Caractérisation morphologique et moléculaire d’Onchocerca fasciata (Nematoda, Onchocercidae) de dromadaires (Camelus dromedarius) en Iran

Skin nodules of Onchocerca fasciata Railliet and Henry, 1910 (Spirurida, Onchocercidae) are a common finding in dromedary camels, though with a minimal clinical impact. There is little information about the morphology, molecular make-up and pathological impact of this parasite. Onchocerca fasciata nodules (1.3-2.1 cm in diameter and 509-841 mg in weight) were detected on the neck region in 31.5% of dromedary camels examined in Kerman province, southeastern Iran. Of 38 isolated nodules, only 23 (60.5%) contained viable worms. Measurement and morphological analyses were performed on isolated female worms by light microscopy. The identification of O. fasciata specimens was confirmed by sequence analysis of two mitochondrial genes (12S rDNA and cox1), which showed 0.4% divergence from available O. fasciata sequences. In addition, a phylogeny of filarial nematodes was constructed, based on these two mitochondrial genes and five nuclear genes (18S rDNA, 28S rDNA, MyoHC, rbp1, hsp70); this indicated that O. fasciata belongs to clade ONC3 of Onchocercidae, with representatives of the genera Onchocerca and Dirofilaria. Within the genus Onchocerca, O. fasciata is grouped with bovine parasitic species and the human parasitic Onchocerca volvulus, which suggests an impact of domestication on the radiation of the genus. Data provided here on the distribution and morphology of O. fasciata contribute to the molecular identification and phylogenetic position of the species

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 flarial 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, microflariae 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 fxed, sectioned and stained with hematoxylin and eosin for histo‑ pathology. Skin microflariae that were isolated from tissues surrounding the nodules were confrmed 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. Discontinu‑ ous 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 microflariae with a rounded anterior extremity measured 210.7×2.5 μm on average. Developed eggs containing microflariae measured 35.9×31.0 μm and their smooth shell surface had characteristic tongue-like appendages. In addition to infammatory 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. Measure‑ ments of the main morphological features of microflariae and eggs, and the shape index of ridges (height/width) in female nematodes are described for the frst tim