Canine ocular onchocercosis in Hungary

Biting midges (Diptera: Ceratopogonidae) as putative vectors of zoonotic Onchocerca lupi (Nematoda: Onchocercidae) in northern Arizona and New Mexico, southwestern United States

Onchocerca lupi (Rodonaja, 1967) is an understudied, vector-borne, filarioid nematode that causes ocular onchocercosis in dogs, cats, coyotes, wolves, and is also capable of infecting humans. Onchocercosis in dogs has been reported with increasing incidence worldwide. However, despite the growing number of reports describing canine O. lupi cases as well as zoonotic infections globally, the disease prevalence in endemic areas and vector species of this parasite remains largely unknown. Here, our study aimed to identify the occurrence of O. lupi infected dogs in northern Arizona, New Mexico, and Utah, United States and identify the vector of this nematode. A total of 532 skin samples from randomly selected companion animals with known geographic locations within the Navajo Reservation were collected and molecularly surveyed by PCR for the presence of O. lupi DNA (September 2019-June 2022) using previously published nematode primers (COI) and DNA sequencing. O. lupi DNA was detected in 50 (9.4%) sampled animals throughout the reservation. Using positive animal samples to target geographic locations, pointed hematophagous insect trapping was performed to identify potential O. lupi vectors. Out of 1,922 insects screened, 38 individual insects and 19 insect pools tested positive for the presence of O. lupi, all of which belong to the Diptera family. This increased surveillance of definitive host and biological vector/intermediate host is the first large scale prevalence study of O. lupi in companion animals in an endemic area of the United States, and identified an overall prevalence of 9.4% in companion animals as well as multiple likely biological vector and putative vector species in the southwestern United States. Furthermore, the identification of these putative vectors in close proximity to human populations coupled with multiple, local zoonotic cases highlight the One Health importance of O. lupi.

Cutaneous filarioid nematodes of dogs in the United States: Are they emerging, neglected, or underdiagnosed parasites?

Filarioid nematodes, which are vector-borne parasites of cosmopolitan distribution, of dogs are medically important. They are represented by species in which microfilariae were found to be circulating in the bloodstream (e.g., Dirofilaria sp., Acanthocheilonema sp., and Brugia sp.) or skin-dwelling (e.g., Cercopithifilaria sp. and Onchocerca sp.). Those species whose microfilariae are detected in blood have been extensively studied, especially Dirofilaria immitis, due to their clinical importance. In recent decades, there has been an increased interest by the scientific community in filarioid nematodes whose microfilariae are detected in the skin because of the zoonotic aspect of Onchocerca lupi. In the United States (US), although D. immitis has been considered the main filarioid infecting dogs, the intense animal movement and global canine filarioid diversity may indicate that the likely presence of cutaneous filarioid nematodes is more common than previously expected. Hence, a question remains: Are these canine filarioid nematodes emerging, neglected, or simply underdiagnosed in the US? In this review, we provide an overview of pertinent information that briefly summarizes the biology of the different canine filarioid nematode species, clinical signs associated with infections, and currently available diagnostic tools using molecular and microscopy-based methods and highlight knowledge gaps where research and surveillance efforts remain necessary. The data herein presented serve as an alert to the scientific community about the importance of filarioid nematodes infecting dogs other than D. immitis. Additionally, the zoonotic potential of several filarioid species reinforces the necessity of a proper diagnosis and the need for broader surveillance to understand their diversity and distribution, to highlight the potential introduction of certain species, and mitigate their establishment in the country and new animal and human cases.

Extensive Aberrant Migration of Onchocerca lupi in a Dog

A 13-year-old Labrador retriever mixed breed dog from Arizona was presented for evaluation of an acute onset of a head tilt as well as vocalization and head shaking upon palpation of the ears. The dog was previously treated for ocular onchocercosis associated with the right eye 10 years earlier. Ophthalmic examination at presentation revealed irregular, tan-colored, masses on the sclera of both eyes. Otoscopic evaluation of the left ear was limited because the canals were stenotic and inaccessible. Cytology did not reveal any infectious etiologies and the dog was subsequently treated with an anti-inflammatory dose of prednisone for 10 days. Two weeks later the dog developed a mild dysphonia and stridor that eventually progressed to include difficulty breathing. The dog was euthanized and postmortem examination revealed white-to-tan nodules identified in the episclera, trachea, subcutis around the nares, external ear canals, and within the fascia overlying the temporalis muscle, as well as in the parietal pleura, and pericardium. There was also a large mass that obliterated the laryngeal cartilage that partially occluded the laryngeal opening. Microscopically, the described nodules consisted predominately of lakes of abundant mineralized debris, admixed with granulomatous inflammation centered around degenerate nematodes that were subsequently confirmed by PCR and sequence analysis to be Onchocerca lupi. The veterinary literature is comprised of only 2 reports that describe aberrant O. lupi migration to the trachea and larynx. Here, we provide the first detailed description of a dog with extensive aberrant onchocercosis.

Onchocerca lupi in imported dogs in the UK: implications for animal and public health

BACKGROUND

Onchocerca lupi is a filarial nematode affecting dogs, and occasionally cats and humans, in continental Europe, North Africa, the Middle East, and the USA. Adult worms are usually found in periocular nodules and enucleation is sometimes required if the infection fails to respond to other treatment options.

CASE PRESENTATION

Here, we report the presence of O. lupi in the UK for the first time. Of two dogs re-homed from continental Europe, one developed an ocular nodule seven years after arrival from Portugal. The conjunctival perilimbal mass in its left eye was surgically removed but despite anthelminthic treatment, a further nodule developed in the same eye six months later. In the second case - a dog imported from Romania 12 months earlier - a perilimbal mass was excised from the left eye and prior anthelminthic treatment was supplemented with oral prednisolone and doxycycline. However, nodules recurred, and the left globe was subsequently enucleated. Conjunctival hyperaemia then appeared in the right eye and neither additional anthelminthic treatment nor removal of worm masses failed to prevent the further development of lesions. Excised adult worms were identified in both cases as O. lupi based on morphological characteristics, as well as PCR and sequencing of cytochrome c oxidase subunit I and 12S rRNA gene fragments.

CONCLUSION

O. lupi parasitosis can apparently remain cryptic in dogs for several years before any clinical signs manifest. Moreover, the progression of infection can be highly aggressive and recalcitrant to both surgical intervention and anthelminthic treatment. Increasingly, former stray dogs of unknown infection status are entering the UK, raising both veterinary and public health concerns.

Major antigen and paramyosin proteins as candidate biomarkers for serodiagnosis of canine infection by zoonotic Onchocerca lupi

Onchocerca lupi (Spirurida: Onchocercidae) is a filarial worm parasitizing domestic carnivores and humans. Adult nematodes usually localize beneath in the sclera or in the ocular retrobulbar of infected animals, whilst microfilariae are found in the skin. Therefore, diagnosis of O. lupi is achieved by microscopic and/or molecular detection of microfilariae from skin biopsy and/or surgical removal of adults from ocular tissues of infected hosts. An urgent non-invasive diagnostic tool for the diagnosis of O. lupi in dog is mandatory. In this study, an immunoproteomic analyses was performed using a combination of immunoblotting and mass spectrometry techniques. Onchocerca lupi major antigen (Ol-MJA) and paramyosin (Ol-PARA) proteins were identified as potential biomarkers for serodiagnosis. Linear epitopes were herein scanned for both proteins using high-density peptide microarray. Sera collected from dog infected with O. lupi and healthy animal controls led to the identification of 11 immunodominant antigenic peptides (n = 7 for Ol-MJA; n = 4 for Ol-PARA). These peptides were validated using sera of dogs uniquely infected with the most important filarioids infesting dogs either zoonotic (Dirofilaria repens, Dirofilaria immitis) or not (Acanthocheilonema reconditum and Cercopithifilaria bainae). Overall, six antigenic peptides, three for Ol-MJA and for Ol-PARA, respectively, were selected as potential antigens for the serological detection of canine O. lupi infection. The molecular and proteomic dataset herein reported should provide a useful resource for studies on O. lupi toward supporting the development of new interventions (drugs, vaccines and diagnostics) against canine onchocercosis.

The diagnosis of Onchocerca lupi (Spirurida: Onchocercidae), a zoonotic nematode of domestic animals, is currently based on microscopic examination of skin snip sediments and on the identification of adults embedded in ocular nodules or by molecular assays. An urgent non-invasive diagnostic tool for the diagnosis of O. lupi in dogs is mandatory. In this context, combined immunoblotting and mass spectrometry-based analyses have been performed to identify two proteins, major antigen and paramyosin, of O. lupi. Peptides herein identified represent suitable candidate biomarker for the development of a specific diagnostic test for canine onchocercosis. An accurate, minimally invasive diagnostic method could prove useful for the control of the canine diseases, for establishing large sero-surveys, for mapping the distribution of the infection in endemic areas as well as in areas where information on the disease is not available and for the reduction of risks for human infection.

Molecular Approach for the Diagnosis of Blood and Skin Canine Filarioids

The zoonotic Onchocerca lupi and tick-transmitted filarioids of the genus Cercopithifilaria remain less well known due to the difficulties in accessing to skin samples as target tissues. Here, we proposed a molecular approach reliying on multiplex qPCR assays that allow the rapid identification of filarioids from canine blood, skin, and tick samples. This includes two newly developed duplex qPCR tests, the first one targeting filarial and C. grassii DNA (CanFil-C. grassii). and the second qPCR assay designed for the detection of Cercopithifilaria bainae and Cercopithifilaria sp. II DNAs (C. bainae-C.spII). The third one is a triplex TaqMan cox 1 assay targeting DNA of blood microfilariae (e.g., Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema reconditum). The novel duplex qPCRs developed were validated in silico and by screening of known DNA collection. The qPCR assays were also used for screening the blood and tick samples of 72 dogs from Algeria. This allowed the identification of canine filariasis infection with 100% of specificity and 89.47% and 100% of sensitivity from naturally infected blood and tick samples, respectively. The prevalences of 26.39% for D. immitis and 5.56% for both D. repens and A. reconditum were reported in blood and tick samples. Cercopithifilaria DNAs were detected only in tick samples, with a prevalence of 4.17% and 5.56% for C. bainae and Cercopithifilaria sp. II, respectively. Co-infections were diagnosed in 6.94% and 13.89% of blood and tick samples, respectively. Whereas all samples were negative for C. grassii DNA. The use of engorged ticks instead of blood and skin samples could be an easier option for the surveillance of all canine filarioids herein investigated. The multiplex qPCR assays herein validated were shown to be useful in the detection of filarial co-infections by overcoming sequencing of positive samples.

Overview on Dirofilaria immitis in the Americas, with notes on other filarial worms infecting dogs

Canine dirofilariosis in the Americas is primarily caused by Dirofilaria immitis, a mosquito-borne filarial worm infecting dogs, which may also infect and cause disease in other mammalian hosts, including humans. Morphological and molecular evidence gathered in the past decades suggest that other Dirofilaria spp. may infect dogs in the American continent, though the actual taxonomic identity of them still needs to be elucidated. In addition, filarial worms belonging to distinct genera have also been reported in dogs in this part of the world, including Acanthocheilonema reconditum, Cercopithifilaria bainae, and Onchocerca lupi. Among these, O. lupi is a species of major clinical significance, which has been reported not only in dogs, but also in cats and humans in North America. The present article provides a current overview on canine dirofilariosis in the Americas, with notes on other filarial worms infecting dogs. It also provides some insights into outstanding research questions that should be responded to fill some of the several knowledge gaps related to this group of parasites in this continent.

Zoonotic nematodes of wild carnivores

For a long time, wildlife carnivores have been disregarded for their potential in transmitting zoonotic nematodes. However, human activities and politics (e.g., fragmentation of the environment, land use, recycling in urban settings) have consistently favoured the encroachment of urban areas upon wild environments, ultimately causing alteration of many ecosystems with changes in the composition of the wild fauna and destruction of boundaries between domestic and wild environments. Therefore, the exchange of parasites from wild to domestic carnivores and vice versa have enhanced the public health relevance of wild carnivores and their potential impact in the epidemiology of many zoonotic parasitic diseases. The risk of transmission of zoonotic nematodes from wild carnivores to humans via food, water and soil (e.g., genera Ancylostoma, Baylisascaris, Capillaria, Uncinaria, Strongyloides, Toxocara, Trichinella) or arthropod vectors (e.g., genera Dirofilaria spp., Onchocerca spp., Thelazia spp.) and the emergence, re-emergence or the decreasing trend of selected infections is herein discussed. In addition, the reasons for limited scientific information about some parasites of zoonotic concern have been examined. A correct compromise between conservation of wild carnivores and risk of introduction and spreading of parasites of public health concern is discussed in order to adequately manage the risk of zoonotic nematodes of wild carnivores in line with the 'One Health' approach.

A real-time PCR tool for the surveillance of zoonotic Onchocerca lupi in dogs, cats and potential vectors

The ocular onchocercosis is caused by the zoonotic parasite Onchocerca lupi (Spirurida: Onchocercidae). A major hindrance to scientific progress is the absence of a reliable diagnostic test in affected individuals. Microscopic examination of skin snip sediments and the identification of adults embedded in ocular nodules are seldom performed and labour-intensive. A quantitative real-time PCR (qPCR) assay was herein standardized for the detection of O. lupi DNA and the results compared with microscopic examination and conventional PCR (cPCR). The specificity of qPCR and cPCR was assessed by processing the most common filarial nematodes infecting dogs, skin samples from O. lupi infected (n = 35 dogs) or uninfected animals (n = 21 dogs; n = 152 cats) and specimens of potential insect vector (n = 93 blackflies; n = 59 mosquitoes/midges). The analytical sensitivity of both assays was assessed using 10-fold serial dilutions of DNA from adult specimen and from a pool of microfilariae. The qPCR on skin samples revealed an analytical specificity of 100% and a sensitivity up to 8 x 10-1 fg/2μl O. lupi adult-DNA and up to 3.6 x 10-1 pg/2μl of mfs-DNA (corresponding to 1 x 10-2 mfs/2μl). Only 9.5% O. lupi-infected skin samples were positive for cPCR with a sensitivity of 8 x 10-1 pg/2μl of DNA. Out of 152 blackflies and mosquitoes/midges, eight specimens experimentally infected (n = 1 S. erythrocephalum; n = 1 S. ornatum; n = 6 Simulium sp.) were positive by qPCR. The qPCR assay herein standardized represents an important step forward in the diagnosis of zoonotic onchocercosis caused by O. lupi, especially for the detection and quantification of low number of mfs. This assay provides a fundamental contribution for the establishment of surveillance strategies aiming at assessing the presence of O. lupi in carnivores and in insect species acting as potential intermediate hosts. The O. lupi qPCR assay will enable disease progress monitoring as well as the diagnosis of apparently clinical healthy dogs and cats.

Evaluation of oxfendazole in the treatment of zoonotic Onchocerca lupi infection in dogs

The genus Onchocerca encompasses parasitic nematodes including Onchocerca volvulus, causative agent of river blindness in humans, and the zoonotic Onchocerca lupi infecting dogs and cats. In dogs, O. lupi adult worms cause ocular lesions of various degrees while humans may bear the brunt of zoonotic onchocercosis with patients requiring neurosurgical intervention because of central nervous system localization of nematodes. Though the zoonotic potential of O. lupi has been well recognized from human cases in Europe, the United States and the Middle East, a proper therapy for curing this parasitic infection in dogs is lacking. To evaluate the efficacy of oxfendazole, 11 out of the 21 client-owned dogs (21/123; 17.1%) positive for skin-dwelling O. lupi microfilariae (mfs), were enrolled in the efficacy study and were treated with oxfendazole (50 mg/kg) per OS once a day for 5 (G2) or 10 (G3) consecutive days or were left untreated (G1). The efficacy of oxfendazole in the reduction of O. lupi mfs was evaluated by microfilarial count and by assessing the percentage of mfs reduction and mean microfilaricidal efficacy, whereas the efficacy in the reduction of ocular lesions was evaluated by ultrasound imaging. All dogs where subjected to follow-ups at 30 (D30), 90 (D90) and 180 (D180) days post-treatment. The percentage of reduction of mfs was 78% for G2 and 12.5% for G3 at D180. The mean microfilaricidal efficacy of oxfendazole in the treatment of canine onchocercosis by O. lupi at D30, D90 and D180 was 41%, 81% and 90%, in G2 and 40%, 65% and 70%, in G3, respectively. Retrobulbar lesions did not reduce from D0 to D180 in control group (dogs in G1), whereas all treated dogs (in G2 and G3) had slightly decreased ocular lesions. Percentage of reduction of ocular lesions by ultrasound examination was 50% and 47.5% in G2 and G3 at D180, respectively. Despite the decrease in ocular lesions in all treated dogs (G2 and G3), oxfendazole was ineffective in reducing ocular lesions and skin-dwelling O. lupi mfs in treated dogs (G2 and G3) in a six-month follow-up period. Here we discuss the need for more reliable diagnostic techniques and efficient treatment protocols to better plan future intervention strategies.

The genus Onchocerca (Spirurida, Onchocercidae) includes Onchocerca volvulus, which is estimated to infect at least 37 million people globally, and zoonotic Onchocerca lupi in carnivores. Infection by O. lupi has been reported in dogs and cats from several European countries and recently also in the U.S. and Canada, causing mainly ocular lesions. In humans, O. lupi displays a marked neurotropism with nematodes embedded in nodules localized in the cervical spine of infant, children and adults. Though the reported severity of infection in humans and the high prevalence detected in dogs are now well-recognized, a proper treatment regime for curing this parasitic infection is lacking, being the surgical removal of the parasitic nodule the therapy of choice in canine patients. Hence, there is an unmet medical need for treatment of this zoonotic disease in both humans and animals. In this study we evaluated the efficacy of oxfendazole under two treatment regimes in the reduction of ocular lesions and skin-dwelling microfilariae of O. lupi in naturally infected dogs.

Keratitis due to microfilariae in dogs: a newly recognized disease

Parasitic agents have been associated with keratitis, but a diagnosis of parasitic keratitis has not been commonly made in domestic animals. The purpose of this study was to describe the clinical and histopathological findings in seven dogs with chronic keratitis caused by microfilariae diagnosed in Brazil. All dogs presented with superficial corneal opacities of varying degrees affecting the perilimbal and central regions of the cornea, with other opaque areas appearing as crystalline deposits and corneal vascularization. The lesions were bilateral and were associated with mild-to-moderate conjunctival hyperemia. There was no history of blepharospasm or pruritus, and no subjects presented with epithelial erosions. Corneal biopsy revealed free microfilariae in the corneal stroma, with varying degrees of inflammation and collagen fiber destruction. The microfilariae were also found in skin lesions by skin snip technique. No adult worms were found in these dogs, and no dogs were on heartworm preventative before diagnosis. Monthly doses of oral ivermectin improved ocular and dermal lesions. One dog showed complete remission with the treatment. The species of the microfilariae was not identified.

Canine ocular onchocerciasis: a retrospective review of the diagnosis, treatment, and outcome of 16 cases in New Mexico (2011-2015)

OBJECTIVE

To describe the clinical exam findings, treatment and outcomes of 16 dogs diagnosed with ocular onchocerciasis in New Mexico.

MATERIALS AND METHODS

Records of dogs diagnosed by the primary author were reviewed (2011-2015). Records that were accessible and included a diagnosis of Onchocerca lupi by histopathologic or molecular identification of the nematode were included.

RESULTS

Sixteen cases were included. 3/16 dogs were treated with year-round heartworm prophylaxis prior to infection. Clinical exam findings included conjunctival hyperemia and/or episcleral injection (16/16), focal subconjunctival mass(es) (14/16), retinal detachment (7/16), corneal edema (4/16), chemosis (3/16), corneal opacity (2/16), exophthalmia (1/16), glaucoma (1/16), strabismus (1/16), blepharospasm (1/16), and vitreal degeneration (1/16). Ocular involvement was unilateral in 7/16 dogs and bilateral in 9/16 dogs. The diagnosis was confirmed via histologic identification of the nematodes and/or PCR. Treatment consisted of medical management or a combination medical and surgical management. Known or suspected recurrence of disease was documented in 10 dogs.

CONCLUSIONS

Canine ocular onchocerciasis is endemic in New Mexico. Histopathology and molecular identification are useful diagnostic tools. Medical management alone was successful in many cases.

Paramyosin of canine Onchocerca lupi: usefulness for the diagnosis of a neglected zoonotic disease

BACKGROUND

Of increasing importance to the medical and veterinary communities is the zoonotic filarioid nematode Onchocerca lupi. Onchocercosis, thus far found in wolves, dogs, cats and humans, is diagnosed via skin snips to detect microfilariae and surgical removal of adults from the eye of the host. These methods are time-consuming, laborious and invasive, highlighting the need for new tools for the diagnosis of O. lupi in susceptible hosts. Symptoms related to the presence of the adults in the eye can range from none apparent to severe, including blindness. No reliable chemotherapeutic protocols are available, as yet, to eliminate the infection. Paramyosin, an invertebrate-specific protein, has been well-studied as an allergen, diagnostic marker and vaccine candidate. The aim of this study, therefore, was to isolate and characterise paramyosin from O. lupi to assess its suitability for the development of a serological diagnostic assay.

METHODS

The adult and microfilarial stages of O. lupi were isolated from the eyes and skin of a 3-year-old male dog. Total RNA was extracted and reverse transcribed into single stranded cDNA. Reverse-transcription PCR was used to isolate a full-length paramyosin cDNA from adult worms and to investigate the temporal expression patterns of this gene. All amplicons were sequenced using dideoxy chain termination sequencing. Bioinformatics was used to predict the amino acid sequence of the gene, to compare the DNA and protein sequences with those available in public databases and to investigate the phylogenetic relationship of all molecules. Antibody binding sites were predicted using bioinformatics and mapped along with published antigenic epitopes against the O. lupi paramyosin protein. The native protein, and three smaller recombinantly expressed peptides, were subjected to western blot using serum from dogs both positive and negative for O. lupi.

RESULTS

Paramyosin of O. lupi was herein molecularly characterized, encoded by a transcript of 2,643 bp and producing a protein of 881 amino acids (101.24 kDa). The paramyosin transcript was detected, by reverse transcription PCR, in adults and microfilariae, but not in eggs. Phylogenetic analysis indicates that this molecule clusters with paramyosins from other filarioids to the exclusion of those from other taxa. A total of 621 unique antibody binding epitopes were predicted for this protein and another 28 were conserved in other organisms. This information was used to design three peptides, for recombinant expression, to identify the antibody binding epitope(s) and reduce potential cross-reactivity with serum from dogs infected with other filarioid nematodes. Native paramyosin, purified from microfilariae and adults, was detected by antibodies present in serum from dogs with known O. lupi infections.

CONCLUSIONS

Data provided herein may assist in the development of a serological diagnostic test, based on antibodies to O. lupi paramyosin, for the diagnosis of this infection, in order to gain more information on the real distribution of this little known filarioid of zoonotic concern.

Major Parasitic Zoonoses Associated with Dogs and Cats in Europe

Some of the most important zoonotic infectious diseases are associated with parasites transmitted from companion animals to man. This review describes the main parasitic zoonoses in Europe related to dogs and cats, with particular emphasis on their current epidemiology. Toxoplasmosis, leishmaniosis, giardiosis, echinococcosis, dirofilariosis and toxocariosis are described from the animal, as well as from the human host perspectives, with an emphasis on parasite life cycle, transmission, pathogenicity, prevention and identification of knowledge gaps. In addition, priorities for research and intervention in order to decrease the risks and burden of these diseases are presented. Preventing zoonotic parasitic infections requires an integrated multidisciplinary 'One Health' approach involving collaboration between veterinary and medical scientists, policy makers and public health officials.

The Emergence of Zoonotic Onchocerca lupi Infection in the United States--A Case-Series

This case-series describes the 6 human infections with Onchocerca lupi, a parasite known to infect cats and dogs, that have been identified in the United States since 2013. Unlike cases reported outside the country, the American patients have not had subconjunctival nodules but have manifested more invasive disease (eg, spinal, orbital, and subdermal nodules). Diagnosis remains challenging in the absence of a serologic test. Treatment should be guided by what is done for Onchocerca volvulus as there are no data for O. lupi. Available evidence suggests that there may be transmission in southwestern United States, but the risk of transmission to humans is not known. Research is needed to better define the burden of disease in the United States and develop appropriately-targeted prevention strategies.

Onchocerciasis caused by Onchocerca lupi: an emerging zoonotic infection. Systematic review

Globalization has increased circulation of people, their food, livestock and pets in the world, and changes in the environment, climate and human behaviour have led to the rapid expansion of emerging infections throughout the world. One of the reasons of a new pathogen affecting humans is the passage from an animal to a human being. Onchocerca (O.) lupi, a filarial worm first described in a wolf in 1967, is an emerging pathogen which has been incriminated as the etiological agent for 205 canine, 2 feline and 18 human infections in Europe, Tunisia, Turkey, Iran and the USA. Most frequent findings in animals and humans are monolateral or asymmetrical variably painful subconjunctival swellings and nodules containing immature or mature worms affecting the eye and/or adjacent tissues accompanied by conjunctival hyperemia. Occasionally, subcutaneous nodules and masses affecting the spinal cord have been observed in humans. Diagnosis of O. lupi is achieved by microscopy of excised adult female worms which exhibit a particular cuticular structure and molecular analysis. Treatment consists in worm removal accompanied by antihelminthic, antibiotic and anti-inflammatory therapy.

Intraocular localization of Onchocerca lupi adult worm in a dog with anterior uveitis: A case report

OBJECTIVE

Canine ocular onchocercosis may represent an important ocular disease with zoonotic potential and widespread geographical distribution. An uncommon localization of Onchocerca lupi adult worm in the anterior chamber of the eye is described for the first time.

ANIMAL STUDIED

A 4-year-old, intact, male, mixed-breed dog was admitted with profuse lacrimation and severe squinting. On the right eye, there were mucopurulent discharge, chemosis, and all typical signs of anterior uveitis which were attributed to the presence of a moving filarial worm within the anterior chamber.

PROCEDURE

Removal of the parasite from the anterior chamber by a limbal incision revealed a mature adult male, 7.65-cm-long O. lupi worm. Periocular skin scrapings for the corresponding microfilariae were negative. Postoperatively, apart from systemic prednisolone and doxycycline hyclate and a topical antibiotic/steroid solution, parenteral melarsomine, followed by ivermectin, was given until the complete disappearance of the ocular lesions.

CONCLUSIONS

Intraocular onchocercosis should be included in the differential diagnosis of canine anterior uveitis in endemic areas. This case highlights the atypical localization of O. lupi in the canine eye emphasizing on the possibility for a complete cure after the surgical removal of the parasite and the filaricidal medication subsequently applied.

Cutaneous distribution and circadian rhythm of Onchocerca lupi microfilariae in dogs

BACKGROUND

Among the arthropod-borne nematodes infesting dogs, Onchocerca lupi (Spirurida: Onchocercidae) is of increasing zoonotic concern, with new human cases of infection diagnosed in Turkey, Tunisia, Iran and the USA. Knowledge of the biology of this nematode is meagre. This study aimed at assessing the distribution and periodicity of O. lupi microfilariae from different body regions in naturally infested dogs.

METHODOLOGY/PRINCIPAL FINDINGS

Skin samples were collected from six dogs infested with O. lupi but without apparent clinical signs. Two skin samples were collected from 18 anatomical regions of dog 1 at necropsy. In addition, single skin biopsies were performed from the forehead, inter-scapular and lumbar regions of dogs 2-6, in the morning, afternoon, and at night. Two aliquots of the sediment of each sample were microscopically observed, microfilariae counted and morphologically and molecularly identified. Most of the 1,667 microfilariae retrieved from dog 1 were in the right ear (59.6%), nose (26.5%), left ear (6.7%), forehead (3.0%), and inter-scapular (2.9%) regions. In dogs 2-6, the overall mean number of microfilariae was larger on the head (n = 122.8), followed by the inter-scapular (n = 119.0) and lumbar (n = 12.8) regions. The overall mean number of microfilariae was larger in the afternoon (153.4), followed by night (75.4) and morning (25.8).

CONCLUSIONS

Onchocerca lupi microfilariae were more common in the head (i.e., ears and nose) than in the remaining part of the dog's body, indicating they tend to aggregate in specific body regions, which are the best sites to collect skin samples for diagnostic purposes. The periodicity pattern of microfilariae of O. lupi and their concentration in specific body regions is most likely a result of the co-evolution with their as-yet-unknown vector. The detection of skin microfilariae in asymptomatic animals, suggests the potential role of these animals as carriers and reservoirs of O. lupi.

Redescription of Onchocerca lupi (Spirurida: Onchocercidae) with histopathological observations

BACKGROUND

Onchocerca lupi is a dog parasite of increasing zoonotic concern, with new human cases diagnosed in Turkey, Tunisia, Iran, and the United States. Information about the morphology of this nematode is scant and a detailed re-description of this species is overdue. In addition, histopathological data of potential usefulness for the identification of O. lupi infections are provided.

METHODS

Male and female nematodes, collected from the connective tissue of a dog, were examined using light microscopy and scanning electron microscopy (SEM), and an histological evaluation was performed on biopsy samples from periocular tissues.

RESULTS

The morphological identification was confirmed by molecular amplification and partial sequencing of cytochrome oxidase subunit 1 gene. This study provides the first comprehensive morphological and morphometric description of O. lupi from a dog based on light microscopy, SEM, molecular characterization, and histological observations.

CONCLUSIONS

Data herein presented contribute to a better understanding of this little known parasitic zoonosis, whose impact on human and animal health is still underestimated. The presence of granulomatous reactions only around the female adult suggests that the release of microfilariae from the uterus might be the cause of the inflammatory reaction observed.

Vector-borne helminths of dogs and humans in Europe

Presently, 45% of the total human population of Europe, as well as their domestic and companion animals, are exposed to the risk of vector-borne helminths (VBH) causing diseases. A plethora of intrinsic biological and extrinsic factors affect the relationship among helminths, vectors and animal hosts, in a constantly changing environment. Although canine dirofilarioses by Dirofilaria immitis and Dirofilaria repens are key examples of the success of VBH spreading into non-endemic areas, another example is represented by Thelazia callipaeda eyeworm, an emergent pathogen of dogs, cats and humans in several regions of Europe. The recent finding of Onchocerca lupi causing canine and human infestation in Europe and overseas renders the picture of VBH even more complicated. Similarly, tick-transmitted filarioids of the genus Cercopithifilaria infesting the skin of dogs were recently shown to be widespread in Europe. Although for most of the VBH above there is an increasing accumulation of research data on their distribution at national level, the overall impact of the diseases they cause in dogs and humans is not fully recognised in many aspects. This review investigates the reasons underlying the increasing trend in distribution of VBH in Europe and discusses the diagnostic and control strategies currently available. In addition, this article provides the authors' opinion on some topics related to VBH that would deserve further scientific investigation.

Human ocular filariasis: further evidence on the zoonotic role of Onchocerca lupi

Background

Among ocular vector-borne pathogens, Onchocerca volvulus, the agent of the so-called “river blindness”, affects about 37 million people globally. Other Onchocerca spp. have been sporadically reported as zoonotic agents. Cases of canine onchocerciasis caused by Onchocerca lupi are on the rise in the United States and Europe. Its zoonotic role has been suspected but only recently ascertained in a single case from Turkey. The present study provides further evidence on the occurrence of O. lupi infesting human eyes in two patients from Turkey (case 1) and Tunisia (case 2). The importance of obtaining a correct sample collection and preparation of nematodes infesting human eyes is highlighted.

Methods

In both cases the parasites were identified with morpho-anatomical characters at the gross examination, histological analysis and anatomical description and also molecularly in case 1.

Results

The nematode from the first case was obviously O. lupi based on their morphology at the gross examination, histological analysis and anatomical description. In the second case, although the diagnostic cuticular characters were not completely developed, other features were congruent with the identification of O. lupi. Furthermore, the morphological identification was also molecularly confirmed in the Turkish case.

Conclusions

The results of this study suggest that O. lupi infestation is not an occasional finding but it should be considered in the differential diagnosis of other zoonotic helminths causing eye infestation in humans (e.g., D. immitis and Dirofilaria repens). Both cases came from areas where no cases of canine onchocerciasis were previously reported in the literature, suggesting that an in depth appraisal of the infestation in canine populations is necessary. Physicians and ophthalmologists are advised on how to preserve nematode samples recovered surgically, to allow a definitive, correct etiological diagnosis.

Onchocerca lupi causing ocular disease in two cats

Although canine ocular onchocerciasis has been well described as an emerging pathogen of dogs in Europe and North America over the past 20 years, there are no previous reports of feline ocular onchocerciasis. This report details the clinical, histopathologic, and molecular diagnosis of two domestic short hair cats residing in the United States infected with Onchocerca lupi causing episcleritis and orbital cellulitis. The results of this report suggest that O. lupi is a newly recognized disease of domestic cats.

On a Cercopithifilaria sp. transmitted by Rhipicephalus sanguineus: a neglected, but widespread filarioid of dogs

BACKGROUND

This study was aimed at investigating the distribution of a Cercopithifilaria sp. sensu Otranto et al., 2011 with dermal microfilariae recently identified in a dog from Sicily (Italy). A large epidemiological survey was conducted by examining skin samples (n = 917) and ticks (n = 890) collected from dogs at different time points in Italy, central Spain and eastern Greece.

RESULTS

The overall prevalence of Cercopithifilaria sp. in the sampled animal populations was 13.9% and 10.5% by microscopy of skin sediments and by PCR on skin samples, respectively. Up to 21.6% and 45.5% of dogs in Spain were positive by microscopical examination and by PCR. Cumulative incidence rates ranging from 7.7% to 13.9% were estimated in dogs from two sites in Italy. A low level of agreement between the two diagnostic tests (microscopical examination and PCR) was recorded in sites where samples were processed in parallel. Infestation rate as determined by tick dissection (from 5.2% to 16.7%) was higher than that detected by PCR (from 0% to 3.9%); tick infestation was significantly associated with Cercopithifilaria sp. infestation in dogs from two out of four sites. Developing larvae found in ticks were morphometrically studied and as many as 1469 larvae were found in a single tick.

CONCLUSIONS

Our data suggest that, in addition to the most common species of filarioids known to infest dogs (i.e., Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema reconditum), Cercopithifilaria sp. with dermal microfilariae should be considered due to its widespread distribution in southern Europe and high frequency in tick-exposed dogs.

Zoonotic helminths affecting the human eye

Nowaday, zoonoses are an important cause of human parasitic diseases worldwide and a major threat to the socio-economic development, mainly in developing countries. Importantly, zoonotic helminths that affect human eyes (HIE) may cause blindness with severe socio-economic consequences to human communities. These infections include nematodes, cestodes and trematodes, which may be transmitted by vectors (dirofilariasis, onchocerciasis, thelaziasis), food consumption (sparganosis, trichinellosis) and those acquired indirectly from the environment (ascariasis, echinococcosis, fascioliasis). Adult and/or larval stages of HIE may localize into human ocular tissues externally (i.e., lachrymal glands, eyelids, conjunctival sacs) or into the ocular globe (i.e., intravitreous retina, anterior and or posterior chamber) causing symptoms due to the parasitic localization in the eyes or to the immune reaction they elicit in the host. Unfortunately, data on HIE are scant and mostly limited to case reports from different countries. The biology and epidemiology of the most frequently reported HIE are discussed as well as clinical description of the diseases, diagnostic considerations and video clips on their presentation and surgical treatment.

Case report: First evidence of human zoonotic infection by Onchocerca lupi (Spirurida, Onchocercidae)

In the past decades, cases of canine ocular onchocercosis have been reported worldwide, particularly in the United States and Europe. Onchocerca lupi, originally described from a wolf, has been implicated in some of these cases, and its zoonotic role has been hypothesized on the basis of the reexamination of two cases of human ocular onchocerciasis. In the present study, we describe, for the first time, the occurrence of O. lupi in the subconjunctival region of the human eye in a patient from Turkey. The nematode was identified as O. lupi based on its morphology and molecular phylogenetic analysis of partial cox1 and 12S ribosomal DNA genes. The results suggest that O. lupi should be considered in the differential diagnosis of other eye parasitic infections in humans. The role of dogs as natural hosts of O. lupi and the vectors of this zoonotic parasite need to be investigated.

Molecular genetic comparison of Onchocerca sp. infecting dogs in Europe with other spirurid nematodes including Onchocerca lienalis

In the past 15 years, subconjunctival onchocercosis has been reported from 63 dogs in south-western United States (Arizona, California, Utah) and Southern and Central Europe (Germany, Greece, Hungary, Portugal, Switzerland). To reveal the taxonomic status of the parasite responsible for these infections, fragments of the mitochondrial cytochrome oxidase subunit I (COI) and NADH dehydrogenase subunit 5 (ND5) genes of three European strains of canine Onchocerca sp. and the 16S ribosomal RNA (16S rRNA) gene of their Wolbachia endosymbionts were sequenced and compared to the homologous sequences of other spirurid nematodes. The evolutionary divergence between COI and ND5 gene sequences of Greek, Hungarian and Portuguese strains of canine Onchocerca sp. were similar in magnitude to that seen within Thelazia callipaeda or Onchocerca lienalis. The evolutionary divergence between the sequences of canine Onchocerca sp. and other Onchocerca spp. including O. lienalis were similar or higher in magnitude to that seen between other Onchocerca spp. The results of the current and earlier phylogenetic analyses indicate that canine Onchocerca sp. separated from other Onchocerca spp. early in the evolution. Based on the similar clinical pictures, the identical morphology of nematodes and the sequence analyses of COI and ND5 genes of the worms and 16S rRNA gene of their wolbachiae, the Onchocerca worms isolated from European dogs appear to belong to the same species. The results support the earlier biological and morphological arguments that a distinct species, most likely O. lupi originally described from the subconjunctival tissues of a Caucasian wolf is responsible for canine ocular onchocercosis in Europe.

Zoonotic intravitreal Onchocerca in Hungary

OBJECTIVE

To report the case of a 65-year-old male patient from western Hungary who presented with rapidly progressive peripheral visual field (VF) loss and the sensation of an actively moving object in his central VF.

DESIGN

Interventional case report. METHOD/INTERVENTION: A live nematode was removed from the anterior vitreous cavity by pars plana vitrectomy.

RESULTS

The worm was successfully removed surgically, and the patient had an uneventful recovery. The nematode was identified as an immature filaria, most likely a member of the genus Onchocerca.

CONCLUSIONS

Only 3 previous reports exist of human infection of the eye caused by zoonotic Onchocerca, 2 involving the subconjunctiva and 1 the cornea. Although rare, zoonotic onchocercal infection of the eye must be considered a differential diagnostic entity even in temperate climates.

Canine ocular onchocerciasis in the United States: two new cases and a review of the literature

Since 1991, 53 cases of canine ocular onchocerciasis have been reported in the literature worldwide, 43 of these were from Greece, five from Hungary, and five from the western United States. Information on the histopathologic features of canine ocular onchocerciasis is limited. We describe the histopathologic features of canine ocular onchocerciasis in two dogs from California that presented clinically with firm episcleral nodules and uveitis unilaterally. Pertinent literature and pathogenesis are reviewed; recognizable clinical features and treatment are discussed. The cases presented were diagnosed via histopathology of the enucleated globes and episcleral granulomas at the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). Positive identification of adult Onchocerca within episcleral granulomas was made based on light-microscopy features. Histopathologic examination of both globes revealed episcleral parasites surrounded by granulomas containing few to moderate numbers of eosinophils. Other sequelae, in both cases, included lymphoplasmacytic uveitis, preiridal fibrovascular membranes, peripheral anterior synechiae, retinal degeneration, and optic nerve head cupping. Both male and female worms were present, as were in utero microfilariae in both cases. Worms in both cases were tentatively identified as Onchocerca lienalis. Ocular onchocerciasis should be a differential consideration in cases of canine conjunctival nodules or periorbital swelling, particularly in dogs from the western United States.

Obstructive, Granulomatous Tracheitis caused by Onchocerca sp. in a Dog

A 3-year-old spayed female dog was admitted with a history of episodes of dyspnoea and coughing. Severe tracheal stenosis was found on radiography. The dog died during an episode of refractory dyspnoea. Necropsy revealed an obstruction of the thoracic part of the trachea because of a chronic granulomatous inflammation protruding into the tracheal lumen. Histological examination revealed nematodes, which were identified as Onchocerca sp. according to their morphological characteristics. In contrast to the common ocular manifestation in dogs, obstructive tracheitis caused by Onchocerca infection has not been reported before.

Extraintestinal nematode infections of red foxes (Vulpes vulpes) in Hungary

A survey was carried out to investigate the prevalence and worm burden of extraintestinal nematodes in 100 red foxes (Vulpes vulpes) of Hungary. The overall prevalence of nematode infections of the respiratory tract was 76%. Eucoleus aerophilus (Capillaria aerophila) was the predominant species (66%), followed by Crenosoma vulpis (24%), Eucoleus (Capillaria) böhmi (8%) and Angiostrongylus vasorum (5%). Pearsonema (Capillaria) plica was found in 52% of the urinary bladders. In 3% of the foxes, Trichinella britovi was present in muscle samples. The high prevalence of lungworms and P. plica and the fox colonisation in urban areas may enhance the prevalence of these nematode infections in domestic dogs and cats, and the flow of T. britovi from the sylvatic cycle to the domestic cycle, enhancing the risk of infections in humans.

Molecular phylogenetic analysis of Onchocerca lupi and its Wolbachia endosymbiont

The morphology of Onchocerca lupi, responsible for canine ocular onchocercosis, is unique within the genus. Earlier analyses of the 5S ribosomal RNA gene spacer region sequence of the parasite and the 16S ribosomal RNA gene sequence of its Wolbachia endosymbiotic bacteria (Rickettsiales) supported the morphological and biological arguments that O. lupi is a distinct species. However, the exact phylogenetic position of O. lupi and its endosymbiont could not be unambiguously determined. Herein we report analyses based on the mitochondrial cytochrome oxidase I (COI) gene of the filarial species and the Wolbachia surface protein (wsp) and the bacterial cell-cycle ftsZ genes of their wolbachiae. Our results indicate that O. lupi separated from other Onchocerca spp. early in evolution. This is in line with the previous morphological analysis demonstrating that O. lupi is an atypical Onchocerca species showing both primitive and evolved characters. The phylogenetic trees generated for the COI sequences of filariae and the wsp and ftsZ sequences of their wolbachiae were congruent with each other, which supports the hypothesis that nematodes and their Wolbachia endobacteria share a long co-evolutionary history.

Ocular onchocercosis in dogs: a review

In recent decades, sporadic cases of ocular Onchocerca species infection have been reported in dogs in the USA and Europe. In the acute stage of the disease severe inflammation of the ocular and periocular tissues was observed. In chronic cases, the strongly coiled, gravid nematodes were incorporated in pea- to bean-sized granulomatous nodules in various parts of the eye, including the retrobulbar space, orbital fascia, eyelid, third palpebra, conjunctiva and sclera. Apart from the ophthalmological significance of the disease, the large number of microfilariae in the skin may be responsible for acute and chronic dermatological problems. The geographical distribution and prevalence of the infection may be greater than currently thought, because the lesions may have been erroneously regarded as other ocular diseases. Onchocerciasis is the world's second most prevalent infectious cause of blindness in human beings and parasitologists have long searched for an experimental model of human onchocerciasis; ocular onchocercosis infections in dogs may provide a useful experimental system.

Subconjunctival zoonotic onchocerciasis in man: aberrant infection with Onchocerca lupi?

In the past few decades, 10 cases of cryptic, zoonotic onchocerciasis, including two subconjunctival infections, have been reported in man. In the majority of cases, Onchocerca cervicalis, O. gutturosa or O. dewittei, which normally infect horses, cattle and wild boar, respectively, were responsible for the lesions. However, the taxonomic status of the parasites involved in the two subconjunctival infections, both of which were European, has never been unambiguously determined. In such infections, the acute phase appears to be characterized by conjunctivitis. A single, strongly coiled, immature, female worm was found incorporated in a large granulomatous nodule, in the ocular and peri-ocular tissues, in the chronic stage of each of the two eye infections. Several, patent, sporadic cases of subconjunctival O. lupi infection have recently been reported in dogs. In terms of the location of the worms, clinical signs and histopathology, these canine infections were very similar to those seen in the two human patients with eye infection. When the parasites recovered from human eyes were compared morphologically with the Onchocerca spp. infecting animals in Europe, they appeared to be most similar to O. lupi. Although O. lupi is normally a parasite of dogs, it may thus also be responsible for aberrant, zoonotic, subconjunctival infections in man.

Subconjunctival filariasis due to Onchocerca sp. in dogs: report of 23 cases in Greece

In the present study, we describe a series of 23 cases of ocular subconjunctival parasitic granulomas in dogs, admitted to the Clinic of Surgery, Faculty of Veterinary Medicine of the Aristotle University of Thessaloniki, Greece, between 1997 and 2000. The ophthalmic manifestations in all animals were periorbital swelling, discomfort, photophobia, conjunctival congestion, and discharge. A more detailed examination revealed the presence of periocular masses (nodules) on the subconjunctival bulbar space. Granulomatous or cyst-like formations were extracted surgically, and were found to contain thread-like nematode parasites. A histologic and parasitologic examination of tissues and parasites was carried out. Diagnosis of parasitic granulomas was made and the parasite was identified as Onchocerca sp. This is the largest series of cases reported of aberrant Onchocerca infections in dogs coming from one geographic location.

Electron microscopic and molecular identification of Wolbachia endosymbionts from Onchocerca lupi: implications for therapy

It was recently demonstrated that Wolbachia intracellular bacteria (alpha 2 proteobacteria, Rickettsiales) living in filarial nematodes are obligatory symbionts of their hosts. Herein, we report the electron microscopic and 16S ribosomal DNA-based (16S rDNA) identification of the endobacteria harboring in Onchocerca lupi. The worm nodules containing the nematodes were removed from three Hungarian dogs naturally infected with O. lupi. Wolbachia-like endobacteria were detected by electron microscopy in the lateral chords of both adult worms and microfilariae. The endosymbionts in O. lupi resemble in location, size, and morphology the wolbachiae found in other filariae. The presence of wolbachiae in O. lupi was also confirmed by PCR amplification of the 16S rDNA of the bacteria. The 16S rDNA-based phylogenetic analysis revealed that the endosymbionts of O. lupi infecting dogs belong to the supergroup C of Wolbachia pipientis and are not identical with those of other Onchocerca spp. sequenced so far. Since intermittent treatment with oxytetracycline has adulticid and microfilaricid activity by depletion of Wolbachia endobacteria, this antibiotic treatment regimen may offer an alternative of ivermectin or diethylcarbamazine in the suppression of postoperative microfilaridermia in Onchocerca-infected dogs and may prevent relapse.

Morphologic and genetic characterization of Onchocerca lupi infecting dogs

In the past decades, sporadic cases of ocular Onchocerca infection have been reported in canids in US and Europe. The present study was undertaken to provide a detailed description of the morphologic characteristics of adults and microfilariae and to characterize the 5S ribosomal rRNA gene (5S rDNA) spacer sequences of Onchocerca lupi causing canine onchocercosis. The morphology of O. lupi is unique within the genus, and morphology based cluster analysis indicates that O. lupi is not closely related to the members of domestic cattle or horse clades occurring in North America and Europe. Similarly, the signature of the 5S rDNA spacer sequences of O. lupi does not resemble any other Onchocerca 5S rDNA spacer sequences including those of the members of domestic cattle or horse clades. The adult and microfilarial morphology and sequence signature supports the biological arguments that a distinct species, O. lupi and not O. lienalis, is responsible for canine ocular onchocercosis.

Ocular onchocercosis in dogs: aberrant infection in an accidental host or lupi onchocercosis?

Four adult dogs that had spent their entire life in Hungary, were found to be infected with filaroid nematodes of the genus Onchocerca. The morphology and location of the parasites as well as pathological lesions were similar to those described earlier in the one Hungarian and five US dogs. Only moderate morphological differences were noted between the adults of Onchocerca sp. infecting dogs and O. volvulus of man or O. lienalis of cattle. Nevertheless, the morphology of microfilariae of Onchocerca from dogs is unique within the genus. Their length was less than half the length of microfilariae of other Onchocerca spp. known so far. In addition to size differences, several characteristic morphological features were observed. The unsuccessful attempt to infect dogs with O. lienalis, the absence of O. volvulus and O. lienalis in endemic regions of canine onchocercosis, the different size, morphology, and location of the adults in dogs and cattle, the exceptionally small size and unique morphology of microfilariae of Onchocerca of canids indicate that a distinct species might be responsible for canine onchocercosis. Since the larval concentration in the skin was high (50-3600 microfilariae g(-1)) in all affected dogs, the diagnosis prior to surgical removal of worm nodules can be based on the examination of a small skin snip collected from the head or abdominal region. Infections in dogs may provide a model to study human onchocercosis, therefore, further studies are encouraged on the feasibility of experimental infection of dogs with this Onchocerca species.