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PubMed2026

Chromosome-Scale Genome of Zoonotic Eyeworm Thelazia callipaeda from China.

Thelazia callipaeda is a vector-borne zoonotic eyeworm infecting companion animals, wildlife, and humans, but chromosome-scale genomic resources from Chinese clinical material remain limited. We generated a genome supported by Pacific Biosciences (PacBio) high-fidelity (HiFi) sequencing and high-throughput chromosome conformation capture (Hi-C) from 100 adult worms recovered from naturally infected dogs in Beijing and compared its chromosome-scale organization with Portuguese assembly GCA_965194785.1. The final assembly spans 119.53 megabases (Mb) and comprises 115 top-level sequences, including four pseudomolecules totaling 91.26 Mb (76.34%) and 111 unanchored sequences. Genome-mode Benchmarking Universal Single-Copy Orthologs (BUSCO) analysis recovered 98.5% complete chromadorean orthologues, and the representative 11,788-protein gene set recovered 92.6%. Sequence-level alignment resolved Chinese chromosomes 1-4 (chr1-chr4) to Portuguese chr1, chrX, chr3, and chr2, respectively, with retained alignments covering 95.9-99.2% of each Chinese pseudomolecule and estimated sequence identities of 99.75-99.91%. Strong chromosome-scale collinearity was accompanied by localized reverse-collinear regions, including 0.243 Mb and 0.115 Mb intervals on chr2-chrX and chr3-chr3. The anchored sequences contained 96.7% of predicted genes and were substantially more gene-dense than the unanchored sequences. These results establish a clinically sourced Chinese chromosome-scale reference and provide a validated framework for future individual-worm, population-genomic, structural-variation, and comparative genomic studies of this parasite.

Hi-C↗
PubMed1995

Two human cases of Thelazia callipaeda infection in Korea.

Thelazia callipaeda were observed from a 7-month old baby who lived in Uijongbu in 1989 and from a 42-year old man who lived in Anyang in 1994. These are the 23rd and 24th records of human thelaziasis in Korea as the literature are concerned.

Adult↗
PubMed1998

Conjunctivitis caused by Thelazia callipaeda infestation in a woman.

Thelazia is a nematode (Spirurida) that can parasitize the mammalian conjunctival sac. This is the first reported case of ocular. Thelazia callipaeda infestation in Taiwan. A 41-year-old woman experienced swelling, itching sensation and occasional blurred vision of the right eye 2 weeks after a small group of flies swarmed her eye while she was hiking. Her symptoms were first misdiagnosed as allergic conjunctivitis at a local medical clinic. During her first visit to our outpatient department, five white thread-like living worms were discovered on the superior and inferior fornices. The worms were cream-colored, slender and approximately 1 cm in length. Follicular and papillary conjunctivitis was noted in her right eye. After removing the worms, the symptoms resolved and no other worms were found in the following 2 months. This case is a remainder to physicians that parasitic infestation should be included in the differential diagnoses of ocular itching, conjunctivities, and blurred vision after insect contact.

Adult↗
PubMed2005

Musca domestica is not a vector of Thelazia callipaeda in experimental or natural conditions.

Thelazia callipaeda Railliet and Henry (Spirurida: Thelaziidae), commonly called oriental eyeworm for its widespread presence in the Far East, has been recently found to affect dogs, cats and foxes in northern and southern Italy. Although the biology of T. callipaeda in the definitive hosts has been recently investigated, many doubts still remain about its biology in insect vectors. It has been suggested that more than one species of Diptera, namely Musca domestica Linnaeus (Diptera: Muscidae) and Amiota okadai Maca (Diptera: Drosophilidae), may be involved in the transmission of T. callipaeda in China. The aim of the work described here was to verify the role of M. domestica as a vector of T. callipaeda both in experimental and natural conditions. A total of 310 m. domestica (Group 1) were put in a cage and allowed to feed for 14 days around the eyes of a dog naturally infected by T. callipaeda. Ten flies were collected daily for 14 days. A total of 149 houseflies (Group 2) were fed with T. callipaeda first stage larvae (L1) and dissected at 1, 2 and 7 days post-infection. From June to August 2003, flies were netted (Group 3) in two different sites every 10 days both from the environment and directly from the periocular region of dogs affected by thelaziosis. Musca flies were examined for eyeworms by dissection and visual inspection of house flies (Groups 1 and 2) and using a molecular approach (Groups 1-3) via a specific amplification of the ribosomal internal transcribed spacer 1 (ITS1) sequence of T. callipaeda. On the whole, 180 pools of M. domestica flies were processed molecularly and all the experimentally infected flies (Groups 1 and 2) were found to be negative both at the visual dissection and at the molecular assay. Similarly, the 234 M. domestica collected from Group 3 were negative for T. callipaeda. The results clearly suggest that M. domestica is unlikely to act as a vector of T. callipaeda in southern Europe, in contrast with a single previous report.

Animals↗
PubMed2002

Enzooticity of the dogs, the reservoir host of Thelazia callipaeda, in Korea.

The reservoir hosts of Thelazia callipaeda were examined. The eyes of the 76 dogs raised at farm. 78 military dogs (shepherds), 96 cattle, and 105 pigs were investigated for the presence of eyeworm. Among them, six worms of T. callipaeda were collected from two dogs raised at farm (2.7%), and 188 worms from 26 shepherds (33.5%). No worms were recovered from the cattle or pigs. These results suggest that the dogs, especially the military dogs are serving as a reservoir host of T. callipaeda in Korea.

Animals↗
PubMed2026

The genome sequence of a nematode, Thelazia callipaeda Railliet & Henry, 1910 (Rhabditida: Thelaziidae).

We present a genome assembly of Thelazia callipaeda (nematode; Nematoda; Chromadorea; Rhabditida; Thelaziidae). The genome sequence has a total length of 117.59 megabases. Most of the assembly (75.82%) is scaffolded into 4 chromosomal pseudomolecules, including the X sex chromosome. The mitochondrial genome has been assembled, with a length of 13.66 kilobases.

Thelazia callipaeda; nematode; genome sequence; ch↗
PubMed2004

Biology of Thelazia callipaeda (Spirurida, Thelaziidae) eyeworms in naturally infected definitive hosts.

Thelazia callipaeda (Spirurida, Thelaziidae) eyeworm causes ocular infection in carnivores and humans in the Far East; this infection has been recently reported also in Europe--northern and southern Italy--in dogs, cats and foxes. The natural vector/s of T. callipaeda is/are unknown and the development of the nematode in its definitive hosts is limited to an experimental trial on dogs. To contribute new insights into the development of T. callipaeda in the definitive host in field conditions, eyeworms were collected from naturally infected dogs from an area with a high prevalence of infection (up to 60.14%) in the Basilicata region of southern Italy, from January 2002 to December 2003. Conjunctival secretions were also collected and examined for the presence of immature stages. The presence of blastomerized eggs throughout the period--except for the months from May to November--indicates a seasonality in the reproductive activity of T. callipaeda, coinciding with the presence/absence of the vector. In fact, 1st-stage larvae were found in the lachrymal secretions of dogs in summer (June--July 2002 and 2003), ready to be ingested by flies feeding about the eyes. The evidence of 4th-stage larvae in March 2002 and April, July and October 2003 may be accounted for by the presence of flies that act as intermediate hosts of T. callipaeda from early spring to early autumn. The presence of immature stages in October indicates an overlapping generation of nematodes and a 2nd cycle of vector infection. This basic knowledge of the development of T. callipaeda will hopefully help future epidemiological studies to identify the intermediate hosts and define the likely risk for vectors in field conditions.

Animals↗
PubMed2006

First Thelazia callipaeda infestation report in a dog in Taiwan.

An ocular Thelazia callipaeda infestation was found in a male domestic dog in Taiwan during regular examination. This is the first report of the parasite from pet animal in Taiwan. The infested dog showed normal bodily condition but slight conjunctival congestion. This parasite has been reported in humans in southeast Asia, China and Korea. In 1998, first human case was reported in the central area of Taiwan. The dogs infected with T. callipaeda may have important implication in the infestation of this parasite to humans as reservoir hosts.

Animals↗
PubMed2005

Nematode biology and larval development of Thelazia callipaeda (Spirurida, Thelaziidae) in the drosophilid intermediate host in Europe and China.

Thelazia callipaeda, commonly known as the 'oriental eyeworm', has been recently reported in Italy and other European countries. The insect/s that act as intermediate hosts and details of larval development inside the vector remain unclear. In order to (1) demonstrate the species of fly that may act as vector/s for T. callipaeda in southern Italy (Site A) and China (Site B) and (2) describe the larval development of the nematode in the body of flies, 847 Phortica (Drosophilidae) flies were collected from the above two sites, each with a history of human and/or canine thelaziosis. Flies were identified as Phortica variegata (245 - site A) and Phortica okadai (602 - site B), experimentally infected by 1st-stage larvae (L1), kept at different temperatures and dissected daily until day 180 post-infection (p.i.). Dead flies from site A were subjected to specific polymerase chain reaction (PCR) assay to detect T. callipaeda. To demonstrate the role of Phortica as vectors of T. callipaeda, 3rd-stage larvae (L3) recovered from the proboscis of flies were deposited onto the cornea of the eyes of dogs and rabbits. Following dissection, 3 (2.9%) of P. variegata in site A were found to be infected by L3 in the proboscis on days +14, +21 and +53 p.i., compared with 26 (18.4%) of Phortica flies recorded as being positive by PCR. Sequences from positive PCR products were 99% identical to sequences of the corresponding species available in GenBank (AY207464). At site B, 106 (17.6%) of 602 dissected P. okadai were found to be infected by T. callipaeda larvae (different stages) and in total 62 L3 were recovered from the proboscis of 34 (5.6%) flies. The shortest time in which L3 were found was at day +14, +17, +19, and +50 p.i. respectively, depending on the environmental temperatures. Of 30 flies overwintered for 6 months, 6 L3 were detected at day +180 p.i. in 3 flies (10%). The biology of larval development was reconstructed on the basis of the dissection of 602 P. okadai-infected flies and the morphology of larval stages in the insect body described. The present work provides evidence that P. variegata and P. okadai act as vectors for T. callipaeda in southern Europe and in China, respectively. The phenomenon of overwintering is described here for the first time for T. callipaeda and discussed. Finally, the relationship between T. callipaeda and its fly vector is considered in light of disease prophylaxis and to model its dissemination into habitats and environments favourable to Phortica flies.

Animals↗
PubMed2003

Thelazia callipaeda (Spirurida, Thelaziidae) of carnivores and humans: morphological study by light and scanning electron microscopy.

Thelazia nematodes cause ocular infection in several mammals and are transmitted by dipteran flies. Thelazia callipaeda Railliet and Henry 1910 (Spirurida, Thelaziidae) is common in the Far East, where it causes eyeworm infection in carnivores and humans. In the past few years, it has also been reported in dogs, cats and foxes in Northern and Southern Italy. Although a great deal of work has been carried out in China and other Eastern countries, knowledge of the morphology of T. callipaeda is scanty. Eighty-three nematodes collected from the eyes of naturally infected dogs from the Basilicata region (southern Italy) were examined by light and scanning electron microscopy, and the most important features of the nematodes were described. The morphological characteristics useful for the identification of T. callipaeda are discussed.

Animals↗
PubMed2005

Treatment of dog thelaziosis caused by Thelazia callipaeda (Spirurida, Thelaziidae) using a topical formulation of imidacloprid 10% and moxidectin 2.5%.

Canine thelaziosis caused by Thelazia callipaeda infects dogs, cats, foxes, rabbits, and humans resulting in conjunctivitis, pain and excessive lacrimation. T. callipaeda live in the eyes under the nictitating membrane and females release first stage larvae which are ingested by flies which act as intermediate hosts. Control of canine thelaziosis is currently based on the removal of nematodes directly from the eyes of affected dogs or on the local instillation of antiparasitic drugs. With the aim of evaluating the efficacy against T. callipaeda of an association of imidacloprid 10% and moxidectin 2.5% by spot-on formulation administered via dermal application, three groups of naturally infected animals were selected: i.e. group A (21 dogs) received a single dose of imidacloprid 10% and moxidectin 2.5% by spot-on; group B (21 dogs) received a single dose of imidacloprid 10% by spot-on and group C (20 dogs) were left untreated. The efficacy of treatments was established by eye inspection and parasite viability and vitality after 1, 5 and 9 days after animal treatments (groups A and B) and after 9 days only in untreated animals (group C). Imidacloprid 10% and moxidectin 2.5% in spot-on formulation showed to be effective with regards the control of dog thelaziosis within 5 (90.47%) to 9 (95.23%) days after treatment. Only one dog from group A presented nematodes after treatment. The presence of parasites in the eyes of dogs from groups B (imidacloprid 10%) and C confirm that the anthelmintic efficacy against T. callipaeda in animal from group A (imidacloprid 10% and moxidectin 2.5%) was most likely attributable to moxidectin 2.5%. The spot-on formulation containing imidacloprid 10% and moxidectin 2.5% is very easy to apply and helps overcome problems linked to the mechanical removal of parasites or to the restraining of the animals for the local instillation of drugs in the eyes.

Administration, Topical↗
PubMed2003

[Longitudinal investigation and experimental studies on thelaziasis and the intermediate host of Thelazia callipaeda in Guanghua county of Hubei province].

OBJECTIVE: To verify houseflies Musca spp. as the intermediate host of Thelazia callipaeda and reveal epidemiological situation of thelaziasis in Hubei province. METHODS: Dogs eyes infected with T. callipaeda, 400 houseflies Musca and 259 fruitflies Amiota okadai in the city of Laohekou city (previously named as Guanghua county) of Hubei province had been investigated since September 2000. The newborn larvae of T. callipaeda from Laohekou suburbs were fed to houseflies Musca and A. okadai. Larvae used for the study were isolated from female T. callipaeda in laboratory and the susceptibility to houseflies Musca and A. okadai was observed. RESULTS: Twenty-one dogs from Laohekou, the original epidemic areas of thelaziasis were examined and 7 positive dogs in 21 (33.3%) and 11 T. callipaeda (9 females and 2 males) were identified. From 1975 to 2000, no thelaziasis cases were found through retrospective surveys. These 200 houseflies Musca and 135 A. okadai were dissected for examination but showed all negative with the infection. However, newborn larvae of T. callipaeda were used to experimentally infect 112 houseflies Musca and 84 A. okadai and all infected flies were examined on the 20th day after inoculation. As a consequence, houseflies Musca failed to be infected but 9 in 84 (10.7%) A. okadai were positive. 26 infective larvae of T. callipaeda were obtained and 21 of them were inoculated into right eye of one rabbit. The female worm began to produce newborn larvae in 37 days after infection and 3 adult T. callipaeda (two females and one male) were obtained. CONCLUSIONS: Fruitflies A. okadai from Hubei province were susceptible to T. callipaeda, which was similar to the result of experimental studies in Anhui province. This survey further confirmed that A. okadai was the intermediate host of T. callipaeda but not houseflies Musca. Infective resources (adult dogs, for instance) had been under controlled thus human thelaziasis had been eradicated in this rural area.

Animals↗
PubMed2003

Current status and epidemiological observation of Thelazia callipaeda (Spirurida, Thelaziidae) in dogs, cats and foxes in Italy: a "coincidence" or a parasitic disease of the Old Continent?

Thelazia callipaeda is a spirurid nematode which causes ocular infections in dogs and man and, occasionally, in cats, foxes and rabbits. The intermediate host and vector of T. callipaeda is unknown. For a long time T. callipaeda incidence was reported only from the Russian Federation and the Far East, but recently it has also been found in Italy. In order to investigate the spread of T. callipaeda in Italy, a survey was carried out in two sites, site A in the Piedmont region (North West Italy), and site B in the Basilicata region (Southern Italy). Dogs, cats and foxes in site A and dogs in site B were examined for eyeworms, using different procedures and timing. From January 1995 to August 2002, 91 dogs, 4 cats and 903 fox carcasses were examined in site A, and from October 1999 to January 2003, 443 dogs were examined in site B, and the eyeworms collected were identified using morphological keys. Twenty-one (23.07%) and 185 (41.76%) of the dogs from sites A and B, respectively, were found to be infected by eyeworms; furthermore, all the cats examined and 46 fox carcasses (5.1%) were positive for eyeworms. All the nematodes collected were identified as T. callipaeda. These results indicate that T. callipaeda is not confined to Eastern Europe and Asia, but that it has spread to the Old Continent, and to both Northern and Southern Italy. Considering the high prevalence of infected dogs reported in some municipalities (e.g. 60.14% of 138 dogs examined in a municipality from site B), it is assumed that one or more vectors are significantly present in the areas under investigation. Furthermore, there is good reason to believe that T. callipaeda is also present in other European countries. Speculation as to the origins of this parasitic infestation in Europe and the biology of T. callipaeda and its vector/s is also discussed.

Animals↗
PubMed1989

Scanning electron microscopic observations of Thelazia callipaeda from human.

Four females and a male nematode isolated from 2 patients who visited eye clinics in Seoul were identified as Thelazia callipaeda and their ultrastructures were observed by scanning electron microscopy (SEM). General features of the worms were slender and attenuated at both ends. Vaginal opening was located at 0.27 mm from the anterior end, and in front of the esophago-intestinal junction. In the body cuticle transverse striations varied characteristically through the body. The number of cuticular transverse striations was 400-650/mm at head portion, 250/mm at middle portion and 300-350/mm at tail portion. The SEM observation of the mouth part of the females showed 6 cord-like cuticular thickenings in hexagonal arrangement and an amphid was observed. A lateral line, a vaginal opening, a pair of phasmids, and an anus were identified in the body portion. A pair of papillae and 6 cord-like cuticular thickenings were on the mouth part of the male. It was difficult to observe structures at the tail of the male except wrinkle-like structures. Most of the larvae isolated from the uterus of a female worm were sheathed and thus cuticular striations were not seen. Others were un-sheathed and revealed cuticular striations. The oval membrane which encysted sheathed larvae was also observed. These are the 18th and 19th record of human thelaziasis in Korea as the literature are concerned.

Animals↗
PubMed2006

Phortica variegata as an intermediate host of Thelazia callipaeda under natural conditions: evidence for pathogen transmission by a male arthropod vector.

Knowledge about Phortica variegata (Drosophilidae, Steganinae), the intermediate host of the eyeworm Thelazia callipaeda (Spirurida, Thelaziidae), is confined to experimental studies. To investigate the role P. variegata plays in the transmission of T. callipaeda under natural conditions, the population dynamics of these flies in the natural environment and their feeding preferences (on vegetables and/or animal lachrymal secretions) were examined. From April to November 2005, a total number of 969 (557 males and 412 females) P. variegata flies were collected weekly in a region of southern Italy with a history of canine thelaziosis. The flies were identified and dissected or subjected to a PCR assay specific for a region within the ribosomal ITS-1 DNA of T. callipaeda. The zoophilic preferences of P. variegata were assessed by collecting flies around the eyes of a person or around a fruit bait. Seven hundred and twenty flies (398 males and 322 females) were dissected under a stereomicroscope; 249 flies (158 males and 91 females) that died prior to the dissection were subjected to molecular investigation. Only P. variegata males were infected with larval T. callipaeda both at dissection (six, 0.83%) and with the specific PCR (seven, 2.81%), representing a total percentage of 1.34% flies infected. Interestingly, only males were collected around the eyes, compared with a male/female ratio of 1:4 around the fruit. This survey indicated that P. variegata males act as intermediate hosts of T. callipaeda under natural conditions in Europe. Both the zoophilic behaviour of P. variegata males on lachrymal secretions and their role as vector of T. callipaeda have been discussed as they represent a peculiarity in medical and veterinary entomology. The synchrony between the fly population dynamics and the biology of the nematode in the definitive host provides an interesting model for exploring the co-evolution of Thelazia spp. with their hosts.

Animals↗
PubMedDate not supplied

Presence of Thelazia callipaeda Railliet & Henry, 1910, in Piedmont, Italy.

A sample of 314 dogs from a zone of 80,000 ha in Piedmont, Italy, were examined for the presence of thelaziae under the nictitating membrane. Sixteen animals from eight districts were infected, the foothills being the main location of the parasitosis. All 44 nematodes collected were identified as Thelazia callipaeda.

Animals↗
PubMed2005

Analysis of genetic variability within Thelazia callipaeda (Nematoda: Thelazioidea) from Europe and Asia by sequencing and mutation scanning of the mitochondrial cytochrome c oxidase subunit 1 gene.

This study investigated genetic variability within the 'eyeworm'Thelazia callipaeda (Nematoda: Thelazioidea) from Europe and Asia by polymerase chain reaction (PCR)-coupled sequencing and mutation scanning of the mitochondrial cytochrome c oxidase subunit 1 gene (cox 1). Eight different sequence variants of cox 1 (haplotypes) were determined for the 50 individual adult specimens of T. callipaeda (from dogs, foxes or cats from Italy, Germany and the Netherlands and from dogs from China and Korea). Nucleotide variation (0.3--2%) was detected at 23 of 649 positions in the cox 1. Six of these positions were invariable among all 37 individuals from Europe and among the 13 individuals from Asia (irrespective of host origin) but differed (five G<-->A and one C<-->T changes) between Europe and Asia. PCR-based single-strand conformation polymorphism (SSCP) analysis of the most variable portion (v-cox 1) of the cox 1 was validated (for a subset of samples) as a tool to rapidly screen for genetic (haplotypic) variability. The results for the SSCP analysis and sequencing were concordant, indicating that the mutation scanning approach provides a useful tool for investigating the population genetics and molecular ecology of T. callipaeda.

Animals↗