Mitochondrial genomes of Heterakis gallinae and Heterakis beramporia support that they belong to the infraorder Ascaridomorpha

Morphology, complete mitochondrial genome and molecular phylogeny of Heterakis pucrasia sp. n. (Nematoda: Ascaridida) from the koklass pheasant Pucrasia macrolopha (Lesson) (Galliformes: Phasianidae) in Pakistan

Species of Heterakis (Ascaridida: Heterakoidea) are commonest nematode parasites occurring in the alimentary canal of wild and domestic birds, which are of major socio-economic importance, due to some Heterakis species causing Heterakidosis in wild birds and poultry. In the present study, a new species of Heterakis, H. pucrasia sp. n., was described using integrated methods based on specimens collected from the koklass pheasant Pucrasia macrolopha (Lesson) (Galliformes: Phasianidae) in Pakistan. The complete mitochondrial genome of H. pucrasia sp. n. was sequenced and annotated for the first time to enrich the mitogenomic data, and reveal the pattern of mitogenomic evolution of the family Heterakidae. Moreover, phylogenetic analyses of the orders Ascaridida, Spirurida, Oxyurida and Rhigonematida based on the amino acid sequences of 12 protein coding genes (PCGs) of mitochondrial genomes, revealed that the order Ascaridida is not monophyletic, and the superfamily Heterakoidea has a closer affinity with Rhigonematida + Oxyurida + Spirurida, than the superfamily Ascaridoidea in Ascaridida. The present findings enriched the global species composition of heterakid nematodes and their mitogenomic data, and also provided novel insight on the phylogenetic relationships between Heterakoidea and its related groups.

Morphological and molecular identification of Heterakis gallinarum in Gallus gallus and its phylogenetic analysis based on ITS1-5.8S-ITS2 rDNA fragment in Kashmir valley, India

Heterakis gallinarum is one of the most common round worms infecting wide range of terrestrial birds including domestic fowl. H. dispar and H. isolonche are the species of same genus which infect other hosts predominantly aquatic birds, but show morphological similarities mainly females of these species are difficult to identify. Here, we described the morphologically distinct features of H. gallinarum along with identification through molecular analysis using ITS1-5.8S-ITS2 ribosomal DNA. Four hundred gastrointestinal tracts of domestic fowl were analysed for a period of 2 years. Light microscopy and Scanning electron microscopy (SEM), was used for determining the morphometric measurements and characteristic morphological features of H. gallinarum. A PCR based DNA sequencing of ITS1-5.8S-ITS2 ribosomal DNA was used for molecular characterization and phylogenetic analysis was carried out through MEGA 11. Ninety gastrointestinal tracts were found to be infected with Heterakis gallinarum. The male worm displayed well developed lateral and caudal alae, caudal end had an anal sucker, 12 pairs of caudal papillae and cloaca from which 2 unequal spicules emerged. Female had visible vaginal bends, vulva present approximately in the middle of the body, and caudal end had a long pointed tail. Sequence analysis revealed that the PCR products of ITS1-5.8S-ITS2 rDNA were 600 bp in size and showed 96-98% similarity with the ITS1-5.8S-ITS2 sequences of H. gallinarum on BLAST analysis. Our ITS sequence of H. gallinarum showed a nucleotide divergence of 4.9% with H. gallinarum of Lucknow India. The phylogenetic analysis clearly differentiated H. gallinarum from the other representatives of the genus and revealed the relationship among different Heterakis species. The study revealed the infection status of Heterakis gallinarum prevailing among domestic fowl, and need of strategic control measures. The results of the study suggest that ITS rDNA would serve as a potential molecular marker in identification, diagnosis and systematics of Heterakis species.

First molecular insights into gastrointestinal helminths of domestic birds in the Caspian Sea Littoral of Iran with an emphasis on the One Health concern

The current investigation was carried out during the period from July 2022 to March 2023, aiming to investigate the prevalence of gastrointestinal helminths in domestic birds collected from traditional markets in Guilan province. One hundred forty-eight domestic birds, including chickens (Gallus gallus domesticus), domestic ducks (Anas platyrhynchos domesticus), greylag geese (Anser anser), and domestic turkeys (Meleagris gallopavo domesticus) were examined. Totally, 42.56% of the investigated birds were positive for helminthic parasites. Morphological analysis revealed varying infection rates among birds: Echinostoma revolutum (5.40%), Hypoderaeum conoideum (2.02%), Cloacotaenia megalops (0.67%), Hymenolepididae family (4.05%), Ascaridia galli (16.89%), and Heterakis gallinarum (4.72%). The investigation involved molecular analysis of the 18S and ITS1 + 5.8S + ITS2 rRNA gene regions. The findings indicated that the 18S region of nematode isolates exhibited a similarity of 92 to 100% with sequences in the GenBank, whereas trematode and cestode isolates showed a gene similarity ranging from 88 to 99%. The ITS regions of nematode, trematode, and cestode isolates exhibited genetic similarities ranging from 87 to 100%, 73-99%, and 75-99%, respectively. Furthermore, phylogenetic analysis confirmed the categorization of the identified species within the Ascaridiidae, Heterakidae, Hymenolepididae, and Echinostomatidae families, indicating their close affinity with previously documented species. Implementing precise control measures such as consistent monitoring, adequate sanitation protocols, and administering anthelmintic treatments is crucial for effectively managing parasitic infections in free-range and backyard poultry farms. Additionally, conducting further surveys is advisable to assess the impact of these parasites on the health and productivity of poultry in the investigated area.

Mitogenomic phylogenies suggest the resurrection of the subfamily Porrocaecinae and provide insights into the systematics of the superfamily Ascaridoidea (Nematoda: Ascaridomorpha), with the description of a new species of Porrocaecum

BACKGROUND

The family Toxocaridae is a group of zooparasitic nematodes of veterinary, medical and economic significance. However, the evolutionary relationship of Porrocaecum and Toxocara, both genera currently classified in Toxocaridae, and the monophyly of the Toxocaridae remain under debate. Moreover, the validity of the subgenus Laymanicaecum in the genus Porrocaecum is open to question. Due to the scarcity of an available genetic database, molecular identification of Porrocaecum nematodes is still in its infancy.

METHODS

A number of Porrocaecum nematodes collected from the Eurasian marsh harrier Circus aeruginosus (Linnaeus) (Falconiformes: Accipitridae) in the Czech Republic were identified using integrated morphological methods (light and scanning electron microscopy) and molecular techniques (sequencing and analyzing the nuclear 18S, 28S and ITS regions). The complete mitochondrial genomes of the collected nematode specimens and of Porrocaecum (Laymanicaecum) reticulatum (Linstow, 1899) were sequenced and annotated for the first time. Phylogenetic analyses of ascaridoid nematodes based on the amino acid sequences of 12 protein-coding genes of mitochondrial genomes were performed using maximum likelihood and Bayesian inference.

RESULTS

A new species of Porrocaecum, named P. moraveci n. sp., is described based on the morphological and genetic evidence. The mitogenomes of P. moraveci n. sp. and P. reticulatum both contain 36 genes and are 14,517 and 14,210 bp in length, respectively. Comparative mitogenomics revealed that P. moraveci n. sp. represents the first known species with three non-coding regions and that P. reticulatum has the lowest overall A + T content in the mitogenomes of ascaridoid nematodes tested to date. Phylogenetic analyses showed the representatives of Toxocara clustered together with species of the family Ascarididae rather than with Porrocaecum and that P. moraveci n. sp. is a sister to P. reticulatum.

CONCLUSIONS

The characterization of the complete mitochondrial genomes of P. moraveci n. sp. and P. reticulatum is reported for the first time. Mitogenomic phylogeny analyses indicated that the family Toxocaridae is non-monophyletic and that the genera Porrocaecum and Toxocara do not have an affinity. The validity of the subgenus Laymanicaecum in Porrocaecum was also rejected. Our results suggest that: (i) Toxocaridae should be degraded to a subfamily of the Ascarididae that includes only the genus Toxocara; and (ii) the subfamily Porrocaecinae should be resurrected to include only the genus Porrocaecum. The present study enriches the database of ascaridoid mitogenomes and provides a new insight into the systematics of the superfamily Ascaridoidea.

Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

Prevalence and magnitude of gastrointestinal helminth infections in cage-free laying chickens in Australia

Helminth infections have been re-emerging with the growing popularity of free-range and floor-based chicken production systems. The aim of this study was to determine the prevalence and worm burdens of intestinal helminth infection in cage-free laying chickens in Australia. In an online survey about worm prevalence, a high proportion of respondents reported the detection of Ascaridia galli (77%), followed by tapeworms (69%) and caecal worms (Heterakis gallinarum) (62%), whereas fewer respondents (23%) reported the presence of hair worms (Capillaria spp.) in their flocks. Total worm recovery from 407 laying hens on four farms found that 92.1% of hens harboured one or more helminth parasite with a prevalence of 73 to 100% across farms. Mixed infections were common with 79% of hens harbouring two or more helminth species. The prevalence of nematode species H. gallinarum, A. galli and Capillaria spp. was 87, 82 and 35% respectively. Five cestode species were found with a low individual chicken prevalence (Raillietina tetragona 4.7%, Raillietina echinobothrida 3.2%, Raillietina cesticillus 5.2%, Choanotaenia infundibulum 4.4%, and Hymenolepis cantaniana 4.4%). The hens harboured an average of 71 worms with H. gallinarum having the highest mean burden (45.5 worms/hen) followed by A. galli (22.0 worms/hen), Capillaria spp. (2.7 worms/hen) and cestodes (0.8 worms/hen). The sex ratio (female:male worms) was 1.38:1 for A. galli, and 1.77:1 for H. gallinarum. There was a strong positive correlation between A. galli female worm count and excreta egg count (EECs) (r_s = 0.94, P < 0.0001) and also between total nematode worm count and EEC (r_s = 0.82, P < 0.0001) in individual hens. When investigating intestinal excreta (n = 10) and caecal excreta (n = 10) of 16 chicken flocks the prevalence of infection with ascarid worms in intestinal and caecal excreta was 71 and 78% respectively and 27% prevalence of Capillaria spp. in intestinal excreta with mean EECs of 407, 404, and 18 eggs/g of excreta (EPG), respectively. These results suggest that most chickens kept in free-range or floor production systems are infected with one or more helminth parasite species. Heavy worm infections would likely affect the production performance and welfare of birds with adverse economic impact. Strategic or tactical anthelmintic treatment with effective anthelmintic could reduce this impact.

The Complete Mitogenome of Toxocara vitulorum: Novel In-Sights into the Phylogenetics in Toxocaridae

Toxocara vitulorum (Ascaridida: Nematoda) is one of the most common intestinal nematodes of cattle and buffalos and, therefore, represents a serious threat to their populations worldwide. Despite its significance in veterinary health the epidemiology, population genetics, and molecular ecology of this nematode remain poorly understood. The mitogenome can yield a foundation for studying these areas and assist in the surveillance and control of T. vitulorum. Herein, the first whole mitogenome of T. vitulorum was sequenced utilizing Illumina technology and characterized with bioinformatic pipeline analyses. The entire genome of T. vitulorum was 15,045 bp in length and contained 12 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs). The gene arrangement (GA) of T. vitulorum was similar to those of other Toxocara species under GA3. The whole genome showed significant levels of AT and GC skew. Comparative mitogenomics including sequence identities, Ka/Ks, and sliding window analysis, indicated a purifying selection of 12 PCGs with cox1 and nad6 having the lowest and highest evolutionary rate, respectively. Whole amino acid sequence-based phylogenetic analysis supported a novel sister-species relationship of T. vitulorum with the congeneric species Toxocara canis, Toxocara cati, and Toxocara malaysiensis in the family Toxocaridae. Further, 12 (PCGs) single gene-based phylogenies suggested that nad4 and nad6 genes shared same topological trees with that of the whole genome, suggesting that these genes were suitable as novel genetic markers for phylogenetic and evolutionary studies of Ascaridida species. This complete mitogenome of T. vitulorum refined phylogenetic relationships in Toxocaridae and provided the resource of markers for population genetics, systematics, and epidemiology of this bovine nematode.

A copro-antigen ELISA for the detection of ascarid infections in chickens

A reliable method of diagnosing the most prevalent helminth infections in chickens is vital for developing effective control strategies. Ascaridia galli and Heterakisgallinarum are phylogenetically close nematode species that can elicit the development of cross-reactive antibodies in chickens. Therefore, an enzyme-linked immunoassay (ELISA) based on Ascaridia galli antigens in faeces of chickens to detect and quantify infections with both A. galli and H. gallinarum was developed. The ELISA utilised polyclonal antibodies that were obtained from rabbits immunised with soluble antigens isolated from A. galli. In two separate experiments, chickens were kept as uninfected controls or were orally infected with either 100 or 1000 of embryonated eggs of A. galli or H.gallinarum. Faecal samples were collected after 28-30 weeks post-infection. The ELISA was then used to quantify the concentration of soluble worm antigens in faecal samples, i.e., the amount of antigen per gram faeces, APG. The APG from infected chickens was significantly higher than non-infected groups in both experiments (P 0.001). Both 100 and 1000 infection dose groups were not significantly different (P = 0.999) in the experiment with H. gallinarum, whereas in the experiment with A. galli, APG was significantly higher in the 1000 infection group (P 0.001). A receiver operation characteristics (ROC) analysis that evaluates the qualitative performance of diagnostics tests was used to calculate the assay parameters within each mono-infection experiment. The result showed that the assay had a high diagnostics accuracy with an area-under-curve (AUC) of 0.99 in detecting infection in A. galli infected chickens and a moderate-high accuracy (AUC = 0.89) in birds infected with H. gallinarum. The diagnostic sensitivity and specificity of the assay at the optimal cut-off point equivalent to Youden index were 93% and 100% for detecting infections in A. galli experiment and 85% and 92% in H. gallinarum experiment, respectively. The correlation between faecal antigen concentration and all worm burden parameters was positive but generally low (r < 0.33), which provided less information about infection intensities. Nonetheless, these results indicate that a reliable and accurate qualitative diagnosis of the two most prevalent intestinal nematodes in chickens can be achieved using a non-invasive copro-antigen ELISA assay.

Development of a multiplex PCR method for discriminating between Heterakis gallinarum, H. beramporia, and H. indica parasites of poultry

Heterakis gallinarum, H. beramporia, and H. indica are common nematodes in gallinaceous poultry in Asian countries, and the infections occasionally lead to declining health of the hosts. These three Heterakis spp. can be identified by the morphological characteristics of the male worms; however, the female worms and eggs cannot be identified because they have no reliable morphological characteristics for discrimination. In addition, H. gallinarum is a well-known vector of fetal protozoan Histomonas meleagridis, making the discrimination between these three Heterakis species important in basic and clinical veterinary parasitology. We analyzed nuclear ribosomal 18S-ITS1-5.8S-ITS2-28S DNA sequences of these three Heterakis species. The 18S, 5.8S, and 28S DNA sequences had very high homology between the species; however, the ITS1 and ITS2 sequence similarity was 68.5 %-93.2 %. H. gallinarum, H. beramporia, and H. indica were divided into separate clades in the ITS1 and ITS2-concatenated phylogenetic tree. Therefore, to develop a multiplex PCR method for discriminating between the three Heterakis species, we designed species-specific reverse primers within the ITS2 region as follows: H. gallinarum-specific HgI2-R, H. beramporia-specific HbI2-R5, and H. indica-specific HiI2-R. The multiplex PCR amplified 396-bp, 272-bp, and 482-bp fragments specific to H. gallinarum, H. beramporia, and H. indica DNA, respectively, and did not amplify the fragments using other chicken nematode DNAs such as Ascaridia galli, Oxyspirura mansoni, Dispharynx nasuta, and Cheilospirura hamulosa. These results suggest that the multiplex PCR would serve as a useful tool for identifying and diagnosing infections of H. gallinarum, H. beramporia, and H. indica in poultry.

The mitogenome of Ophidascaris wangi isolated from snakes in China

Different species of the genus Ophidascaris (Baylis, 1921; Nematoda: Ascaridida, Ascaridoidea) are intestinal parasites of various snake species. More than 30 Ophidascaris species have been reported worldwide; however, few molecular genetic studies have been conducted on this genus. We sequenced the complete mitogenome of Ophidascaris wangi parasitizing two snake species of the family Colubridae, i.e., Elaphe carinata (Günther, 1864) and Dinodon rufozonatum. The mitogenome sequence of O. wangi was approximately 14,660 base pairs (bp) long and encoded 36 genes, including 12 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, and 22 transfer RNA genes. Gene arrangement, genome content, and transcription direction were in line with those in Toxascaris leonina (Linstow, 1902; Ascaridida: Ascarididae). Phylogenetics of O. wangi and other ascaridoids were reconstructed based on the concatenated amino acid sequences of 12 PCGs, and on nucleotide sequences of 12 PCGs and two rRNA genes. Phylogenetic analyses were performed using maximum likelihood and Bayesian inference methods, and the results suggested that O. wangi constitutes a sister clade of Ascaris, Parascaris, Baylisascaris, and Toxascaris within the family Ascarididae, which is a sister clade of Toxocaridae. The mitogenome sequence of O. wangi obtained from the present study will be useful for future identification of the nematode worms in the genus Ophidascaris and will increase the understanding of population genetics, molecular epidemiology, and phylogenetics of ascaridoid nematodes in snakes.

Mitochondrial phylogenomics of human-type Ascaris, pig-type Ascaris, and hybrid Ascaris populations

Ascaris lumbricoides and Ascaris suum are parasitic nematodes in human and pig intestines. The two species can cross infect and produce hybrids, which contribute to the controversy concerning the taxonomy of A. lumbricoides and A. suum. The purpose of this study was to investigate the microevolutionary process and evolutionary history of human-type Ascaris, pig-type Ascaris, and hybrid Ascaris and provide a theoretical basis for the prevention and control of human and animal ascariasis. The mitochondrial phylogenomics of human-type Ascaris (n = 5), pig-type Ascaris (n = 6), and hybrid Ascaris (n = 6) populations were analyzed using high-throughput sequencing technology. The mitochondrial genomes of human-type Ascaris, pig-type Ascaris, and hybrid Ascaris contained 36 genes (atp8 was missing), including 12 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. All genes were located on the heavy chain. The initiation codons used for protein-coding genes were ATT and TTG and the termination codons were TAA and TAG. The base distribution showed obvious AT preference. The phylogenetic tree based on the Ascaris mitochondrial genomes showed three main clusters (A, B, and C). The Ascaris populations sequenced in this study were all gathered in cluster B. The human-type and hybrid Ascaris populations belonged to different sub-clusters, but the pig-type Ascaris population was more scattered. The mitochondrial genome sequences of the 17 Ascaris individuals in this study did not differ much. The results of this study indicate that Ascaris populations were geographically isolated before host shift. In addition, the data show that there are differences between hybrid Ascaris, human-type Ascaris, and pig-type Ascaris. The information has important theoretical significance and application value.

Heterakis gallinarum, the Cecal Nematode of Gallinaceous Birds: A Critical Review

Heterakis gallinarum is a heavily prevalent poultry parasite that thrives in the ceca of various species of gallinaceous birds. It is a small roundworm, measuring between 4 and 15 mm long, in the family Heterakidae. Heterakis gallinarum has a direct life cycle not requiring an intermediate host to complete development, and it is generally believed that poultry raised at high density on litter are at greatest risk for accumulating large numbers of the nematode. This species typically only causes mild pathology that does not significantly affect bird performance. However, H. gallinarum is recognized as an economically important parasite by the poultry industry because its ovum serves as the vector for the protozoal parasite Histomonas meleagridis, the cause of histomonosis in poultry. Diagnosis of the nematode typically relies on fecal egg counts, which are prone to false negative diagnoses. Molecular tools are available for studying the nematode and diagnosing infected flocks. Treating and preventing H. gallinarum infection is made difficult due to the low efficacy of anthelmintics for eradicating H. gallinarum from infected birds and of disinfectants for destroying H. gallinarum ova on contaminated farms.

The mitochondrial genome of Acrobeloides varius (Cephalobomorpha) confirms non-monophyly of Tylenchina (Nematoda)

The infraorder Cephalobomorpha is a diverse and ecologically important nematode group found in almost all terrestrial environments. In a recent nematode classification system based on SSU rDNA, Cephalobomorpha was classified within the suborder Tylenchina with Panagrolaimomorpha, Tylenchomorpha and Drilonematomorpha. However, phylogenetic relationships among species within Tylenchina are not always consistent, and the phylogenetic position of Cephalobomorpha is still uncertain. In this study, in order to examine phylogenetic relationships of Cephalobomorpha with other nematode groups, we determined the complete mitochondrial genome sequence of Acrobeloides varius, the first sequenced representative of Cephalobomorpha, and used this sequence for phylogenetic analyses along with 101 other nematode species. Phylogenetic analyses using amino acid and nucleotide sequence data of 12 protein-coding genes strongly support a sister relationship between the two cephalobomorpha species A. varius and Acrobeles complexus (represented by a partial mt genome sequence). In this mitochondrial genome phylogeny, Cephalobomorpha was sister to all chromadorean species (excluding Plectus acuminatus of Plectida) and separated from Panagrolaimomorpha and Tylenchomorpha, rendering Tylenchina non-monophyletic. Mitochondrial gene order among Tylenchina species is not conserved, and gene clusters shared between A. varius and A. complexus are very limited. Results from phylogenetic analysis and gene order comparison confirms Tylenchina is not monophyletic. To better understand phylogenetic relationships among Tylenchina members, additional mitochondrial genome information is needed from underrepresented taxa representing Panagrolaimomorpha and Cephalobomorpha.

Morphological and Molecular Characteristics of the Gastro-Intestinal Nematode Parasite Ascaridia columbae Infecting the Domestic Pigeon Columba livia domestica in Saudi Arabia

BACKGROUND

Parasitism is a complex problem that is often ignored in companion animals, including birds, unless it develops into a severe clinical disorder. The present study was, therefore, aimed to investigate the presence of the gastrointestinal nematode infecting the domestic pigeon and provide a complete morphological description and clarify its taxonomic position through phylogenetic analysis of the ITS1-5.8s-ITS2 rDNA gene region.

MATERIALS AND METHODS

During the current study, a total of twenty-six domestic pigeons, Columba livia domestica, were collected and internal organs examined for helminth detection. Using light and scanning electron microscopy, the recovered parasite species are studied. In addition, the selected gene region was obtained and sequenced using appropriate primers that aid in the formation of the phylogenetic dendrogram for the recovered parasite species with others retrieved from GenBank.

RESULTS

Morphological examination showed that this nematode parasite belongs to the Ascaridiidae family within the genus Ascaridia. The material was assigned to the previously described Ascaridia columbae by providing all the characteristic features as the presence of a mouth opening surrounded by three tri-lobed lips; each lip has two triangular teeth with a spoon-like structure, cephalic papillae and amphidal pores on lips surface, presence of lateral cuticular alae and pre-cloacal sucker, 10 pairs of caudal papillae, and two equal spicules in male worms. The morphological investigations of this species were supplemented by molecular analysis of ITS1-5.8s-ITS2 rDNA gene region. The data showed that the present A. coulmbae is deeply embedded in the Ascaridia genus with a 74-99% sequence similarity to other species in the Chromadorea class. Ascaridiidae appears as monophyly and represented as a sister group to Heterakidae. The ascaridiid species examined belong to the Ascaridia genus and displaced a close relationship with the previously described A. coulmbae (gb| KF147909.1, gb| AJ001509.1, gb| KC905082.1, gb| JQ995321.1, gb| JX624729.1) as putative sister taxa.

CONCLUSION

The present study revealed that the species Ascaridia is the first account of this genus as an endoparasite from the domestic pigeon inhabiting Saudi Arabia. Therefore, the combination of morphological and molecular studies helps to identify this species correctly and identified as Ascaridia columbae.

PCR detection of Heterakis gallinarum in environmental samples

Heterakis gallinarum is a widely distributed cecal nematode that parasitizes gallinaceous birds including chickens and turkeys. H. gallinarum infection poses a problem for the poultry industry as the nematode egg serves as a vector for the protozoan parasite, Histomonas meleagridis, the causative agent of histomonosis. The only means of detecting H. gallinarum in the environment is microscopic identification of the eggs in soil or feces; however, H. gallinarum eggs are often mistaken for those of Ascaridia galli. Three primer sets were designed from sequences cloned from the H. gallinarum genome to develop a diagnostic PCR. Each of these primer sets amplified a single product from H. gallinarum, but were unable to amplify DNA from H. meleagridis, Ascaridia galli, or Cestode sp. H. gallinarum DNA was amplified from Lumbricus sp. (earthworms) and Alphitobius diaperinus (darkling beetles), confirming that the earthworm acts as a paratenic host for H. gallinarum and suggesting that the darkling beetle may be a carrier for this nematode.

Characterization of the Complete Mitochondrial Genome of Ostertagia trifurcata of Small Ruminants and its Phylogenetic Associations for the Trichostrongyloidea Superfamily

The complete mitochondrial (mt) genome of Ostertagia trifurcata, a parasitic nematode of small ruminants, has been sequenced and its phylogenetic relationship with selected members from the superfamily Trichostrongyloidea was investigated on the basis of deduced datasets of mt amino acid sequences. The entire mt genome of Ostertagia trifurcata is circular and 14,151 bp in length. It consists of a total of 36 genes comprising 12 genes coding for proteins (PCGs), 2 genes for ribosomal RNA (rRNA), 22 transfer RNA (tRNA) genes and 2 non-coding regions, since all genes are transcribed in the same direction. The phylogenetic analysis based on the concatenated datasets of predicted amino acid sequences of the 12 protein coding genes supported monophylies of the Haemonchidae, Dictyocaulidae and Molineidae families, but rejected monophylies of the Trichostrongylidae family. The complete characterization and provision of the mtDNA sequence of Ostertagia trifurcata provides novel genetic markers for molecular epidemiological investigations, systematics, diagnostics and population genetics of Ostertagia trifurcata and its correspondents.

Co-expulsion of Ascaridia galli and Heterakis gallinarum by chickens

Worm expulsion is known to occur in mammalian hosts exposed to mono-species helminth infections, whilst this phenomenon is poorly described in avian hosts. Mono-species infections, however, are rather rare under natural circumstances. Therefore, we quantified the extent and duration of worm expulsion by chickens experimentally infected with both Ascaridia galli and Heterakis gallinarum, and investigated the accompanying humoral and cell-mediated host immune responses in association with population dynamics of the worms. Results demonstrated the strong co-expulsion of the two ascarid species in three phases. The expulsion patterns were characterized by non-linear alterations separated by species-specific time thresholds. Ascaridia galli burden decreased at a daily expulsion rate (e) of 4.3 worms up to a threshold of 30.5 days p.i., followed by a much lower second expulsion rate (e = 0.46), which resulted in almost, but not entirely, complete expulsion. Heterakis gallinarum was able to induce reinfection within the experimental period (9 weeks). First generation H. gallinarum worms were expelled at a daily rate of e = 0.8 worms until 36.4 days p.i., and thereafter almost no expulsion occurred. Data on both humoral and tissue-specific cellular immune responses collectively indicated that antibody production in chickens with multispecies ascarid infections is triggered by Th2 polarisation. Local Th2 immune responses and mucin-regulating genes are associated with the regulation of worm expulsion. In conclusion, the chicken host is able to eliminate the vast majority of both A. galli and H. gallinarum in three distinct phases. Worm expulsion was strongly associated with the developmental stages of the worms, where the elimination of juvenile stages was specifically targeted. A very small percentage of worms was nevertheless able to survive, reach maturity and induce reinfection if given sufficient time to complete their life cycle. Both humoral and local immune responses were associated with worm expulsion.

Diurnal variation in egg excretion by Heterakis gallinarum

Periodicity in nematode egg excretion may be of evolutionary origin as it can favour dispersal of the eggs in the environment. We investigated whether egg excretion by Heterakis gallinarum shows a repeatable pattern of periodicity. The faecal egg concentration and total number of eggs excreted within 4-h intervals were significantly affected by the sampling time within 1 day, but remained unaffected by the sampling day or interaction effects. By contrast, the total number of eggs excreted within 24 h did not differ among the 4 days of the study, collectively indicating repeatable egg excretion patterns. Both host feces and parasite egg excretion increased from night to late afternoon, followed by a decrease in the evening, resulting in higher egg excretion during daytime than the dark period. Feces excretion and worm fecundity showed overlapping diurnal rhythms with similarly timed phases, suggesting the existence of synchronicity between the host feces and nematode egg excretion patterns. We conclude that egg excretion by H. gallinarum is synchronized with host feces excretion and is higher during the daytime than during the dark period. This overlaps with the maximum activity of the day-active host and allows a maximal dispersal of the eggs in the environment.

Characterization of the complete mitochondrial genome of Setaria digitata (Nematoda: Setariidae) from China

Setaria digitata is a filarial parasite that causes fatal cerebrospinal nematodiasis in goats, horses and sheep, resulting in substantial economic losses to livestock farmers. In the present study, the complete mitochondrial (mt) genome of S. digitata from China was determined, characterized and compared with that of S. digitata from Sri Lanka. The identity of the mt genomes was 98.3% between S. digitata from China and Sri Lanka, and the complete mt genome sequence of S. digitata from China was slightly shorter (25 bp) than that from Sri Lanka. For the 12 protein genes, this comparison revealed sequence differences at both the nucleotide (1.4%) and amino acid (2.2%) levels. The present study determined the complete mt genome sequence of S. digitata from China, providing novel genetic markers for the study of the population genetics and molecular epidemiology of S. digitata in animals.

Effect of the nematophagous fungus Pochonia chlamydosporia on soil content of ascarid eggs and infection levels in exposed hens

BACKGROUND

The nematophagous fungus Pochonia chlamydosporia can degrade ascarid (e.g. Ascaridia galli) eggs in agar and soil in vitro. However, it has not been investigated how this translates to reduced infection levels in naturally exposed chickens. We thus tested the infectivity of soil artificially contaminated with A. galli (and a few Heterakis gallinarum) eggs and treated with P. chlamydosporia. Sterilised and non-sterilised soils were used to examine any influence of natural soil biota.

METHODS

Unembryonated eggs were mixed with sterilised (S)/non-sterilised (N) soil, either treated with the fungus (F) or left as untreated controls (C) and incubated (22 °C, 35 days) to allow eggs to embryonate and fungus to grow. Egg number in soil was estimated on days 0 and 35 post-incubation. Hens were exposed to the soil (SC/SF/NC/NF) four times over 12 days by mixing soil into the feed. On day 42 post-first-exposure (p.f.e.), the hens were euthanized and parasites were recovered. Serum A. galli IgY level and ascarid eggs per gram of faeces (EPG) were examined on days -1 and 36 (IgY) or 40 p.f.e. (EPG).

RESULTS

Egg recovery in SF soil was substantially lower than in SC soil, but recovery was not significantly different between NF and NC soils. SF hens had a mean worm count of 76 whereas the other groups had means of 355-453. Early mature/mature A. galli were recovered from SF hens whereas hens in the other groups harboured mainly immature A. galli. Heterakis gallinarum counts were low overall, especially in SF. The SF post-exposure IgY response was significantly lower while EPG was significantly higher compared to the other groups.

CONCLUSIONS

Pochonia chlamydosporia was very effective in reducing ascarid egg numbers in sterilised soil and thus worm burdens in the exposed hens. However, reduced exposure of hens shifted A. galli populations toward a higher proportion of mature worms and resulted in a higher faecal egg excretion within the study period. This highlights a fundamental problem in ascarid control: if not all eggs in the farm environment are inactivated, the resulting low level infections may result in higher contamination levels with associated negative long-term consequences.

Characterization of the complete mitochondrial genome of Marshallagia marshalli and phylogenetic implications for the superfamily Trichostrongyloidea

Marshallagia marshalli (Nematoda: Trichostrongylidae) infection can lead to serious parasitic gastroenteritis in sheep, goat, and wild ruminant, causing significant socioeconomic losses worldwide. Up to now, the study concerning the molecular biology of M. marshalli is limited. Herein, we sequenced the complete mitochondrial (mt) genome of M. marshalli and examined its phylogenetic relationship with selected members of the superfamily Trichostrongyloidea using Bayesian inference (BI) based on concatenated mt amino acid sequence datasets. The complete mt genome sequence of M. marshalli is 13,891 bp, including 12 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. All protein-coding genes are transcribed in the same direction. Phylogenetic analyses based on concatenated amino acid sequences of the 12 protein-coding genes supported the monophylies of the families Haemonchidae, Molineidae, and Dictyocaulidae with strong statistical support, but rejected the monophyly of the family Trichostrongylidae. The determination of the complete mt genome sequence of M. marshalli provides novel genetic markers for studying the systematics, population genetics, and molecular epidemiology of M. marshalli and its congeners.

The complete mitochondrial genome of Engyodontium album and comparative analyses with Ascomycota mitogenomes

Engyodontium album is a widespread pathogen that causes different kinds of dermatoses and respiratory tract diseases in humans and animals. In spite of its perniciousness, the basic genetic and molecular background of this species remains poorly understood. In this study, the mitochondrial genome sequence of E. album was determined using a high-throughput sequencing platform. The circular mitogenome was found to be 28,081 nucleotides in length and comprised of 17 protein-coding genes, 24 tRNA genes, and 2 rRNA genes. The nucleotide composition of the genome was A+T-biased (74.13%). Group-II introns were found in the nad1, nad5, and cob genes. The most frequently used codon of protein-coding genes was UAU. Isoleucine was identified as the most common amino acid, while proline was the least common amino acid in protein-coding genes. The gene-arrangement order is nearly the same when compared with other Ascomycota mitogenomes. Phylogenetic relationships based on the shared protein-coding genes revealed that E. album is closely related to the Cordycipitaceae family, with a high-confidence support value (100%). The availability of the mitogenome of E. album will shed light on the molecular systematic and genetic differentiation of this species.

Genetic variation in mitochondrial cox2 of Heterakis gallinarum from poultry in Sichuan, China

Heterakis gallinarum is one of the common parasitic nematodes found in the caecum of poultry. To investigate the genetic diversity and genetic structure of the H. gallinarum population in Sichuan, we amplified and sequenced the complete mitochondrial (mt) cytochrome c oxidase subunit II (cox2) gene of 59 H. gallinarum isolates from seven different geographical regions, then analyzed their genetic polymorphisms. All cox2 genes of the 59 H. gallinarum isolates were 696 bp in length, with an average A + T content of 67.1%. Fifty-nine sequences contained 34 variable sites, and were classified into 23 haplotypes (HS1-HS23). The values of haplotype diversity (Hd) and nucleotide diversity (π) were 0.688 and 0.00288, respectively. Based on values of F_ST and Nm (F_ST = 0.01929, Nm = 12.71), there was a frequent gene flow but no significant genetic differentiation observed among the populations. The network map showed that the most prominent haplotype was HS1, and the other haplotypes (HS2-HS23) were centered on HS1 with a star-like topology, indicating that H. gallinarum had previously experienced a population expansion. To our knowledge, this is the first research on the population genetics of H. gallinarum based on mitochondrial cox2.

A comprehensive evaluation of an ELISA for the diagnosis of the two most common ascarids in chickens using plasma or egg yolks

BACKGROUND

Classical faecal egg counts (FEC) provide less reliable diagnostic information for nematode infections in chickens. We developed an ELISA based on Ascaridia galli antigens and tested two hypotheses, as follows: (i) IgY antibodies developed against A. galli will also be useful to identify Heterakis gallinarum infections, and (ii) circulating antibodies stored in egg yolks are as good as plasma samples, so a non-invasive diagnosis is possible. The aim of this study, therefore, was to compare the diagnostic accuracy of the ELISA system with FEC, using both plasma and egg yolks from experimentally infected hens. In addition, naturally infected animals were evaluated to validate the assay.

RESULTS

The assay quantified large differences (P < 0.001) in plasma or in egg-yolk IgY concentrations between infected and uninfected animals in two experiments, each performed with either of the nematode species. The assay performed with high accuracy as quantified with the area under the ROC curve (AUC) values of > 0.90 for both nematodes using either plasma or egg yolks. Sensitivity of the assay was 94 and 93% with plasma and egg yolk samples, respectively, whereas FEC yielded in a sensitivity of 84% in A. galli experiment. Total test accuracy of the assay with plasma samples (AUC = 0.99) tended to be higher (P = 0.0630) than FEC (AUC = 0.92) for A. galli, while the assay with either sample matrix performed similar to FEC (AUC ≥ 0.91) for H. gallinarum. Among the three tests, the FECs correlated better with A. galli burden than the ELISA. Although 90% of naturally infected hens were correctly identified by the ELISA, 45% of the infected hens tested negative with FEC, indicating the validity of the higher test accuracy of the ELISA.

CONCLUSIONS

Antigens of A. galli can be used successfully to identify H. gallinarum-infected animals, indicating that chickens develop cross-reactive antibodies against the two closely related species. Egg yolks are as informative as plasma samples, so that animal welfare-friendly sampling is possible. Although the assay with plasma samples reveals qualitative information of higher quality than FECs on the infection status of naturally infected birds, the latter is still a better tool to assess the intensity of A. galli but not of H. gallinarum infections.

Complete mitochondrial genomes of Gnathostoma nipponicum and Gnathostoma sp., and their comparison with other Gnathostoma species

Gnathostomiasis is a foodborne zoonotic parasitosis caused by Gnathostoma nematodes. It has caused significant public problems worldwide, but its molecular biology is limited. The purpose of this study was to decode the complete mitochondrial (mt) genomes of Gnathostoma nipponicum and Gnathostoma sp., and compare their mt sequences with other Gnathostoma species. The complete mt genome sequences were amplified by long-range PCR and determined by subsequent primer walking. The complete mt genomes of G. nipponicum and Gnathostoma sp. were 14,093bp and 14,391bp, respectively. Both of the two mt genomes contain 12 protein-coding genes (PCGs), 2 ribosomal RNA genes and 22 transfer RNA genes. The gene order and transcription direction are the same as G. spinigerum and G. doloresi. The sequence difference across the entire mt genomes varied from 14.4% to 18.2% between G. nipponicum, Gnathostoma sp., G. spinigerum and G. doloresi of Japan and China isolates. Phylogenetic analyses by Bayesian inference (BI) using concatenated amino acid sequences of 12 PCGs showed that G. nipponicum and Gnathostoma sp. are two distinctive species of Gnathostoma, and G. nipponicum are more closely related to Gnathostoma sp. than to G. spinigerum. The mtDNA datasets provide abundant resources of novel markers, which can be used for the studies of molecular epidemiology and diagnosis of Gnathostoma spp.

Mitochondrial Phylogenomics yields Strongly Supported Hypotheses for Ascaridomorph Nematodes

Ascaridomorph nematodes threaten the health of humans and other animals worldwide. Despite their medical, veterinary and economic importance, the identification of species lineages and establishing their phylogenetic relationships have proved difficult in some cases. Many working hypotheses regarding the phylogeny of ascaridomorphs have been based on single-locus data, most typically nuclear ribosomal RNA. Such single-locus hypotheses lack independent corroboration, and for nuclear rRNA typically lack resolution for deep relationships. As an alternative approach, we analyzed the mitochondrial (mt) genomes of anisakids (~14 kb) from different fish hosts in multiple countries, in combination with those of other ascaridomorphs available in the GenBank database. The circular mt genomes range from 13,948-14,019 bp in size and encode 12 protein-coding genes, 2 ribosomal RNAs and 22 transfer RNA genes. Our analysis showed that the Pseudoterranova decipiens complex consists of at least six cryptic species. In contrast, the hypothesis that Contracaecum ogmorhini represents a complex of cryptic species is not supported by mt genome data. Our analysis recovered several fundamental and uncontroversial ascaridomorph clades, including the monophyly of superfamilies and families, except for Ascaridiidae, which was consistent with the results based on nuclear rRNA analysis. In conclusion, mt genome analysis provided new insights into the phylogeny and taxonomy of ascaridomorph nematodes.