Thelazia callipaeda in mustelids from Romania with the European badger, Meles meles, as a new host for this parasite

Thelazia callipaeda as a potential new threat to european wildcats: insights from an eco-epidemiological study

Global warming and displacement of vectors and wild and domestic hosts by humans greatly change host-parasite interactions and parasite transmission rates. Thelazia callipaeda Railliet and Henry, 1910 (Spirurida: Thelaziidae) is a zoonotic parasite rapidly colonizing Europe from its Asian native range. This nematode is vectored by Phortica flies and may cause ocular disorders, such as keratitis and corneal ulcers, in wild mammals, dogs, cats and humans. With the aim of detecting possible threats for the European wildcat (Felis silvestris) in one of its last Mediterranean strongholds, we initiated in 2017 a long-term monitoring program in Sierra Arana (southeastern Spain), which includes exploring its epidemiological and spatial relationships with domestic cats (Felis catus). During routine medical check-ups, we detected ocular nematodes in 3 of 17 (17.6%) wildcats and 1 of 23 (4.3%) domestic cats tested, confirmed to be T. callipaeda by microscopic and molecular analyses. This nematode species was first detected in the study area in 2021. To our knowledge, this is the first case of infection in wildcats in Spain. Through telemetry, we detected little spatial overlap between the home ranges of wildcats and domestic cats, which seems to be sufficient to facilitate the inter-specific transmission of T. callipaeda. Our findings suggest that this pathogen could be a new threat to the wildcat, a locally endangered wild felid. Further eco-epidemiological monitoring and sanitary control of domestic cats will be strongly needed, especially given the ongoing global warming scenario.

First report of Thelazia callipaeda Railliet & Henry, 1910 in a zoo lion (Panthera leo) (Linnaeus, 1758) from Romania

Thelazia callipaeda, the zoonotic "oriental eye worm", is an emerging nematode known to infect a wide range of hosts, particularly carnivores (wild and domestic canids and felids, mustelids, and ursids), but also other mammal groups (suids, lagomorphs, monkeys, and humans), across a wide geographical area. New host-parasite associations and human cases have mostly been reported in endemic areas. A less studied group of hosts is represented by zoo animals that may harbor T. callipaeda.A 23-year old male lion (Panthera leo) that was born in a public zoo in Reșița (Caraș-Severin County, Romania) was submitted to the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca for investigations after death from unknown reasons in November 2022. Four nematodes were collected from the right eye during the necropsy and submitted to morphological and molecular characterization.Collected nematodes were morphologically identified as three females and one male T. callipaeda. The BLAST analysis revealed 100% nucleotide identity to numerous isolates of T. callipaeda haplotype 1.The present paper presents a new host-parasite association between T. callipaeda and P. leo from a zoo in Romania.

Zoonotic helminths - why the challenge remains

Helminth zoonoses remain a global problem to public health and the economy of many countries. Polymerase chain reaction-based techniques and sequencing have resolved many taxonomic issues and are now essential to understanding the epidemiology of helminth zoonotic infections and the ecology of the causative agents. This is clearly demonstrated from research on Echinococcus (echinococcosis) and Trichinella (trichinosis). Unfortunately, a variety of anthropogenic factors are worsening the problems caused by helminth zoonoses. These include cultural factors, urbanization and climate change. Wildlife plays an increasingly important role in the maintenance of many helminth zoonoses making surveillance and control increasingly difficult. The emergence or re-emergence of helminth zoonoses such as Ancylostoma ceylanicum, Toxocara, Dracunculus and Thelazia exacerbate an already discouraging scenario compounding the control of a group of long neglected diseases.

Thelazia lacrymalis in horses from Romania: epidemiology, morphology and phylogenetic analysis

Background

Equine thelaziosis is a neglected vector-borne parasitic disease in modern veterinary medicine, lacking recent reports. It is transmitted by Musca autumnalis, and potentially other Muscidae species, by ingesting the lachrymal secretions of its equine host. The distribution of both Thelazia lacrymalis and its intermediate hosts remains largely unknown throughout Europe, with most studies dating back 20 years. The aim of this study was to assess the presence, prevalence and distribution of T. lacrymalis in horses from Romania.

Methods

The eyes of 273 horses, slaughtered at two abattoirs from the Northwestern and Western regions of Romania, were examined for the presence of T. lacrymalis between March and November 2021. Upon detection, the nematodes were collected and morphologically identified using the keys from literature. Following identification, one specimen from each animal was selected for molecular analysis while the rest underwent detailed morphometric measurements. Mapping and distribution, according to ecoregions, was done using the QGis 3.20 software, while sequences obtained were compared to those available in GenBank through BLAST analysis using the MEGA X software.

Results

Of the 273 animals sampled, 12 (4.39%) were positive for Thelazia spp. infection. Eighty-seven nematodes were recovered, all morphologically identified as T. lacrymalis. The intensity of infestation varied between one and 33 nematodes/animal while five animals presented a bilateral infestation and seven a unilateral one. The highest prevalence was encountered in Pannonian ecoregion (12.12%) while the lowest was in the Alpine ecoregion (0%). Seventy-five intact specimens underwent detailed morphometric analysis, of the 18–20 parameters, resulting in notable differences in striation lengths compared to the data available in other reports. BLAST analysis identified a 96.46–98.60% similarity to the only other COI gene sequence available for T. lacrymalis.

Conclusions

The current study represents the first report of T. lacrymalis in horses in Romania. The low prevalence rates are probably linked to the wide use of macrocyclic lactones.

Graphic Abstract

European Hares, Lepus europaeus, Represent a Reservoir Host for Thelazia callipaeda in Romania

Thelaziosis caused by Thelazia callipaeda is an emerging disease in Europe. Only two reports of naturally infected lagomorphs have been published so far. The aim of this study was to evaluate the status of the Romanian populations of European brown hares, Lepus europaeus as reservoir hosts for T. callipaeda. Between November 2019 and November 2021, the eyes of 326 L. europaeus carcasses were examined for the presence of ocular parasites. Nematodes were stored in plastic vials with physiological saline, followed by morphological and molecular identification. QGis 3.20 and EpiInfoTM 7 were used for mapping and statistical analysis. Four (1.23%) hares harbored T. callipaeda infection, with a total of 84 nematodes collected (mean intensity 21 nematodes/host), with 45 males, 39 females (two sexually immature, seven with only eggs, and 30 with eggs and larvae). One specimen from each host was successfully sequenced resulting in a 100% similarity with several other sequences of T. callipaeda haplotype 1. Statistical analysis revealed no significant results. The current study represents a first report of T. callipaeda in the European brown hare in Romania, and the second in Europe, also reiterating the role of lagomorphs as reservoir hosts for this zoonotic ocular nematode.

Laboratory Culture and Life Cycle of Thelazia callipaeda in Intermediate and Definitive Hosts

Human thelaziasis caused by Thelazia callipaeda is being increasingly reported worldwide. Notably, an epidemic trend is observed in Southwest China. Whether Phortica okadai found in Southwest China can act as a vector of T. callipaeda and human-derived T. callipaeda animal infections has not been widely reported. Here, P. okadai was maintained in a laboratory and experimentally infected with first-stage larvae collected from adult T. callipaeda that were isolated from infected human subjects. Dead P. okadai were subjected to PCR assay and dissected every two days to detect T. callipaeda. Subsequently, live flies were used to infect a rabbit. The infection procedures were performed once a day (20 min) for two weeks. The results show that L1 collected from the adult T. callipaeda could successfully parasitize P. okadai captured in Zunyi, a city in Southwest China, and developed into L3, and a rabbit was successfully infected with T. callipaeda using P. okadai as the intermediate host. The present study demonstrates a human-derived T. callipaeda infection in rabbits, through P. okadai, under laboratory conditions for the first time. These results provide insights into the transmission cycle of T. callipaeda and constitute a foundation to develop an effective treatment protocol for T. callipaeda infection.

Morphological and Morphometrical Aspects of the Auditory Ossicles in the European Badger (Meles Meles)

Simple Summary

The little-described morphology of the ear ossicles in the badger provides some interesting morphological features alongside some metrical data. For the malleus, we notice the standard framing into the known shape, with the mentioned presence at the level of the column of all three processes (lateral, rostral and medial), from which the rostral one is the most developed. The malleal manubrium is long and triangularly shaped on a cross-section. For the incus we notice the overall shape of a biradicular molar with the existence of the two crura in acute angulation, while the long crus is continuing with the lenticular process. The presence of a bony blade that links to the lenticular process is also noted. For the stapes, the almost equal two crura and the quite round intercrural foramen is described.

Abstract

Given the scarce morphological data regarding the middle ear anatomy of this species, the paper attempts to describe the morphological and morphometrical data of the auditory ossicles in the badger. The study was performed using the standard morphological investigations and provides a complete morphological description of the ossicular assembly (malleus, incus and stapes) with some comparative features and attempts to provide a complete set of standardized metrical data for each ossicle. A more-detailed attempt to compare some functional aspects in the light of combined metrical ratios is also implied.

Zoonotic Thelazia callipaeda eyeworm in brown bears (Ursus arctos): A new host record in Europe

Thelazia callipaeda (Spirurida, Thelaziidae) eyeworm, a zoonotic parasite transmitted by lachryphagus drosophilids, causes subclinical to clinical ocular disease in a wide range of vertebrates, including humans. In the past 20 years, the infection spread primarily in areas where the vector thrives, and now is endemic in many European countries. Recently, this nematode has been reported also in the United States. Here, we describe the first record of the brown bear (Ursus arctos) as a host of T. callipaeda. Eight (26.7%) out of 30 bears were found to be infected with T. callipaeda adult worms. In addition, the parasite was detected in 13 wolves (Canis lupus) sharing the same environment with the brown bears. At the molecular characterization, all nematodes belonged to the haplotype 1, which is the only one recorded in Europe, as yet. This finding demonstrates that brown bears may act as hosts for this parasite, suggesting its potential role in the maintenance of the cycle not only in the wild but also in captivity. Under the above circumstances, the brown bear may represent a potential zoonotic risk for humans, both in rural and urban areas where other reservoirs may be infected.

The Vector-Borne Zoonotic Nematode Thelazia callipaeda in the Eastern Part of Europe, with a Clinical Case Report in a Dog in Poland

Thelazia callipaeda is a zoonotic nematode transmitted by drosophilid flies. It causes ocular thelaziosis, a disease of carnivores, such as dogs, cats, and foxes, and also humans. The parasite has thus far been observed in various areas of Eurasia, including 20 countries within Europe. The present study documents its presence in the south-east region of Poland, near the Ukraine border. An adult nematode was removed from the conjunctival sac of a dog showing ocular inflammation and purulent discharge. The dog’s precise origin is unknown. Based on its localization and morphometrical features, the nematode was identified as a Thelazia callipaeda adult male. The present study is the first report of T. callipaeda in a dog in Poland.

Systematic review on infection and disease caused by Thelazia callipaeda in Europe: 2001-2020

Cases of thelaziosis by Thelazia callipaeda have been increasing considerably in Europe throughout the 21st century, with recent emphasis on Eastern Europe. A systematic review was conducted using defined search terms across three major databases and, additionally, with the examination of the references of the 56 articles selected. Available information about epidemiological and clinical features of all cases of thelaziosis by T. callipaeda in companion animals, wildlife and humans was extracted, evaluated and subjected to qualitative and quantitative analysis. In all cross-sectional studies about dogs, cats and red foxes, males were more frequently infected than females (dogs: p = 0.0365; cats: p = 0.0164; red foxes: p = 0.0082). Adult dogs seem to be more prone to infection (p < 0.0001), as well as large-sized dogs (p < 0.0001), and companion animals that live exclusively outdoors (p < 0.0001). Dogs and red foxes involved in these cross-sectional studies harboured significantly more female than male nematodes (p < 0.0001). Thelaziosis by T. callipaeda is far from controlled in Europe. Only through updated epidemiological data, knowledge improvement and awareness can correct diagnosis and appropriate treatment and prevention be ensured to tackle this zoonosis.

Thelazia rhodesi in a dairy farm in Romania and successful treatment using eprinomectin

Bovine thelaziosis can be caused by Thelazia rhodesi Desmarest 1828, Thelazia gulosa Railliet & Henry 1910 and Thelazia skrjabini Erschow 1928 which are known to be transmitted by species of Muscidae. Therapeutic measures in cattle include mechanical removal of the adult parasites, followed by irrigation of the conjunctival sac with different solutions such as levamisole (1%) or administration of ivermectin (0.2 mg/kg SC), doramectin (0.2 mg/kg SC or pour-on) both with high efficacy, however, the use of such macrocyclic lactones can be problematic in lactating cattle. Nematodes harboured in the eyes of some cattle from Romania were morphologically identified as Thelazia rhodesi and the PCR analysis confirmed the diagnosis with a 98.0% nucleotide similarity for ITS1 sequence, with other sequences available in GenBank. The present paper reports the presence of T. rhodesi in cattle from a dairy farm in Romania and the recovery after treatment with eprinomectin. To the best of our knowledge this is the first report on the efficacy of eprinomectin against Thelazia spp. and the first molecular confirmation of T. rhodesi in Romania.

First report of Thelazia callipaeda in a free-ranging Iberian wolf (Canis lupus signatus) from Spain

Thelazia callipaeda (Spirurida, Thelaziidae) is a vector-borne zoonotic eyeworm able to infect a broad spectrum of carnivores. Here, we describe the first case of bilateral infection by T. callipaeda in the eyes of an adult female Iberian wolf (Canis lupus signatus) in central Spain. Nematodes collected were morphologically identified (n = 42), and two specimens were molecularly characterized. At the sequence analysis of the partial mitochondrial cytochrome c oxidase subunit 1 gene, T. callipaeda haplotype 1 (the only haplotype circulating in Europe) was detected. The role of the Iberian wolf as a natural reservoir for T. callipaeda in the life cycle of this emerging zoonosis and the implications in conservation are discussed.

Canine thelaziosis in the Czech Republic: the northernmost autochthonous occurrence of the eye nematode Thelazia callipaeda Railliet et Henry, 1910 in Europe

The eye nematode Thelazia callipaeda Railliet et Henry, 1910 (Spirurida: Thelaziidae) is a vector-borne zoonotic nematode infecting a range of wild and domestic carnivores as well as humans. It is considered to be a causative agent of emerging and neglected disease and currently invades central part of Europe. Nematodes were collected from the eye of a dog living in Prague, which never travelled outside the Czech Republic. The nematodes were identified based on their morphology and partial sequence of the cox1 gene as T. callipaeda haplotype 1. This finding represents the northernmost record of autochthonous canine thelaziosis in Europe. The insufficient control of imported animals as well as free movement of dogs and wild carnivores within Europe probably facilitates spreading of T. callipaeda throughout the continent. To better understand the spreading of T. callipaeda and to prevent its zoonotic transmissions, information about the risk of this infection in newly invaded countries should be disseminated not only among veterinarians and physicians, but also within the community of pet owners and hunters.

Temperature is a common climatic descriptor of lachryphagous activity period in Phortica variegata (Diptera: Drosophilidae) from multiple geographical locations

Background

The drosophilid Phortica variegata is known as vector of Thelazia callipaeda, the oriental eyeworm native to Asia that has become an emergent zoonotic agent in several European regions. Unlike almost all other arthropod vectors of pathogens, only P. variegata males feed of lachrymal secretions of animals, ingesting first-stage larvae (L1) of the worm living in the orbital cavities of the host, and allowing with the same behaviour the introduction of infective L3. Despite the increased detection of T. callipaeda in many European countries, information about the length of the lachryphagous activity period of P. variegata and a deep knowledge of the environmental and climatic variables involved are still limited.

Methods

We herein present the results of a multicentre study involving five sites from four different countries (Italy, Spain, UK and USA) where canine thelaziosis is endemic and/or where it has already been ascertained the presence of P. variegata. Field data have been obtained on a fortnightly basis from mid-April to the end of November 2018 from a contemporary standardized sampling (same sampling effort and time of collection in all sites) of lachryphagous flies collected around the eyes of a human bait using an entomological net. These data have been associated to data collection of local climatic variables (day length, temperature, wind speed, barometric pressure and relative humidity).

Results

Overall, a total of 4862 P. variegata flies (4637 males and 224 females) were collected, with high differences in densities among the different sampling sites. Significant positive correlations were found between P. variegata male density and temperature and wind speed, while negative correlations were observed for barometric pressure and relative humidity. However, the above significant differences are confirmed in each sampling site separately only for the temperature.

Conclusions

This multicentre study highlights that temperature is the major common environmental driver in describing the lachryphagous activity of P. variegata in Europe and USA and, therefore, the transmission risk of thelaziosis.

Thelaziosis due to Thelazia callipaeda in Europe in the 21st century-A review

Thelazia callipaeda was first described at the beginning of the 20th century in Asia, but this eyeworm is now frequently reported in Europe in the 21st century. To date, thelaziosis has been described in the following European countries (in order of appearance): Italy, France, Germany, Switzerland, Spain, Portugal, Belgium, Bosnia and Herzegovina, Croatia, Serbia, Romania, Greece, Bulgaria, Hungary, Slovakia, the United Kingdom, Turkey and Austria. The infected vertebrate host species include domestic carnivores (dogs and cats), wild carnivores (red foxes, wolves, beech martens, wildcats and golden jackals), lagomorphs (brown hares and wild European rabbits) and humans. In Europe, 11 cases of human thelaziosis have been reported, the majority of which are autochthonous. However, some of them have been imported, a fact which highlights the importance of surveillance policies to restrict cross-border spread of the parasite. The objectives of this article are to review key aspects of the epidemiology of T. callipaeda, summarise animal and human cases in Europe and emphasise the importance of education and awareness among veterinarians, physicians (particularly ophthalmologists) and animal, in order to owners to tackle this zoonosis.