First report of Onchocerca lupi from Israel and confirmation of two genotypes circulating among canine, feline and human hosts

Development of an indirect ELISA for the serodiagnosis of canine infection by Onchocerca lupi

Onchocerca lupi is a zoonotic filarioid parasite of dogs and cats with widespread distribution. A specific non-invasive diagnostic assay for the detection of O. lupi infections remains unavailable. This study aimed to assess the accuracy, specificity, and sensitivity of an ELISA test designed using nine peptides from two O. lupi proteins. Sera (n = 54) collected from O. lupi infected dogs from endemic areas (Portugal and USA), alongside sera from dogs positive for Dirofilaria immitis, D. repens, Cercopithifilaria bainae, and Acanthocheilonema reconditum (n = 53) from a non-endemic area for O. lupi, as well as from helminth-free dogs (n = 60), were tested. The checkerboard titration method was applied for the optimization of peptide concentrations and conjugate anti-dog dilutions. Sensitivity, specificity, and optimal cut-off values were calculated using ROC curve analysis. All peptides reacted against sera of O. lupi, with no correlation between optic density (OD) values and microfilariae (mfs) loads. Sensitivity and specificity values ranging from 85.45 to 100%, and 88.89% to 100%, respectively, were recorded for all peptides examined, with 100% specificity and sensitivity observed for peptides 40_3, 40_5, 130_3, 120_3 and 40_1, 130_5, respectively. The maximum cut-off value was observed for peptides 40_5 (0.765) and 40_3 (0.708). Testing of sera from dogs positive for other filarioids resulted in lower OD values (up to 1.565) for peptides 40_3 and 40_5 when compared with O. lupi (up to 2.929). The availability of this assay will be of value in epidemiological studies of canine O. lupi infection in both endemic and non-endemic areas, and in assessing the risk for zoonotic transmission.

Cryptic diversity in a gastrointestinal acanthocephalan of New World primates from Costa Rica

Prosthenorchis elegans is a worm of the family Archiacanthocephala that infects non-human primates in the Americas, producing an intestinal pathology that may compromise the life of its hosts. Squirrel monkeys, Saimiri oerstedii citrinellus, were found with P. elegans in Costa Rica. Histopathological analysis revealed a severe pyogranulomatous response composed by macrophages, neutrophils, eosinophils, fibroblasts and lymphocytes. Morphological worm analyses revealed 36 hooks in the proboscis distributed in six rows; and total body, hook and lemnisci length were compatible to the original descriptions of P. elegans. In addition, phylogenetic, haplotype network and genetic distance analyses were done on cytochrome oxidase subunit 1, cox1, sequences obtained from the collected specimens. Sequences obtained herein clustered separately with high posterior probabilities in a Bayesian Inference tree and showed 8.12% nucleotide differences when compared to P. elegans from Colombia. This high divergence was confirmed in the TCS network that separated Colombian and Costa Rican sequences by 32 mutational steps, a genetic distance PCA which separated sequences from both geographical locations by 89.5% and an F_ST value of 0.655, indicating the presence of cryptic diversity in P. elegans. Additional studies from specimens collected from other definitive hosts and geographical locations are required to better understand the biodiversity of this species.

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.

Genetic and geographical delineation of zoonotic vector-borne helminths of canids

Several zoonotic vector-borne helminths (VBHs) infesting canids cause serious veterinary and medical diseases worldwide. Increasing the knowledge about their genetic structures is pivotal to identify them and therefore to settle effective surveillance and control measures. To overcome the limitation due to the heterogeneity of large DNA sequence-datasets used for their genetic characterization, available cytochrome c oxidase subunit 1 (cox1) (n = 546) and the 12S rRNA (n = 280) sequences were examined using combined bioinformatic approach (i.e., distance-clustering, maximum likelihood phylogeny and phylogenetic evolutionary placement). Out of the 826 DNA available sequences from GenBank, 94.7% were characterized at the haplotype level regardless sequence size, completeness and/or their position. A total of 89 different haplotypes were delineated either by cox1 (n = 35), 12S rRNA (n = 21) or by both genes (n = 33), for 14 VBHs (e.g., Acanthocheilonema reconditum, Brugia spp., Dirofilaria immitis, Dirofilaria repens, Onchocerca lupi and Thelazia spp.). Overall, the present approach could be useful for studying global genetic diversity and phylogeography of VBHs. However, as barcoding sequences were restricted to two mitochondrial loci (cox1 and 12S rRNA), the haplotype delineation proposed herein should be confirmed by the characterization of other nuclear loci also to overcome potential limitations caused by the heteroplasmy phenomenon within the mitogenome of VBHs.

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.