Wild carnivores and Thelazia callipaeda zoonotic eyeworms: A focus on wolves

Eyeworms of wild birds and new record of Thelazia (Thelaziella) aquilina (Nematoda: Spirurida)

The eyeworms of the subgenus Thelaziella infect orbital cavities, conjunctival sacs and lachrymal ducts of many wild birds, being able to cause conjunctivitis. In Brazil, at least 10 species of Thelaziella have been described. Here we present a brief review of cases of Thelazia (Thelaziella) aquilina and describe the infection of this parasite in Harpia harpyja, as a new host record. Two nematodes were collected from the surface of the cornea of an adult female H. harpyja in the Amazon region (Brazil) and were morphologically identified as two males of T. (T.) aquilina. This data demonstrated the need for further studies focused on elucidating the transmission, biological cycle, and phylogenetic positioning of Thelaziella as subgenus.

Wildlife parasitology: sample collection and processing, diagnostic constraints, and methodological challenges in terrestrial carnivores

Wild terrestrial carnivores play a crucial role as reservoir, maintenance, and spillover hosts for a wide parasite variety. They may harbor, shed, and transmit zoonotic parasites and parasites of veterinary importance for domestic hosts. Although wild carnivores are globally distributed and comprise many different species, some living in close proximity to human settlements, only a few studies have investigated parasites of wild terrestrial carnivores using non-specific techniques. Access to samples of wild carnivores may be challenging as some species are protected, and others are secretive, possibly explaining the data paucity. Considering the importance of wild carnivores' health and ecological role, combined with the lack of specific diagnostic methodologies, this review aims to offer an overview of the diagnostic methods for parasite investigation in wild terrestrial carnivores, providing the precise techniques for collection and analysis of fecal, blood, and tissue samples, the environmental impact on said samples, and the limitations researchers currently face in analyzing samples of wild terrestrial carnivores. In addition, this paper offers some crucial information on how different environmental factors affect parasite detection postmortem and how insects can be used to estimate the time of death with a specific highlight on insect larvae. The paper contains a literature review of available procedures and emphasizes the need for diagnostic method standardization in wild terrestrial carnivores.

Mansonella sp. and associated Wolbachia endosymbionts in ring-tailed coatis (Nasua nasua) in periurban areas from Midwestern Brazil

Coatis (Nasua nasua) are wild carnivorous well adapted to anthropized environments especially important because they act as reservoirs hosts for many arthropod-borne zoonotic pathogens. Information about filarioids from coatis and associated Wolbachia spp. in Brazil is scant. To investigate the diversity of filarial nematodes, blood samples (n = 100 animals) were obtained from two urban areas in midwestern Brazil and analyzed using blood smears and buffy coats and cPCR assays based on the cox1, 12S rRNA, 18S rRNA, hsp70 and myoHC genes for nematodes and 16S rRNA for Wolbachia. When analyzing coati blood smears and buffy coats, 30% and 80% of the samples presented at least one microfilaria, respectively. Twenty-five cox1 sequences were obtained showing 89% nucleotide identity with Mansonella ozzardi. Phylogenetic analyses clustered cox1 sequences herein obtained within the Mansonella spp. clade. Sequences of both myoHC and two hsp70 genes showed 99.8% nucleotide identity with Mansonella sp. and clustered into a clade within Mansonella sp., previously detected in coatis from Brazil. Two blood samples were positive for Wolbachia, with a 99% nucleotide identity with Wolbachia previously found in Mansonella perstans, Mansonella ozzardi and Mansonella atelensis and in ectoparasites of the genus Pseudolynchia, Melophagus and Cimex. The study showed a high prevalence of Mansonella sp. in the coati population examined, suggesting that this animal species play a role as reservoirs of a novel, yet to be described, species within the Onchocercidae family.

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.

Occurrence of Thelazia callipaeda and its vector Phortica variegata in Austria and South Tyrol, Italy, and a global comparison by phylogenetic network analysis

The zoonotic nematode Thelazia callipaeda infects the eyes of domestic and wild animals and uses canids as primary hosts. It was originally described in Asia, but in the last 20 years it has been reported in many European countries, where it is mainly transmitted by the drosophilid fruit fly Phortica variegata. We report the autochthonous occurrence of T. callipaeda and its vector P. variegata in Austria. Nematodes were collected from clinical cases and fruit flies were caught using traps, netting, and from the conjunctival sac of one dog. Fruit flies and nematodes were morphologically identified and a section of the mitochondrial cytochrome c oxidase subunit I gene (COI) was analysed. A DNA haplotype network was calculated to visualize the relation of the obtained COI sequences to published sequences. Additionally, Phortica spp. were screened for the presence of DNA of T. callipaeda by polymerase chain reaction. Thelazia callipaeda and P. variegata were identified in Burgenland, Lower Austria, and Styria. Thelazia callipaeda was also documented in Vienna and P. variegata in Upper Austria and South Tyrol, Italy. All T. callipaeda corresponded to haplotype 1. Twenty-two different haplotypes of P. variegata were identified in the fruit flies. One sequence was distinctly different from those of Phortica variegata and was more closely related to those of Phortica chi and Phortica okadai. Thelazia callipaeda could not be detected in any of the Phortica specimens.

Molecular characterization of oriental eyeworm (Thelazia callipaeda) detected from raccoon (Procyon lotor) and Japanese raccoon dog (Nyctereutes viverrinus) in Kanto region, Japan

BACKGROUND

The oriental eyeworm Thelazia callipaeda (Spirurida: Thelaziidae) is an emerging parasitic ocular nematode of carnivores and humans. In domestic animals and humans, the infection causes varying degrees of inflammation and lacrimation, and wild carnivores represent an important reservoir. In this study we examined the infection status and molecular characterization of T. callipaeda in two urban carnivores, raccoons Procyon lotor and wild Japanese raccoon dogs Nyctereutes viverrinus, in the Kanto region of Japan.

METHODS

From January 2020 to December 2021, 193 carcasses including 178 raccoons and 15 raccoon dogs were examined for the presence of worms in the eye. The worms from infected animals (one worm per host) were morphologically identified as T. callipaeda. Worms (1-5 worms per host) were subjected to genetic analysis using mitochondrial cytochrome c oxidase subunit I gene sequences.

RESULTS

The prevalence of T. callipaeda in raccoons and Japanese raccoon dogs was 20.2% (36/178) and 13.3% (2/15), respectively. The cox1 sequences from 56 worms from 38 animals revealed three haplotypes (h9, h10, and h12). Analysis of multiple worms for five raccoons showed co-infection of two different haplotypes (h9 and h10) in a single host. Comparing our data with published sequences, three sequences obtained from raccoons and raccoon dogs shared the same haplotypes as those reported in humans, dogs, and cats in Japan.

CONCLUSIONS

Our findings show a high prevalence of T. callipaeda in raccoons, suggesting that this invasive carnivore species serves as an important natural reservoir of T. callipaeda in the Kanto region of Japan, an area with the highest human population of the country.

Wolf Is Back: A Novel Sensitive Sentinel Rejoins the Trichinella Cycle in the Western Alps

Trichinella is a foodborne parasite whose wildlife reservoirs are represented by carnivores and omnivores with predatory and scavenger behavior. The aim of the present study was to investigate the occurrence of Trichinella infection in grey wolves (Canis lupus) that recolonized the Western Alps from the end of the past century, and discuss the epidemiological role played by this apex predator in the early phases of its return. During the period 2017–2022, diaphragm samples were obtained from 130 individuals collected in the frame of a wolf mortality survey. Trichinella larvae were found in 15 wolves (11.53%) with a parasite intensity of 11.74 larvae per gram. Trichinella britovi was the only species identified. This is the first prevalence survey of Trichinella in wolves recolonizing the Alps. Results suggest that, in this particular biotope, the wolf has rejoined the Trichinella cycle and has the potential to play an increasingly important role as maintenance host. Arguments in favor and against this perspective are discussed and knowledge gaps highlighted. The calculated Trichinella larval biomass in the estimated wolf population roaming in Northwest Italy will serve as baseline value to explore possible shifts in the relative importance of wolves as Trichinella reservoir within the regional carnivore community. Finally, wolves re-colonizing the Alps already appear as sensitive sentinels to monitor the risk of Trichinella zoonotic transmission by infected wild boar meat.

Identification and Functional Characterization of CYP4D2 Putatively Associated with β-Cypermethrin Detoxification in Phortica okadai

Phortica okadai, a polyphagous pest, serves as a vector for Thelazia callipaeda in China. Currently, there are no effective control strategies for this vector. Agricultural pest control may cause P. okadai to become a threat due to the development of pesticide resistance. Cytochrome P450s (CYP450) plays a significant role in detoxifying xenobiotics in insects. In this study, we performed RNA sequencing of P. okadai exposed to β-cypermethrin for 0 and 1 h and then gene cloning of the five up-regulated CYP450 genes. Three CYP450 genes were successfully cloned, and their expression patterns in different developmental stages and in different tissues were analyzed by RT-qPCR. Pocyp4d2 was observed to have the highest expression in the midgut (fold change 2.82 for Pocyp4d2, 2.62 for Pocyp49a1, and 1.77 for Pocyp28d2). Functional analysis was carried out according to overexpression in S2 cells from the pfastbac1 vector and RNAi with siRNA. The results of the CCK8 assay indicated that the overexpression of the recombinant protein PoCYP4D2 suppressed the decrease in S2 cell viability due to β-cypermethrin. The expression levels of PoCYP4D2 decreased significantly, and the mortality rates increased from 6.25% to 15.0% at 3 h and from 15.0% to 27.5% at 6 h after Pocyp4d2-siRNA injection. These results suggest that Pocyp4d2 may be an essential key gene in the metabolism of β-cypermethrin in P. okadai. This study constitutes a foundation to explore further the functions of P. okadai CYP450 genes in insecticide metabolism.

Subcutaneous Ticks in Wild Carnivores: Any Host-Related Differences?

Ticks under the skin have been shown in different canid species such as red fox, domestic dog, and raccoon dog. Despite being increasingly reported in Europe in the last decade, the biological mechanisms associated to subcutaneous ticks (SCT), as well as the predisposing factors, are not yet clear. The main goal of this study was to investigate the presence of SCT in wild carnivores in Northwestern Italy. Sixty-three wild carnivores were examined, and SCT were submitted to histological examination or stored in ethanol for morphological and molecular identification. A portion of the cox1 gene and 16S rDNA were amplified, and positive PCR products were sequenced. Fifty-one small brown-coloured nodules of about 2 × 3 mm containing ticks in different decomposition stages were observed in 11 out of 30 foxes. Seven ticks were classified as Ixodes ricinus, while 14 ticks were determined only at the genus level (Ixodes spp.), and in two ticks no morphological key was applicable due to the advanced degradation status. By PCR, the rDNA fragment of six ticks (26.1%, 95% CI: 12.6-46.5%) was amplified, and BLAST analysis revealed a 99-100% nucleotide similarity to I. ricinus. At the histological examination, the inflammatory response varied from a mild to a moderate mixed infiltrate, primarily composed by neutrophils and lymphocytes. The results of this study confirm foxes as the main wild reservoir for SCT. The absence of SCT in other carnivores (badgers and martens) is in accordance with other studies. Ixodes ricinus is the most frequently reported tick species, corroborating the idea that longirostral ticks might be more frequently associated to SC embedment than brevirostral ticks.

Efficacy of a formulation of sarolaner/moxidectin/pyrantel (Simparica Trio®) for the prevention of Thelazia callipaeda canine eyeworm infection

Background

For a long time known as the oriental eyeworm, Thelazia callipaeda is a zoonotic nematode that infects the eyes of a wide range of vertebrate hosts including dogs, cats, wildlife carnivores, lagomorphs, and humans. The high occurrence of this infection in Europe and the first cases in the United States have increased scientific interest in the parasite, as it also represents a risk for people living in endemic areas. Therefore, treatment and prevention of thelaziosis in canine population are advocated to reduce the risk of human infection as well. Here, we assessed the efficacy of a formulation containing sarolaner/moxidectin/pyrantel (Simparica Trio^®) administered orally at monthly intervals, for the prevention of establishment of infection with T. callipaeda in naturally infected dogs. In this formulation, moxidectin is expected to have efficacy against eyeworms, whereas sarolaner and pyrantel are not.

Methods

The study was conducted in eyeworm endemic areas of Italy and France, where dogs (n = 125) were assigned into two groups consisting of a negative control group (G1; n = 62), in which animals were treated monthly with a control product (sarolaner; Simparica^®), and a treatment group (G2; n = 63) in which animals were treated monthly with Simparica Trio (sarolaner/moxidectin/pyrantel) from day 0 to day 150. In total, nine animals were withdrawn from the study (two animals became positive at day 30, and seven for reasons unrelated to eyeworm infection), resulting in 116 animals (n = 58 for G1; n = 58 for G2).

Results

In G1, 16 out of 58 animals (27.6%) were observed with eyeworms during the study, and none of the animals from G2 were ever observed with eyeworms, resulting in 100% efficacy (P < 0.0001) in the prevention of establishment of T. callipaeda infection. Adult nematodes and fourth-instar (L4)-stage larvae were recovered from the eyes of positive animals, counted, and morphologically identified as T. callipaeda. In addition, specimens from Italy were molecularly confirmed as belonging to the haplotype 1 (i.e., the only one circulating in Europe so far).

Conclusions

Data presented herein demonstrated 100% efficacy of Simparica Trio for the prevention of T. callipaeda eyeworm infection in dogs from highly endemic areas of France and Italy. The use of this formulation is advantageous, as it is a licensed product in Europe with a wide efficacy spectrum against other nematodes, multiple tick species, and fleas. In addition, preventing the development of infection in dogs could also be a prophylaxis measure for zoonotic T. callipaeda infection in humans inhabiting endemic areas.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05501-6.

Unintentional Recovery of Parasitic Diversity Following Restoration of Red Deer (Cervus elaphus) in North-Western Italy

Simple Summary

In the early sixties, free ranging red deer (Cervus elaphus, L.) were absent in Piedmont. Human-driven translocations and spontaneous migration of red deer from Switzerland and France resulted in the successful redistribution of this wild ungulate. In parallel, host-specific parasites harbored by red deer populations disappeared in the same area until the restoration of red deer in north-western Italy. The parasitic community has been enriched with at least two species-specific taxa, Onchocerca jakutensis and Pharyngomyia picta, suggesting that the recovery of parasitic biodiversity could be included amongst future conservation goals of this intensively managed game.

Abstract

Red deer (Cervus elaphus) populations in north-western Italy have been remodeled in recent decades. Multiple translocations and the spontaneous migration from Switzerland and France resulted in the successful redistribution of the red deer after human-driven extirpation during the 18th century. The scarcely diverse parasitic community harbored by these cervids has been enriched with two species-specific taxa, Onchocerca jakutensis and Phayigomyia picta, suggesting that the recovery of parasitic biodiversity could be included amongst future conservation goals of this intensively managed game. Nodular onchocercosis was reported in three red deer populations since 2011, while nasal bots were reported since 2018. Hypoderma spp. larvae were identified for the first time in 1989, then a second record was made in 2014 in the province of Biella, where a yearling male in poor condition infested with Hypoderma diana was observed. In the perspective that the restoration of species-specific parasite communities of native mammals in Europe is increasingly perceived as a conservation target, with similar dignity as the conservation of their hosts, baseline data presented in this communication may give new insights for future parasite conservation efforts.

Wolf Dispersal Patterns in the Italian Alps and Implications for Wildlife Diseases Spreading

Simple Summary

Wildlife dispersal directly influences population expansion patterns, and may have indirect effects on the spread of wildlife diseases. For many species, little is known about dispersal, despite its importance to conservation. We documented the natural dispersal processes of an expanding wolf (Canis lupus) population in the Italian Alps to understand the dynamics of the recolonization pattern and identify diseases that might be connected with the process through the use of non-invasive genetic sampling over a 20-year period. By documenting 55 dispersal events, with an average minimum straight dispersal distance of 65.8 km (±67.7 km), from 7.7 km to 517.2 km, we discussed the potential implications for maintaining genetic diversity of the population and for wildlife diseases spreading.

Abstract

Wildlife dispersal directly influences population expansion patterns, and may have indirect effects on the spread of wildlife diseases. Despite its importance to conservation, little is known about dispersal for several species. Dispersal processes in expanding wolf (Canis lupus) populations in Europe is not well documented. Documenting the natural dispersal pattern of the expanding wolf population in the Alps might help understanding the overall population dynamics and identifying diseases that might be connected with the process. We documented 55 natural dispersal events of the expanding Italian wolf alpine population over a 20-year period through the use of non-invasive genetic sampling. We examined a 16-locus microsatellite DNA dataset of 2857 wolf samples mainly collected in the Western Alps. From this, we identified 915 individuals, recaptured 387 (42.3%) of individuals, documenting 55 dispersal events. On average, the minimum straight dispersal distance was 65.8 km (±67.7 km), from 7.7 km to 517.2 km. We discussed the potential implications for maintaining genetic diversity of the population and for wildlife diseases spreading.