribosomal DNA (ITS-2) of all lungworms parasitising harbour porpoises and harbour seals in German waters were sequenced to characterise and compare the different species. The phylogenetic relationship among the lungworm species was analysed by means of their ITS-2 nucleotide sequences and the species-specific traits of the ITS-2 were used to screen wild fish as possible intermediate hosts for larval lungworms. Molecular markers were developed to identify larval nematodes via in-situ hybridisation of tissues of harbour porpoise and harbour seal prey fish. Potential wild intermediate fish hosts from the North Sea were dissected and found to harbour larval nematodes. Histological examination and in-situ hybridisation of tissue samples from these fish showed lungworm larvae within the intestinal wall. Based on larval ITS-2 nucleotide sequences, larval nematodes were identified as Pseudalius inflexus and Parafilaroides gymnurus. Turbot (Psetta maxima) bred and raised in captivity were experimentally infected with live L1s of Otostrongylus circumlitus and ensheathed larvae were recovered from the gastrointestinal tract of turbot and identified using molecular tools. Our results show that fish intermediate hosts play a role in the transmission of metastrongyloid nematodes of harbour porpoises and harbour seals.

Preliminary molecular characterization of the human pathogen Angiostrongylus cantonensis

Background

Human angiostrongyliasis is an emerging food-borne public health problem, with the number of cases increasing worldwide, especially in mainland China. Angiostrongylus cantonensis is the causative agent of this severe disease. However, little is known about the genetics and basic biology of A. cantonensis.

Results

A cDNA library of A. cantonensis fourth-stage larvae was constructed, and ~1,200 clones were sequenced. Bioinformatic analyses revealed 378 cDNA clusters, 54.2% of which matched known genes at a cutoff expectation value of 10^-20. Of these 378 unique cDNAs, 168 contained open reading frames encoding proteins containing an average of 238 amino acids. Characterization of the functions of these encoded proteins by Gene Ontology analysis showed enrichment in proteins with binding and catalytic activity. The observed pattern of enzymes involved in protein metabolism, lipid metabolism and glycolysis may reflect the central nervous system habitat of this pathogen. Four proteins were tested for their immunogenicity using enzyme-linked immunosorbent assays and histopathological examinations. The specificity of each of the four proteins was superior to that of crude somatic and excretory/secretory antigens of larvae, although their sensitivity was relatively low. We further showed that mice immunized with recombinant cystatin, a product of one of the four cDNA candidate genes, were partially protected from A. cantonensis infection.

Conclusion

The data presented here substantially expand the available genetic information about the human pathogen A. cantonensis, and should be a significant resource for angiostrongyliasis researchers. As such, this work serves as a starting point for molecular approaches for diagnosing and controlling human angiostrongyliasis.

The small subunit (SSU) ribosomal (r) RNA gene as a genetic marker for identifying infective 3rd juvenile stage Angiostrongylus cantonensis

We have developed a molecular method using PCR-direct sequencing to identify the infective 3rd juvenile stage of Angiostrongylus cantonensis, a nematode parasite of rodents that can accidentally infect humans and cause eosinophilic meningitis. We demonstrate that the 5' end of the small subunit (SSU) ribosomal (r) RNA gene is a suitable marker to identify A. cantonensis and distinguish it from other closely related Angiostrongylus species. When the SSU rRNA marker was employed on nematode populations extracted from the black slug Laevicaulis altae collected in 2 test sites in the Philippines, the infective 3rd juvenile stage A. cantonensis was detected without difficulty. The phylogenetic position of other non-angiostrongylid nematodes isolated was also determined. The molecular technique developed in this study provides a rapid and accurate method for the identification of A. cantonensis when morphological identification proves difficult or inadequate.

Molecular phylogeny of the pinworms of mice, rats and rabbits, and its use to develop molecular beacon assays for the detection of pinworms in mice

Though pinworm infestation has been prevalent since the early years of laboratory animal medicine, the genomes of these parasites have not yet been sequenced. The authors used high-fidelity polymerase chain reaction to amplify a large portion of the ribosomal gene complex of four pinworm species commonly found in lab rodents and rabbits (Aspiculuris tetraptera, Passalurus ambiguus, Syphacia muris and Syphacia obvelata). They determined DNA sequences for these complexes and carried out phylogenetic analysis. Using this information, the authors developed real-time molecular beacon assays for pinworm detection, comparing the new diagnostic approach with traditional methods such as perianal tape testing, fecal flotation and direct examination of intestinal content.

Molecular phylogeny of clade III nematodes reveals multiple origins of tissue parasitism

Molecular phylogenetic analyses of 113 taxa representing Ascaridida, Rhigonematida, Spirurida and Oxyurida were used to infer a more comprehensive phylogenetic hypothesis for representatives of 'clade III'. The posterior probability of multiple alignment sites was used to exclude or weight characters, yielding datasets that were analysed using maximum parsimony, likelihood, and Bayesian inference methods. Phylogenetic results were robust to differences among inference methods for most high-level taxonomic groups, but some clades were sensitive to treatments of characters reflecting differences in alignment ambiguity. Taxa representing Camallanoidea, Oxyurida, Physalopteroidea, Raphidascarididae, and Skrjabillanidae were monophyletic in all 9 analyses whereas Ascaridida, Ascarididae, Anisakidae, Cosmocercoidea, Habronematoidea, Heterocheilidae, Philometridae, Rhigonematida and Thelazioidea were never monophyletic. Some clades recovered in all trees such as Dracunculoidea and Spirurina included the vast majority of their sampled species, but were non-monophyletic due to the consistent behaviour of one or few 'rogue' taxa. Similarly, 102 of 103 clade III taxa were strongly supported as monophyletic, yet clade III was paraphyletic due to the grouping of Truttaedacnitis truttae with the outgroups. Mapping of host 'habitat' revealed that tissue-dwelling localization of nematode adults has evolved independently at least 3 times, and relationships among Spirurina and Camallanina often reflected tissue predilection rather than taxonomy.

Restoration of Parafilaroides (Dougherty, 1946) (Nematoda: Metastrongyloidea) with description of two new species from pinnipeds of eastern central Pacific

The lungs of a northern elephant seal, Mirounga angustirostris (Gill, 1866), and Pacific harbor seal, Phoca vitulina richardii (Gray, 1864), from the eastern central Pacific, central California coast, were examined for parasites. This represents the first thorough description and identification of Parafilaroides species from northern elephant seals and Pacific harbor seals on the west coast of North America. From this study, 2 new species of Filaroides (Parafilaroides) are described, illustrated, and differentiated by shape of vaginal sphincter, body morphometrics, and spicule shape from the 4 existing, recognized species in the subgenus. In addition, the subgenus Parafilaroides is proposed to be reestablished to full generic status in the Filaroididae based on the presence of caudal papillae and DNA.

The evolutionary origins of nematodes within the order Strongylida are related to predilection sites within hosts

The evolutionary relationships of the different groups of nematodes within the order Strongylida based on morphological data have been speculative and the subject of conjecture. In this paper, we present a multigene phylogenetic analysis, using sequence data of the 18S and 28S ribosomal RNA genes from representatives of all four suborders and seven superfamilies of the Strongylida, to test existing hypotheses proposed for the relationships of the suborders based on morphological data sets. The results obtained demonstrated that the Strongylida is a monophyletic assemblage, with only the Metastrongylina (but not the other suborders) forming a distinct monophyletic clade. We show that, in contrast to all previous hypotheses, one major lineage comprises taxa which occur exclusively in the pulmonary, circulatory or nervous systems of marsupial and eutherian mammals, whereas a second lineage comprises species occurring in the gastrointestinal tracts or perirenal tissues of vertebrates, or in the lungs of birds. The findings suggest that the predilection site of adult nematodes and host type reflect the evolutionary origin of the different taxonomic groups within the Strongylida.

The use of nuclear ribosomal DNA markers for the identification of bursate nematodes (order Strongylida) and for the diagnosis of infections

Many bursate nematodes are of major importance to animal health. Animals are often parasitized by multiple species that differ in their prevalence, relative abundance and/or pathogenicity. Implementation of effective management strategies for these parasites requires reliable methods for their detection in hosts, identification to the species level and measurement of intensity of infection. One major problem is the difficulty of accurately identifying and distinguishing many species of bursate nematode because of the remarkable morphological similarity of their eggs and larvae. The inability to identify, with confidence, individual nematodes (irrespective of their life-cycle stage) to the species level by morphological methods has often led to a search for species-specific genetic markers. Studies over the past 15 years have shown that sequences of the internal transcribed spacers of ribosomal DNA provide useful genetic markers, providing the basis for the development of PCR-based diagnostic tools. Such molecular methods represent powerful tools for studying the systematics, epidemiology and ecology of bursate nematodes and, importantly, for the specific diagnosis of infections in animals and humans, thus contributing to improved control and prevention strategies for these parasites.

A new species of Skrjabingylus Petrov, 1927 (Nematoda: Metastrongyloidea) from the frontal sinuses of the hooded skunk, Mephitis macroura (Mustelidae)

Skrjabingylus santaceciliae n. sp. is described based on specimens from the frontal sinuses of a hooded skunk, Mephitis macroura, collected from the Area de Conservación Guanacaste, Costa Rica. Skrjabingylus santaceciliae n. sp. differs from the other 5 species in the genus in having pointed spicule tips that lack a rounded or lobed formation and by lacking a prominent distal projection at the tail tip. Morphometric comparisons show that S. santaceciliae n. sp. is much smaller than the only other valid species from Mephitis, Skrjabingylus chitwoodorum Hill, 1939. Likewise, morphometric comparisons also distinguish S. santaceciliae n. sp. from other described Skrjabingylus species.

Sexual transmission of a nematode parasite of Wood Mice (Apodemus sylvaticus)?

Sexual transmission occurs commonly in microparasites such as viruses and bacteria, but this is an unusual transmission route for macroparasites. Here we present evidence which suggests that a nematode parasite of Wood Mice (Apodemus sylvaticus) may be sexually transmitted and we have classified the nematode using molecular data. Wood Mice were collected annually in the course of work on their reproductive physiology. Larval nematodes were found in the epididymides of 19.6% of males. It seems likely that they would be transmitted to females at ejaculation. To identify these larval nematodes, which we were unable to do using morphological features, we sequenced the 18S rDNA. Sequence comparisons with the molecular phylogeny of Blaxter et al. (1998) demonstrated that they were bursate nematodes (Order Strongylida). The relationships between strongylid taxa were poorly resolved by 18S rDNA. However, both distance and parsimony analyses grouped the nematode with the superfamily Metastrongylidea in a clade containing Filaroides and Angiostrongylus sp. Importantly, the sequences were distinct from those of Heligmosomoides polygyrus and Angiostrongylus dujardini, two common strongylid nematodes of Apodemus. We were therefore unable positively to identify these worms by matching their sequences with those from morphologically identifiable adult strongylid nematodes infecting Apodemus. These results demonstrate that an as yet unidentified strongylid is quite commonly found in large numbers in the male reproductive tract of Wood Mice. Further work is required to understand the biology and transmission dynamics of this interesting system.