Thelazia callipaeda in free-ranging brown bears (Ursus arctos) from Romania.

Phortica okadai (Diptera: Steganinae) is the primary vector of the zoonotic eyeworm Thelazia callipaeda (Nematoda: Spirurida). However, standardized laboratory rearing protocols for this vector are still lacking, which limits research on its biology and vector competence. We evaluated the effects of five diets (fermented apple, pear, banana, and two artificial diets) on life history traits of P. okadai using age stage, two sex life table analysis under controlled conditions (28 ± 1°C, 75 ± 5% RH, 14:10h L:D). Life table parameters and population dynamics were analyzed with TWOSEX-MSChart and TIMING-MSChart (100,000 bootstrap replicates). All tested diets supported complete development. Fermented pear yielded the shortest pre adult duration (17.34 days), the highest fecundity (116.6 eggs per female), and the greatest intrinsic rate of increase (r = 0.0902/day). Population projection showed that 10 initial eggs on fermented pear produced more than 1,200 adults within 90 days, which was approximately 10 fold higher than on other diets. Fermented pear is the most suitable substrate for establishing laboratory colonies of P. okadai. These findings facilitate vector competence studies and indicate that pear orchards are potential high risk habitats for T. callipaeda transmission, supporting targeted One Health surveillance and control.

Phortica okadai and Phortica variegata are the primary vectors of the zoonotic eyeworm Thelazia callipaeda, which infects humans and various mammals. Climate change and intensified human activities have altered the potential suitable habitats of these vectors, posing a risk of expanded T. callipaeda transmission. This study aims to predict the current potential suitable habitats and future distribution patterns of the two species, providing a scientific basis for vector-borne disease prevention and control. Species occurrence records were compiled from the Global Biodiversity Information Facility (GBIF; https://www.gbif.org/ ) and systematic literature reviews. The MaxEnt model was utilized to identify key environmental determinants influencing vector distribution. Climate data from WorldClim, future climate scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5), elevation data, and Human Footprint Index (HFP) were integrated to predict potential suitable habitats and future distributions (2041-2060) across China and Europe. The key environmental drivers for P. okadai are warmest quarter precipitation, HFP, and temperature seasonality, and for P. variegata they are HFP, coldest quarter precipitation, and temperature annual range. Currently, the suitable habitats of P. okadai are concentrated in central, eastern, and northeastern coastal China, with only sporadic low-suitability patches recorded in Europe. P. variegata exhibits a wide distribution across the UK, France, Belgium, and Italy, with nearly the entire Mediterranean coastal belt and its associated offshore islands falling within its suitable range. Under future climate scenarios, the suitable area of P. okadai is projected to expand significantly in Central/Western Europe (Italy, Austria, Switzerland, and western Russia). In contrast, the suitable habitats of P. variegata will shift significantly: The central-southern-eastern European transitional belt will lose almost all suitable habitat across scenarios, while the Mediterranean littoral and its offshore islands remain climatically suitable. The suitable area for P. okadai is projected to increase significantly, whereas that for P. variegata is expected to decline. Temperature and precipitation emerge as primary drivers of these contrasting distribution shifts. These findings underscore the need for enhanced vector surveillance and control strategies for T. callipaeda, particularly regarding the expanding P. okadai populations in Europe.

Current understanding of Thelazia callipaeda infection in Japan: Integrating data from humans, companion animals, wildlife, and vectors.

Thelazia callipaeda in Vitreous Cavity after Cataract Surgery.

The oriental eyeworm Thelazia callipaeda has been present in Europe since the late 1980s. Its occurrence in the Carpathian Basin has been known since 2014. Despite the central position of Hungary in the radial expansion of T. callipaeda in Central and Eastern Europe, no comprehensive surveillance has been conducted to date to determine the reservoir role of wild carnivores within the Carpathian Basin. The study involved the analysis of samples from 180 red foxes (Vulpes vulpes), 119 European badgers (Meles meles), 62 golden jackals (Canis aureus), and 10 stone martens (Martes foina) harvested in the framework of an authorised wildlife management programme. Among the mustelids (family Mustelidae), no infected individuals were found. In the red fox, prevalence and mean intensity were 12.2% (95% CI: 8.0–18.0%) and 2.6 (95% CI: 1.7–4.9), respectively; while in the golden jackal, these values were 9.7% (95% CI: 4.3–20.0%) and 3.0 (95% CI: 1.5–6.5), respectively. The difference in prevalence and mean intensity of infection between the two hosts proved non-significant. The generalised linear models suggested that the presence of hygrophilous beech (Fagus sylvatica) forests positively influenced the occurrence of infection in wild carnivores. Although the receiver operating characteristic (ROC) curve analysis showed only a modest discriminatory power for the models, these findings highlighted the potential of humidity in the spread of T. callipaeda in the Carpathian Basin.

Unwelcome guests: Nematodes of zoonotic and animal health importance in native and invasive carnivores of Hungary.

Thelazia callipaeda is a vector-borne parasite infecting the eyes of domestic and wild animals, as well as humans, across Europe. In Spain, it is endemic in several regions, with high prevalence reported in dogs and cats, but data on wildlife remain scarce. This study investigated the prevalence of T. callipaeda in Iberian wolves (Canis lupus signatus) from northwestern Spain and explored epidemiological factors associated with infection. Between 2016 and 2025, 182 wolves from Asturias and Galicia (A Coruña, Lugo, Ourense and Pontevedra) were sampled after necropsy. Eyeworms were collected and identified using morphological and molecular methods, with all specimens corresponding to T. callipaeda genotype h1. The overall prevalence was 17%, with higher rates of infection in Galicia (18.2%) than Asturias (8.7%). Infections were restricted to Ourense (37.2%) and Lugo (26.5%). Parasite burdens were higher in females and immature wolves (1-3 years) compared to older animals and those in good body condition (BC 4-5). The distribution of infected wolves was associated with the vegetation around Miño and Sil river basins, which may favor the development of the vector Phortica variegata. Lower prevalence in pups could be linked to smaller eye size and lower body condition, while sex- and age-related differences may reflect behavioral or immunological factors. These results indicate that Iberian wolves can act as reservoirs of T. callipaeda in northwestern Spain, underscoring the need for further research into their role in the epidemiology of this zoonotic parasite.

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.

Background: The unprecedented scale of global travel has amplified the diagnostic challenge of ocular parasitoses in non-endemic regions. These infections, while rare, can cause severe visual morbidity and are often misdiagnosed. This systematic review synthesizes the current evidence on parasitic eye infections in international travelers to create a comprehensive, state-of-the-art resource for clinicians. Methods: A systematic literature search was conducted in PubMed, Scopus, ProQuest, and the Cochrane Library in accordance with the PRISMA 2020 guidelines. The search included terms for parasitic eye diseases and international travelers. All case reports, case series, and observational studies published in English detailing confirmed ocular parasitic infections in patients with a history of international travel were eligible. Data on demographics, travel, clinical presentation, diagnosis, and management were extracted from all eligible studies, and their methodological quality was assessed using the Joanna Briggs Institute (JBI) checklist. A qualitative narrative synthesis of the findings was performed. Results: From an initial 1,408 records, 19 studies met the full inclusion criteria and were included in the final synthesis. These studies detailed infections from a wide range of helminthic and protozoan pathogens, including Loa loa, Dirofilaria spp., Thelazia callipaeda, Gnathostoma spp., Onchocerca volvulus, Toxoplasma gondii, Trypanosoma cruzi, Acanthamoeba spp., and Taenia solium (cysticercosis). Infections were acquired across Africa, Asia, and the Americas. Clinical presentations were highly diverse, ranging from migrating subconjunctival worms to sight-threatening chorioretinitis, keratitis, and intraocular cysts. Diagnosis consistently relied on a combination of high-magnification biomicroscopy, advanced serological and molecular assays like PCR, and targeted imaging. Management was pathogen-specific, involving microsurgical extraction for accessible helminths and tailored antimicrobial therapy for protozoan and systemic infections. Conclusion: Ocular parasitoses represent a critical diagnostic challenge in returning travelers. A detailed travel and exposure history is the single most important tool to guide the differential diagnosis. Effective management requires a high index of suspicion and a collaborative, interdisciplinary approach to prevent irreversible vision loss.

Thelazia callipaeda is an emerging zoonotic nematode that infects the eyes of domestic and wild mammals across Europe and is transmitted by drosophilid flies of the genus Phortica. Despite increasing reports across the continent, its distribution in wildlife in southeastern Europe remains poorly understood. To our knowledge, this study represents the first comprehensive parasitological and molecular investigation of T. callipaeda in wild carnivores in Croatia. Between 2020 and 2023, a total of 2632 animals, either legally hunted or found dead, were examined. These included 1794 red foxes (Vulpes vulpes), 443 golden jackals (Canis aureus), 180 European badgers (Meles meles), and 215 stone martens (Martes foina). Ocular examination and nematode collection were conducted, followed by morphological identification and COI gene sequencing for species confirmation. The overall prevalence of T. callipaeda infection was 3.9% in red foxes and 4.3% in golden jackals. No infections were detected in badgers or martens. The infections were geographically restricted to continental regions, with the highest prevalence recorded in eastern counties. Seasonal patterns were evident in red foxes, where infection rates and reproductive activity peaked in autumn and winter. In contrast, golden jackals showed more stable infection rates throughout the year. A significant proportion of infections involved gravid females, particularly in jackals (73.7%), suggesting their critical role in sustaining transmission cycles. Molecular analysis confirmed that all isolates belonged to T. callipaeda haplotype 1. These findings highlight the established presence of T. callipaeda in Croatian wildlife and reveal distinct host-specific patterns in prevalence, seasonality, and reproductive dynamics. Red foxes may act as seasonal reservoirs of infection, while golden jackals could serve as year-round reservoirs. Considering the zoonotic potential of this parasite, further surveillance and integrated monitoring of vectors and vertebrate hosts are essential for evaluating future risks to public and veterinary health in the region.

BackgroundThe variegated fruit fly, Phortica variegata (Drosophilidae: Steganinae), is native to Europe and has emerged as a major vector of ocular nematosis caused by Thelazia callipaeda (Rhabditida: Thelaziidae), following the its introduction into Europe from Asia. Male P. variegata transmit these nematodes by feeding on tears of mammals, including wild and domestic carnivores (foxes, beech martens, wild cats, and dogs), lagomorphs, and humans. Understanding the olfactory responses of P. variegata to volatile cues is essential for developing attractant-based surveillance and control strategies, yet its olfactory ecology remains largely unexplored.MethodsWe used gas chromatography coupled electroantennography to measure antennal responses to synthetic and natural volatile blends. A comparative analysis was performed on the antennal responses of both sexes of P. variegata and its well-studied relative, Drosophila melanogaster. Components of the synthetic blends were selected based on the odorant receptor repertoire of D. melanogaster and established mosquito attractants, with the rationale that conserved olfactory receptors among dipterans may allow P. variegata to detect similar compounds. Volatile extracts collected using active carbon adsorbent traps were also tested on the antennae and analyzed using gas chromatography coupled mass spectrometry.ResultsMale P. variegata showed higher antennal responses to phenol, 3-octanone, and sulcatone than females, indicating olfactory sexual dimorphism. Compared to D. melanogaster, the antennae of P. variegata did not respond to several common plant alcohols and terpenoids. Instead, they showed stronger responses to compounds such as anisole, ethyl propanoate, butyl propanoate, propyl acetate, 3-octanone, nonanal, and decanal, suggesting that peripheral olfaction in P. variegata may be more tuned to microbial volatiles.ConclusionsPhortica variegata exhibits sexual dimorphism in olfactory responsivity, with males showing greater responsiveness to volatiles associated with host-seeking in other zoophilic dipterans, potentially guiding them to mammalian hosts for tear-feeding. Compared to D. melanogaster, P. variegata is more responsive to microbial and yeast-related volatiles and less responsive to plant-derived terpenoids, suggesting a foraging ecology linked to microbial substrates. The antennally detected volatiles identified in this study can be used as candidates for further behavioral studies to develop lures for vector management.Graphical

Thelazia callipaeda (T. callipaeda) is a zoonotic ocular parasite that poses a public health risk. Current treatment depends on mechanical parasite extraction and specific prophylactic anthelmintics, but direct ocular deworming agents are limited and expensive, and mechanical removal is often incomplete, causing animal stress and ocular injury. Levamisole eye drops have been applied; however, their efficacy and safety remain undefined. We established a standardized T. callipaeda viability assessment system (TVAS) and an animal infection model to evaluate candidate drugs. In vivo, 5 mg/mL levamisole was administered at escalating frequencies. Ocular symptoms, complete blood count (CBC), and serum biochemistry were measured, and cytotoxicity was assessed using Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays on rabbit conjunctival epithelial cells (RCECs).Four doses of 5 mg/mL levamisole applied at 30 min intervals cleared T. callipaeda from infected eyes within 2 h without significant changes in CBC, serum biochemistry, or ocular symptom scores. CCK-8 and LDH assays indicated minimal cytotoxicity in RCECs within 4 h. However, prolonged exposure (6-12 h) led to a significant decrease in RCEC viability, suggesting potential cytotoxicity with extended use and highlighting the need for further safety evaluation. A regimen of four topical administrations of 5 mg/mL levamisole at 30 min intervals cleared T. callipaeda from infected eyes with minimal cytotoxicity, supporting its safety and efficacy as a topical treatment.

Phortica okadai, a vector of Thelazia callipaeda, is associated with an increasing incidence of thelaziasis. The complex habitat and chemosensory system of P. okadai are critical for its proliferation and expansion. However, ultrastructural data across developmental stages remain limited. This study used scanning electron microscopy to examine the ultrastructure of P. okadai developmental stages, with a focus on head sensilla. The results showed that the eggs of P. okadai are dark brown and cylindro-oval. The larvae are vermiform, divided into 11 segments. The pupae are marked by a conspicuous respiratory tubercle, and the posterior spiracle contains three distinct spiracular slits. Among five types of sensilla (trichoid, intermediate, chaetica, coeloconic, and basiconic), coeloconic, intermediate, and trichoid sensilla were predominantly found on the antennae, while basiconic and chaetica sensilla were distributed on both the antennae and the maxillary palps of P. okadai. The analysis revealed that the absence of dorsal appendages on the eggs distinguishes P. okadai from D. melanogaster. Males have longer antennae and exhibit sexual dimorphism in the length of sensilla (ChII, TB, and LB). This study provides the first comprehensive ultrastructural characterization of P. okadai developmental stages and head sensilla, laying a foundation for species identification and olfactory system research.

Thelazia callipaeda is a spirurid nematode that parasitizes the eyes of mammals, including carnivores, lagomorphs, and humans. Although this parasite has been reported in domestic and wild animals in Japan, its presence in the Japanese marten, Martes melampus melampus (Carnivora: Mustelidae), has not been documented. In this study, we examined the ocular parasites of a wild Japanese marten collected in Tsukuba, Ibaraki Prefecture, Japan, and identified T. callipaeda based on morphological and molecular analyses. This is the first record of T. callipaeda infection in the Japanese marten. Our findings suggest that wild Japanese martens serve as a natural host for T. callipaeda, contributing to its transmission in the sylvatic cycle.

Thelazia callipaeda, azoonotic nematode, primarily infests the ocular tissues of mammals, occasionally humans. Infestations in infants under 1year of age are rarely reported. This case describes an 8‑month-old male infant diagnosed with ocular T.callipaeda infestation in Hubei, China. The infant was brought to the hospital by his mother, who reported that he had been rubbing his right eye for 3days, accompanied by increased ocular discharge and mild tearing. Upon examination, awhitish, motile, thread-like worm was observed in the conjunctival sac of the right eye. During ophthalmological surgical exploration, atotal of 10worms were removed from the right eye, with 8sent for identification. All 8adult nematodes collected were morphologically identified as T.callipaeda, consisting of 4females and 4males. Following the removal of the nematodes, the infant's ocular symptoms rapidly resolved, with no recurrence noted during a2-month follow-up.

Проведено клінічні випробування виробничої серії антигельмінтного препарату ветеринарного призначення «Міпранол для собак» (таблетки, діючі речовини – мілбеміцину оксим та празіквантел) на цільових тваринах (собаки) із метою вивчення терапевтичної і протипаразитарної ефективності та безпечності засобу при лікуванні собак, уражених цестодами – Dipylidium caninum, Taenia spp., Echinococcus spp., Mesocestoides spp.; нематодами – Ancylostoma caninum, Toxocara canis, Toxascaris leonina, Trichuris vulpis, Thelazia callipaeda; Angiostrongylus vasorum, Crenosoma vulpis, Dirofilaria immitis, в тому числі при комбінованих нематодо-цестодозних інвазіях. Дослідження проводили на дорослих собаках (n=170) з клінічно і лабораторно підтвердженою спонтанною інвазією шлунково-кишковими, легеневими паразитами та Thelazia callipaeda і окремо на здорових тваринах (n=12) для визначення профілактичного ефекту препарату проти дирофіляріозу. В результаті досліджень була встановлена висока (100 %) терапевтична ефективність, безпечність та відсутність сторонньої дії препарату на організм собак. Виключенням щодо абсолютної гельмінтоцидної дії засобу були два вида нематод – A. vasorum і Th. callipaeda: при покращенні клінічного стану хворих тварин, інтенсивність інвазії в їх організмі зменшилась до 25,9 і 21,6 % відповідно від початкового рівня. Також підтверджена ефективність антигельмінтика як профілактичного засобу для запобігання захворювання собак дирофіляріозом. Щомісячне застосування «Міпранолу для собак» в період активного льоту кровосисних комах у неблагополучних регіонах убезпечує тварин від розвитку клінічного дирофіляріозу шляхом знищення у крові інокульованих мікрофілярій. Застосування «Міпранолу для собак» (виробництво ТОВ «БРОВАФАРМА»), у рекомендованих дозах і термінах застосування забезпечує достатню нематодо- і цестодоцидну терапевтичну ефективність проти цільових видів гельмінтів собак. Розроблений препарат проявив себе як безпечний антигельмінтний засіб, котрий не спричиняв негативної та сторонньої дії на організм дорослих собак під час та після його перорального застосування.

Thelazia callipaeda (Spirurida, Thelaziidae), a parasitic eye worm causing thelaziasis has been reported in humans and dogs in Korea. However, its occurrence in other potential reservoir hosts, including wild animals, remains unclear. In the present study, we described the 2 cases of thelaziasis from both of feral and captive wild animal in Korea. In August and November 2017, 2 cases of the parasitic infections were found in the third eyelid of rescued leopard cat Prionailurus bengalensis and reared raccoon dog Nyctereutes procyonoides at the Chungnam Wild Animal Rescue Center. A total of 20 and 24 worms were detected from the left and right eyes of leopard cat, respectively. In the left eye of the raccoon dog, 5 worms were recognized. Male worms were 969-11,860 μm long (10,600 μm on average) and 300-320 μm width (315 μm on average). Female worms were 13,430-15,330 (14,480) μm long and 320-370 (344) μm wide in size. They commonly had a characteristic scalariform buccal cavity and short esophagus. The vulva openings were located at the anterior of esophago-intestinal junction in females. The thelaziasis is reported in 2 species of wildlife, P. bengalensis and N. procyonoides, for the first time in Korea.

Thelaziosis in central Italy: Molecular detection of a variant haplotype in a human case and epidemiological aspects

BackgroundThelaziasis is a zoonotic disease mainly caused by Thelazia callipaeda (Spirurida, Thelaziidae, Thelazia), which can cause mild to severe signs and lesions, such as foreign body sensation, itching, tearing, eye pain, conjunctival bleeding, conjunctivitis, corneal ulcers, and even blindness. Thelaziasis cases have been reported mainly in agricultural areas and areas with high potential for contact with domestic animals [1].Case presentationWe report a case of Thelazia callipaeda infection in the right eye of a 41-year-old woman working in an office. The patient presented with persistent foreign body sensation, pruritus, and redness despite initial treatment with polyethylene glycol and levofloxacin eye drops. Subsequent examination revealed the presence of multiple Thelazia callipaeda worms, which were successfully removed. Postoperative treatment with gatifloxacin eye ointment resulted in significant symptom relief with no recurrence over two months.ConclusionsThis case highlights the thelaziasis in urban settings, emphasizing the need for ophthalmologists to consider parasitic infections in differential diagnosis even in well-maintained environments. Then, we provided an overview of human thelaziasis in China by mining publicly available databases from 2014 to 2023, suggesting a difference in regional distribution that warrants further epidemiological studies.