A gastrointestinal nematode in pregnant and lactating mice alters maternal and neonatal microbiomes

The maternal microbiome is understood to be the principal source of the neonatal microbiome but the consequences of intestinal nematodes on pregnant and lactating mothers and implications for the neonatal microbiome are unknown. Using pregnant CD1 mice infected with Heligmosomoides bakeri, we investigated the microbiomes in maternal tissues (intestine, vagina, and milk) and in the neonatal stomach using MiSeq sequencing of bacterial 16S rRNA genes. Our first hypothesis was that maternal nematode infection altered the maternal intestinal, vaginal, and milk microbiomes and associated metabolic pathways. Maternal nematode infection was associated with increased beta-diversity and abundance of fermenting bacteria as well as Lactobacillus in the maternal caecum 2 days after parturition, together with down-regulated carbohydrate, amino acid and vitamin biosynthesis pathways. Maternal nematode infection did not alter the vaginal or milk microbiomes. Our second hypothesis was that maternal infection would shape colonization of the neonatal microbiome. Although the pup stomach microbiome was similar to that of the maternal vaginal microbiome, pups of infected dams had higher beta-diversity at day 2, and a dramatic expansion in the abundance of Lactobacillus between days 2 and 7 compared with pups nursing uninfected dams. Our third hypothesis that maternal nematode infection altered the composition of neonatal microbiomes was confirmed as we observed up-regulation of several putatively beneficial microbial pathways associated with synthesis of essential and branched-chain amino acids, vitamins, and short-chain fatty acids. We believe this is the first study to show that a nematode living in the maternal intestine is associated with altered composition and function of the neonatal microbiome.

New records of cucullanid nematodes from marine fishes off New Caledonia, with descriptions of five new species of Cucullanus (Nematoda, Cucullanidae)

Recent examinations of cucullanid nematodes (Cucullanidae) from marine fishes off New Caledonia, collected in the years 2004–2009, revealed the presence of the following five new species of Cucullanus Müller, 1777, all parasitic in Perciformes: Cucullanus variolae n. sp. from Variola louti (type host) and V. albimarginata (both Serranidae); Cucullanus acutospiculatus n. sp. from Caesio cuning (Caesionidae); Cucullanus diagrammae n. sp. from Diagramma pictum (Haemulidae); Cucullanus parapercidis n. sp. from Parapercis xanthozona (type host) and P. hexophtalma (both Pinguipedidae); and Cucullanus petterae n. sp. from Epinephelus merra (type host) and E. fasciatus (both Serranidae). An additional congeneric species, Cucullanus bioccai Orecchia et Paggi, 1987 was recorded from Mugil cephalus (Mugilidae, Mugiliformes) (first record in the Pacific Ocean) and Cucullanus sp. (only female) was found in Arothron manilensis (Tetraodontidae, Tetraodontiformes). Furthermore, two known cucullanid species, Dichelyne (Cucullanellus) branchiostegi (Yamaguti, 1941) in Branchiostegus wardi (Malacanthidae, Perciformes) (new host and geographical records) and Dichelyne (Cucullanellus) bodiani Moravec et Justine, 2019 in Bodianus busellatus (new host) and B. perditio (both Labridae, Perciformes), were found; Dichelyne (Cucullanellus) sp. (only females) coinfecting the latter host may represent an unknown species. Most species are described based on light and electron microscopical studies. The specimens described by Xu et al., 2017 as Cucullanus bourdini Petter et Le Bel, 1992 from Caesio xanthonota (Caesionidae) in the Taiwan Strait are considered to represent a new species, for which the name Cucullanus sinensis n. sp. is proposed.

Structural and biochemical analysis of phosphoethanolamine methyltransferase from the pine wilt nematode Bursaphelenchus xylophilus

In free-living and parasitic nematodes, the methylation of phosphoethanolamine to phosphocholine provides a key metabolite to sustain phospholipid biosynthesis for growth and development. Because the phosphoethanolamine methyltransferases (PMT) of nematodes are essential for normal growth and development, these enzymes are potential targets of inhibitor design. The pine wilt nematode (Bursaphelenchus xylophilus) causes extensive damage to trees used for lumber and paper in Asia. As a first step toward testing BxPMT1 as a potential nematicide target, we determined the 2.05 Å resolution x-ray crystal structure of the enzyme as a dead-end complex with phosphoethanolamine and S-adenosylhomocysteine. The three-dimensional structure of BxPMT1 served as a template for site-directed mutagenesis to probe the contribution of active site residues to catalysis and phosphoethanolamine binding using steady-state kinetic analysis. Biochemical analysis of the mutants identifies key residues on the β1d-α6 loop (W123F, M126I, and Y127F) and β1e-α7 loop (S155A, S160A, H170A, T178V, and Y180F) that form the phosphobase binding site and suggest that Tyr127 facilitates the methylation reaction in BxPMT1.

New records of anisakid nematodes from marine fishes off New Caledonia, with descriptions of five new species of Raphidascaris (Ichthyascaris) (Nematoda, Anisakidae)

Recent examinations of anisakid nematodes (Anisakidae) from marine fishes off New Caledonia, collected in the years 2003–2008, revealed the presence of the following five new species of Raphidascaris Railliet et Henry, 1915, all belonging to the subgenus Ichthyascaris Wu, 1949: Raphidascaris (Ichthyascaris) spinicauda n. sp. from the redbelly yellowtail fusilier Caesio cuning (Caesionidae, Perciformes); Raphidascaris (Ichthyascaris) fasciati n. sp. from the blacktip grouper Epinephelus fasciatus (Serranidae, Perciformes); Raphidascaris (Ichthyascaris) nudicauda n. sp. from the brushtooth lizardfish Saurida undosquamis (Synodontidae, Aulopiformes); Raphidascaris (Ichthyascaris) euani n. sp. from the Japanese large-eye bream Gymnocranius euanus (Lethrinidae, Perciformes); and Raphidascaris (Ichthyascaris) elopsis n. sp. from the Hawaiian ladyfish Elops hawaiensis (Elopidae, Elopiformes). An additional two congeneric species, R. (I.) etelidis Moravec et Justine, 2012 and R. (I.) sillagoides (Bruce, 1990) were found in the deep-water red snapper Etelis carbunculus (new host record) and the deepwater longtail red snapper Etelis coruscans (both Lutjanidae, Perciformes), and the silver sillago Sillago sihama (Sillaginidae, Perciformes) (new host and geographical records), respectively. Two unidentified congeneric species, Raphidascaris (Ichthyascaris) sp. 1 from the trumpet emperor Lethrinus miniatus (Lethrinidae, Perciformes) and Raphidascaris (Ichthyascaris) sp. 2 from the white-spotted puffer Arothron hispidus (Tetraodontidae, Tetraodontiformes) were recorded. Moreover, two species of Hysterothylacium Ward et Magath, 1917, H. alatum Moravec et Justine, 2015 and H. epinepheli (Yamaguti, 1941), were found in the leopard coralgrouper Plectropomus leopardus (type host) and the highfin grouper Epinephelus maculatus (new host) (both Serranidae, Perciformes), respectively. This is the second finding of H. epinepheli since its original description in Japan 79 years ago. Most species are described based on light and electron microscopical studies.

An integrative taxonomic assessment of Procamallanus (Spirocamallanus) huacraensis (Nematoda: Camallanidae), infecting the freshwater catfish Trichomycterus spegazzinii (Siluriformes: Trichomycteridae) in Argentina

Procamallanus (Spirocamallanus) huacraensis infecting the catfish Trichomycterus spegazzinii from Escoipe River, Salta province (Argentina), is redescribed and genetically characterised for the first time, based on three genetic markers (nuclear 18S and 28S rRNA; cytochrome c oxidase subunit I [cox1] mtDNA). The phylogeny of Camallanidae was also discussed. Morphological evaluation of P. (S.) huacraensis using light and scanning electron microscopy revealed the previously undescribed features: location of deirids, accurate morphology of larvae (L1) and ovijector in females, as well as phasmids in males. Differences were found comparing the newly collected material and the type specimens, probably because the original description lacked detailing. Unfortunately, type specimens of P. (S.) huacraensis were no available for loan. The results of morphological and genetic analyses supported the validity of P. (S.) huacraensis. Inconsistencies regarding the taxonomic identification of species of Camallanidae in GenBank database were noted. Based on the current genetic database of Camallanidae, phylogenetic reconstructions using the 18S rRNA sequences were most consistent, due to the inclusion of higher number of taxa. Procamallanus (S.) huacraensis appeared as sister group of P. (S.) rarus, also isolated from a catfish in a neighbouring region. The order and habitat of hosts were also similar within some well-supported parasite lineages, but without common geographic origin. However, it is still premature to make definitive affirmations regarding the role of such features in the phylogenetic patterns of Camallanidae, given the scarcity of genetic data. The phylogenetic reconstructions also confirmed the artificiality of the morphology-based systematics of the family.

Epidemiology of Sulcascaris sulcata (Nematoda: Anisakidae) ulcerous gastritis in the Mediterranean loggerhead sea turtle (Caretta caretta)

Sulcascaris sulcata Rudolphi 1819 is a gastric nematode parasite of sea turtles. Here, we report the occurrence and describe for the first time the pathological changes caused by S. sulcata in the Mediterranean loggerhead sea turtle (Caretta caretta) stranded along the Tyrrhenian coast and northern Adriatic coast of Italy. Prevalence of infection was significantly higher in loggerhead sea turtles from the Adriatic Sea. Both prevalence and abundance of infection showed an increasing trend along with host age classes from both geographical localities. Nevertheless, while many small loggerhead sea turtles were found infected from the Adriatic Sea, only bigger individuals were infected from the Tyrrhenian Sea. The most common gross pathological change was a mucous gastritis with focal to multifocal raised ulcerous lesions roundish to irregular in shape ranging from 1 to over 20 cm in length, and cream-yellowish to greenish in color. The severity grade of gastritis increased with higher number of S. sulcata individuals. Microscopic pathological changes ranged from atrophic gastritis with heterophilic infiltration in the lamina propria to the destruction of the mucosal and sub-mucosal surfaces and necrosis. Results here obtained demonstrate that S. sulcata may cause ulcerous gastritis in both samples of loggerhead sea turtles studied from the Mediterranean Sea. Observed differences in S. sulcata infection among the different host age classes and between the two studied basins are likely linked to the differences of regional habitat and intermediate prey host availability.

Redescription of Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Nematoda: Philometridae), a gonad-infecting parasite of the red grouper Epinephelus morio (Serranidae) in the Gulf of Mexico

The insufficiently known nematode species Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Philometridae) is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the gonad of the type host, the red grouper Epinephelus morio (Valenciennes) (Serranidae, Perciformes), in the northern Gulf of Mexico off Florida, USA. Also, new prevalence data for females of P. margolisi were derived from 188 fish, and a subset of these (n = 38) were used to determine prevalence and intensity of male nematodes. The male of this species was studied with SEM for the first time, which revealed some new, taxonomically important morphological features. The male posterior end had a V-shaped caudal mound, four pairs of minute adanal papillae, a pair of large papillae located posterior to the cloacal aperture and a pair of very small phasmids. The distal end of the gubernaculum is unique among all gonad-infecting species of Philometra parasitizing serranids in that its ventral surface is flat, smooth, without the usual two longitudinal grooves; the dorsal lamellate structures on the gubernaculum are also different in this species. In contrast to data in the original species description, the body length of gravid females of P. margolisi was 132-280 mm. Overall prevalence for male nematodes (76.3%) was much higher than for females (15.4%), and female nematode prevalence was higher in samples collected during host spawing season than out of season (27.1% and 3.3%, respectively).

RNA interference in adult Ascaris suum--an opportunity for the development of a functional genomics platform that supports organism-, tissue- and cell-based biology in a nematode parasite

The sustainable control of animal parasitic nematodes requires the development of efficient functional genomics platforms to facilitate target validation and enhance anthelmintic discovery. Unfortunately, the utility of RNA interference (RNAi) for the validation of novel drug targets in nematode parasites remains problematic. Ascaris suum is an important veterinary parasite and a zoonotic pathogen. Here we show that adult A. suum is RNAi competent, and highlight the induction, spread and consistency of RNAi across multiple tissue types. This platform provides a new opportunity to undertake whole organism-, tissue- and cell-level gene function studies to enhance target validation processes for nematode parasites of veterinary/medical significance.