Scanning electron microscopy of digestive tract parasites in jungle cat (Felis chaus).

Among the 10 native cats of Iran, the Felis chaus is considered as one of the largely unknown species. Despite the reports on jungle cats in southeast Iran, there is no comprehensive information about their parasitic diseases. Scanning electron microscope (SEM) provides a valuable tool for the study of these organisms. In October 2022, a 15-year-old male jungle cat (F. chaus) was examined for gastrointestinal parasites using SEM which revealed exact parasite structures such as the mouth, shape of the lips, teeth and their position, papillae, excretory pore, and amphids. SEM of the Taenia taeniaeformis found in the F. chaus intestinal epithelium revealed that this tapeworm consisted of four unarmed suckers and a large armed rostellum. The rostellum was observed bearing double rings of alternating and circular hook arrangements. There were 21 large hooks in the anterior ring and 21 slightly smaller hooks in the posterior one. This study is the first report of Joyeuxiella echinorhyncoides from a jungle cat (F. chaus) in southeastern Iran. The rostellum was cylindrical and armed with thorn shape hooks that covered the whole rostellum with similar density. It was armed with 20-30 long hooks arranged in 16 rows. Four big suckers were visible at the base of the rostellum, two on each side. The suckers were round, and unlike the rostellum, these structures were unarmed. The results of the present study observed under SEM, indicated that organs such as sucker and rostellum in cestodes and mouth and the shape of lips and teeth in nematodes played a significant role in the biology of these helminths. The SEM reveals the surface structures and their relationships which results in better distinguishing the species and showing their detailed differences. More SEM studies need to be conducted on other species of cestodes and nematodes, along with pathological tests, to obtain more comprehensive and precise information about how these parasites harm this jungle cat host. The results of present study indicate that morphological details are important which should be considered in the classification. Meanwhile, external structures described herein using SEM, further investigation using transmission electron microscope provide more data on the biology of the parasites. RESEARCH HIGHLIGHTS: Light microscopy is the first step to identify the parasites. High magnification 3D images of the SEM reveal the surface structures of parasites and their relationships precisely. SEM study of the parasites results in distinguishing the species and showing their detailed differences.

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.

Morphological and molecular characterization of Onchocerca fasciata (Nematoda, Onchocercidae) from dromedary camels (Camelus dromedarius) in 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.