Zoonotic ocular onchocercosis caused by Onchocerca lupi in dogs in Romania

Autochthonous Onchocerca lupi infection of a domestic dog in Austria

Onchocerca lupi is an emerging canine ocular pathogen with zoonotic potential. In Europe, known endemic areas are the Iberian Peninsula and Greece, but the parasite has also been found in Romania, Hungary, and Germany. A 5-year-old Irish Wolfhound was presented in August 2021 with ocular discharge. A subconjunctival granulomatous nodule containing several nematode fragments was removed. Molecular analysis of the mitochondrial cytochrome c oxidase subunit I gene confirmed the presence of O. lupi genotype 1. This is the first report of autochthonous O. lupi infection in a dog from Austria.

Case Report: A New Geographic Area for the Presence of the Zoonotic Ocular Nematode, Onchocerca lupi in Romania

Introduction

Onchocerca lupi is a zoonotic parasite of carnivores reported in countries from Europe, North America, Asia and Africa. In Romania, canine ocular onchocercosis was first reported in dogs in 2016 from Târgovişte (Dâmboviţa County) and Oneşti (Bacău County) and more recently, it was detected in an adult stray dog exported to UK from an unspecified location in Romania.

Methods

A 4-years old male mongrel dog was referred to a private veterinary clinic in Năvodari (Constanţa County), Romania due to ocular disorders. The dog was originally from a public dog shelter in Balş (Olt County) and transferred in June 2020 to a dog shelter in Medgidia (Constanţa County). A cytological examination followed by surgical removal of the granuloma localized at the internal angle of the right eye, and molecular identification of the extracted nematode were done.

Results

The cytological examination confirmed a parasitic granuloma. Skin biopsy and PCR confirmed the infection with O. lupi. Two doses of moxidectin and imidacloprid were administered after the surgery. No relapse observed after a period of follo-up of 11 months.

Conclusion

Onchocerca lupi is present in dogs from Romania with its actual distribution remaining unknown.

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.

Zoonotic Ocular Onchocercosis by Onchocerca lupi

The parasitic filarioid Onchocerca lupi causes ocular disease characterized by conjunctivitis and nodular lesions. This nematode was first described in 1967 in a wolf from Georgia, and since then cases of infection from dogs and cats with ocular onchocercosis and sporadically from humans also with subcutaneous and cervical lesions caused by O. lupi have been reported from the Middle East, Europe, and North America. Due to its zoonotic potential, this parasitic infection has gained attention in the past 20 years. Phylogenetic studies have highlighted the recent divergence of O. lupi from other Onchocerca spp. and the importance of domestication in the evolutionary history of this worm. Moreover, the finding of an O. lupi genotype associated with subclinical and mild infection in the Iberian Peninsula, raises important questions about the pathogenicity of this presently enigmatic parasite.

Canine ocular onchocerciasis in New Mexico: Risk factors for disease

OBJECTIVE

To determine whether dogs are at variable risk of developing canine ocular onchocerciasis based on coat color or size, factors that may influence feeding behavior of the putative vectors of Onchocerca lupi¸ the filarial nematode parasite causing this disease.

ANIMALS STUDIED

One hundred twenty-five client-owned dogs diagnosed with confirmed or suspected onchocerciasis. 1255 dogs without signs of this disease were utilized for comparison.

PROCEDURES

Dogs lacking signs of canine onchocerciasis were assessed for coat color and weight. Proportions of dogs with these characteristics were used to predict signalment in a group of dogs with this disease, if the investigated characteristics were unrelated to disease risk. Predicted values were compared statistically with observed values in the diseased dog population. Black fly color preference was assessed utilizing black, brown, and white traps and statistically assessing any differences in trapping based on trap color.

RESULTS

Results suggest that large, black dogs are more likely to develop canine ocular onchocerciasis than was predicted by chance alone (p = 0.012). Results for smaller dogs with other coat colors were not significant. An increased risk for black dogs was supported by trapping data, as black flies were trapped significantly more often in black traps (p < 0.001).

CONCLUSION

While factors other than size and color probably also influence the likelihood of O. lupi infection and disease development, our results may assist clinicians in their diagnosis of canine ocular onchocerciasis and provide them with a tool to help educate their clients as to their dogs' risk of developing this disease.

Filarial worms: a systematic review and meta-analysis of diversity in animals from Iran with emphasis on human cases

Current systematic review and meta-analysis demonstrate the prevalence reports of filariasis in animals in Iran along with human cases. Studies were screened, relevant papers were selected and the random-effect model was used by forest plot with 95% confidence interval (CI). Of 17 records of human case-reports, particularly from Khuzestan province (5 cases), Dirofilaria repens was the most detected parasite (10 cases) with higher involvement of the right eye (7 cases) than other organs. Eleven animal species were reported to be parasitised by filarioids in Iran. The prevalence of Dirofilaria immitis in canids was 14.69% (95% CI: 10.33-19.67), with highest rates (20.92%; 95% CI: 13.84-29.03) in free-ranging dogs. Male (10.07%; 95% CI: 5.10-16.47) and more than 1-year old (20.77%; 95% CI: 8.66-36.42) dogs were more likely to be found infected. The frequency of other filarioids of zoonotic interest was: Acanthocheilonema reconditum in dogs 2.15% (95% CI: 0.71-4.33), Dipetalonema evansi in camels 10.16% (95% CI: 4.73-17.34), Onchocerca cervicalis in horses 3.63% (95% CI: 1.44-6.75%) and Onchocerca fasciata 16.57% (95% CI: 10.12-24.24%) in camels. Still, our knowledge on parasitic filariae in Iran is limited and more investigation is needed in both human and animal populations.

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.

Seroepidemiological survey of human exposure to Dirofilaria spp. in Romania and Moldova

The present study aimed to evaluate the extent of Dirofilaria immitis and D. repens exposure in humans from eastern and southern areas of Romania and central Moldova by serological methods. The serological screening was performed on a total of 450 serum samples (187 from Romania and 263 from Moldova). The sera were collected using a convenience sampling with the help of physicians from the hospitals of the study areas. All samples were analysed by a non-commercial ELISA test for the detection of IgG antibodies against adult somatic antigens of D. immitis and D. repens. The results showed a total of 49 (10.9%; 95% CI = 8.3-14.1%) individuals from Romania and Moldova with a positive response to IgG antibodies against both adult somatic antigens of D. immitis and D. repens. Specifically, 48 (10.7%; 95% CI = 8.0-14.0%) patients were positive for IgG-antibodies against adult somatic antigens of D. immitis, one (0.2%; 95% CI = 0.4-1.2%) against D. repens antigens, and four (0.9%; 95% CI = 0.4-3.3%). were positive for antigens of both parasites. At country level, out of 187 samples from Romania, 13 (6.9%; 95% CI = 4.1-11.5%) were positive for anti-D. immitis IgG with high exposure in the southern part of the country (Bucharest). Of the 263 people from Moldova, 36 (13.7%; 95% CI = 10.0-18.4%) were positive for D. immitis antigens from which three (1.1%, 95% CI = 0.4-3.3%) were positive for the antibodies against antigens of both parasites. Only one sample was found positive for anti-D. repens IgG. Positive IgG-ELISA results were confirmed by Western blot analysis. In addition, for further confirmation, a complementary ELISA was performed for anti-WSP IgG antibodies against Wolbachia endosymbionts. Our findings showed a noticeable exposure of humans from Romania and Moldova to Dirofilaria parasites. Serology can be useful for indicating exposure to Dirofilaria spp. in a healthy population in order to obtain useful data on the epidemiological scenario of human dirofilariosis in Eastern Europe.

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.

Filarioid infections in wild carnivores: a multispecies survey in Romania

BACKGROUND

Filarioids are vector-borne parasitic nematodes of vertebrates. In Europe, eight species of filarioids, including zoonotic species, have been reported mainly in domestic dogs, and occasionally in wild carnivores. In Romania, infections with Dirofilaria spp. and Acanthocheilonema reconditum are endemic in domestic dogs. Despite the abundant populations of wild carnivores in the country, their role in the epidemiology of filarioid parasites remains largely unknown. The aim of the present study was to assess the host range, prevalence and distribution of filarioid infections in wild carnivores present in Romania.

METHODS

Between May 2014 and February 2016, 432 spleen samples originating from 14 species of wild carnivores have been tested for the presence of DNA of three species of filarioids (D. immitis, D. repens and A. reconditum).

RESULTS

Overall 14 samples (3.24%) were molecularly positive. The most prevalent species was D. immitis (1.62%), accounting for 50% (n = 7) of the positive animals. The prevalence of D. repens was 1.39%, while that of A. reconditum was 0.23%. No co-infections were detected. Dirofilaria immitis DNA was detected in five golden jackals, Canis aureus (7.58%), one red fox, Vulpes vulpes (0.33%), and one wildcat, Felis silvestris (10%). The presence of D. repens DNA was detected in two red foxes (0.66%), two golden jackals (3.03%), one grey wolf (7.14%), and one least weasel, Mustela nivalis (33.33%). Acanthocheilonema reconditum DNA was found only in one red fox (0.33%).

CONCLUSION

The present study provides molecular evidence of filarial infections in wild carnivore species in Romania, suggesting their potential epidemiological role and reports a new host species for D. repens.

Mosquitoes in the Danube Delta: searching for vectors of filarioid helminths and avian malaria

BACKGROUND

Mosquitoes are arthropods of major importance to animal and human health because they are able to transmit pathogenic agents such as filarioids (Spirurida), vector-borne nematodes, which reside in the tissues of vertebrates. In Europe, recent research has mostly focused on mosquito-borne zoonotic species, while others remain neglected. Mosquitoes are also vectors of avian malaria, which has an almost worldwide distribution, and is caused by several Plasmodium species and lineages, the most common being P. relictum. The Danube Delta region of Romania is one of the most important stopover sites for migratory birds. The local mosquito fauna is diverse and well represented, while filarial infections are known to be endemic in domestic dogs in this area. The aim of the present study was thus to assess the potential vector capacity for various filarial helminths and avian malaria of mosquitoes trapped in the Danube Delta.

METHODS

In July 2015, mosquitoes were collected at seven sites located in and around a rural locality in the Danube Delta region of Romania, using CO₂-baited traps and hand aspirators. Additionally, a trap was placed next to a microfilaremic dog co-infected with Dirofilaria repens and D. immitis. All randomly trapped mosquitoes were identified to the species level and pooled according to date, sampling site, and taxon. Three hundred individual mosquitoes sampled next to the microfilaremic dog were processed individually and divided into abdomen and thorax/head. Following DNA extraction, all samples were screened for the presence of DNA of filarioid helminths and avian malaria agents by PCR techniques.

RESULTS

All 284 pools (a total of 5855 mosquitoes) were negative for filarioid DNA. One pool of Culex modestus mosquitoes was positive for Plasmodium sp. lineage Donana03. In the individually extracted mosquitoes, one abdomen of Aedes vexans was positive for D. repens DNA, one thorax/head of Ae. vexans was positive for DNA of Setaria labiatopapillosa, and two thorax/head of Cx. pipiens f. pipiens were positive for P. relictum lineage pSGS1.

CONCLUSION

The present study suggests the vector competence of Cx. modestus and Cx. pipiens for avian Plasmodium including pathogenic species P. relictum and Ae. vexans for mammalian filarioids. Moreover, it indicates the role of Cx. pipiens f. pipiens as a potential natural vector of P. relictum lineage pSGS1 in nature.

Whence river blindness? The domestication of mammals and host-parasite co-evolution in the nematode genus Onchocerca

The genus Onchocerca includes 34 described species and represents one of the largest genera of the filarial nematodes within the family Onchocercidae. Representative members of this genus are mainly parasites of ungulates, with some exceptions such as Onchocerca lupi and Onchocerca volvulus, infecting carnivores and/or humans. For a long time, the evolutionary relationships amongst onchocercids remained poorly studied, as the systematics of this genus was impaired by the high morphological variability of species included in the taxon. Although some molecular phylogenies were developed, these studies were mainly focused on bovine Onchocerca spp. and O. volvulus, including assessments of Wolbachia endosymbionts. In the present study, we analysed 13 Onchocerca spp. from a larger host spectrum using a panel of seven different genes. Analysis of the coxI marker supports its usefulness for the identification of species within the genus. The evolutionary history of the genus has been herein revised by multi-gene phylogenies, presenting three strongly supported clades of Onchocerca spp. Analyses of co-evolutionary scenarios between Onchocerca and their vertebrate hosts underline the effect of domestication on Onchocerca speciation. Our study indicates that a host switch event occurred between Bovidae, Canidae and humans. Cophylogenetic analyses between Onchocerca and the endosymbiotic bacterium Wolbachia indicate the strongest co-evolutionary pattern ever registered within the filarial nematodes. Finally, this dataset indicates that the clade composed by O. lupi, Onchocerca gutturosa, Onchocerca lienalis, Onchocerca ochengi and O. volvulus derived from recent speciation.

First detection of Onchocerca lupi infection in dogs in southern Spain

Background

Onchocerca lupi causes ocular pathology of varying severity in dogs from south-western United States, western Europe and northern Asia. This filarioid has also been recognized as a zoonotic agent in Tunisia, Turkey, Iran and the USA, though the information about the biology and epidemiology of this infection is largely unknown. In Europe, O. lupi has been reported in dogs from Germany, Greece, Hungary, Portugal and Romania and in a cat from Portugal. The present study was designed to establish the occurrence of O. lupi in dogs in southwestern Spain.

In the present study a total of 104 dogs of different breed, sex, and age living in a shelter in Huelva (SW Spain) were examined. Skin snip samples were collected using a disposable scalpel in the forehead and inter-scapular regions and stored as aliquots in saline solution (0.5 ml) before light microscopy observation of individual sediments (20 μl) and molecular examination.

Results

Of the 104 dogs examined, 5 (4.8 %) were skin snip-positive for O. lupi: two by microscopy and three by PCR. One of the O. lupi infected dogs showed neurological signs but ocular ultrasonography and/or MRI detected no abnormalities.

Conclusions

This first report of O. lupi infection in dogs in southern Spain expands the range of geographical distribution of this parasite and sounds an alarm bell for practitioners and physicians working in that area.