Prevalence and pathogenesis of some filarial nematodes infecting donkeys in Egypt

An investigation of the prevalence of equine filariosis in North and Northeast of Iran

Worldwide, equines are affected by equine filariosis, an endemic vector-borne disease caused by heterogenous parasitic nematodes. The main objective of this study was to determine the prevalence of filarial infection among horses in the North and Northeast of Iran. Between October 2021 and July 2022, 145 equine blood samples were investigated, of which 49 cases were from the northeast and 96 were from the north of Iran. Blood samples were taken for microfilariae using Knott's method. Out of 145 blood samples, only 2 cases (1.37%) from northern Iran were positive for microfilaria of Setaria equina, and no positive samples were found from northeast Iran. The first positive sample was a 3-year-old male Iranian horse displaying clinical symptoms of weakness, while the second, an 8-month-old Arabian breed colt, exhibited no clinical signs. According to the results of the current study, the prevalence of equine filariosis is low, contrary to nearby countries. To prevent and control filarial infections among horses and improve their management system, it is therefore important to emphasize filarial infection prevention, control, and management.

Graphical abstract

Filarial nematodes in domestic dogs and mosquitoes (Diptera: Culicidae) from semi-rural areas in Central Chile

Climate change, competent vectors, and reservoir animals are the main factors for developing vector-borne zoonotic diseases. These diseases encompass a significant and widespread category of pathogens (e.g., viruses, bacteria, protozoa, and helminths) transmitted by blood-feeding arthropods, including ticks, fleas, lice, triatomines, mosquitoes, sandflies, and blackflies. In Chile, several studies have explored the role of dogs as reservoirs of vector-borne pathogens; however, there is a lack of research investigating the presence of pathogens in arthropods. Specifically, within the order Diptera, limited knowledge exists regarding their roles as carriers of pathogens. This study aimed to examine the presence of zoonotic filarial nematodes in mosquitoes and dogs within a previously unstudied semi-rural area of Central Chile. Two hundred samples of dog blood and seven hundred and twenty-four mosquitoes were collected during 2021-2022 and studied for filarial nematodes by PCR. The prevalence of microfilaremic dogs detected by Knott's test was 7.5%, with Acanthocheilonema reconditum being the only species identified. Aedes (Ochlerotatus) albifasciatus was the most abundant mosquito species collected, and 15 out of 65 pools were positive for filarial nematodes. Among these pools, 13 tested positive for Acanthocheilonema reconditum, and two tested positive for Setaria equina through PCR. Additionally, five Culex pipiens specimens were positive for Acanthocheilonema reconditum. Despite the absence of zoonotic filarial species, these findings underscore the significance of monitoring pathogens in mosquitoes and animal hosts and continued research into the dynamics of vector-borne diseases, particularly in unexplored regions.

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.

A new application of continuous sample drop flow microextraction using octanoic acid as a green extraction solvent for the determination of antibiotic drugs in urine samples

In this study, octanoic acid (OA) was used as an extraction solvent for the pre-concentration and determination of three antibiotic drugs (levofloxacin, metronidazole, and tinidazole) in urine samples. To extract the antibiotic drugs, a green solvent was used as the extraction solvent in the continuous sample drop flow microextraction method, followed by a high-performance liquid chromatography photodiode array detector. According to the findings, the present study offers an environmentally friendly analytical method with a high capacity for the microextraction of the antibiotic drugs at very low concentrations. The calculated detection limits were 6.0-10.0 µg/L and the linear range was found between 20 and 780 µg/L. The proposed method showed excellent repeatability with the RSD values ranging from 2.8 to 5.5%. The relative recoveries were between 79.0 and 92.0% in the urine samples with spiked levels of 40.0-100.0 µg/L for metronidazole and tinidazole, and 100.0-200.0 μg/L for levofloxacin.

Emergent and Neglected Equine Filariosis in Egypt: Species Diversity and Host Immune Response

Equine filariosis (EF) is a neglected vector-borne disease caused by nematode species belonging to the Onchocercidae and Setariidae families. Aside from their zoonotic potential, some species are responsible for serious health problems in equids worldwide, leading to significant economic difficulties. Here, we molecularly investigated equine blood samples (320 horses and 109 donkeys from Egypt) and four adult worms isolated from the peritoneal cavity of 5 out of the 94 slaughtered donkeys. In addition, quantitative enzyme-linked immunoassays (ELISAs) targeting circulating cytokines were used to identify whether the immunological profile of the infected animals is a Th1 (i.e., INF-gamma as indicator) or Th2 (i.e., IL-5 and IL-10 as indicators) response type. Overall, 13.8% and 0.3% of the donkeys and horses, respectively, were scored as positive for filaroid DNA. The 18S phylogeny revealed the occurrence of three different filaroid species, identified here as Mansonella (Tetrapetalonema) sp., Setaria digitata and Dirofilaria repens. Th1 (INF-gamma and IL-5) and Th2 (IL-10) immune response types were identified in equines infected with S. digitata and Mansonella (T.) sp., respectively. These results provide new data on the species diversity of EF in Egypt and extend knowledge of the downregulation of the protective immune response by the potentially zoonotic Mansonella (T) sp. There is an urgent need to implement control measures to preserve equine health and limit the propagation of these vector-borne filaroids in Egypt.

Multiple vector-borne pathogens of domestic animals in Egypt

Vector Borne Diseases (VBDs) are considered emerging and re-emerging diseases that represent a global burden. The aim of this study was to explore and characterize vector-borne pathogens in different domestic animal hosts in Egypt. A total of 557 blood samples were collected from different animals using a convenience sampling strategy (203 dogs, 149 camels, 88 cattle, 26 buffaloes, 58 sheep and 33 goats). All samples were tested for multiple pathogens using quantitative PCR and standard PCR coupled with sequencing. We identified Theileria annulata and Babesia bigemina in cattle (15.9 and 1.1%, respectively), T. ovis in sheep and buffaloes (8.6 and 7.7%, respectively) and Ba. canis in dogs (0.5%) as well as Anaplasma marginale in cattle, sheep and camels (20.4, 3.4 and 0.7%, respectively) and Coxiella burnetii in sheep and goats (1.7 and 3%; respectively). New genotypes of An. centrale, An. ovis, An. platys-like and Borrelia theileri were found in cattle (1.1,3.4, 3.4 and 3.4%, respectively), An. platys-like in buffaloes (7.7%), An. marginale, An. ovis, An. platys-like and Bo. theileri in sheep (3.4, 1.7, 1.7 and 3.4%, respectively), An. platys, An. platys-like and Setaria digitata in camels (0.7, 5.4 and 0.7%, respectively) and Rickettsia africae-like, An. platys, Dirofilaria repens and Acanthocheilonema reconditum in dogs (1.5, 3.4, 1 and 0.5%, respectively). Co-infections were found in cattle, sheep and dogs (5.7, 1.7, 0.5%, respectively). For the first time, we have demonstrated the presence of several vector-borne zoonoses in the blood of domestic animals in Egypt. Dogs and ruminants seem to play a significant role in the epidemiological cycle of VBDs.

First Molecular Confirmation of Equine Ocular Setaria digitata in China

A 5-year-old Mongolian mare (Equus caballus Linnaeus, 1758) was observed to have corneal opacity and excessive ocular discharge. An ophthalmic examination revealed a moving thread-like cylindrical worm in the anterior chamber of the right eye. The parasite was successfully removed surgically. The worm was observed under light microscopy and confirmed as Setaria digitata by 12S rRNA gene amplification and sequencing. Phylogenetic analysis demonstrated similarity with Setaria digitata in the National Center for Biotechnology Information (NCBI) GenBank database isolated from other Asian countries. This report is the first confirmed case of equine ocular setariasis by molecular diagnosis in China, which may indicate its presence in livestock and promote research on its epidemiology.

Prevalence of endo- and ecto-parasites of equines in Iran: A systematic review

Equines are subject to infection with many parasites, which threaten their health. In the present study, we systematically reviewed existing literature on the prevalence of endo- and ectoparasites of equines in Iran. Major electronic databases, including PubMed, PubMed Central, Google Scholar, Science Direct and Scientific Information Database (SID), were searched (Last updated 11/05/2018) for relevant literature of parasites that have been identified from equines in Iran. Of the 1809 titles produced by bibliographic search, 38 were included in the review. Twenty-seven of the studies were on horses, six on donkeys, three on both horses and donkeys, and one study was on both horses and mules. Furthermore, 24 of the studies reported infections caused by protozoa, thirteen by helminths, two by ectoparasites, and one by both protozoa and helminths. The overall pooled prevalence of parasitic infection was 28.8% (95%CI: 22.9-35.7, I²  = 93.4%). Helminths were the most prevalent parasites 46.7% (95% CI: 24.1-70.7, I²  = 96.0%). Furthermore, donkeys were the most affected equine, with a prevalence of 70.7% (95% CI: 53.2-83.7, I²  = 92.5%). The protozoa frequently reported included nine species belonging to the genera: Neospora, Toxoplasma, Theileria, Babesia and Eimeria. Also, the helminths frequently reported included 21 species belonging to the genera: Strongylus, Dicrocoelium, Oxyuris, Habronema, Echinococcus, Dictyocaulus, Cyathostomum, Probstmayria, Anoplocephala, Setaria and Fasciola. Ticks were the only ectoparasites frequently reported. Parasitic fly species of the genera Gasterophilus were also reported. The study-level risk of bias was likely to be high because of differences in study design. Parasitic infections of equines in Iran are frequent and caused by a diversity of parasites, which threatens the health and well-being of these animals. Further research is needed in the area to identify the risk factors of infection for effective control of the parasites.

Skin Diseases in Donkeys and Mules-An Update

Simple Summary

Equids are part of the history of many countries, including Brazil, where they were used in trade routes and expansion of the current states. Several skin diseases affect these animals; however, visibility is higher on horses than on donkeys and mules, which is linked to regional cultural and socioeconomic factors, even resulting in a decline of the world population of these animals. In this context, the objective of this study was to review which skin diseases have been reported in the scientific literature with emphasis on skin pathologies.

Abstract

The skin of donkeys and mules represents a promising source of income; however, cultural, productive, and infectious factors can directly interfere with the quality of the integumentary tissue and well-being of these species. The objective of this study is to present a literature review on equine dermatopathies. This literature review included scientific articles related to equine medicine and breeding according to pre-established search terms and expressions published in recently articles. The evaluation of the clinical and pathological behavior of dermatopathies implies the use of control strategies and the recognition of pathological patterns that may be particular to the species.

Suspensory Ligament Desmitis Caused by Onchocerca sp. in Three Donkeys

Three donkeys were presented with progressive lameness and distal suspensory ligament breakdown in multiple limbs. Treatment with nonsteroidal anti-inflammatory drugs was only partially effective and eventually the donkeys were euthanized due to further progression of the lameness and concerns for their welfare. At necropsy, the distal part of the suspensory ligaments in multiple limbs, including the suspensory ligament branches, was markedly thickened, enlarged, and mottled white and brown on cut section. In one case, adult Onchocerca sp. nematodes were grossly identified embedded within the suspensory ligaments. Histopathologic examination revealed chronic, multifocal to coalescing, moderate to severe, lymphoplasmacytic, eosinophilic, and fibrosing desmitis and tendinitis with intralesional, coiled adult nematodes of Onchocerca sp., accompanied by osseous and cartilaginous metaplasia. To the authors' knowledge, this is the first histopathologic description of suspensory ligament desmitis and tendinitis associated with Onchocerca sp. in donkeys.

Morphological and molecular characterization of Setaria equina in donkeys

Background

Adult worms of Setaria equina mainly found in the peritoneal cavity of equine. They were nonpathogenic but might induce varied degrees of peritonitis and might migrate to the eye, brain, lung, and scrotum causing lacrimation, blindness, paraplegia, locomotor, and neurological disturbances. Identification by light microscopy is insufficient to differentiate Setaria species, and so scanning electron microscopy (SEM) is required to observe their ultrastructures. The study was performed on 80 donkeys from May 2018 to January 2019 for the detection of microfilaria in blood and the adult worms in the peritoneal cavity. The blood samples were either stained with Giemsa stain or examined by modified Knott’s technique for the detection of microfilariae. Adult worms were morphologically characterized based on light microscope and scanning electron microscopy (SEM). PCR was performed targeting the 12S rRNA gene followed by sequencing and phylogenetic analysis.

Results

The current study recorded 21.6% and 16.2% prevalence rates for adult worms and microfilariae, respectively. By using SEM, this study was able to clarify the detailed structure of amphids, predeirids, vulva, arrangement, and number of male caudal papillae. PCR amplified products for 12S rRNA gene (408 bp) for adult worm and microfilaria. Sequence and phylogenetic analysis revealed that S. equina isolated in the current study from donkeys in Egypt (accession no., MH345965) shared 100% identity with isolates from horse and man in Italy and Iran, respectively and clustered in the same clade with S. digitata, S. tundra and S. labiatopapillosa.

Conclusions

Identification with light microscopy lacked the ability to characterize different Setaria species, and so using scanning electron microscopy is considered a good choice to distinguish the ultrastructures. In addition, performing the phylogenetic analysis was necessary to detect relationships between different filarial worms, which could not detect by the morphological characterization of adult worms.

Incidental Detection of Onchocerca Microfilariae in Donkeys (Equus asinus) in Italy: Report of Four Cases

This paper reports the occurrence for the first time in Italy of autochthonous Onchocerca infection in donkeys. Four jennies, bred on the same farm, were referred to the Veterinary Teaching Hospital of Pisa for a check-up on ovarian activity (n = 3) or for veterinary support during the delivery (n = 1). Microfilariae were incidentally detected during the blood smear examination of one jenny. Peripheral blood samples were then collected from the other three jennies and the presence of microfilariae was investigated by Knott's test. Circulating unsheathed microfilariae were identified in all the animals. The level of microfilaraemia was between 1 and 31 microfilariae in 2 mL of blood. Hematological changes showed moderate eosinophilia in one case or both remarkable eosinophilia and basophilia in another case. Based on molecular findings by PCR and sequencing, the microfilariae showed 98% sequence similarity with Onchocerca sp. in the NCBI GenBank database (Accession No.: MK541848.1). The present report provides evidence that Onchocerca is an etiological agent of parasitic infection in donkeys in Italy. Our findings highlight the importance of screening in donkeys for Onchocerca even in the absence of clinical indications.

Zoonotic Implications of Onchocerca Species on Human Health

The genus Onchocerca includes several species associated with ungulates as hosts, although some have been identified in canids, felids, and humans. Onchocerca species have a wide geographical distribution, and the disease they produce, onchocerciasis, is generally seen in adult individuals because of its large prepatency period. In recent years, Onchocerca species infecting animals have been found as subcutaneous nodules or invading the ocular tissues of humans; the species involved are O. lupi, O. dewittei japonica, O. jakutensis, O. gutturosa, and O. cervicalis. These findings generally involve immature adult female worms, with no evidence of being fertile. However, a few cases with fertile O. lupi, O. dewittei japonica, and O. jakutensis worms have been identified recently in humans. These are relevant because they indicate that the parasite’s life cycle was completed in the new host—humans. In this work, we discuss the establishment of zoonotic Onchocerca infections in humans, and the possibility of these infections to produce symptoms similar to human onchocerciasis, such as dermatitis, ocular damage, and epilepsy. Zoonotic onchocerciasis is thought to be an emerging human parasitic disease, with the need to take measures such as One Health Strategies, in order to identify and control new cases in humans.

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.

First report of the isolation and phylogenetic characterization of equine Setaria digitata from India based on mitochondrial COI, 12S rDNA, and nuclear ITS2 sequence data

Equine ocular setariasis arising mainly from ectopic infestation of Setaria digitata is a common vision impairing ophthalmic disease in India, and the identification of this filarial nematode is based solely on morphology. However, morphological characters alone are inadequate to detect and differentiate S. digitata from its congeners. The present communication reports the first phylogenetic characterization of equine S. digitata from India based on sequences derived from the mitochondrial cytochrome c oxidase subunit 1 (COI), the mitochondrial small subunit ribosomal DNA (12S rDNA), and the nuclear internal transcribed spacer 2 (ITS2). Three isolates were characterized for each gene, and respective sequences were submitted to NCBI database (MN078131, MN078132, and MN095798). The sequences were also compared with the other related sequences available from PubMed around the globe, and phylogenetic analysis was carried out in conjunction with nucleotide homologies. There was no intraspecific variation among the Indian isolates. The phylogenetic analysis of S. digitata, inferred from these genes, showed that the isolate sequences obtained from different host species created a separate monophyletic clade within the genus Setaria with minor sequence variations revealing similar molecular characteristics of S. digitata isolates throughout the globe. In addition, the studied Indian isolates were found closer to Sri Lankan isolates. The S. digitata and S. labiatopapillosa appeared as sister species.

Identification of the complement 9-binding protein in Setaria equina excretory-secretory products

The current study aimed to detect the complement-binding proteins in the excretory-secretory (ES) products of adult filarial parasite Setaria equina (SeqES). Tests for complement activation pathways (CH₅₀ and APH₅₀ ) in normal human serum (NHS) after incubation with SeqES were performed. Quantitative detection of complement activation products like C3d and sC5b-9 by ELISA in inulin-activated NHS before and after addition of SeqES was estimated. Immunoblotting for 1D and 2D electrophoresed SeqES were performed for detection of C9-binding protein. MALDI mass sequencing and multiple sequence alignment were performed for identification of the protein. The results showed an inhibitory effect of SeqES for complement activation pathways. This was confirmed by an obvious reduction in C3d and sC5b-9 in inulin-activated NHS. Immunoblotting showed the reaction of a protein at 21 kDa with human C9. The latter protein was identified as OV-16 based on MALDI mass sequencing and multiple sequence alignment. In conclusion, S equina OV-16 is the complement regulatory protein by its ability to bind C9 and inhibit the classical and alternative pathways of complement activation. This protein can be used as a target for therapeutic treatment or as an anti-inflammatory agent in human diseases.