Coyotes as Reservoirs for Onchocerca lupi, United States, 2015-2018

A footworm in the door: revising Onchocerca phylogeny with previously unknown cryptic species in wild North American ungulates

Onchocerca is an important genus of vector-borne filarial nematodes that infect both humans and animals worldwide. Many Onchocerca spp., most of medical and veterinary health relevance, are the focus of a variety of diagnostic and molecular research. However, despite the importance of these parasites, there is growing evidence of previously unexplored genetic diversity of these nematodes, particularly among wild ungulate hosts in North America. These understudied parasites prevent us from comprehending the evolutionary history of the genus Onchocerca, monitoring potential One Health threats, and improving our filarioid diagnostic capabilities. In order to fill these knowledge gaps, we identified five uncharacterized Onchocerca lineages and compared them with other well-known filarioid species using single and concatenated gene regions (i.e., nd5, cox1, 12S, 18S, 28S, hsp70, MyoHC, rbp1). Phylogenetic analyses revealed that the novel Onchocerca lineages of wild North American ungulates segregate into two clades. One clade comprised Onchocerca lineages II, IV, and V and other species found mainly in domestic animals and humans, and the second comprised Onchocerca lineages I and III and other species from a variety of hosts including cervids, bovids, and equids. The formation of two clearly separate clades supports the idea of at least two independent expansion events of ancestral Onchocerca spp. into the North American continent via the Bering land bridge. Cophylogenetic analysis shows evidence of ancestral Onchocerca spp. of Bovidae host-switching to wild Cervidae and giving rise to the novel Onchocerca spp. Lastly, pairwise analysis confirms informative molecular markers of diagnostic relevance in both mitochondrial and nuclear gene regions of filarioid nematodes. The overall information provides greater context to the genus Onchocerca and emphasizes the need to discover, characterize, and monitor neglected parasites, especially those of wildlife origin.

Status of Onchocerciasis Elimination in Gabon and Challenges: A Systematic Review

Control and treatment programs (CDTI) have been set up nationally in all endemic countries to overcome the impact of onchocerciasis on the affected populations. However, Gabon must still succeed in setting up real onchocerciasis control programs. Here, various database articles have been used to provide the scientific community with a summary document showing the mapping of this disease in Gabon. The articles dealing with onchocerciasis, animal reservoirs, surveillance, and elimination were analyzed. Results showed that little research has been performed. Most studies are concentrated in one region (The area of Lastourville). In addition, we observed that the distribution of the disease varies significantly across the country. Indeed, specific environments present a hyper-endemicity of the disease, while others are meso and hypo-endemic. So, we found some departments with a prevalence ranging from 0% to over 20%; within them, villages had infection levels comprising 10% to 60%, indicating potential hotspots. Vectors activities were studied in some areas. This paper showed the challenges encountered in the country to eliminate this disease. One solution is a deeper understanding of the disease's bioecology to establish effective health policies to eliminate onchocerciasis in Gabon effectively.

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.

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.

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.

Neuroinvasive Onchocerca lupi Infection in a Ten-Year-Old Girl

The nematode Onchocerca lupi is an emerging human pathogen. Though its life cycle is not well studied, it likely infects humans after a bite from a black fly vector, which in turn acquires infective microfilariae from an infected canid. These microfilariae mature into an infective larval stage within the fly. Among six reported cases in the United States, five involved children, and all occurred in the southwest. In this report, we present a case of O. lupi infection with cervical spine invasion in a healthy 10-year-old girl. She presented with five months of neurological symptoms from a rural and medically underserved area, highlighting a need for clinical vigilance in such settings for this emerging infectious threat in the American southwest.

LupiQuant: A real-time PCR based assay for determining host-to-parasite DNA ratios of Onchocerca lupi and host Canis lupus from onchocercosis samples

Onchocerca lupi is a filarial nematode that causes ocular onchocercosis in canines globally including North America and areas of Europe, North Africa, and the Middle East. Reported incidence of this parasite in canines has continued to steadily escalate since the early 21st century and was more recently documented in humans. Whole genome sequencing (WGS) of this parasite can provide insight into gene content, provide novel surveillance targets, and elucidate the origin and range expansion. However, past attempts of whole genome sequencing of other Onchocerca species reported a substantial portion of their data unusable due to the variable over-abundance of host DNA in samples. Here, we have developed a method to determine the host-to-parasite DNA ratio using a quantitative PCR (qPCR) approach that relies on two standard plasmids each of which contains a single copy gene specific to the parasite genus Onchocerca (major body wall myosin gene, myosin) or a single copy gene specific to the canine host (polycystin-1 precursor, pkd1). These plasmid standards were used to determine the copy number of the myosin and pkd1 genes within a sample to calculate the ratio of parasite and host DNA. Furthermore, whole genome sequence (WGS) data for three O. lupi isolates were consistent with our host-to-parasite DNA ratio results. Our study demonstrates, despite unified DNA extraction methods, variable quantities of host DNA within any one sample which will likely affect downstream WGS applications. Our quantification assay of host-to-parasite genome copy number provides a robust and accurate method of assessing canine host DNA load in an O. lupi specimen that will allow informed sample selection for WGS. This study has also provided the first whole genome draft sequence for this species. This approach is also useful for future focused WGS studies of other parasites.

First Description of the Mitogenome Features of Neofoleyellides Genus (Nematoda: Onchocercidae) Isolated from a Wild Bird (Pyrrhocorax pyrrhocorax)

Simple Summary

Filarioidea, a superfamily of nematodes, presently includes 42 species divided into six genera, mainly in the family Onchocercidae, which have been reported to infect a wide range of hosts, including reptiles, birds, and mammals. Current limitations in molecular characterization methods and species identification are the main obstacles to a better understanding of the biology of Onchocercidae species, particularly in wildlife. Thus, the objective of the present study was to sequence and analyze the complete mt genome of Neofoleyellides sp. isolated from a wild bird (Pyrrhocorax pyrrhocorax) and to assess its phylogenetic position in the Onchocercidae family. The evaluated Neofoleyellides sp. mt genome was consistent with the molecular pattern of the Onchocercidae family: 36 subunits consisting of 12 PCGs, 2 rRNAs, and 22 tRNAs. Phylogenetic analyses based on the 18S rRNA gene, cox1 gene, and 12 PCGs showed consistent results, which strongly supported monophyly of the genus Neofoleyellides. These findings enriched the gene database and improved our knowledge of the molecular characteristics of the Onchocercidae family, which provide useful genetic markers to study the population genetics, molecular biology, and phylogenetics of these Onchocercidae nematodes.

Abstract

The Onchocercidae family is composed of more than 30 valid nematode species with notable zoonotic potential. Current limitations in molecular characterization methods and species identification are the main obstacles to a better understanding of the biology of Onchocercidae species, particularly in wildlife. This study describes for the first time the complete mitochondrial (mt) genome sequence of Neofoleyellides sp. isolated from a wild bird (Pyrrhocorax pyrrhocorax) and belonging to the Neofoleyellides genus (Nematoda: Onchocercidae). The mt genome of Neofoleyellides sp. (GenBank accession number: ON641583) was a typical circular DNA molecule of 13,628 bp in size with an AT content of 76.69%. The complete mt genome comprised 36 functional subunits, including 12 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. The most common start codon was ATT/ATG except for nad2 with TTG, and TAA was the termination codon for all protein-coding genes (PCGs). Phylogenetic analysis of the concatenated and aligned amino acid sequences of the 12 PCGs showed that the trees generated using different methods (Bayesian inference and maximum likelihood) with different partition schemes shared similar topologies. The isolated Neofoleyellides sp. was placed in the Onchocercidae family and formed a sister branch with the genera Onchocerca and Dirofilaria. The entire mt genome of Neofoleyellides sp. presented in this study could provide useful data for studying the population genetics and phylogenetic relationships of Onchocercidae species.

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.

Presence of a cryptic Onchocerca species in black flies of northern California, USA

Background

Black flies (Diptera: Simuliidae) serve as arthropod vectors for various species of Onchocerca (Nematoda: Onchocercidae) that may be associated with disease in humans, domestic animals, and wildlife. The emergence of zoonotic Onchocerca lupi in North America and reports of cervid-associated zoonotic onchocerciasis by Onchocerca jakutensis highlight the need for increased entomological surveillance. In addition, there is mounting evidence that Onchocerca diversity in North America is far greater than previously thought, currently regarded as Onchocerca cervipedis species complex. This study reports new geographic records and black fly vector associations of an uncharacterized Onchocerca species.

Methods

To better understand the biodiversity and geographic distribution of Onchocerca, 485 female black flies (2015: 150, 2016: 335) were collected using CO₂-baited traps from February to October 2015–2016 in Lake County, northern California, USA. Individual flies were morphologically identified and pooled (≤ 10 individuals) by species, collection date, and trap location. Black fly pools were processed for DNA extraction, and subsequent PCR and sequencing targeting of the NADH dehydrogenase subunit 5 gene of filarioids.

Results

Among the pools of black flies, there were 158 individuals of Simulium tescorum (2015: 57, 2016: 101), 302 individuals of Simulium vittatum (sensu lato [s.l.]) (2015: 82, 2016: 220), 16 individuals of Simulium clarum “black” phenotype (2015: 5, 2016: 11), and 13 individuals of S. clarum “orange” phenotype (2015: 6, 2016: 7). PCR analysis revealed the percentage of filarioid-positive pools were 7.50% (n = 3) for S. tescorum, 3.75% (n = 3) for S. vittatum (s.l., likely S. tribulatum), 7.69% (n = 1) for S. clarum “black” phenotype, and no positives for S. clarum “orange” phenotype. Genetic distance and phylogenetic analyses suggest that the northern California Onchocerca isolates belong to the same species reported in black flies from southern California (average pairwise comparison: 0.32%), and seem closely related to Onchocerca isolates of white-tailed deer from upstate New York (average pairwise comparison: 2.31%).

Conclusion

A cryptic Onchocerca species was found in Lake County, California, and may be a part of a larger, continentally distributed species complex rather than a single described species of North America. In addition, there are at least three putative vectors of black flies (S. clarum, S. tescorum, S. vittatum) associated with this cryptic Onchocerca species. A comprehensive reassessment of North American Onchocerca biodiversity, host, and geographic range is necessary.

Graphical abstract

Confirmed cases of human Onchocerca lupi infection: a systematic review of an emerging threat

Diverse Onchocerca species are present mostly parasitizing ungulates, with the exception of Onchocerca volvulus (O. volvulus) in humans and O. lupi in canids and cats. The human cases due to the O. lupi have been more highlighted during last years. So, the present review was performed to determine the detailed characteristics of confirmed human O. lupi case reports documented worldwide. Hence, a systematic search was done using English international databases (Scopus, PubMed, Web of Science, Embase, ProQuest, and Google Scholar). Totally, 14 confirmed human cases were documented during the last decade, mostly from the USA and Turkey with 7 and 3 cases, respectively. Most cases (7 individuals) were male with the age range of 22-month-old to 54-year-old. The parasite was frequently isolated from the right eye (5 cases), followed by the left eye (4 cases), cervical spinal canal (3 cases), scalp, and right forearm (one case each). Molecular identification of the isolated agent was the preferred way of diagnosis in most cases (9 records). In conclusion, human O. lupi cases have been more highlighted in recent years, whether due to the improved diagnostics and/or host-switching phenomenon, and both veterinarians and healthcare authorities should be alerted.

Complete mitochondrial genome of Onchocerca lupi (Nematoda, Onchocercidae)

Onchocerca lupi, Rodonaja 1967, is an emerging, zoonotic filarial nematode parasite that causes ocular disease in dogs, cats, wild canids, and humans. It is the causative agent of ocular onchocercosis in canines with increasing incidence in both North America and the Old World during the early twenty-first century. We report the complete mitochondrial genome of an O. lupi isolate from a dog from Arizona, southwestern USA, and its genetic differentiation from related Onchocerca species. The whole mitochondrial genome was obtained from whole genome sequencing of genomic DNA isolated from an adult worm. This mitogenome is 13,766 bp in size and contains 36 genes and a control region. This mitogenome provides a valuable resource for future studies involving epidemiological surveillance, population genetics, phylogeography, and comparative mitogenomics of this emerging pathogen and other parasitic nematodes.

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.

Autochthonous, zoonotic Onchocerca lupi in a South Texas dog, United States

BACKGROUND

Onchocerca lupi is an emerging, zoonotic filarioid nematode associated with ocular disease in companion animals in North America and the Old World. The areas where this parasite is assumed to be endemic in the USA comprise southwestern states. Thus far, all cases reported outside of the southwest are associated with travel or animal movement.

METHODS

An 11-year-old, castrated male Pitbull dog from McAllen, Hidalgo County, southern Texas, with no travel history, was diagnosed with a perforating corneal ulceration of the right eye. Enucleation was performed and tissues submitted for histopathology.

RESULTS

Histologically, sections of two filarioid nematodes were observed. DNA was extracted from formalin-fixed paraffin-embedded tissue using a commercial kit. We performed PCR targeting the cox1 gene of the mitochondrial DNA, followed by sequencing and phylogenetic analysis. Altogether, these results confirmed the identification of the nematode specimens as O. lupi, phylogenetically belonging to haplotype 1.

CONCLUSION

We report the first autochthonous case of O. lupi in a dog from Hidalgo County, southern Texas, USA. Our finding suggests Texas as an additional state where this zoonotic nematode is endemic. Further investigations are required to understand the epidemiology of this parasite along the USA/Mexico border.