Mapping the presence of Wolbachia pipientis on the phylogeny of filarial nematodes: evidence for symbiont loss during evolution

The Wolbachia Symbiont: Here, There and Everywhere

Wolbachia symbionts, first observed in the 1920s, are now known to be present in about 30-70% of tested arthropod species, in about half of tested filarial nematodes (including the majority of human filarial nematodes), and some plant-parasitic nematodes. In arthropods, they are generally viewed as parasites while in nematodes they appear to be mutualists although this demarcation is not absolute. Their presence in arthropods generally leads to reproductive anomalies, while in nematodes, they are generally required for worm development and reproduction. In mosquitos, Wolbachia inhibit RNA viral infections, leading to populational reductions in human RNA virus pathogens, whereas in filarial nematodes, their requirement for worm fertility and survival has been channeled into their use as drug targets for filariasis control. While much more research on these ubiquitous symbionts is needed, they are viewed as playing significant roles in biological processes, ranging from arthropod speciation to human health.

Systematic Review of Wolbachia Symbiont Detection in Mosquitoes: An Entangled Topic about Methodological Power and True Symbiosis

Wolbachia is an endosymbiotic bacterium that naturally infects several arthropods and nematode species. Wolbachia gained particular attention due to its impact on their host fitness and the capacity of specific Wolbachia strains in reducing pathogen vector and agricultural pest populations and pathogens transmission. Despite the success of mosquito/pathogen control programs using Wolbachia-infected mosquito release, little is known about the abundance and distribution of Wolbachia in most mosquito species, a crucial knowledge for planning and deployment of mosquito control programs and that can further improve our basic biology understanding of Wolbachia and host relationships. In this systematic review, Wolbachia was detected in only 30% of the mosquito species investigated. Fourteen percent of the species were considered positive by some studies and negative by others in different geographical regions, suggesting a variable infection rate and/or limitations of the Wolbachia detection methods employed. Eighty-three percent of the studies screened Wolbachia with only one technique. Our findings highlight that the assessment of Wolbachia using a single approach limited the inference of true Wolbachia infection in most of the studied species and that researchers should carefully choose complementary methodologies and consider different Wolbachia-mosquito population dynamics that may be a source of bias to ascertain the correct infectious status of the host species.

Plant-Mediated Horizontal Transmission of Asaia Between White-Backed Planthoppers, Sogatella furcifera

Asaia is a bacterial symbiont of sugar-feeding insects that has been shown to be vertically transmitted by maternal transmission and paternal transmission mechanism, and to be horizontally transmitted via co-feeding artificial diet and venereal routes. Here, the first case of plant-mediated horizontal transmission of Asaia between white-backed planthoppers (WBPH), Sogatella furcifera, was reported. In Asaia-infected WBPH, Asaia was detected mostly in salivary glands and to a less extent in stylets. The rice leaf sheaths fed by Asaia-infected WBPH for 12 h were all positive with Asaia, where Asaia persisted for at least 30 d but was localized in the feeding sites only. When confined to Asaia-infected leaf sheaths for 7 d at the sites pre-infested by the Asaia-infected WBPH, all Asaia-free WBPH became infected with Asaia and the acquired Asaia could be vertically transmitted to their offspring. Phylogenetic analysis confirmed an identical Asaia strain in the Asaia-infected donor WBPH, the Asaia-infected leaf sheaths, and the newly infected recipient WBPH. Our findings provide direct evidence for the first time that rice plant can mediate horizontal transmission of Asaia between WBPH, which may contribute to the spread of Asaia in the field WBPH populations.

Diminutive, degraded but dissimilar: Wolbachia genomes from filarial nematodes do not conform to a single paradigm

Wolbachia are alpha-proteobacteria symbionts infecting a large range of arthropod species and two different families of nematodes. Interestingly, these endosymbionts are able to induce diverse phenotypes in their hosts: they are reproductive parasites within many arthropods, nutritional mutualists within some insects and obligate mutualists within their filarial nematode hosts. Defining Wolbachia 'species' is controversial and so they are commonly classified into 17 different phylogenetic lineages, termed supergroups, named A-F, H-Q and S. However, available genomic data remain limited and not representative of the full Wolbachia diversity; indeed, of the 24 complete genomes and 55 draft genomes of Wolbachia available to date, 84 % belong to supergroups A and B, exclusively composed of Wolbachia from arthropods. For the current study, we took advantage of a recently developed DNA-enrichment method to produce four complete genomes and two draft genomes of Wolbachia from filarial nematodes. Two complete genomes, wCtub and wDcau, are the smallest Wolbachia genomes sequenced to date (863 988 bp and 863 427 bp, respectively), as well as the first genomes representing supergroup J. These genomes confirm the validity of this supergroup, a controversial clade due to weaknesses of the multilocus sequence typing approach. We also produced the first draft Wolbachia genome from a supergroup F filarial nematode representative (wMhie), two genomes from supergroup D (wLsig and wLbra) and the complete genome of wDimm from supergroup C. Our new data confirm the paradigm of smaller Wolbachia genomes from filarial nematodes containing low levels of transposable elements and the absence of intact bacteriophage sequences, unlike many Wolbachia from arthropods, where both are more abundant. However, we observe differences among the Wolbachia genomes from filarial nematodes: no global co-evolutionary pattern, strong synteny between supergroup C and supergroup J Wolbachia, and more transposable elements observed in supergroup D Wolbachia compared to the other supergroups. Metabolic pathway analysis indicates several highly conserved pathways (haem and nucleotide biosynthesis, for example) as opposed to more variable pathways, such as vitamin B biosynthesis, which might be specific to certain host-symbiont associations. Overall, there appears to be no single Wolbachia-filarial nematode pattern of co-evolution or symbiotic relationship.

An Earliest Endosymbiont, Wolbachia massiliensis sp. nov., Strain PL13 from the Bed Bug (Cimex hemipterus), Type Strain of a New Supergroup T

The symbiotic Wolbachia are the most sophisticated mutualistic bacterium among all insect-associated microbiota. Wolbachia-insect relationship fluctuates from the simple facultative/parasitic to an obligate nutritional-mutualistic association as it was the case of the bedbug-Wolbachia from Cimexlectularius. Understanding this association may help in the control of associated arthropods. Genomic data have proven to be reliable tools in resolving some aspects of these symbiotic associations. Although, Wolbachia appear to be fastidious or uncultivated bacteria which strongly limited their study. Here we proposed Drosophila S2 cell line for the isolation and culture model to study Wolbachia strains. We therefore isolated and characterized a novel Wolbachia strain associated with the bedbug Cimexhemipterus, designated as wChem strain PL13, and proposed Wolbachiamassiliensis sp. nov. strain wChem-PL13 a type strain of this new species from new supergroup T. Phylogenetically, T-supergroup was close to F and S-supergroups from insects and D-supergroup from filarial nematodes. We determined the 1,291,339-bp genome of wChem-PL13, which was the smallest insect-associated Wolbachia genomes. Overall, the wChem genome shared 50% of protein coding genes with the other insect-associated facultative Wolbachia strains. These findings highlight the diversity of Wolbachia genotypes as well as the Wolbachia-host relationship among Cimicinae subfamily. The wChem provides folate and riboflavin vitamins on which the host depends, while the bacteria had a limited translation mechanism suggesting its strong dependence to its hosts. However, the clear-cut distinction between mutualism and parasitism of the wChem in C. hemipterus cannot be yet ruled out.

Bacterial Communities of Ixodes scapularis from Central Pennsylvania, USA

Native microbiota represent a potential resource for biocontrol of arthropod vectors. Ixodes scapularis is mostly inhabited by the endosymbiotic Rickettsia buchneri, but the composition of bacterial communities varies with life stage, fed status, and/or geographic location. We compared bacterial community diversity among I. scapularis populations sampled within a small geographic range in Central Pennsylvania. We collected and extracted DNA from ticks and sequenced amplicons of the eubacterial 16S rRNA gene from individuals and pooled samples. We then used taxon-specific PCR and/or qPCR to confirm the abundance or infection frequency of select pathogenic and symbiotic bacteria. Bacterial communities were more diverse in pools of males than females and the most abundant taxon was Rickettsia buchneri followed by Coxiellaceae (confirmed by sequencing as an unknown Rickettsiella species). High Rickettsiella titers in pools were likely due to a few heavily infected males. We determined that the infection frequency of Borrelia burgdorferi ranged from 20 to 75%. Titers of Anaplasma phagocytophilum were significantly different between sexes. Amplicon-based bacterial 16S sequencing is a powerful tool for establishing the baseline community diversity and focusing hypotheses for targeted experiments, but care should be taken not to overinterpret data based on too few individuals. We identified intracellular bacterial candidates that may be useful as targets for manipulation.

Pseudoscorpion Wolbachia symbionts: diversity and evidence for a new supergroup S

Background

Wolbachia are the most widely spread endosymbiotic bacteria, present in a wide variety of insects and two families of nematodes. As of now, however, relatively little genomic data has been available. The Wolbachia symbiont can be parasitic, as described for many arthropod systems, an obligate mutualist, as in filarial nematodes or a combination of both in some organisms. They are currently classified into 16 monophyletic lineage groups (“supergroups”). Although the nature of these symbioses remains largely unknown, expanded Wolbachia genomic data will contribute to understanding their diverse symbiotic mechanisms and evolution.

Results

This report focuses on Wolbachia infections in three pseudoscorpion species infected by two distinct groups of Wolbachia strains, based upon multi-locus phylogenies. Geogarypus minor harbours wGmin and Chthonius ischnocheles harbours wCisc, both closely related to supergroup H, while Atemnus politus harbours wApol, a member of a novel supergroup S along with Wolbachia from the pseudoscorpion Cordylochernes scorpioides (wCsco). Wolbachia supergroup S is most closely related to Wolbachia supergroups C and F. Using target enrichment by hybridization with Wolbachia-specific biotinylated probes to capture large fragments of Wolbachia DNA, we produced two draft genomes of wApol. Annotation of wApol highlights presence of a biotin operon, which is incomplete in many sequenced Wolbachia genomes.

Conclusions

The present study highlights at least two symbiont acquisition events among pseudoscorpion species. Phylogenomic analysis indicates that the Wolbachia from Atemnus politus (wApol), forms a separate supergroup (“S”) with the Wolbachia from Cordylochernes scorpioides (wCsco). Interestingly, the biotin operon, present in wApol, appears to have been horizontally transferred multiple times along Wolbachia evolutionary history.

Seasonal Filarial Infections and Their Black Fly Vectors in Chiang Mai Province, Northern Thailand

The transmission of zoonotic filarial parasites by black flies has so far been reported in the Chiang Mai and Tak provinces, Thailand, and the bites of these infected black flies can cause a rare disease—human zoonotic onchocerciasis. However, species identification of the filarial parasites and their black fly vectors in the Chiang Mai province were previously only based on a morphotaxonomic analysis. In this study, a combined approach of morphotaxonomic and molecular analyses (mitochondrial cox1, 12S rRNA, and nuclear 18S rRNA (SSU HVR-I) genes) was used to clarify the natural filarial infections in female black flies collected by using human and swine baits from two study areas (Ban Lek and Ban Pang Dang) in the Chiang Mai province from March 2018 to January 2019. A total of 805 and 4597 adult females, belonging to seven and nine black fly taxa, were collected from Ban Lek and Ban Pang Dang, respectively. At Ban Lek, four of the 309 adult females of Simulium nigrogilvum were positive for Onchocerca species type I in the hot and rainy seasons. At Ban Pang Dang, five unknown filarial larvae (belonging to the same new species) were detected in Simulium sp. in the S. varicorne species-group and in three species in the S. asakoae species-group in all seasons, and three non-filarial larvae of three different taxa were also found in three females of the S. asakoae species-group. This study is the first to molecularly identify new filarial species and their vector black fly species in Thailand.

Scanning electron microscopy of Onchocerca fasciata (Filarioidea: Onchocercidae) adults, microfilariae and eggs with notes on histopathological findings in camels

BACKGROUND

Onchocerca fasciata is a prevalent filarial species in camelids of Asia and Africa forming nodules in the skin of dromedary and Bactrian camels. In spite of recent advances in the biology and epidemiology of this nematode species, a relatively scant number of studies have focussed on the morphology of this parasite. The main objective of this study was to describe morphological characteristics of adults, microfilariae and eggs of O. fasciata by scanning electron microscopy (SEM), staining and histology.

METHODS

From April 2016 to March 2017 dromedary camels (n = 456) were inspected for infection with O. fasciata in a slaughterhouse in Kerman (south of Iran). Adult worms in nodules were isolated by digestion of nodules in collagenase and used for SEM. Skin nodules were also fixed, sectioned and stained with hematoxylin and eosin for histopathology. Skin microfilariae that were isolated from tissues surrounding the nodules were confirmed as O. fasciata by sequencing of the cytochrome c oxidase subunit 1 (cox1) and 12S rRNA genes and used for SEM and Giemsa staining.

RESULTS

Single or multiple O. fasciata nodules (1.2-2.2 cm in diameter and 507-845 mg in weight) were found in 30.3% of the examined camels. SEM analysis helped identify 18 papillae in the caudal region of the male. Discontinuous longitudinal cuticular crests were observed in the posterior region of the male. In female nematodes, the ridges had a rounded shape with a height/width ratio of 7/16 in longitudinal sections. Unsheathed skin microfilariae with a rounded anterior extremity measured 210.7 × 2.5 μm on average. Developed eggs containing microfilariae measured 35.9 × 31.0 μm and their smooth shell surface had characteristic tongue-like appendages. In addition to inflammatory reactions surrounding the parasites, accumulation of intracellular ceroid pigment, golden-yellow to brown in colour, was observed within macrophages upon histopathological examination.

CONCLUSIONS

We found longitudinal crests on the surface of the posterior region of the male nematode. Measurements of the main morphological features of microfilariae and eggs, and the shape index of ridges (height/width) in female nematodes are described for the first time.

Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand

Zoonotic onchocerciasis is a human infection caused by Onchocerca species of animal origins and transmitted by black fly vectors. The reported incidence of this disease has increased throughout the world. This study aims to clarify the vectorial roles of black fly species in zoonotic filarial transmission in Tak province, western Thailand. The integrated approach of morphological and DNA sequence-based analyses was used to identify species of both wild-caught female black flies and infective filarial larvae found in the infected black flies. All of 494 female black flies captured were identified as Simulium nigrogilvum, through scanning electron microscopy (SEM) and DNA sequence analyses based on the cytochrome c oxidase subunit I (COI) and subunit II (COII), and the fast-evolving nuclear elongation complex protein 1 (ECP1) genes. Four females of S. nigrogilvum harbored one to three third-stage larvae (infective larvae) in their thoraces, with an infection rate of 0.81% (4/494). All infective larvae were similar in morphology and size to one another, being identified as Onchocerca species type I (= O. sp. type A), a bovine filaria, originally reported from Japan, and also as O. sp. found in S. nodosum in Thailand, based on their body lengths and widths being 1,068-1,346 µm long by 25-28 µm wide, and morphological characters. Comparisons of cytochrome c oxidase subunit I (COI) and 12S rRNA sequences of mitochondrial DNA (mtDNA) and phylogenetic analyses with those of previous reports strongly supported that all larvae were O. sp. type I. This report is the first indicating the presence of O. sp. type I in Thailand and its vector being S. nigrogilvum.

Canine vector-borne pathogens from dogs and ticks from Tamil Nadu, India

Canine vector-borne diseases (CVBDs) pose a major health problem in dogs globally, with the potential to cause zoonoses, in particular in developing countries where scientific knowledge on the topic is minimal. Blood samples and ticks were collected from stray dogs in Tamil Nadu, South India to assess the prevalence of CVBD-causing pathogens (Anaplasma spp., Babesia spp., Ehrlichia spp., Hepatozoon spp., filarioids and Leishmania spp.). Of the 230 dogs examined, 229 (99.6%) were infested by ticks (mean intensity, 5.65) with Rhipicephalus sanguineus sensu lato and Rhipicephalus haemaphysaloides being morphologically identified in the 98.3% and 1.7% of the infested dogs, respectively. Overall, the 67.8% (n = 156) of dogs was positive for at least one pathogen with Hepatozoon canis being the most prevalent (37.8%) followed by Anaplasma platys (22.6%), Ehrlichia canis (16.1%) Babesia vogeli (10%), Anaplasma phagocytophilum (0.4%) and Babesia gibsoni (0.4%). Two filarioids (Dirofilaria sp. "hongkongensis" and Brugia malayi, 0.4%) were diagnosed in sampled animals. Co-infection with H. canis and A. platys was the most prevalent (8.3%, P = 0.00001), whilst all animals scored negative for Leishmania spp.. Out of 295 ticks analysed, 215 R. sanguineus s.l. (75.4%) and 8 R. haemaphysaloides (88.9%) were positive for at least one pathogen with H. canis as the predominant species (42.5%), followed by A. platys (33.8%), E. canis (16.9%), B. vogeli (3.8%) and A. phagocytophilum (0.3%). Fifty-six dogs (35.9%) harboured the same pathogen as the respective tick specimens, while 29 dogs (18.6%) had a different pathogen. Thirteen sequence types (STs) were identified for H. canis, with ST2 (49.4%) as the most representative in dogs and ST1 (73.5%) in ticks. Similarly, seven STs were found for Anaplasma spp. (i.e., five for A. platys, one for A. phagocytophilum and one for Anaplasma sp.), with ST2 as the most representative in dogs (70.6%) and ST3 (52.5%) in ticks for A. platys. Only one ST was identified for B. vogeli, B. gibsoni, E. canis, D. sp. "hongkongensis" and B. malayi. Regular surveillance and adoption of adequate treatment and control measures are needed to reduce the risk of disease-causing pathogens in stray dogs and of pathogens with zoonotic potential.

Anti-Wolbachia therapy for onchocerciasis & lymphatic filariasis: Current perspectives

Onchocerciasis and lymphatic filariasis (LF) are human filarial diseases belonging to the group of neglected tropical diseases, leading to permanent and long-term disability in infected individuals in the endemic countries such as Africa and India. Microfilaricidal drugs such as ivermectin and albendazole have been used as the standard therapy in filariasis, although their efficacy in eliminating the diseases is not fully established. Anti-Wolbachia therapy employs antibiotics and is a promising approach showing potent macrofilaricidal activity and also prevents embryogenesis. This has translated to clinical benefits resulting in successful eradication of microfilarial burden, thus averting the risk of adverse events from target species as well as those due to co-infection with loiasis. Doxycycline shows potential as an anti-Wolbachia treatment, leading to the death of adult parasitic worms. It is readily available, cheap and safe to use in adult non-pregnant patients. Besides doxycycline, several other potential antibiotics are also being investigated for the treatment of LF and onchocerciasis. This review aims to discuss and summarise recent developments in the use of anti-Wolbachia drugs to treat onchocerciasis and LF.

Molecular phylogeny of Megalobatrachonema (Nematoda: Ascaridida), with description of a new species based on morphological and molecular evidence

Species of MegalobatrachonemaYamaguti, 1941 (Ascaridida: Cosmocercoidea) are important nematode parasites in amphibians and reptiles. However, the phylogenetic relationship of its included two subgenera Megalobatrachonema and Chabaudgolvania remains unclear. In the present study, a new species of Megalobatrachonema, M. (Chabaudgolvania) wangi sp. nov., was described based on the specimens collected from the lesser spiny frog Quasipaa exilispinosa (Liu & Hu) (Amphibia: Anura) in China. The ribosomal [large ribosomal DNA (28S) and internal transcribed spacer (ITS1-5.8S-ITS2)] and mitochondrial [12S small subunit ribosomal DNA and cytochrome c oxidase subunit 1 (cox1)] target regions of the new species and M. (Chabaudgolvania) terdentatum, together with the 12S region of M. (Megalobatrachonema) hainanensis, were amplified and sequenced for molecular identification and phylogeny. Moreover, in order to clarify the systematic position of the new species and the phylogenetic relationship of the two subgenera Megalobatrachonema and Chabaudgolvania, phylogenetic analyses based on 28S + ITS1-5.8S-ITS2 + 12S sequence data were performed using maximum likelihood (ML) inference and Bayesian inference (BI). The molecular phylogenetic results conflicted with the current classification and challenged the validity of the subgenus Chabaudgolvania, that should be a synonym of the subgenus Megalobatrachonema. The presence or absence of valves in the oesophageal bulb as a key criterion for delimitation of the two subgenera Megalobatrachonema and Chabaudgolvania seems to be unreliable.

First report of the isolation and phylogenetic characterization of equine Setaria digitata from India based on mitochondrial COI, 12S rDNA, and nuclear ITS2 sequence data

Equine ocular setariasis arising mainly from ectopic infestation of Setaria digitata is a common vision impairing ophthalmic disease in India, and the identification of this filarial nematode is based solely on morphology. However, morphological characters alone are inadequate to detect and differentiate S. digitata from its congeners. The present communication reports the first phylogenetic characterization of equine S. digitata from India based on sequences derived from the mitochondrial cytochrome c oxidase subunit 1 (COI), the mitochondrial small subunit ribosomal DNA (12S rDNA), and the nuclear internal transcribed spacer 2 (ITS2). Three isolates were characterized for each gene, and respective sequences were submitted to NCBI database (MN078131, MN078132, and MN095798). The sequences were also compared with the other related sequences available from PubMed around the globe, and phylogenetic analysis was carried out in conjunction with nucleotide homologies. There was no intraspecific variation among the Indian isolates. The phylogenetic analysis of S. digitata, inferred from these genes, showed that the isolate sequences obtained from different host species created a separate monophyletic clade within the genus Setaria with minor sequence variations revealing similar molecular characteristics of S. digitata isolates throughout the globe. In addition, the studied Indian isolates were found closer to Sri Lankan isolates. The S. digitata and S. labiatopapillosa appeared as sister species.

Wolbachia Infection in Two Species: Novel Views on the Colonization Ability of Wolbachia in Aphids

Wolbachia pipientis (Rickettsiales: Anaplasmataceae) is an intracellular symbiont residing in arthropods and filarial nematodes. Sixteen supergroups have been described from different host taxa. Four supergroups A, B, M, and N were found in aphids according to prior studies. The cotton aphid, Aphis gossypii, and the green peach aphid, Myzus persicae, are typical polyphagous species with global distributions. We conducted an extensive and systematic survey of Wolbachia infections in these aphids from China. High incidences of Wolbachia infection were detected. The total infection incidence was 60% in A. gossypii and 88% in M. persicae. Both aphid species were infected with supergroups A, B and M. Different incidences of infection were observed among the seven geographical regions in China, which suggested a positive relationship between Wolbachia infections and the geographical distribution of aphid species. Furthermore, multiple infection patterns (M, B, A&M, B&M, and A&B&M) were observed. Infection patterns M and B&M were detected in almost all populations. Patterns A&B&M and B showed geographical restriction in North China. Three factors can possibly influence the Wolbachia infection incidences and patterns: the geographical distribution, aphid species, and different supergroup types.

Encephalopathy in a patient with loiasis treated with albendazole: A case report

BACKGROUND

Loiasis is a vector-borne parasitic infection endemic across many areas of Central and West Africa. Its treatment is tricky due to the risk of serious neurologic adverse events occurring after the administration of microfilaricidal drugs, like diethylcarbamazine or ivermectin, in subjects with high pre-treatment microfilarial load. Albendazole is currently recommended to slowly reduce microfilaremia before curative regimen is prescribed.

CASE PRESENTATION

We report the case of a 25-year-old man from Guinea-Conakry who was incidentally diagnosed with highly microfilaremic Loa loa infection. A three weeks regimen of albendazole was prescribed. Minor neurologic side effects occurred after two weeks of administration, while serious encephalopathy developed one week later. Clinical and electroencephalographic features of the patient resembled those of an immune-mediated encephalitis. After exclusion of other causes of encephalopathy, treatment-related Loa loa encephalopathy induced by albendazole was suspected. Corticosteroid treatment was administered and the patient recovered.

DISCUSSION

Our case confirms that Loa loa treatment-related encephalopathy may occur even during albendazole treatment. The clinical and electroencephalographic similarities between Loa loa albendazole-related encephalopathy and immune-mediated encephalitis suggest the possibility of an underlying inflammation-based pathogenesis. Although corticosteroid administration is not recommended in Loa loa ivermectin-induced encephalopathy, in this case of Loa loa albendazole-induced encephalopathy it may have played a therapeutic role.

Human dirofilariosis of buccal mucosa - First molecularly confirmed case and literature review

When presented in unusual manner, human dirofilariosis is hard to recognize and often leads to misdiagnosis and unjustified use of various medications. Herein, we report a rare case of Dirofilaria infection localized in buccal mucosa. A 45-year-old male, residing in the Central Serbia, developed striking edema of buccal mucosa followed by leucocytosis, with both neutrophylia and eosinophylia. Thirty days after first symptoms occurred, nodule was formed along the lateral edge of right maxilla. Therefore, patient underwent surgical extirpation and subsequent histopathological analysis of the specimen revealed the presence of a nematode. Based on morphological characteristics of detected parasite, the diagnosis of submucosal Dirofilaria repens-like infection was made. The diagnosis was confirmed, being the first case in the world analyzed by molecular methods. So far, only 13 such cases have been reported worldwide and our paper brings attention to rare form of this zoonosis and updates the data about human dirofilariosis in buccal mucosa.

Screening of mosquitoes for filarioid helminths in urban areas in south western Poland-common patterns in European Setaria tundra xenomonitoring studies

In recent years, numerous studies screening mosquitoes for filarioid helminths (xenomonitoring) have been performed in Europe. The entomological monitoring of filarial nematode infections in mosquitoes by molecular xenomonitoring might serve as the measure of the rate at which humans and animals expose mosquitoes to microfilariae and the rate at which animals and humans are exposed to the bites of the infected mosquitoes. We hypothesized that combining the data obtained from molecular xenomonitoring and phenological studies of mosquitoes in the urban environment would provide insights into the transmission risk of filarial diseases. In our search for Dirofilaria spp.-infected mosquitoes, we have found Setaria tundra-infected ones instead, as in many other European studies. We have observed that cross-reactivity in PCR assays for Dirofilaria repens, Dirofilaria immitis, and S. tundra COI gene detection was the rule rather than the exception. S. tundra infections were mainly found in Aedes mosquitoes. The differences in the diurnal rhythm of Aedes and Culex mosquitoes did not seem a likely explanation for the lack of S. tundra infections in Culex mosquitoes. The similarity of S. tundra COI gene sequences found in Aedes vexans and Aedes caspius mosquitoes and in roe deer in many European studies, supported by data on Ae. vexans biology, suggested host preference as the most likely cause of the mosquito genus-biased infections. High diversity of the COI gene sequences isolated in the city of Wroclaw in south western Poland and the presence of identical or almost identical sequences in mosquitoes and roe deer across Europe suggests that S. tundra has been established in most of Europe for a very long time.

Plant-Mediated Horizontal Transmission of Hamiltonella defensa in the Wheat Aphid Sitobion miscanthi

Hamiltonella defensa is mainly vertically transmitted, but evidence suggests that horizontal transmission may occur. Here, the first case of plant-mediated horizontal transmission of H. defensa between wheat aphids, Sitobion miscanthi, was reported. H. defensa was harbored in sheath cells, secondary bacteriocytes, and hemolymph. After Hamiltonella-infected aphids fed on wheat leaves, H. defensa was observed in aphid stylets and plant phloem. H. defensa persisted in wheat leaves for at least 10 days. Most Hamiltonella-uninfected aphids became infected with H. defensa after sustained feeding on infected plant leaves and showed almost 100% stable vertical transmission over the next five generations. These horizontal transmission experiments were replicated using two other plants, rice and corn, and two different wheat aphid species, Rhopalosiphum padi and Schizaphis graminum. Surprisingly, aphid feeding induced plant infection only locally rather than systemically in leaves. Our findings indicate that plants may act as horizontal transmission intermediaries, contributing to the ubiquity of the otherwise maternally inherited H. defensa.

Museum metabarcoding: A novel method revealing gut helminth communities of small mammals across space and time

Natural history collections spanning multiple decades provide fundamental historical baselines to measure and understand changing biodiversity. New technologies such as next generation DNA sequencing have considerably increased the potential of museum specimens to address significant questions regarding the impact of environmental changes on host and parasite/pathogen dynamics. We developed a new technique to identify intestinal helminth parasites and applied it to shrews (Eulipotyphla: Soricidae) because they are ubiquitous, occupy diverse habitats, and host a diverse and abundant parasite fauna. Notably, we included museum specimens preserved in various ways to explore the efficacy of using metabarcoding analyses that may enable identification of helminth symbiont communities from historical archives. We successfully sequenced the parasite communities (using 12S mtDNA, 16S mtDNA, 28S rDNA) of 23 whole gastrointestinal tracts. All gastrointestinal tracts were obtained from the Museum of Southwestern Biology, USA, and from recent field collections, varying both in time since fixation (ranging from 4 months to 16 years) and preservation method (70% or 95% ethanol stored at room temperature, or flash frozen in liquid nitrogen and stored at -80 °C). Our proof of concept demonstrates the feasibility of applying next generation DNA sequencing techniques to authoritatively identify the parasite/pathogen communities within whole gastrointestinal tracts from museum specimens of varying age and fixation, and the value of future preservation of host-associated whole gastrointestinal tracts in public research archives. This powerful approach facilitates future comparative examinations of the distributions and interactions among multiple associated groups of organisms through time and space.

Microbiome Interaction Networks and Community Structure From Laboratory-Reared and Field-Collected Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus Mosquito Vectors

Microbial interactions are an underappreciated force in shaping insect microbiome communities. Although pairwise patterns of symbiont interactions have been identified, we have a poor understanding regarding the scale and the nature of co-occurrence and co-exclusion interactions within the microbiome. To characterize these patterns in mosquitoes, we sequenced the bacterial microbiome of Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus caught in the field or reared in the laboratory and used these data to generate interaction networks. For collections, we used traps that attracted host-seeking or ovipositing female mosquitoes to determine how physiological state affects the microbiome under field conditions. Interestingly, we saw few differences in species richness or microbiome community structure in mosquitoes caught in either trap. Co-occurrence and co-exclusion analysis identified 116 pairwise interactions substantially increasing the list of bacterial interactions observed in mosquitoes. Networks generated from the microbiome of Ae. aegypti often included highly interconnected hub bacteria. There were several instances where co-occurring bacteria co-excluded a third taxa, suggesting the existence of tripartite relationships. Several associations were observed in multiple species or in field and laboratory-reared mosquitoes indicating these associations are robust and not influenced by environmental or host factors. To demonstrate that microbial interactions can influence colonization of the host, we administered symbionts to Ae. aegypti larvae that either possessed or lacked their resident microbiota. We found that the presence of resident microbiota can inhibit colonization of particular bacterial taxa. Our results highlight that microbial interactions in mosquitoes are complex and influence microbiome composition.

A novel quantitative real-time PCR diagnostic assay for seal heartworm (Acanthocheilonema spirocauda) provides evidence for possible infection in the grey seal (Halichoerus grypus)

The distinct evolutionary pressures faced by Pinnipeds have likely resulted in strong coevolutionary ties to their parasites (Leidenberger et al., 2007). This study focuses on the phocid seal filarial heartworm species Acanthocheilonema spirocauda. A. spirocauda is known to infect a variety of phocid seals, but does not appear to be restricted to a single host species (Measures et al., 1997; Leidenberger et al., 2007; Lehnert et al., 2015). However, to date, seal heartworm has never been reported in grey seals (Halichoerus grypus) (Measures et al., 1997; Leidenberger et al., 2007; Lehnert et al., 2015). The proposed vector for seal heartworm is Echinophthirius horridus, the seal louse. Seal lice are known to parasitize a wide array of phocid seal species, including the grey seal. With the advent of climate change, disease burden is expected to increase across terrestrial and marine mammals (Harvell et al., 2002). Accordingly, increased prevalence of seal heartworm has recently been reported in harbor seals (Phoca vitulina) (Lehnert et al., 2015). Thus, the need for improved, rapid, and cost-effective diagnostics is urgent. Here we present the first A. spirocauda-specific rapid diagnostic test (a quantitative real-time PCR assay), based on a highly repetitive genomic DNA repeat identified using whole genome sequencing and subsequent bioinformatic analysis. The presence of an insect vector provides the opportunity to develop a multifunctional diagnostic tool that can be used not only to detect the parasite directly from blood or tissue specimens, but also as a molecular xenomonitoring (XM) tool that can be used to assess the epidemiological profile of the parasite by screening the arthropod vector. Using this assay, we provide evidence for the first reported case of seal heartworm in a grey seal.

Allopatric speciation of Meteterakis (Heterakoidea: Heterakidae), a highly dispersible parasitic nematode, in the East Asian islands

To clarify how the species diversity of highly dispersible parasites has developed, molecular phylogenetic analyses of Meteterakis spp., multi-host endoparasitic nematodes of reptiles and amphibians from the East Asian islands, were conducted. The results demonstrated the existence of two major clades, the J- and A-groups, with exclusive geographic ranges that are discordant with the host faunal province. However, diversification within the J-group was concordant with the host biogeography and suggested co-divergence of this group with vicariance of the host fauna. In contrast, the phylogenetic pattern within the A-group was discordant with host biogeography and implied diversification by repeated colonization. In addition, the mosaic distribution pattern of a J-group and an A-group species in the Japanese Archipelago, along with comparison of population genetic parameters and the genetic distance from their closest relatives, suggested the initial occurrence of a J-group lineage followed by exclusion in the western part of this region caused by invasion of an A-group lineage. Thus, the present study suggested that the species diversity of highly dispersible parasites including Meteterakis is formed not only by co-divergence with host faunal vicariance but also by peripatric speciation and exclusive interactions between species.

Candidatus Dirofilaria hongkongensis as Causative Agent of Human Ocular Filariosis after Travel to India

We report a human case of ocular Dirofilaria infection in a traveler returning to Austria from India. Analysis of mitochondrial sequences identified the worm as Candidatus Dirofilaria hongkongensis, a close relative of Dirofilaria repens, which was only recently described in Hong Kong and proposed as a new species.

Mansonellosis: current perspectives

Mansonellosis is a filarial disease caused by three species of filarial (nematode) parasites (Mansonella perstans, Mansonella streptocerca, and Mansonella ozzardi) that use humans as their main definitive hosts. These parasites are transmitted from person to person by bloodsucking females from two families of flies (Diptera). Biting midges (Ceratopogonidae) transmit all three species of Mansonella, but blackflies (Simuliidae) are also known to play a role in the transmission of M. ozzardi in parts of Latin America. M. perstans and M. streptocerca are endemic in western, eastern, and central Africa, and M. perstans is also present in the neotropical region from equatorial Brazil to the Caribbean coast. M. ozzardi has a patchy distribution in Latin America and the Caribbean. Mansonellosis infections are thought to have little pathogenicity and to be almost always asymptomatic, but occasionally causing itching, joint pains, enlarged lymph glands, and vague abdominal symptoms. In Brazil, M. ozzardi infections are also associated with corneal lesions. Diagnosis is usually performed by detecting microfilariae in peripheral blood or skin without any periodicity. There is no standard treatment at present for mansonellosis. The combination therapy of diethylcarbamazine plus mebendazole for M. perstans microfilaremia is presently one of the most widely used, but the use of ivermectin has also been proven to be very effective against microfilariae. Recently, doxycycline has shown excellent efficacy and safety when used as an antimicrobial against endosymbiotic Wolbachia bacteria harbored by some strains of M. perstans and M. ozzardi. Diethylcarbamazine and ivermectin have been used effectively to treat M. streptocerca infection. There are at present no estimates of the disease burden caused by mansonellosis, and thus its importance to many global health professionals and policy makers is presently limited to how it can interfere with diagnostic tools used in modern filarial disease control and elimination programs aimed at other species of filariae.

Population structure analysis of the neglected parasite Thelazia callipaeda revealed high genetic diversity in Eastern Asia isolates

Background

Thelazia callipaeda is the causative agent of thelaziasis in canids, felids and humans. However, the population genetic structure regarding this parasite remains unclear.

Methodology/principal findings

In this study, we first explored the genetic variation of 32 T. callipaeda clinical isolates using the following multi-molecular markers: cox1, cytb, 12S rDNA, ITS1 and 18S rDNA. The isolates were collected from 13 patients from 11 geographical locations in China. Next, the population structure of T. callipaeda from Europe and other Asian countries was analyzed using the cox1 sequences collected during this study and from the GenBank database. In general, the Chinese clinical isolates of T. callipaeda expressed high genetic diversity. Based on the cox1 gene, a total of 21 haplotypes were identified. One only circulated in European countries (Hap1), while the other 20 haplotypes were dispersed in Korea, Japan and China. There were five nucleotide positions in the cox1 sequences that were confirmed as invariable among individuals from Europe and Asia, but the sequences were distinct between these two regions. Population differences between Europe and Asian countries were greater than those among China, Korea and Japan. The T. callipaeda populations from Europe and Asia should be divided into two separate sub-populations. These two groups started to diverge during the middle Pleistocene. Neutrality tests, mismatch distribution and Bayesian skyline plot (BSP) analysis all rejected possible population expansion of T. callipaeda.

Conclusions

The Asian population of T. callipaeda has a high level of genetic diversity, but further studies should be performed to explore the biology, ecology and epidemiology of T. callipaeda.

Thelazia callipaeda is the causative agent of thelaziasis canids, felids and humans. Despite the existing threat of thelaziosis in China, the genetic diversity of T. callipaeda has not been investigated across its wide geographical distribution in China, yet such information may provide insight into the disease epidemiology and the development of specific control measures. In this study, the genetic variation of 32 T. callipaeda clinical isolates collected from 13 patients from 11 geographical locations in China were explored using the following multi-molecular markers: cox1, cytb, 12S rDNA, ITS1 and 18S rDNA. In addition, the population structure of T. callipaeda from Europe and other Asian countries was analyzed using the cox1 sequences collected during this study and from the GenBank database. In general, the Chinese clinical isolates of T. callipaeda demonstrated high genetic diversity. Based on the cox1 gene, a total of 21 haplotypes were identified, one circulated in European countries (Hap1), while the other 20 haplotypes were dispersed in Korea, Japan and China. There were five nucleotide positions in the cox1 that were confirmed as invariable among individuals from Europe and Asia, but the sequences were distinct between these two regions. Population differences between Europe and Asian countries were greater than those among China, Korea and Japan, such that the T. callipaeda population from Europe and Asia should be divided into two separate sub-populations. These two groups started to diverge during the middle Pleistocene.

Dirofilaria repens transmission in southeastern Finland

BACKGROUND

The spread of vector-borne diseases to new regions has become a global threat due to climate change, increasing traffic, and movement of people and animals. Dirofilaria repens, the canine subcutaneous filarioid nematode, has expanded its distribution range northward during the last decades. The northernmost European locations, where the parasite life-cycle has been confirmed, are Estonia and the Novgorod Region in Russia.

RESULTS

Herein, we describe an autochthonous D. repens infection in a Finnish woman. We also present two cases of D. repens infection in imported dogs indicating the life-cycle in the Russian Vyborg and St Petersburg areas, close to the Finnish border.

CONCLUSIONS

The most obvious limiting factor of the northern distribution of D. repens is the summer temperature, due to the temperature-dependent development of larvae in vectors. With continuing climate change, further spread of D. repens in Fennoscandia can be expected.

Detection of Dirofilaria immitis in a brown bear (Ursus arctos) in Greece

Dirofilaria immitis (canine heartworm) is a filarial nematode found in the pulmonary circulation and the heart of susceptible hosts. It represents an important zoonotic vector-borne disease of domestic dogs and several wildlife species. Herein we report for the first time, the finding of Dirofilaria immitis worms in a brown bear killed in a vehicle collision in Northern Greece. The worms were morphologically identified; molecular examination, based on the analysis of the mitochondrial genes 12S (433 bp) and CO1 (610 bp), verified the identification by demonstrating 100% similarity to D. immitis specimens deposited in GenBank. Brown bears in Greece occupy habitats that are shared with the potential wild and domestic hosts and the vectors of D. immitis and thus may be particularly susceptible to this parasite. This report contributes to the knowledge of dirofilariosis spread in Europe and on the epidemiological threats that may affect the survival of the endangered brown bear in Greece.

GRANULOMATOUS FILARIAL ENCEPHALOMYELITIS CAUSED BY CHANDLERELLA QUISCALI IN A NORTHERN CRESTED CARACARA (CARACARA CHERIWAY)

A northern crested caracara (Caracara cheriway) was presented after being found nonambulatory in a field. On physical examination, the bird had severe hind-limb paresis. The bird did not improve after 10 days of hospitalization and was euthanized. Histologic examination of the cerebrum and spinal cord revealed multiple adult filarial nematodes surrounded by granulomatous inflammation with several multinucleated giant cells. These parasites were confirmed to be Chandlerella quiscali with polymerase chain reaction. This is the first report of C. quiscali in a bird of prey.

Morphological and molecular characteristics of Malayfilaria sofiani Uni, Mat Udin & Takaoka n. g., n. sp. (Nematoda: Filarioidea) from the common treeshrew Tupaia glis Diard & Duvaucel (Mammalia: Scandentia) in Peninsular Malaysia

Background

The filarial nematodes Wuchereria bancrofti (Cobbold, 1877), Brugia malayi (Brug, 1927) and B. timori Partono, Purnomo, Dennis, Atmosoedjono, Oemijati & Cross, 1977 cause lymphatic diseases in humans in the tropics, while B. pahangi (Buckley & Edeson, 1956) infects carnivores and causes zoonotic diseases in humans in Malaysia. Wuchereria bancrofti, W. kalimantani Palmieri, Pulnomo, Dennis & Marwoto, 1980 and six out of ten Brugia spp. have been described from Australia, Southeast Asia, Sri Lanka and India. However, the origin and evolution of the species in the Wuchereria-Brugia clade remain unclear. While investigating the diversity of filarial parasites in Malaysia, we discovered an undescribed species in the common treeshrew Tupaia glis Diard & Duvaucel (Mammalia: Scandentia).

Methods

We examined 81 common treeshrews from 14 areas in nine states and the Federal Territory of Peninsular Malaysia for filarial parasites. Once any filariae that were found had been isolated, we examined their morphological characteristics and determined the partial sequences of their mitochondrial cytochrome c oxidase subunit 1 (cox1) and 12S rRNA genes. Polymerase chain reaction (PCR) products of the internal transcribed spacer 1 (ITS1) region were then cloned into the pGEM-T vector, and the recombinant plasmids were used as templates for sequencing.

Results

Malayfilaria sofiani Uni, Mat Udin & Takaoka, n. g., n. sp. is described based on the morphological characteristics of adults and microfilariae found in common treeshrews from Jeram Pasu, Kelantan, Malaysia. The Kimura 2-parameter distance between the cox1 gene sequences of the new species and W. bancrofti was 11.8%. Based on the three gene sequences, the new species forms a monophyletic clade with W. bancrofti and Brugia spp. The adult parasites were found in tissues surrounding the lymph nodes of the neck of common treeshrews.

Conclusions

The newly described species appears most closely related to Wuchereria spp. and Brugia spp., but differs from these in several morphological characteristics. Molecular analyses based on the cox1 and 12S rRNA genes and the ITS1 region indicated that this species differs from both W. bancrofti and Brugia spp. at the genus level. We thus propose a new genus, Malayfilaria, along with the new species M. sofiani.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2105-9) contains supplementary material, which is available to authorized users.

Whence river blindness? The domestication of mammals and host-parasite co-evolution in the nematode genus Onchocerca

The genus Onchocerca includes 34 described species and represents one of the largest genera of the filarial nematodes within the family Onchocercidae. Representative members of this genus are mainly parasites of ungulates, with some exceptions such as Onchocerca lupi and Onchocerca volvulus, infecting carnivores and/or humans. For a long time, the evolutionary relationships amongst onchocercids remained poorly studied, as the systematics of this genus was impaired by the high morphological variability of species included in the taxon. Although some molecular phylogenies were developed, these studies were mainly focused on bovine Onchocerca spp. and O. volvulus, including assessments of Wolbachia endosymbionts. In the present study, we analysed 13 Onchocerca spp. from a larger host spectrum using a panel of seven different genes. Analysis of the coxI marker supports its usefulness for the identification of species within the genus. The evolutionary history of the genus has been herein revised by multi-gene phylogenies, presenting three strongly supported clades of Onchocerca spp. Analyses of co-evolutionary scenarios between Onchocerca and their vertebrate hosts underline the effect of domestication on Onchocerca speciation. Our study indicates that a host switch event occurred between Bovidae, Canidae and humans. Cophylogenetic analyses between Onchocerca and the endosymbiotic bacterium Wolbachia indicate the strongest co-evolutionary pattern ever registered within the filarial nematodes. Finally, this dataset indicates that the clade composed by O. lupi, Onchocerca gutturosa, Onchocerca lienalis, Onchocerca ochengi and O. volvulus derived from recent speciation.

Detection and molecular characterization of the mosquito-borne filarial nematode Setaria tundra in Danish roe deer (Capreolus capreolus)

Setaria tundra is a mosquito-borne filarial nematode of cervids in Europe. It has recently been associated with an emerging epidemic disease causing severe morbidity and mortality in reindeer and moose in Finland. Here, we present the first report of S. tundra in six roe deer (Capreolus capreolus) collected between October 2010 and March 2014 in Denmark. The deer originated from various localities across the country: the eastern part of the Jutland peninsular and four locations on the island Zealand. With the exception of one deer, with parasites residing in a transparent cyst just under the liver capsule, worms (ranging from 2 to >20/deer) were found free in the peritoneal cavity. The worms were identified as S. tundra by morphological examination and/or molecular typing of the mitochondrial 12S rRNA and cox1 genes, which showed 99.1–99.8% identity to previously published S. tundra isolates from Europe. Roe deer are generally considered as asymptomatic carriers and their numbers in Denmark have increased significantly in recent decades. In light of climatic changes which result in warmer, more humid weather in Scandinavia greater numbers of mosquitoes and, especially, improved conditions for development of parasite larvae in the mosquito vectors are expected, which may lead to increasing prevalence of S. tundra. Monitoring of this vector-borne parasite may thus be needed in order to enhance the knowledge of factors promoting its expansion and prevalence as well as predicting disease outbreaks.

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Setaria tundra was recovered from six roe deer in Denmark.

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Infected deer originated from Jutland and Zealand.

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Worms were found in the peritoneal cavity and under the liver capsule.

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12S rRNA and cox1sequences showed 99.1–99.8% identity to other European isolates.

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Climatic changes and increasing density of deer may affect prevalence of S. tundra.

Ocular dirofilariasis by Dirofilaria immitis in a child in Iran: A case report and review of the literature

This report describes a rare case of ophthalmic dirofilariasis in a 2-year-old boy with redness, irritation, pain and foreign body sensation in the right eye. Slit lamp examination demonstrated a thread-like whitish nematode in the anterior chamber of the right eye that twisted around itself. The nematode worm (35mm long and 150-200μm width) was removed surgically. The presence of the smooth cuticular surface without longitudinal ridges and the vulva showed that it could be a female Diroflaria immitis. PCR amplification was done to verify the Diroflaria species. PCR amplification and sequence analysis of mitochondrial 12S rDNA confirmed that recovered worm was D. immitis. Ocular dirofilariasis caused by D. immitis is very rare, but it must be considered in humans living in endemic areas.

Subconjunctival setariasis due to Setaria equina infection; a case report and a literature review

A rare case of human subconjunctival setariasis due to Setaria equina infection is reported herein. A 15-years old girl was referred with a 24h history of edema and redness in her left eye. On slit lamp examination, a thread-like cylindrical worm was moving in the subconjunctival area. The worm was extracted, stained and measured 110mm in length 510μm in width. The isolated worm was identified as adult female S. equina based on morphometric criteria. Identification of the species of the worm was confirmed using molecular methods. For this purpose, the 12S rRNA gene was PCR-amplified and the purified amplicon was directly sequenced. After alignment, phylogenetic analysis revealed that the 12S rRNA sequence of this worm (Accession no.: KU291446) showed 100% identity with that of S. equina. This is the first case in Iran and provides evidence that S. equina can be an etiological agent of subconjunctival infection was isolated and diagnosed as where it located Middle East.

Temporal and spatial mosaics: deep host association and shallow geographic drivers shape genetic structure in a widespread pinworm, Rauschtineria eutamii

Climate and host demographic cycling often shape both parasite genetic diversity and host distributions, processes that transcend a history of strict host-parasite association. We explored host associations and histories based on an evaluation of mitochondrial and nuclear sequences to reveal the underlying history and genetic structure of a pinworm, Rauschtineria eutamii, infecting 10 species of western North American chipmunks (Rodentia:Tamias, subgenus Neotamias). Rauschtineria eutamii contains divergent lineages influenced by the diversity of hosts and variation across the complex topography of western North America. We recovered six reciprocally monophyletic R. eutamii mitochondrial clades, largely supported by nuclear gene trees, exhibiting divergence levels comparable to intraspecific variation reported for other nematodes. Phylogenetic relationships among pinworm clades suggest that R. eutamii colonized an ancestral lineage of western chipmunks and lineages persisted during historical isolation in diverging Neotamias species or species groups. Pinworm diversification, however, is incongruent and asynchronous relative to host diversification. Secondarily, patterns of shallow divergence were shaped by geography through events of episodic colonization reflecting an interaction of taxon pulses and ecological fitting among assemblages in recurrent sympatry. Pinworms occasionally infect geographically proximal host species; however, host switching may be unstable or ephemeral, as there is no signal of host switching in the deeper history of R. eutamii.

An appraisal of canine and human cases reveals an endemic status of dirofilariosis in parts of Serbia

Dirofilaria immitis and D. repens are mosquito-borne nematodes that primarily infect canids, and can also cause mild to serious superficial or visceral infection in humans. In the present survey, peripheral blood from 150 asymptomatic dogs from Serbia were examined using the modified Knott's technique. Dirofilaria immitis, identified based on morphological and morphometric characteristics, was prevalent in dogs not receiving preventative treatment (in 44% and 60% of pound and pet dogs, respectively). These results, together with findings of autochthonous cases of subcutaneous D. repens infection in human patients from Southeastern Serbia emphasize the need for further investigations of this veterinary and public health problem.

Dirofilaria repens: emergence of autochthonous human infections in the Czech Republic (case reports)

Background

Human dirofilariasis is a zoonotic infection that continues to spread to previously unaffected areas of Europe. In the South Moravian Region of the Czech Republic (CR), imported as well as autochthonous canine infections were recorded in the last decade, and parasite DNA was detected in mosquitoes of Aedes vexans. In the present paper, human Dirofilaria infections are reported from the country for the first time.

Case presentation

The samples from five patients with suspected tissue helminthiases were investigated. In particular cases, nematodes were isolated from various tissues including skin of lower leg, soft tissues of finger, subcutaneous tissue of hypogastrium, lymph node and peritoneum. The diagnosis was based on light microscopic morphology and/or DNA analysis of the worms. In addition, ELISA examination of patients’ sera for anti-filaria IgG antibodies was performed.

Conclusions

In the CR, five cases of human dirofilariasis caused by Dirofilaria repens were recorded during 2010–2014 (species determination for three of them was confirmed besides morphological also by DNA analysis). At least, three of the cases were of autochthonous origin (the patients are Czech citizens residing in South Moravian Region who have never travelled abroad). The findings confirm the natural setting of D. repens in South Moravian Region of the CR. Dirofilariasis should be therefore considered as endemic in this area where it may represent a significant risk factor for public health.

Breakdown of coevolution between symbiotic bacteria Wolbachia and their filarial hosts

Wolbachia is an alpha-proteobacterial symbiont widely distributed in arthropods. Since the identification of Wolbachia in certain animal-parasitic nematodes (the Onchocercidae or filariae), the relationship between arthropod and nematode Wolbachia has attracted great interest. The obligate symbiosis in filariae, which renders infected species susceptible to antibiotic chemotherapy, was held to be distinct from the Wolbachia-arthropod relationship, typified by reproductive parasitism. While co-evolutionary signatures in Wolbachia-arthropod symbioses are generally weak, reflecting horizontal transmission events, strict co-evolution between filariae and Wolbachia has been reported previously. However, the absence of close outgroups for phylogenetic studies prevented the determination of which host group originally acquired Wolbachia. Here, we present the largest co-phylogenetic analysis of Wolbachia in filariae performed to date including: (i) a screening and an updated phylogeny of Wolbachia; (ii) a co-phylogenetic analysis; and (iii) a hypothesis on the acquisition of Wolbachia infection. First, our results show a general overestimation of Wolbachia occurrence and support the hypothesis of an ancestral absence of infection in the nematode phylum. The accuracy of supergroup J is also underlined. Second, although a global pattern of coevolution remains, the signal is derived predominantly from filarial clades associated with Wolbachia in supergroups C and J. In other filarial clades, harbouring Wolbachia supergroups D and F, horizontal acquisitions and secondary losses are common. Finally, our results suggest that supergroup C is the basal Wolbachia clade within the Ecdysozoa. This hypothesis on the origin of Wolbachia would change drastically our understanding of Wolbachia evolution.

Absence of the Filarial Endosymbiont Wolbachia in Seal Heartworm (Acanthocheilonema spirocauda) but Evidence of Ancient Lateral Gene Transfer

The symbiotic relationship of Wolbachia spp. was first observed in insects and subsequently in many parasitic filarial nematodes. This bacterium is believed to provide metabolic and developmental assistance to filarial parasitic nematodes, although the exact nature of this relationship remains to be fully elucidated. While Wolbachia is present in most filarial nematodes in the family Onchocercidae, it is absent in several disparate species such as the human parasite Loa loa . All tested members of the genus Acanthocheilonema, such as Acanthocheilonema viteae, have been shown to lack Wolbachia. Consistent with this, we show that Wolbachia is absent from the seal heartworm (Acanthocheilonema spirocauda), but lateral gene transfer (LGT) of DNA sequences between Wolbachia and A. spirocauda has occurred, indicating a past evolutionary association. Seal heartworm is an important pathogen of phocid seals and understanding its basic biology is essential for conservation of the host. The findings presented here may allow for the development of future treatments or diagnostics for the disease and also aid in clarification of the complicated nematode-Wolbachia relationship.

The occurrence of the filarial nematode Dirofilaria repens in canine hosts from Maio Island, Cape Verde

The prevalence of canine Dirofilaria infection in Maio Island (Cape Verde) was analysed by serology, morphological and molecular identification of the parasite species. Blood and sera were collected from 150 dogs and 80 cats aged over 6 months from various localities of the island. DNA was extracted from blood and samples were screened by polymerase chain reaction (PCR) using microfilaria-specific primers. No Dirofilaria immitis was found in dogs while D. repens microfilariae were found in 5.3% of dogs and 6% were positive by PCR. The species identity was confirmed by sequencing of PCR products, which showed almost 100% homology with D. repens European sequences published in GenBank. No difference in Dirofilaria infection was observed between males and females or in dogs with different weights. However, older dogs and those from the western part of Maio Island were more frequently infected. No Dirofilaria was found in cats. This study represents the first evidence of D. repens in Cape Verde (West Africa) and highlights the need for implementing control measures and for a better surveillance of dirofilariosis in Africa.

Dirofilaria repens Microfilaremia in Three Dogs in Estonia

In Europe, the zoonotic parasite Dirofilaria repens continues to spread northward. We describe three likely autochthonous canine microfilaremic D. repens infections from Estonia, an European Union country located in the Baltic region of northern Europe. The parasite species was confirmed with sequencing. These are new northernmost D. repens findings in Europe and show that the zoonotic parasite has spread farther north. Infection with D. repens should be included in the list of differential diagnoses for human and animal hosts also in northern Europe.

Diversity, Host Specialization, and Geographic Structure of Filarial Nematodes Infecting Malagasy Bats

We investigated filarial infection in Malagasy bats to gain insights into the diversity of these parasites and explore the factors shaping their distribution. Samples were obtained from 947 individual bats collected from 52 sites on Madagascar and representing 31 of the 44 species currently recognized on the island. Samples were screened for the presence of micro- and macro-parasites through both molecular and morphological approaches. Phylogenetic analyses showed that filarial diversity in Malagasy bats formed three main groups, the most common represented by Litomosa spp. infecting Miniopterus spp. (Miniopteridae); a second group infecting Pipistrellus cf. hesperidus (Vespertilionidae) embedded within the Litomosoides cluster, which is recognized herein for the first time from Madagascar; and a third group composed of lineages with no clear genetic relationship to both previously described filarial nematodes and found in M. griveaudi, Myotis goudoti, Neoromicia matroka (Vespertilionidae), Otomops madagascariensis (Molossidae), and Paratriaenops furculus (Hipposideridae). We further analyzed the infection rates and distribution pattern of Litomosa spp., which was the most diverse and prevalent filarial taxon in our sample. Filarial infection was disproportionally more common in males than females in Miniopterus spp., which might be explained by some aspect of roosting behavior of these cave-dwelling bats. We also found marked geographic structure in the three Litomosa clades, mainly linked to bioclimatic conditions rather than host-parasite associations. While this study demonstrates distinct patterns of filarial nematode infection in Malagasy bats and highlights potential drivers of associated geographic distributions, future work should focus on their alpha taxonomy and characterize arthropod vectors.

Molecular identification and phylogenetic analysis of Dipetalonema evansi (LEWIS, 1882) in camels (Camelus dromedarius) of Iran

Despite the economic importance of camels, the parasites that affect them have not received adequate attention so far and molecular studies are scarce compared to other livestock. In this study, we characterized peripheral blood microfilariae in 200 healthy one-humped camels (Camelus dromedarius) from south-east Iran by microscopy and molecular tools to receive a more detailed insight into prevalence and species that affect them. Moreover, adult specimens of the filarial nematode Dipetalonema evansi were collected from the carcass of an infected animal. Microscopic examination was performed on Giemsa-stained blood smears, and blood was also spotted on Whatman FTA(®) cards for DNA analysis. Genomic DNA was extracted, and PCR was carried out for the detection of filaroid helminths, followed by sequence analysis of positive samples. Four samples were positive for microfilariae by microscopy, while 16 animals (8 %) were positive by PCR. Sequence analysis revealed D. evansi in all cases. Phylogenetic analysis of a cytochrome C oxidase subunit I (COI) sequence of filaroid nematodes showed that most species in a single genus cluster in the same clade; however, D. evansi and D. gracile are not monophyletic and branch rather at the base of the tree. Further studies on the life cycle of D. evansi, specifically the identification of intermediate host(s), have become feasible with the provision of the first specific COI sequences in this study.

What's in your next-generation sequence data? An exploration of unmapped DNA and RNA sequence reads from the bovine reference individual

BACKGROUND

Next-generation sequencing projects commonly commence by aligning reads to a reference genome assembly. While improvements in alignment algorithms and computational hardware have greatly enhanced the efficiency and accuracy of alignments, a significant percentage of reads often remain unmapped.

RESULTS

We generated de novo assemblies of unmapped reads from the DNA and RNA sequencing of the Bos taurus reference individual and identified the closest matching sequence to each contig by alignment to the NCBI non-redundant nucleotide database using BLAST. As expected, many of these contigs represent vertebrate sequence that is absent, incomplete, or misassembled in the UMD3.1 reference assembly. However, numerous additional contigs represent invertebrate species. Most prominent were several species of Spirurid nematodes and a blood-borne parasite, Babesia bigemina. These species are either not present in the US or are not known to infect taurine cattle and the reference animal appears to have been host to unsequenced sister species.

CONCLUSIONS

We demonstrate the importance of exploring unmapped reads to ascertain sequences that are either absent or misassembled in the reference assembly and for detecting sequences indicative of parasitic or commensal organisms.

Discovery of filarial nematode DNA in Amblyomma americanum in Northern Virginia

Ticks collected in 2011 were screened for the presence of filarial nematode genetic material, and positive samples were sequenced for analysis. Monanema-like filarial nematode DNA was recently discovered in Amblyomma americanum in northern Virginia, marking the first time genetic material from this parasite has been discovered in ticks in the state. Phylogenetic analysis revealed that this material was directly related to a previously discovered filarial nematode in A. americanum populations in Maryland as well as recently identified parasites in Ixodes scapularis from southern Connecticut. Further study is warranted to visually confirm the presence of these nematodes, characterize their distribution, and determine if these ticks are intermediate hosts.