Molecular and Histopathological Data on Levisunguis subaequalis Curran, Overstreet, Collins & Benz, 2014 (Pentastomida: Eupentastomida: Porocephalida: Porocephaloidea: Sebekidae: Sebekinae) from Gambusia affinis in Alabama, USA

Linguatula serrata in an imported dog in Germany: Single-case or emerging disease?

Linguatula serrata is a worm-like parasite with zoonotic potential that inhabits the nasal cavities of canids. Although most cases of linguatulosis are associated with unspecific and rather mild respiratory symptoms, cases of unusual infestations and severe courses in both animals and humans have been reported. In central and northern Europe, the pathogen used to appear only sporadically, however, within the last few years the number of detections has increased noticeably. In July 2020 an approximately nine-month-old dog, imported from Romania, was presented in a veterinary practice in Gotha, central Germany, due to persistent worsening cough. Despite antibiotic treatment the tussis became more severe until the dog expectorated multiple worm-like structures. Three of these specimens were sent to the Institute of Parasitology (Faculty of Veterinary Medicine, University of Leipzig, Leipzig) for morphological and genetic species identification. The latter was based on a 1000-bp fragment of the mitochondrial cytochrome c oxidase subunit I gene (cox1) and the complete nuclear 18S rRNA gene. The dog presented in this study suffered from a severe respiratory impairment caused by worm-like parasites inhabiting its upper respiratory tract. The detected parasites were morphologically identified as female specimens of the so-called tongue-worm L. serrata, which was confirmed by pairwise alignment and phylogenetic analysis of the produced sequences. We report an unusually severe case of L. serrata infection in an imported dog and discuss the spread of this potentially dangerous parasite in central and northern Europe.

28S rRNA sequences for Linguatula spp

Identification of specimens belonging to the genus Linguatula (Pentastomida) is relatively easy due to their unique morphology. However, differentiation between species of Linguatula can be challenging for several reasons, including considerable differences between different developmental stages of the parasite within and between species. Currently, 18S rRNA and Cox1 sequences are the only available comparable sequences in GenBank, but recent research has discussed the utility of 28S rRNA for pentastomid phylogenetics. This study presents 28S rRNA gene sequences for two members of the genus Linguatula. Sequences of 28S rRNA were successfully obtained from well-identified samples of L.serrata (collected in Australia) and L.nuttalli (collected in South Africa), with voucher specimens. Phylogenetic analysis of the 28S rRNA region showed 6% difference between L.serrata and L.nuttalli, with low levels of intraspecific variation. In comparison, 18S rRNA and Cox1 sequences from the same specimens showed 0.23% and 13% interspecific differences, respectively. The results of this study show that 28S rRNA has greater genetic diversity to allow for improved differentiation between species of Linguatula than 18S rRNA but is on par with Cox1. Records that do not provide adequate morphological or molecular data to justify independent specific diagnoses must be regarded cautiously, and the need for continued research on species of Linguatula, using a combined morphological and molecular analysis, across a number of different hosts, development stages, geographical regions and molecular markers is highlighted.

New data on Henneguya postexilis Minchew, 1977, a parasite of channel catfish Ictalurus punctatus, with notes on resolution of molecular markers for myxozoan phylogeny

Previous morphological and histological data are supplemented with molecular and ultrastructural data for a Henneguya sp. isolated from farm-raised channel catfish Ictalurus punctatus in Mississippi, USA. Myxospores were cryptic, encapsulated within a thin layer of epithelium in the gill lamellae with spore measurements consistent with the original description of Henneguya postexilis Minchew, 1977. Myxospores were 42.7-49.1 µm in total length with spore bodies 12.1-17.2 × 3.6-4.8 × 2.9-3 µm. Polar capsules were of unequal length, with the longer capsule being 4.4-6.7 × 1.1-1.6 µm and the shorter capsule being 4.4-6.4 × 1.1-1.6 µm. Polar tubules had 6-8 turns. Caudal processes were 25.7-38.1 µm in length. Spores were encapsulated in a thin layer of epithelium in the gill lamellae. Molecular data from the most commonly used markers for myxozoan identification and phylogeny, partial 18S small subunit ribosomal gene (SSU), partial 28S large subunit ribosomal gene (LSU), and elongation factor 2 (EF2) were generated for H. postexilis. Additionally, novel data for LSU and EF2 were generated for archived myxozoan specimens from farm-raised catfish (H. mississippiensis, H. ictaluri, H. exilis, H. adiposa, H. sutherlandi, H. bulbosus, Unicauda fimbrethilae), as well as archived specimens from wild fish (H. laseeae [from Pylodictis olivaris], Hennegoides flockae [from Aphredoderus sayanus], Myxobolus cloutmani [from Cycleptus elongatus]. These include the first EF2 sequence data for the genera Hennegoides and Unicauda. Phylogenetic analyses using these data placed H. postexilis in well supported clades with other ictalurid-infecting Henneguya species. Phylogenetic signal assessments on these analyses suggest that while SSU provided the greatest phylogenetic signal, LSU yielded comparable signal, supporting previous work implying this region may be underutilised in reconstructing myxobolid phylogenies.

The first Linguatula serrata case in an imported dog in Finland

Linguatula serrata is a pentastomid parasite infecting carnivores as definitive hosts and herbivores as intermediate hosts. In carnivores, including dogs, it usually parasitises the nasal cavity and sinuses, causing upper respiratory signs. This case report presents the first canine Linguatula case in Finland in an imported dog originating from Spain. In addition to the unremarkable clinical history of the dog, the treatment, parasite's morphology and molecular analysis are described, and the zoonotic potential is discussed.

Characterisation of myxozoan fauna of western mosquitofish, Gambusia affinis (Baird and Gerard) (Cyprinodontiformes: Poeciliidae), inhabiting experimental catfish ponds in Mississippi, USA

Characterising myxozoan taxa parasitising fish hosts in catfish aquaculture ponds is crucial to understanding myxozoan community dynamics in these diverse and complex ecological systems. This work investigated the myxozoan fauna of the western mosquitofish, Gambusia affinis, a common, incidental species found in catfish aquaculture ponds in the southeastern United States. 598 fish were sampled in May of 2018 and 2019 from the pond facility of the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, USA. Fish were examined microscopically using wet mount preparations of fresh tissue and histology for myxozoans. 18S rRNA gene sequences were amplified from myxospores obtained at necropsy. Updated morphologic, histologic, and 18S rRNA gene sequence features are provided for Henneguya gambusi, Myxobolus pharyngeus, and Myxidium phyllium. Two potentially novel myxozoans were observed during this survey, an undocumented Myxobolus sp. associated with chondrolysis of bones throughout the body and a putative Myxobilatus sp. observed histologically in the renal tubules, ureters, and urinary bladder. However, inadequate samples were obtained for proper species descriptions. Lastly, the life cycle of M. pharyngeus, which is thought to utilize the oligochaete worm Dero digitata as their definitive host, was putatively confirmed by 18S rRNA sequence matching to actinospore stages from oligochaetes in catfish ponds in Mississippi. This work provides novel and expanded morphologic, histologic, molecular and biologic data of five myxozoan parasites of G. affinis, expanding our knowledge of myxozoan diversity in catfish aquaculture ponds.

Morphological and molecular description of Armillifer moniliformis larvae isolated from Sri Lankan brown palm civet (Paradoxurus montanus)

We report Armillifer moniliformis species infecting the endemic Sri Lankan brown palm civet (Paradoxurus montanus) from the Knuckles Range Forest Conservation Area, Sri Lanka. Larval stages of A. moniliformis were found during the postmortem of three civet cats found dead. Morphological studies were done by a light microscope and a scanning electron microscope (SEM). Histopathological examination was conducted using tissue samples obtained from the liver. For the molecular analysis, DNA was extracted from the isolated third-stage larvae. The NADH dehydrogenase subunit 5 (ND5) and the second internal transcribed spacer region (ITS-2), a portion of the large subunit nuclear ribosomal DNA (28S), a portion of 18S ribosomal rRNA gene (18S), and cytochrome c oxidase subunit 1 gene (COX1) were amplified using polymerase chain reaction (PCR). Excysted third-stage larvae were observed in the lungs, omentum, the pleural cavity, the abdominal cavity, and the surface of the spleen and the pericardium. Around 88 third-stage larvae were isolated from three civet cats. First-stage larvae in the liver were surrounded by outer fibrous layer over the inner germinal layer and filled with clear fluid. Slight hemorrhage, leukocyte infiltration, and mild hepatocellular degeneration in the liver were observed. The SEM examination indicated the unique oral apparatus comprises the oval-shaped mouth opening in between two pairs of curved, retractile hamuli. The sequences obtained for ND5, ITS-2, 28S, 18S, and COX1 were 301, 382, 325, 414, and 644 bp in length respectively. Morphology, sequence similarity search, sequence alignment, and phylogenetic analysis identified this parasite as A. moniliformis.