Morphological differentiation among three Thelazia species (Nematoda: Thelaziidae) by scanning electron microscopy

Thelazia species (eyeworms) infection in cattle: Prevalence, species diversity, seasonal dynamics and its ocular effects in South Gondar zone, Northwest Ethiopia

Thelaziasis is a neglected vector-borne disease widely distributed throughout the world and is responsible for severe economic losses in cattle. The disease is caused by parasitic nematodes of the genus Thelazia (Spirurida, Thelaziidae). So far, limited attention has been given to ungulate-associated Thelazia species though it is a highly prevalent disease that raises concerns for animal welfare and potential economic impacts. A cross sectional study was carried out between August 2023 to July 2024 in the South Gondar Zone of Northwest Ethiopia, aiming to estimate the prevalence, investigate the seasonal dynamics, identify the species involved, demonstrate the ocular effects, and to assess the potential risk factors associated with the occurrence of thelaziasis in cattle. A multistage sampling technique was employed to select study animals. Data analysis was performed with logistic regression using SPSS software version 27.0. A total of 690 cattle were examined, of which 165 tested positive for Thelazia, resulting in an overall prevalence of 23.9 % (95 % CI: 20.7-27.2). Thelazia rhodesi and Thelazia gulosa were the identified species infecting cattle. Sex, body condition score and district of cattle were not associated with the occurrence of thelaziasis (p > 0.05). However, age, breed, management and season had influenced the occurrence of parasitosis (p < 0.05). Adult cattle (30.6 %), local breed (26.9 %), and extensive management system (29.8 %) categories have demonstrated higher infection rates than young (15.3 %), crossbreed (16.5 %), and semi-intensive management system (10.5 %). The occurrence of infection showed apparent seasonality (p < 0.001) with the maximum prevalence appeared in autumn (39.7 %). Ocular lesions such as lacrimation, conjunctivitis and ulceration were detected in 142 (20.6 %) of examined cattle, and the occurrence of ocular lesions exhibited significant association with the prevalence of parasitosis (p < 0.001). The occurrence of Thelazia species with high prevalence in the study area alarms the significance of incorporating this parasite in the differential diagnosis of eye diseases in cattle, especially when adults affected in areas with free grazing management system.

Diversity of Thelazia spp. in domestic cattle from Romania: epidemiology and molecular diagnosis by a novel multiplex PCR

BACKGROUND

Thelaziosis is a neglected vector-borne disease caused by parasitic nematode worms of the genus Thelazia which affects various hosts. Limited attention has been given to ungulate-associated Thelazia species. Current diagnosis of thelaziosis and the identification/differentiation of species heavily relies on morphological features. Therefore, we conducted an epidemiological study in Romanian cattle, with the aim to obtain morphological and molecular data that can be used for species identification.

METHODS

The eyes of 705 slaughtered cattle were sampled and subjected to morphological identification, morphometric analysis, and molecular characterization. PCR amplification and sequence analysis were performed based on the cytochromec oxidase subunit 1 (COI) gene. Statistical tests assessed the correlations between infection parameters and ecological or biogeographical factors. A novel PCR method was developed based on the consensus sequence from each species. Specific forward primers were designed for each of the three species, and a reverse primer (COIintR) was used for all reactions. A consensus thermal profile was established by gradient PCR amplification of each species separately.

RESULTS

Of the sampled cattle, 19.3% were infected with Thelazia spp. Prevalence varied significantly with ecogeographical factors. A total of 585 Thelazia nematodes were recovered, with T. rhodesi being the most abundant, followed by T. skrjabini and T. gulosa. Morphometric and molecular analyses supported the morphological identification, yielding unique sequences for each species. From the 59 T. rhodesi specimens sequenced, 29 unique sequences were obtained, with a 99.1-99.85% nucleotide identity to the only other COI sequence present in GenBank®. All nine T. gulosa isolates were unique (99.37-100% nucleotide identity to other sequences), while T. skrjabini specimens displayed 98.47-100% nucleotide identity to the sole available sequence.

CONCLUSIONS

Bovine thelaziosis is prevalent in Romania, raising concerns for animal welfare and potential economic impacts. Infected cattle grazing alongside vulnerable wild ruminants, such as the European bison, may affect conservation efforts. Our newly developed multiplex PCR shows promise as a valuable surveillance tool, enabling the detection of occult infections in apparently healthy animals through lachrymal secretion testing.

The Nematodes Thelazia gulosa Railiet and Henry, 1910 and Thelazia skrjabini Erschov, 1928 as a Cause of Blindness in European Bison (Bison bonasus) in Poland

PURPOSE

The nematodes of the genus Thelazia are the cause of eye diseases of wild and domestic ruminants throughout the world. The aim of the study was to describe clinical cases of thelasiosis in European bison (Bison bonasus) in Poland, and provide morphometrical features of Thelazia gulosa Railiet and Henry, 1910 and Thelazia skrjabini Erschov, 1928 regarded as potentially useful for species differentiation METHODS: The conjunctival sacs, tear ducts, the surface of the cornea and nicitating membrane collected from bison were rinsed with saline solution. Any nematodes isolated from the sediment were subjected to morphometric analysis.

RESULTS

Thirteen of the 16 examined European bison were infected with Thelazia nematodes, belonging to the species T. gulosa and T. skrjabini. The intensity of infection ranged from one to six (mean intensity 5), and four to 29 (mean intensity 14) nematodes T. skrjabini and T. gulosa respectively. Congestion of conjunctival sac, keratitis and corneal opacity, corneal ulceration and perforation as well as purulent eyeball inflammation were observed in infected animals.

CONCLUSIONS

Thelazia gulosa and T. skrjabini can be identified by morphometrical features. As thelasiosis might be a serious threat for protected population of European bison, further studies are needed of the epidemiology and pathology of this emerging parasitosis in Poland.

Parasitic diseases of equids in Iran (1931-2020): a literature review

Parasitic infections can cause many respiratory, digestive and other diseases and contribute to some performance conditions in equids. However, knowledge on the biodiversity of parasites of equids in Iran is still limited. The present review covers all the information about parasitic diseases of horses, donkeys, mules and wild asses in Iran published as articles in Iranian and international journals, dissertations and congress papers from 1931 to July 2020. Parasites so far described in Iranian equids include species of 9 genera of the Protozoa (Trypanosoma, Giardia, Eimeria, Klossiella, Cryptosporidium, Toxoplasma, Neospora, Theileria and Babesia), 50 helminth species from the digestive system (i.e., 2 trematodes, 3 cestodes and 37 nematodes) and from other organs (i.e., Schistosoma turkestanica, Echinococcus granulosus, Dictyocaulus arnfieldi, Parafilaria multipapillosa, Setaria equina and 3 Onchocerca spp.). Furthermore, 16 species of hard ticks, 3 mite species causing mange, 2 lice species, and larvae of 4 Gastrophilus species and Hippobosca equina have been reported from equids in Iran. Archeoparasitological findings in coprolites of equids include Fasciola hepatica, Oxyuris equi, Anoplocephala spp. and intestinal strongyles. Parasitic diseases are important issues in terms of animal welfare, economics and public health; however, parasites and parasitic diseases of equines have not received adequate attention compared with ruminants and camels in Iran. The present review highlights the knowledge gaps related to equines about the presence, species, genotypes and subtypes of Neospora hughesi, Sarcocystis spp., Trichinella spp., Cryptosporidium spp., Giardia duodenalis, Blastocystis and microsporidia. Identification of ticks vectoring pathogenic parasites, bacteria and viruses has received little attention, too. The efficacy of common horse wormers also needs to be evaluated systematically.

Case Report: Conjunctival Infestation with Thelazia gulosa: A Novel Agent of Human Thelaziasis in the United States

We report a case of thelaziasis in a 26-year-old female, acquired in Oregon. A total of 14 worms were removed from the patient's left eye and were morphologically identified as being Thelazia gulosa. Until now, only two species of Thelazia have been implicated in causing human disease, Thelazia callipaeda in Asia and Europe and occasional reports of Thelazia californiensis from the United States of America. Here, we describe a third, previously unreported parasite of humans, T. gulosa (the cattle eyeworm) as an agent of human thelaziasis and the first reported case of human thelaziasis in North America in over two decades.

Ultrastructural characterization of male and female Physaloptera rara (Spirurida: Physalopteridae): feline stomach worms

Physaloptera rara (Spirurida: Physalopteridae) has been found in dogs, coyotes, raccoons, wolves, foxes, cats, and bobcats in North America. The parasites' developmental cycles involve insects, including beetles, cockroaches, and crickets, as intermediate hosts. The nematodes firmly attach to the wall of the stomach and duodenum, where they feed on the mucosa and suck blood. Frequent movement of these nematodes results in erosions and ulcers in the gastrointestinal tract. The present study reports the morphological features of adult P. rara using scanning electron microscopy. Adult worms were removed from the stomach of an infected domestic cat. Male and female worms measured 25-29 and 27-41 mm, respectively. The worms were stout and the cuticle was reflected over the lips to form a large cephalic collarette with fine transverse striations. The worms possessed two large, simple triangular lateral pseudolabia, each armed with one external tooth, three internal teeth, two submedian cephalic papillae, an amphid, and three porous-like circumscribed regions. The internal margins of the lips had a pair of cuticular folds. At the anterior end of both male and female worms, an excretory pore was located on the ventral side and a pair of lateral ciliated cervical papillae was seen. The vulva was anterior to the middle of the body of female worms. The tail ends of the female worms were stumpy, with two large phasmids near their extremities. The males' tails bore large lateral alae. Ventral ornamentation, in male worms, was composed of three different cuticular patterns; coblestone-like formations, longitudinal cuticular ridges, and rows of bead-like structures. The spicules were unequal and dissimilar; the right spicule had a thick end and the left spicule had a sharp tip. At the posterior end of the males, four pairs of stalked precloacal papillae, three pairs of postcloacal papillae, and two phasmids were present. Three and four sessile papillae were seen directly anterior and posterior to the cloaca, respectively. The middle papilla of the three sessile papillae, directly anterior to cloaca was different in shape and size.

Local transmission of the eye worm Thelazia callipaeda in southern Germany

This report describes the first assumed locally transmitted case of the eye worm Thelazia callipaeda in a dog living in southern Germany. A 4-year-old male golden retriever from the town of Bühl in north eastern Baden-Württemberg, about 10 km from the German-French border, showed one sided lacrimation for over 2 weeks. Despite the application of antibiotics, there was no improvement, and the dog additionally showed blepharospasmus, epiphora and red conjunctivas. A deepened eye inspection revealed five whitish filiform parasites that were morphologically identified as T. callipaeda. The partial sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1, 605 bp) from one specimen revealed a novel haplotype, which differs by 1.3% from the only one (haplotype 1) identified in Europe so far. Since the infected dog had never been abroad with the exception of two daytrips to the close Alsace region in France, the transmission of T. callipaeda most probably was domestic. With the presence of end hosts and Phortica flies nourishing on lachrymal secretions acting as intermediate hosts and an increasing number of dogs travelling to and coming from endemic regions in the South, the establishment of T. callipaeda in large parts of Europe cannot be excluded.

Local transmission of the eye worm Thelazia callipaeda in southern Germany

This report describes the first assumed locally transmitted case of the eye worm Thelazia callipaeda in a dog living in southern Germany. A 4-year-old male golden retriever from the town of Bühl in north eastern Baden-Württemberg, about 10 km from the German-French border, showed one sided lacrimation for over 2 weeks. Despite the application of antibiotics, there was no improvement, and the dog additionally showed blepharospasmus, epiphora and red conjunctivas. A deepened eye inspection revealed five whitish filiform parasites that were morphologically identified as T. callipaeda. The partial sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1, 605 bp) from one specimen revealed a novel haplotype, which differs by 1.3% from the only one (haplotype 1) identified in Europe so far. Since the infected dog had never been abroad with the exception of two daytrips to the close Alsace region in France, the transmission of T. callipaeda most probably was domestic. With the presence of end hosts and Phortica flies nourishing on lachrymal secretions acting as intermediate hosts and an increasing number of dogs travelling to and coming from endemic regions in the South, the establishment of T. callipaeda in large parts of Europe cannot be excluded.