Multiple drug resistance in the canine hookworm Ancylostoma caninum: an emerging threat?

Development of a New LAMP Assay for the Detection of Ancylostoma caninum DNA (Copro-LAMPAc) in Dog Fecal Samples

Ancylostoma caninum is a zoonotic nematode which is able to affect animals and humans. Diagnosis in the definitive host and environmental detection are key to prevent its dissemination and achieve control. Herein, a new coprological LAMP method for the detection of A. caninum (Copro-LAMPAc) DNA was developed. DNA extraction was performed using a low-cost method and a fragment of the cox-1 gene was used for primer design. The analytical sensitivity, evaluated with serial dilutions of genomic DNA from A. caninum adult worms, was 100 fg. A specificity of 100% was obtained using genomic DNA from the host and other pathogens. The Copro-LAMPAc was evaluated using environmental canine fecal samples. When compared with gold standard optical microscopy in epidemiological studies, it proved to be more sensitive. This new LAMP assay can provide an alternative protocol for screening and identification of A. caninum for epidemiological studies in endemic areas.

Practices employed by veterinary practitioners for controlling canine gastrointestinal helminths and ectoparasites

The present study attempted to evaluate the practical experience and methods employed by Brazilian veterinary practitioners for control of parasites. Twenty-one questions were asked of 403 veterinary practitioners based in different climatic zones with reference to parasite epidemiology from the country. Administration of a combination of drugs at three-month intervals was the most common regime recommended for prophylaxis against gastrointestinal helminths, with a single treatment repeated after 15 days. Routine prophylaxis against dog ectoparasites was recommended by 82.4% veterinary practitioners, and 46.6% changed the drug compound used. Monthly prophylaxic treatments for ectoparasites, using systemic, topical and/or collar-impregnated drugs, was recommended by 21.5% veterinary practitioners. Side-effects of ectoparasiticide-impregnated collars were suspected by 58% of the veterinary practitioners. Isoxazolines were the most frequently used chemical group to treat ectoparasites in dogs. Poor efficacy of fipronil in controlling ticks was suspected by 79.5% of the veterinary practitioners. The isoxazolines and combination of anthelmintic compounds are the most common drugs to prevent or treat ectoparasites and gastrointestinal nematodes, respectively. The suspect of the inefficacy of antiparasitic drugs is shared among the veterinary practitioners from part of Brazil. Guidelines are needed, specifically for the control of gastrointestinal helminths and ectoparasites in Brazilian dogs.

Characterization of the β-tubulin gene family in Ascaris lumbricoides and Ascaris suum and its implication for the molecular detection of benzimidazole resistance

Background

The treatment coverage of control programs providing benzimidazole (BZ) drugs to eliminate the morbidity caused by soil-transmitted helminths (STHs) is unprecedently high. This high drug pressure may result in the development of BZ resistance in STHs and so there is an urgent need for surveillance systems detecting molecular markers associated with BZ resistance. A critical prerequisite to develop such systems is an understanding of the gene family encoding β-tubulin proteins, the principal targets of BZ drugs.

Methodology and principal findings

First, the β-tubulin gene families of Ascaris lumbricoides and Ascaris suum were characterized through the analysis of published genomes. Second, RNA-seq and RT-PCR analyses on cDNA were applied to determine the transcription profiles of the different gene family members. The results revealed that Ascaris species have at least seven different β-tubulin genes of which two are highly expressed during the entire lifecycle. Third, deep amplicon sequencing was performed on these two genes in more than 200 adult A. lumbricoides (Ethiopia and Tanzania) and A. suum (Belgium) worms, to investigate the intra- and inter-species genetic diversity and the presence of single nucleotide polymorphisms (SNPs) that are associated with BZ resistance in other helminth species; F167Y (TTC>TAC or TTT>TAT), E198A (GAA>GCA or GAG>GCG), E198L (GAA>TTA) and F200Y (TTC>TAC or TTT>TAT). These particular SNPs were absent in the two investigated genes in all three Ascaris populations.

Significance

This study demonstrated the presence of at least seven β-tubulin genes in Ascaris worms. A new nomenclature was proposed and prioritization of genes for future BZ resistance research was discussed. This is the first comprehensive description of the β-tubulin gene family in Ascaris and provides a framework to investigate the prevalence and potential role of β-tubulin sequence polymorphisms in BZ resistance in a more systematic manner than previously possible.

Benzimidazole (BZ) drugs remain the standard of treatment in large-scale deworming programs that aim to control the morbidity caused by intestinal worms. As these deworming programs are expanding world-wide, there is an increasing risk of worms becoming resistant to BZ drugs, highlighting the necessity for tools to detect gene mutations associated with drug resistance. However, the development of such tools is impeded by a lack of insights into the genes that are coding for β-tubulin proteins, which are the principal targets of BZ drugs. The aim of this study was to comprehensively characterize these genes in the worm species Ascaris lumbricoides and Ascaris suum. The findings highlight that these species have at least seven β-tubulin genes. Only two genes are highly expressed throughout the different life stages of the worm, and hence are more likely to be involved in the development of BZ resistance. No mutations that have previously been associated with BZ resistance in other intestinal worms were found. This study provides a baseline towards more efficient and accurate monitoring of drug resistance in large-scale deworming programs.

Improving stool sample processing and pyrosequencing for quantifying benzimidazole resistance alleles in Trichuris trichiura and Necator americanus pooled eggs

BACKGROUND

There is an urgent need for an extensive evaluation of benzimidazole efficacy in humans. In veterinary science, benzimidazole resistance has been mainly associated with three single-nucleotide polymorphisms (SNPs) in the isotype-1 β-tubulin gene. In this study, we optimized the stool sample processing methodology and resistance allele frequency assessment in Trichuris trichiura and Necator americanus anthelmintic-related SNPs by pyrosequencing, and standardized it for large-scale benzimidazole efficacy screening use.

METHODS

Three different protocols for stool sample processing were compared in 19 T. trichiura-positive samples: fresh stool, egg concentration using metallic sieves with decreasing pore size, and egg concentration followed by flotation with saturated salt solution. Yield of each protocol was assessed by estimating the load of parasite DNA by real-time PCR. Then, we sequenced a DNA fragment of the β-tubulin gene containing the putative benzimidazole resistance SNPs in T. trichiura and N. americanus. Afterwards, resistant and susceptible-type plasmids were produced and mixed at different proportions, simulating different resistance levels. These mixtures were used to compare previously described pyrosequencing assays with processes newly designed by our own group. Once the stool sample processing and the pyrosequencing methodology was defined, the utility of the protocols was assessed by measuring the frequencies of putative resistance SNPs in 15 T. trichiura- and 15 N. americanus-positive stool samples.

RESULTS

The highest DNA load was provided by egg concentration using metallic sieves with decreasing pore size. Sequencing information of the β-tubulin gene in Mozambican specimens was highly similar to the sequences previously reported, for T. trichiura and N. americanus, despite the origin of the sample. When we compared pyrosequencing assays using plasmids constructs, primers designed in this study provided the most accurate SNP frequencies. When pooled egg samples were analysed, none of resistant SNPs were observed in T. trichiura, whereas 17% of the resistant SNPs at codon 198 were found in one N. americanus sample.

CONCLUSIONS

We optimized the sample processing methodology and standardized pyrosequencing in soil-transmitted helminth (STH) pooled eggs. These protocols could be used in STH large-scale screenings or anthelmintic efficacy trials.

Multiple drug resistance in hookworms infecting greyhound dogs in the USA

Ancylostoma caninum is the most prevalent nematode parasite of dogs. We confirmed multiple-drug resistance (MDR) in several A. caninum isolates to all anthelmintic drug classes approved for the treatment of hookworms in dogs in the USA. Cases of MDR hookworms appear to be highly overrepresented in greyhounds. The aims of this study were to evaluate the drug-resistant phenotypes and genotypes of the A. caninum infecting greyhounds. Fecal samples from greyhounds of the USA were acquired from two greyhound adoption kennels, one active greyhound racing kennel, and three veterinary practices. Fecal egg counts (FECs) were performed on fecal samples from 219 greyhounds, and despite treatment with anthelmintics, the mean FEC was 822.4 eggs per gram (EPG). Resistance to benzimidazoles and macrocyclic lactones were measured using the egg hatch assay (EHA) and the larval development assay (LDA), respectively. We performed 23 EHA and 22 LDA on either individual or pooled feces, representing 54 animals. Mean and median IC₅₀ and IC₉₅ values for the EHA were 5.3 μM, 3.6 μM, and 24.5 μM, 23.4 μM, respectively. For the LDA, the median IC₅₀ value was >1000 nM. These values ranged 62–81 times higher than our susceptible laboratory isolate. Only post-treatment samples were available. For samples collected <10 days post-treatment with albendazole, moxidectin, or a combination of febantel-pyrantel-moxidectin, the mean FEC were 349, 333, and 835 EPG, respectively. We obtained DNA from hookworm eggs isolated from 70 fecal samples, comprised of 60 individual dogs and 10 pools. Deep sequencing of the isotype 1 β-tubulin gene only revealed the presence of the F167Y (TTC>TAC) resistance polymorphism in 99% of these samples. These clinical, in vitro, and genetic data provide strong evidence that greyhound dogs in the USA are infected with MDR A. caninum at very high levels in prevalence and infection intensity.

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Conclusive evidence that most racing greyhounds in the USA are infected with MDR A. caninum.

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79% of the samples from racing or retired greyhounds were positive.

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IC₅₀ values for BZs and MLs were 62–81 times higher in greyhounds.

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The F167Y SNP was detected in 99% of samples, and in more than 2/3 the frequency was ≥ 75%.

Retrospective study of canine endoparasites diagnosed by fecal flotation methods analyzed across veterinary parasitology diagnostic laboratories, United States, 2018

Background

Companion animal endoparasites play a substantial role in both veterinary medicine and public health. Updated epidemiological studies are necessary to identify trends in occurrence and distribution of these parasites, and their associated risk factors. This study aimed to assess the occurrence of canine endoparasites  retrospectively, using fecal flotation  test data available through participating academic veterinary parasitology diagnostic laboratories across the United States of America (USA).

Methods

Canine fecal flotation records from ten veterinary diagnostic laboratories located in nine states in the USA acquired from January 1, 2018, to December 31, 2018, were included.

Results

A total of 4692 fecal flotation test results were obtained, with a majority comprised of client-owned dogs (3262; 69.52%), followed by research dogs (375; 8.00%), and shelter dogs (122; 2.60%). Samples from 976 (20.80%) dogs were positive for at least one parasite, and co-infections of two or more parasites were found in 3.82% (179/4692) of the samples. The five most commonly detected parasites were: Giardia sp., (8.33%; 391/4692), Ancylostomatidae (5.63%; 264/4692), Cystoisospora spp. (4.35%; 204/4692), Toxocara canis (2.49%;117/4692), and Trichuris vulpis (2.43%; 114/4692). Various other internal parasites, including gastrointestinal and respiratory nematodes, cestodes, trematodes, and protozoans were detected in less than 1% of samples.

Conclusions

These data illustrate the importance of parasite prevention, routine fecal screening, and treatment of pet dogs. Additionally, pet owners should be educated about general parasite prevalence, prevention, and anthelmintic treatment regimens to reduce the risks of environmental contamination and zoonotic transmission.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04960-7.

Spread of anthelmintic resistance in intestinal helminths of dogs and cats is currently less pronounced than in ruminants and horses - Yet it is of major concern

Anthelmintic resistance (AR) has thus far only rarely been reported for intestinal helminths of dogs and cats, in contrast to parasites of livestock and horses. We highlight possible reasons for this striking and important discrepancy, including ecological, biological and genetic factors and/or intervention regimens of key intestinal helminths concerning both host groups. In view of the current knowledge related to the genetics, mechanisms and principles of AR development, we point at issues which in our view contribute to a comparatively lower risk of AR development in intestinal helminths of dogs and cats. Finally, we specify research needs and provide recommendations by which, based on the available information about AR in ruminant and equine helminths, the development of AR in dog and cat helminths may best be documented, prevented or at least postponed.

Effectiveness of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio® Plus) for the treatment of larval and immature adult stages of Ancylostoma caninum in experimentally infected dogs

BACKGROUND

The hookworm, Ancylostoma caninum, is a common and important zoonotic intestinal nematode parasite that infects dogs globally. Both the immature and adult stages of A. caninum ingest large volumes of blood during the feeding process and can cause severe anemia and death in young dogs, even before patent infections can be diagnosed using routine faecal examination methods. Thus, effective treatment of any pre-patent stages of immature hookworms can reduce or eliminate the risk of clinical disease in infected dogs and additionally reduce environmental contamination of eggs and infective larvae. Two randomized, blinded, GCP-compliant, pivotal laboratory dose confirmation studies were conducted to evaluate the effectiveness and safety of a new novel combination of lotilaner and milbemycin oxime tablets (Credelio Plus^®) administered orally to dogs experimentally infected with immature (L4 and immature adult [L5]) stages of A. caninum.

METHODS

Treatments using the intended global commercial tablet formulation of Credelio Plus were administered in a time frame relative to inoculation with infective larvae so that effectiveness could be assessed against each specific immature stage of A. caninum. In each study, dogs were randomized to one of six (study 1) or four (study 2) treatment groups. Each treatment group contained 8 (study 1) or 10 (study 2) dogs that had been experimentally inoculated with infective A. caninum larvae on day 0 and were dosed once on day 7 or day 11. Enrolled subjects were administered placebo tablets, Credelio Plus tablets, or lotilaner mono tablets to provide minimum dosages of 0.75 mg/kg of milbemycin oxime and 20 mg/kg of lotilaner. All dogs were necropsied 5 days after their respective treatment. All nematodes recovered from the gastrointestinal tract at necropsy were counted by species and stage.

RESULTS

For both dose confirmation studies and based on geometric mean worm counts, efficacy of Credelio Plus was ≥ 97.3% against L4 larval stage of A. caninum and ≥ 98.7% against immature adult (L5) A. caninum.

CONCLUSIONS

These studies demonstrated that the orally administered Credelio Plus combination tablet was highly efficacious in treating immature (L4 and immature adult [L5]) stages of A. caninum in experimentally infected dogs.

Nanotechnological Improvement of Veterinary Anthelmintics

Helminths infections are among the most important problems in animal health and husbandry. Moreover, zoonotic helminths endanger rural communities, particularly in developing countries. Helminthiasis are not only important in relation to the harmful effects of parasites; additional issues like anthelmintic resistance spread became more important over time. As new anthelmintic development takes many years and millions of dollars of investment, some strategies are currently focused on the modification of already available drugs, in order to improve their efficacy and overcome their limitations. In this field, nanotechnology has brought a novel approach, showing advantages like the regulation of the drug's delivery and kinetics, reaching of specific targets, and possibilities to avoid the systemic spread and side effects. Taking this into account, the present review aims to introduce some of the current knowledge in anthelmintic improvement based on nanotechnology, and how researchers could benefit from this technology in order to overcome the drugs limitations. Finally, some insights into potential field applications are discussed, based on the most important concerns of current anthelmintic therapy.

Chemogenomic approach to identifying nematode chemoreceptor drug targets in the entomopathogenic nematode Heterorhabditis bacteriophora

Parasitic nematodes constitute one of the major threats to human health, causing diseases of major socioeconomic importance worldwide. Recent estimates indicate that more than 1 billion people are infected with parasitic nematodes around the world. Current measures to combat parasitic nematode infections include anthelmintic drugs. However, heavy exposure to anthelmintics has selected populations of livestock parasitic nematodes that are no longer susceptible to the drugs, rendering several anthelmintics useless for parasitic nematode control in many areas of the world. The rapidity with which anthelmintic resistance developed in response to these drugs suggests that increasing the selective pressure on human parasitic nematodes will also rapidly generate resistant worm populations. Therefore, development of new anthelmintics is of major importance before resistance becomes widespread in human parasitic nematode populations. G-Protein Coupled Receptors (GPCRs) represent an important target for many pharmacological interventions due to their ubiquitous expression in various cell types. GPCRs contribute to numerous physiological processes, and their ligand binding sites located on cell surfaces make them accessible targets and attractive substrates in terms of druggability. In fact, ∼35 % of Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved drugs target GPCRs and their associated proteins, with over 300 additional drugs targeting GPCRs at the clinical trial stage. Nematode Chemosensory GPCRs (NemChRs) are unique to nematodes, and therefore represent ideal substrates for target-based drug discovery. Here we set out to identify NemChRs that are transcriptionally active inside the host, and to use these NemChRs in a reverse pharmacological screen to impede parasitic development. Our data identified several NemChRs, and we focused on one that was expressed in neuronal cells and exhibited the highest fold change in transcription after host activation. Next, we performed homology modelling and molecular dynamics simulations of this NemChR in order to conduct a virtual screening campaign to identify candidate drug targets which were ranked and selected for experimental testing in bioassays. Taken together, our results identify and characterize a candidate NemChR drug target, and provide a chemogenomic pipeline for identifying nematicide substrates.

Reduced Efficacy of Fenbendazole and Pyrantel Pamoate Treatments against Intestinal Nematodes of Stud and Performance Horses

Nematodes are an important cause of disease and loss of performance in horses. Changes in the parasitic fauna of horses have occurred in the past few decades, making cyathostomins the major parasites in adult horses, while large strongyles have become less prevalent. Parascaris spp. remains the most important parasite infecting foals and weanlings. Anthelmintic resistance is highly prevalent in cyathostomins and Parascaris spp. worldwide and it must be factored into treatment decisions. To assess anthelmintic efficacy in Northern Italy, we sampled 215 horses from 17 sport and horse-breeding farms. Fecal egg count reduction tests (FECRT) were used to assess anthelmintic efficacy. Copromicroscopic analysis was performed using MiniFLOTAC before treatment with fenbendazole, pyrantel pamoate or ivermectin, and repeated 14 days post-treatment. Strongyle-type eggs were detected in 66.91% of horses (CI95% 61.40-73.79%), while Parascaris spp. was detected in 2.79% (CI95% 1.94-5.95%). Reduced efficacy against cyathostomins was observed for fenbendazole in 55.56% of the treated animals (CI95% 41.18-69.06%), and for pyrantel pamoate in 75% of animals (CI95% 30.06-95.44%). Ground-based actions must be set in place to promote the uptake of state-of-the-art worm control plans that will prevent clinical disease while minimizing the selection pressure of resistant parasites.

Pharyngeal Pumping and Tissue-Specific Transgenic P-Glycoprotein Expression Influence Macrocyclic Lactone Susceptibility in Caenorhabditis elegans

Macrocyclic lactones (MLs) are widely used drugs to treat and prevent parasitic nematode infections. In many nematode species including a major pathogen of foals, Parascaris univalens, resistance against MLs is widespread, but the underlying resistance mechanisms and ML penetration routes into nematodes remain unknown. Here, we examined how the P-glycoprotein efflux pumps, candidate genes for ML resistance, can modulate drug susceptibility and investigated the role of active drug ingestion for ML susceptibility in the model nematode Caenorhabditis elegans. Wildtype or transgenic worms, modified to overexpress P. univalens PGP-9 (Pun-PGP-9) at the intestine or epidermis, were incubated with ivermectin or moxidectin in the presence (bacteria or serotonin) or absence (no specific stimulus) of pharyngeal pumping (PP). Active drug ingestion by PP was identified as an important factor for ivermectin susceptibility, while moxidectin susceptibility was only moderately affected. Intestinal Pun-PGP-9 expression elicited a protective effect against ivermectin and moxidectin only in the presence of PP stimulation. Conversely, epidermal Pun-PGP-9 expression protected against moxidectin regardless of PP and against ivermectin only in the absence of active drug ingestion. Our results demonstrate the role of active drug ingestion by nematodes for susceptibility and provide functional evidence for the contribution of P-glycoproteins to ML resistance in a tissue-specific manner.

Considerations for anthelmintic resistance emergence in hookworm at a single locus

Over 800 million people are infected with hookworms around the world. Hookworms of the genus Ancylostoma and Necator are examples of nematodes that harbor the ability to enter a host by penetrating the skin, and after entry the infective larvae migrate to the small intestine where they encounter host-specific signals that initiate developmental pathways and culminate in maturation to the adult stage. Currently no vaccine is available for the treatment of hookworm infection. The control strategy is limited to anthelmintic drugs, which run the risk of losing efficacy as resistance grows. Genetic resistance has developed against all classes of anthelmintic drugs against livestock parasites, and recently markers of anthelmintic resistance in human hookworm populations have been reported. As anthelmintic resistance develops in human populations of hookworm, new drugs and novel control methods like vaccines will be required in the future to control hookworm transmission. This review outlines how population genetics and anthelmintic resistance could interact at a single locus to influence current control strategies.

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This review outlines how population genetics and anthelmintic resistance may interact to influence current control strategies.

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Altering mutation rate modifies rate of emergence of anthelmintic resistance.

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Genotypic fitness changes the efficacy of anthelmintic administration.

Complementary Approaches with Free-living and Parasitic Nematodes to Understanding Anthelmintic Resistance

Anthelmintic drugs are the major line of defense against parasitic nematode infections, but the arsenal is limited and resistance threatens sustained efficacy of the available drugs. Discoveries of the modes of action of these drugs and mechanisms of resistance have predominantly come from studies of a related nonparasitic nematode species, Caenorhabditis elegans, and the parasitic nematode Haemonchus contortus. Here, we discuss how our understanding of anthelmintic resistance and modes of action came from the interplay of results from each of these species. We argue that this 'cycle of discovery', where results from one species inform the design of experiments in the other, can use the complementary strengths of both to understand anthelmintic modes of action and mechanisms of resistance.

Where are all the anthelmintics? Challenges and opportunities on the path to new anthelmintics

Control of helminth parasites is a key challenge for human and veterinary medicine. In the absence of effective vaccines and adequate sanitation, prophylaxis and treatment commonly rely upon anthelmintics. There are concerns about the development of drug resistance, side-effects, lack of efficacy and cost-effectiveness that drive the need for new classes of anthelmintics. Despite this need, only three new drug classes have reached the animal market since 2000 and no new classes of anthelmintic have been approved for human use. So where are all the anthelmintics? What are the barriers to anthelmintic discovery, and what emerging opportunities can be used to address this? This was a discussion group focus at the 2019 8th Consortium for Anthelmintic Resistance and Susceptibility (CARS) in Wisconsin, USA. Here we report the findings of the group in the broader context of the human and veterinary anthelmintic discovery pipeline, highlighting challenges unique to antiparasitic drug discovery. We comment on why the development of novel anthelmintics has been so rare. Further, we discuss potential opportunities for drug development moving into the 21st Century.

A Functional Comparison of Homopentameric Nicotinic Acetylcholine Receptors (ACR-16) Receptors From Necator americanus and Ancylostoma ceylanicum

Effective control of hookworm infections in humans and animals relies on using a small group of anthelmintics. Many of these drugs target cholinergic ligand-gated ion channels, yet the direct activity of anthelmintics has only been studied in a subset of these receptors, primarily in the non-parasitic nematode, Caenorhabditis elegans. Here we report the characterization of a homopentameric ionotropic acetylcholine receptor (AChR), ACR-16, from Necator americanus and Ancylostoma ceylanicum, the first known characterization of human hookworm ion channels. We used two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes to determine the pharmacodynamics of cholinergics and anthelmintics on ACR-16 from both species of hookworm. The A. ceylanicum receptor (Ace-ACR-16) was more sensitive to acetylcholine (EC50 = 20.64 ± 0.32 μM) and nicotine (EC50 = 24.37 ± 2.89 μM) than the N. americanus receptor (Nam-ACR-16) (acetylcholine EC50 = 170.1 ± 19.23 μM; nicotine EC50 = 597.9 ± 59.12 μM), at which nicotine was a weak partial agonist (% maximal acetylcholine response = 30.4 ± 7.4%). Both receptors were inhibited by 500 μM levamisole (Ace-ACR-16 = 65.1 ± 14.3% inhibition, Nam-ACR-16 = 79.5 ± 7.7% inhibition), and responded to pyrantel, but only Ace-ACR-16 responded to oxantel. We used in silico homology modeling to investigate potential structural differences that account for the differences in agonist binding and identified a loop E isoleucine 130 of Nam-ACR-16 as possibly playing a role in oxantel insensitivity. These data indicate that key functional differences exist among ACR-16 receptors from closely related species and suggest mechanisms for differential drug sensitivity.

The Kubic FLOTAC microscope (KFM): a new compact digital microscope for helminth egg counts

The Kubic FLOTAC microscope (KFM) is a compact, low-cost, versatile and portable digital microscope designed to analyse fecal specimens prepared with Mini-FLOTAC or FLOTAC, in both field and laboratory settings. In this paper, we present the characteristics of the KFM along with its first validation for fecal egg count (FEC) of gastrointestinal nematodes (GINs) in cattle. For this latter purpose, a study was performed on 30 fecal samples from cattle experimentally infected by GINs to compare the performance of Mini-FLOTAC either using a traditional optical microscope (OM) or the KFM. The results of the comparison showed a substantial agreement (concordance correlation coefficient = 0.999), with a very low discrepancy (−0.425 ± 7.370) between the two microscopes. Moreover, the KFM captured images comparable with the view provided by the traditional OM. Therefore, the combination of sensitive, accurate, precise and standardized FEC techniques, as the Mini-FLOTAC, with a reliable automated system, will permit the real-time observation and quantification of parasitic structures, thanks also to artificial intelligence software, that is under development. For these reasons, the KFM is a promising tool for an accurate and efficient FEC to improve parasite diagnosis and to assist new generations of operators in veterinary and public health.

Parasites and vector-borne diseases disseminated by rehomed dogs

The Companion Vector-Borne Diseases (CVBD) World Forum is a working group of leading international experts who meet annually to evaluate current scientific findings and future trends concerning the distribution, pathogenesis, clinical presentation, diagnosis and prevention of vector-borne infections of dogs and cats. At the 14th Symposium of the CVBD World Forum in Trieste, Italy (March 25-28, 2019), we identified the need to (i) bring attention to the potential spread of parasites and vectors with relocated dogs, and (ii) provide advice to the veterinary profession regarding the importance of surveillance and treatment for parasites and vector-borne infections when rehoming dogs. This letter shares a consensus statement from the CVBD World Forum as well as a summary of the problem faced, including the role of veterinary professionals in parasite surveillance, causal issues, and the importance of interdisciplinary cooperation in addressing the problem. To limit opportunities for dissemination of parasites and vectors, whenever possible, underlying problems creating the need for dog rehoming should be addressed. However, when it is necessary to rehome dogs, this should ideally take place in the country and national region of origin. When geographically distant relocation occurs, veterinary professionals have a vital role to play in public education, vigilance for detection of exotic vectors and infections, and alerting the medical community to the risk(s) for pathogen spread. With appropriate veterinary intervention, dog welfare needs can be met without inadvertently allowing global spread of parasites and their vectors.

Animal toxins - Nature's evolutionary-refined toolkit for basic research and drug discovery

Venomous animals have evolved toxins that interfere with specific components of their victim's core physiological systems, thereby causing biological dysfunction that aids in prey capture, defense against predators, or other roles such as intraspecific competition. Many animal lineages evolved venom systems independently, highlighting the success of this strategy. Over the course of evolution, toxins with exceptional specificity and high potency for their intended molecular targets have prevailed, making venoms an invaluable and almost inexhaustible source of bioactive molecules, some of which have found use as pharmacological tools, human therapeutics, and bioinsecticides. Current biomedically-focused research on venoms is directed towards their use in delineating the physiological role of toxin molecular targets such as ion channels and receptors, studying or treating human diseases, targeting vectors of human diseases, and treating microbial and parasitic infections. We provide examples of each of these areas of venom research, highlighting the potential that venom molecules hold for basic research and drug development.

Antiparasitics in Animal Health: Quo Vadis?

Antiparasitics acting on endo- or ectoparasites represent the second largest segment of the global animal health market, accounting for 23% of market share. However, relatively few novel antiparasitic agents have been introduced into the market during recent decades. One exception, and a groundbreaking 21st century success story, are the isoxazolines, whose full potential has not yet been entirely explored. Unfortunately, resistance issues are present across most parasitic diseases, which generates a clear market need for novel resistance-breaking antiparasitics with new modes/mechanisms of action. Recent advances in science and technologies strongly suggest that the time is right to invest in new modalities such as parasitic vaccines or in environmentally friendly interventions.

Comparison of the Level of Awareness about the Transmission of Echinococcosis and Toxocariasis between Pet Owners and Non-Pet Owners in Greece

Ζoonotic parasitic diseases that can occur through animal contact pose risks to pets, their owners and to their bond. This study aims to assess the level of knowledge about zoonoses, specifically echinococcosis and toxocariasis, among cat/dog owners and non-pet owners in Greece. Multiple-choice questionnaires were designed to obtain data regarding the knowledge of pet and non-pet owners on echinococcosis and toxocariasis, including signs and symptoms of these zoonoses, ways of transmission and precautions that need to be taken into account in order to avoid it. A total of 185 questionnaires were retrieved and data was expressed as absolute (Ν) and relative frequencies (%). Associations between pet ownership, residence and outcome variables were evaluated using the Fisher exact test and Chi-squared test, respectively. Multifactorial linear regression analysis was used to investigate the cross-sectional association between demographic characteristics and the awareness of helminthic zoonoses. All tests were two-sided and statistical significance was set at p < 0.05. Our study revealed a disturbing lack of awareness of echinococcosis and toxocariasis (mean zoonotic knowledge score 8.11 ± 3.18) independently of pet ownership. Surprisingly, in some cases the ignorance of pet owners exceeded that of non-pet owners. Given the progressive impact of toxocariasis in public health and the high prevalence of echinococcosis in the Mediterranean region, measures should be taken to inform people about zoonoses and eliminate their putative transmission.

TroCCAP recommendations for the diagnosis, prevention and treatment of parasitic infections in dogs and cats in the tropics

The Tropical Council for Companion Animal Parasites Ltd. (TroCCAP) is a not-for-profit organisation whose mission is to independently inform, guide and make best-practice recommendations for the diagnosis, treatment and control of companion animal parasites in the tropics and sub-tropics, with the aim of protecting animal and human health. In line with this primary mission, TroCCAP recently developed guidelines for the diagnosis, treatment and control of feline and canine parasites in the tropics. The development of these guidelines required unique and complex considerations to be addressed, often inapplicable to developed nations. Much of the tropics encompass middle-to-low income countries in which poor standards of environmental hygiene and large populations of stray dogs and cats coexist. In these regions, a range of parasites pose a high risk to companion animals, which ultimately may place their owners at risk of acquiring parasitic zoonoses. These considerations led to the development of unique recommendations with regard, for example, to deworming and endoparasite testing intervals for the control of both global and 'region-specific' parasites in the tropics. Moreover, the 'off-' or 'extra'-label use of drugs for the treatment and control of parasitic infections is common practice in many tropical countries and many generic products lack manufacturers' information on efficacy, safety, and quality control. Recommendations and advice concerning the use of such drugs and protocols are also addressed in these guidelines. The formation of these guidelines is an important first step towards improving the education of veterinarians specifically regarding best-practice for the diagnosis, treatment and control of canine and feline parasites in the tropics.

Detection of gastrointestinal parasitism at recreational canine sites in the USA: the DOGPARCS study

BACKGROUND

The rapid growth in off-leash dog parks provides opportunity for canine socialization activities but carries risk of exposure to intestinal parasites. This study assessed the prevalence of these infections in dogs visiting off-leash dog parks.

METHODS

Fresh defecations were collected from dogs visiting parks in 30 metropolitan areas across the USA. Samples were analyzed by coproantigen immunoassay (CAI) (Fecal Dx® and Giardia Test, IDEXX Laboratories, Inc.) and zinc sulfate centrifugal flotation (CF). Owners responded to a questionnaire on their dog's signalment and use of heartworm/intestinal parasite control medications (HWCM).

RESULTS

Samples were examined from 3006 dogs, 87.9% aged at least 12 months, visiting 288 parks. At least one intestinal parasite was detected in 622 (20.7%) samples, nematodes in 263 (8.8%), with hookworms, whipworms and ascarids in 7.1, 1.9 and 0.6% of samples, respectively. A sample positive for one or more intestinal parasites was found in 245 (85.1%) parks, with nematodes found in 143 (49.7%). Combined, CAI and CF detected 78.4% more intestinal nematode infections than CF alone. Hookworm and whipworm infections were detected in all age groups, but ascarids were only detected in dogs less than 4 years-old. Approximately 42% of dogs aged less than 1 year were positive for nematodes or Giardia. Based on owner reports, HWCM was current for 68.8% of dogs, dogs previously diagnosed with intestinal parasitism were more likely to be receiving a HWCM than those without such history, and a significantly lower (P = 0.0003) proportion of dogs receiving a HWCM were positive for intestinal nematodes compared with those not on such medication.

CONCLUSIONS

Intestinal parasites, the most common of which were Giardia, Ancylostoma caninum and Trichuris vulpis, were found in 20% of dogs and 85% of dog parks across the USA. Enhanced detection of canine intestinal parasitism was achieved by combining CF and CAI. Canine intestinal parasites are common across the USA and dog health can be improved by regular testing of fecal samples and routine administration of medications effective against the most common infections.

Retrospective survey of endoparasitism identified in feces of client-owned dogs in North America from 2007 through 2018

Our main study objective was to determine the prevalence and trend of parasitic infection in client-owned dogs examined at the veterinary parasitology diagnostic laboratory of Oklahoma State University over the past 12 years. All results of centrifugal flotation, saline direct smear, sedimentation, Baermann, acid-fast staining for Cryptosporidium detection, and Giardia antigen examinations on fecal samples from client-owned dogs submitted to the Boren Veterinary Medical Hospital and Oklahoma Animal Disease Diagnostic Laboratory of Oklahoma State University from 2007 through 2018 were included. The impact of sex, age, and seasonality on the prevalence of parasitic infection was also statistically evaluated. A total of 7,409 cases were included for this study. Majority of cases (79.58%; 5,896/7,409) did not include any parasites, eggs, larva, oocysts, or cysts. Approximately 15.41% (1,142/7,409) of client-owned dogs were infected by at least one parasite, and 5.01% (371/7,409) of dogs were infected by multiple parasites. The most common parasite stage observed was Ancylostoma eggs (8.23%; 610/7,409), followed by Cystoisospora oocysts (5.02%; 372/7,409), Giardia cysts/antigen (4.06%; 301/7,409), Trichuris vulpis eggs (2.74%; 203/7,409), Toxocara canis eggs (2.54%; 188/7,409), Dipylidium caninum proglottids/egg packets (0.84%; 62/7,409), taeniid proglottids/eggs (0.47%; 35/7,409), Sarcocystis sporocysts (0.38%; 28/7,409), Cryptosporidium oocysts (0.30%; 22/7,409), Strongyloides stercoralis larvae (0.20%; 15/7,409), Alaria eggs (0.19%; 14/7,409), Toxascaris leonina eggs (0.18%; 13/7,409), Capillaria eggs (0.16%; 12/7,409), Hammondia-like small coccidian oocysts (0.16%; 12/7,409), Uncinaria stenocephala eggs (0.13%; 10/7,409), Spirometra eggs (0.09%; 7/7,409), Physaloptera eggs (0.09%; 7/7,409), Heterobilharzia americana eggs (0.08%; 6/7,409), Nanophyetus salmincola eggs (0.08%; 6/7,409), trichomonads (0.08%; 6/7,409), Mesocestoides proglottids/eggs (0.05%; 4/7,409), Baylisascaris eggs (0.01%; 1/7,409), Macracanthorhynchus eggs (0.01%; 1/7,409), and Paragonimus kellicotti eggs (0.01%; 1/7,409). In addition to endoparasites, some ectoparasites, such as Demodex mites (0.22%; 16/7,409), Otodectes cynotis mites (0.01%; 1/7,409), Rhipicephalus sanguineus ticks (0.01%; 1/7,409), and Sarcoptes scabiei mites (0.01%; 1/7,409), were detected by fecal examinations. Pseudo/spurious parasites were identified in approximately 4.35% of cases (322/7,409). There was no statistically significant difference for parasite prevalence between sexes (p = 0.3231). However, statistically significant differences were observed with certain parasites when compared by age groups, and generally, prevalence of parasitism decreased as age of client-owned dogs increased (p < 0.0001). Statistical analyses also revealed significant differences by months (p = 0.0013). Overall, the prevalence of parasitic infection in client-owned dogs decreased over the past 12 years (p < 0.0001).

Comparison of ITS-2 rDNA nemabiome sequencing with morphological identification to quantify gastrointestinal nematode community species composition in small ruminant feces

Mixed gastrointestinal nematode (GIN) infections are a common and significant cause of financial loss for small ruminant producers. Morphologic examination of third-stage larvae (L₃) can be used to identify species composition in feces but has limitations due to the requirement for specialized expertise and the extensive time (8-15 d depending on method used) and labour involved. Moreover, differential development and survival of larvae during coproculture to the third stage often occurs. Deep amplicon sequencing of the ITS-2 rDNA locus of first-stage larvae (L₁) allows for higher throughput with reduced specialist labour and reduces the risk of misidentification. Harvesting of L₁ soon after hatching is also faster and further reduces labour as well as biases that can occur due to differential larval development and survival. This study compares the results of morphologic examination of L₃ with those of ITS-2 rDNA deep amplicon sequencing of L₁ from a set of pooled fecal samples. The proportions of eggs that were successfully recovered as larvae following culture to L₃ and L₁ were also compared. Larval recovery rate was significantly lower from L₃ cultures than from L₁ cultures (p < 0.001); eggs were 238.7 times less likely to develop to L₃ than to L₁ (95 % confidence interval for odds ratio 80.0-712.0). Significantly lower proportions of Teladorsagia circumcincta (odds ratio = 3.1, p = 0.008) and higher proportions of Trichostrongylus spp. (p = 0.009) were identified using morphologic examination of L₃ compared with deep amplicon sequencing of L₁ on the same samples. This is consistent with previous reports of differential survival of these species in L₃ cultures. These results indicate that deep amplicon sequencing of L₁ may reduce bias introduced by differential GIN survival to L₃ in small ruminants.

Efficacy evaluation of anthelmintic products against an infection with the canine hookworm (Ancylostoma caninum) isolate Worthy 4.1F3P in dogs

Ancylostoma caninum is the most prevalent intestinal nematode of dogs, and has a zoonotic potential. Multiple-drug resistance (MDR) has been confirmed in a number of A. caninum isolates, including isolate Worthy 4.1F3P, against all anthelmintic drug classes approved for hookworm treatment in dogs in the United States (US). The cyclooctadepsipeptide emodepside is not registered to use in dogs in the US, but in a number of other countries/regions. The objective of this study was to evaluate the efficacy of emodepside + praziquantel, as well as three commercial products that are commonly used in the US for treatment of hookworms, against a suspected (subsequently confirmed) MDR A. caninum isolate Worthy 4.1F3P. 40 dogs infected on study day (SD) 0 with 300 third-stage larvae, were randomly allocated to one of five treatment groups with eight dogs each: pyrantel pamoate (Nemex®-2), fenbendazole (Panacur® C), milbemycin oxime (Interceptor®), emodepside + praziquantel tablets and non-treated control. Fecal egg counts (FEC) were performed on SDs 19, 20, 22, 27, 31 and 34. All treatments were administered as per label requirements on SD 24 to dogs in Groups 1 through 4. Two additional treatments were administered on SDs 25 and 26 to dogs in Group 2 as per label requirements. Dogs were necropsied on SD 34 and the digestive tract was removed/processed for worm recovery and enumeration. The geometric mean (GM) worm counts for the control group was 97.4, and for the pyrantel pamoate, fenbendazole, milbemycin oxime, and emodepside + praziquantel groups were 74.8, 72.0, 88.9, and 0.4, respectively. These yielded efficacies of 23.2%, 26.1%, and 8.8%, and 99.6%, respectively. These data support previous findings of the MDR status of Worthy 4.1F3P as treatments with pyrantel pamoate, fenbendazole and milbemycin oxime lacked efficacy. In sharp contrast, Worthy 4.1F3P was highly susceptible to treatment with emodepside + praziquantel.

Plant-Based Natural Products for the Discovery and Development of Novel Anthelmintics against Nematodes

Intestinal parasitic nematodes infect approximately two billion people worldwide. In the absence of vaccines for human intestinal nematodes, control of infections currently relies mainly on chemotherapy, but resistance is an increasing problem. Thus, there is an urgent need for the discovery and development of new anthelmintic drugs, especially ones with novel mechanisms of action. Medicinal plants hold great promise as a source of effective treatments, including anthelmintic therapy. They have been used traditionally for centuries and are mostly safe (if not, their toxicity is well-known). However, in most medicinal plants the compounds active against nematodes have not been identified thus far. The free-living nematode C. elegans was demonstrated to be an excellent model system for the discovery of new anthelmintics and for characterizing their mechanism of action or resistance. The compounds discussed in this review are of botanical origin and were published since 2002. Most of them need further studies of their toxicity, mechanisms and structure-activity relationship to assess more fully their potential as drugs.