Reflecting on the past and fast forwarding to present day anthelmintic resistant Ancylostoma caninum-A critical issue we neglected to forecast

Anthelmintic Resistance in Ancylostoma caninum: A Comprehensive Review

Ancylostoma caninum, a zoonotic hookworm species, significantly affects the global health of companion animals, humans and wildlife populations. This parasitic infection is prevalent in various environments, particularly in regions with warm climates, and affects a wide range of canids, including dogs, where it is most commonly found. A. caninum is a major concern not only due to its zoonotic potential but also because of its growing resistance to anthelmintic treatments. The development of resistance in parasitic species is primarily driven by genetic mutations that allow the parasite to survive treatment with commonly used drugs and presents a serious challenge to parasite control efforts. This review explores the biology and epidemiology of A. caninum, focusing on the mechanisms and prevalence of anthelmintic resistance. By reviewing worldwide studies, this paper highlights the prevalence of resistance across different anthelmintic classes and its implications for veterinary and public health. The findings emphasize the need for better management strategies and innovative solutions to address this growing problem.

Efficacy of Simparica Trio® against induced infections of Ancylostoma braziliense and Ancylostoma ceylanicum in dogs

BACKGROUND

Hookworm infections such as Ancylostoma braziliense and A. ceylanicum pose a significant threat to pets and are implicated in causing zoonotic diseases. Despite the availability of preventatives, compliance can be lacking. Increasing pet owner options and combining endo- and ectoparasite treatments might improve this compliance. In four separate studies, we investigated the efficacy of Simparica Trio® (Zoetis Inc., Parsippany, NJ, USA) containing minimum dosages of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel against fourth- and fifth-stage larvae (L4 and L5, respectively) and adults of A. braziliense and adults of A. ceylanicum in dogs.

METHODS

Four negatively controlled, randomised and blinded laboratory studies were conducted against induced infections of A. braziliense and A. ceylanicum, with the interval between infection and treatment selected to evaluate efficacy against each targeted stage. Each treated dog received a single oral dose of Simparica Trio® at the recommended label dose. Necropsy was conducted for worm recovery on day 7 or 8 post-treatment.

RESULTS

No treatment-related adverse events were recorded in any of the studies. No worms were recovered from any of the Simparica Trio®-treated dogs in all four studies, thus resulting in 100% efficacy (P ≤ 0.0005) of Simparica Trio® against all stages of A. braziliense and the adult stage of A. ceylanicum in dogs.

CONCLUSIONS

Simparica Trio® containing sarolaner, moxidectin and pyrantel was highly effective against induced infections of L4, L5 and adult stages of A. braziliense and the adult stage of A. ceylanicum in dogs.

Investigation of risk factors associated with Ancylostoma spp. infection and the benzimidazole F167Y resistance marker polymorphism in dogs from the United States

Ancylostoma caninum is the most significant intestinal nematode parasite of dogs. We acquired fecal surveillance data from a large population of dogs in the United States (US). A diagnostic test using real-time PCR (qPCR) for Ancylostoma spp. and allele-specific qPCR detecting the SNP F167Y in the isotype 1 of the Beta-tubulin gene, was used in 885,424 randomized canine fecal samples collected between March 2022 and December 2023. Overall, Ancylostoma spp. had a prevalence of 1.76% (15,537/885,424), with the highest in the South 3.73% (10,747/287,576), and the lowest in the West 0.45% (632/140,282). Within the subset of Ancylostoma spp.-detected dogs used for further analysis, the F167Y SNP had an overall prevalence of 14.44% with the highest in the West and the lowest in the Midwest (10.76%). The greyhound exhibited a higher prevalence of Ancylostoma spp. infections (17.03%) and a higher prevalence of the F167Y polymorphism (33.6%) compared to non-greyhounds (13.7% and 2.08%), respectively, but were not associated with the highest risk for the F167Y polymorphism. Sex did not influence hookworm infection nor F167Y polymorphism prevalence. Intact dogs had a prevalence of hookworm infection and F167Y polymorphism of 3.88% and 15.66%, respectively. Puppies showed increased prevalence of hookworms (3.70%) and the F167Y SNP (17.1%). Greyhounds, bluetick coonhounds, and boerboels had the highest relative risks for hookworm infection, while Cavalier King Charles spaniels, Havanese, and shiba inus had the lowest. The top and bottom three with the highest and lowest RR for the F167Y SNP were the old English sheepdog, American foxhound, and toy poodle Toy, and shih tzu, Maltese, and Australian cattle dogs, respectively. This study highlights the value of an accessible diagnostic qPCR test with fast turnaround in unraveling the molecular epidemiology of hookworms and benzimidazole resistance, as well as explore potentially important risk factorsin dogs with routine veterinary care.

Widespread occurrence of benzimidazole resistance single nucleotide polymorphisms in the canine hookworm, Ancylostoma caninum, in Australia

Canine hookworm (Ancylostoma caninum), a gastrointestinal nematode of domestic dogs, principally infects the small intestine of dogs and has the potential to cause zoonotic disease. In greyhounds and pet dogs in the USA, A. caninum has been shown to be resistant to multiple anthelmintics. We conducted a molecular survey of benzimidazole resistance in A. caninum from dogs at veterinary diagnostic centers in Australia and New Zealand. First, we implemented an internal transcribed spacer (ITS)-2 rDNA deep amplicon metabarcoding sequencing approach to ascertain the species of hookworms infecting dogs in the region. Then, we evaluated the frequency of the canonical F167Y and Q134H isotype-1 β-tubulin mutations, which confer benzimidazole resistance, using the same sequencing approach. The most detected hookworm species in diagnostic samples was A. caninum (90%; 83/92); the related Northern hookworm (Uncinaria stenocephala) was identified in 11% (10/92) of the diagnostic samples. There was a single sample with coinfection by A. caninum and U. stenocephala. Both isotype-1 β-tubulin mutations were present in A. caninum, 49% and 67% for Q134H and F167Y, respectively. Mutation F167Y in the isotype-1 β-tubulin mutation was recorded in U. stenocephala for the first known time. Canonical benzimidazole resistance codons 198 and 200 mutations were absent. Egg hatch assays performed on a subset of the A. caninum samples showed significant correlation between 50% inhibitory concentration (IC50) to thiabendazole and F167Y, with an increased IC50 for samples with > 75% F167Y mutation. We detected 14% of dogs with > 75% F167Y mutation in A. caninum. Given that these samples were collected from dogs across various regions of Australia, the present study suggests that benzimidazole resistance in A. caninum is widespread. Therefore, to mitigate the risk of resistance selection and further spread, adoption of a risk assessment-based approach to limit unnecessary anthelmintic use should be a key consideration for future parasite control.

Isolation of anti-Ancylostoma-secreted protein 5 (ASP5) antibody from a naïve antibody phage library

Ancylostoma species are parasitic nematodes that release a multitude of proteins to manipulate host immune responses to facilitate their survival. Among the released proteins, Ancylostoma-secreted protein 5 (ASP5) plays a pivotal role in mediating host-parasite interactions, making it a promising target for interventions against canine hookworm infections caused by Ancylostoma species. Antibody phage display, a widely used method for generating human monoclonal antibodies was employed in this study. A bacterial expression system was used to produce ASP5 for biopanning. A single-chain fragment variable (scFv) monoclonal antibody against ASP5 was generated from the naïve Human AntibodY LibrarY (HAYLY). The resulting scFv antibody was characterized to elucidate its antigen-binding properties. The identified monoclonal antibody showed good specificity and binding characteristics which highlights its potential for diagnostic applications for hookworm infections.

Identifying Zoonotic Parasites in Domiciled and Non-Domiciled Dogs (Canis lupus familiaris) Within an Urban Zone of the Eastern State of Mexico

BACKGROUND

There are over 42 million dogs in Mexico, with a significant population living on the streets, especially in the State of Mexico. These dogs can act as carriers of zoonotic pathogens, placing children and individuals with chronic diseases or immunodeficiencies at risk.

OBJECTIVES

To evaluate the prevalence of zoonotic parasites in feral and domestic dogs in the urban area of the eastern State of Mexico and assess their potential impact on public health.

METHODS

The study was conducted from July 2022 to March 2023 in the urban area located in the eastern region of the State of Mexico. A total of 134 samples of dog faces were collected through convenience sampling, from both domiciled and non-domiciled dogs.

RESULTS

Fifty-one dogs were identified with Ancylostomatidae family (38.1%, 95% CI: 27.0%-52.1%), 10 with Toxocara spp. (7.5%, 95% CI: 3.6%-13.3%), 7 with Dipylidium caninum (5.5%, 95% CI: 2.1%-10.5%), 8 with Cystoisospora spp. (6.0%, 95% CI: 2.6%-11.4%), 6 with Giardia spp. (4.5%, 95% CI: 1.7-9.5%) and 2 positive cases for Hymenolepis spp. (1.5%, 95% CI: 0.2%-5.3%) were identified.

CONCLUSIONS

This study highlights a public health concern related to non-domiciled dogs, which can serve as carriers of zoonotic parasites. Interactions among non-domiciled dogs, domiciled dogs and humans heighten the risk of transmission. Implementing prevention, control and awareness strategies is crucial to reduce the spread of these parasites.

A comparative field efficacy trial of three treatment programs against endo- and ectoparasites in naturally infected dogs

Introduction

Tropical climates in remote Aboriginal and Torres Strait Islander communities in northern Australia are conducive to the transmission of canine helminths such as hookworms, as well as ectoparasites such as fleas and ticks. In addition to their veterinary importance, these parasites may present a zoonotic risk either directly, or as potential vectors for bacterial pathogens. These factors necessitate efficacious and effective antiparasitic treatment programs for community dogs.

Methods

A cluster-randomised trial was performed on three islands in the Torres Strait to examine the short-term efficacy and medium-term effectiveness of three treatment programs. Treatments administered included oral oxibendazole/praziquantel (Paragard®) and oral afoxolaner (Nexgard®); topical moxidectin/imidacloprid (Advocate®) and imidacloprid/flumethrin collars (Seresto®); and off-label oral ivermectin (Bomectin®). Canine faecal samples were collected and examined for endoparasites by faecal flotation and real-time PCR at baseline, 7-11 days after treatment and 6 months later.

Results

The proportion of dogs positive for Ancylostoma caninum at baseline and negative at day 7-11 was 9% (95% CI 4.4-17.4) for dogs treated with oxibendazole, 56.4% (95% CI 41-70.7) for moxidectin, and 89.7% (95% CI 73.6-96.4) for ivermectin. Faecal flotation results showed a greater than 90% egg reduction in 29.2% (95% CI 19.9-40.5) of dogs treated with oxibendazole, 79.4% (95% CI 63.2-89.7) for moxidectin, and 95% (95% CI 76.4-99.1) for off-label ivermectin. Elimination of ectoparasite infestation was observed at day 7-11 in 69.9% (95% CI 56.7-80.1) of dogs treated with afoxolaner, 80% (95% CI 60.9-91.1) with imidacloprid/flumethrin collars, and 0% (95% CI 0-11.7) for off-label ivermectin. Mixed effects modelling revealed only treatment group to be significantly associated with outcome measures.

Discussion

Based on these study results, the poor efficacy of oxibendazole against A. caninum renders it inept for treatment, while ivermectin and moxidectin were suitable. Ivermectin was unsuitable for ectoparasite treatment due to its poor efficacy, while afoxolaner and imidacloprid/flumethrin collars appear suitable.

Control of companion animal parasites and impact on One Health

The last decades have witnessed an increase in the global population and movements of companion animals, contributing to changes in density and distribution of pet parasites. Control of companion animal parasites (CAPs) becomes increasingly relevant because of the intensifying human-animal bond. Parasites impact on the health of humans and their pets, but also of wildlife and the environment. We conducted a qualitative review on the current advancements, gaps and priorities for the monitoring and treatment of CAPs with a focus on securing public health. There is a need to raise awareness, coordinate global surveillance schemes and better quantify the impact of companion animal parasites on One Health.

Anti-inflammatory and immunomodulatory effects of mesenchymal stem cell therapy on parasitic drug resistance

INTRODUCTION

The emergence of antiparasitic drug resistance poses a concerning threat to animals and humans. Mesenchymal Stem Cells (MSCs) have been widely used to treat infections in humans, pets, and livestock. Although this is an emerging field of study, the current review outlines possible mechanisms and examines potential synergism in combination therapies and the possible harmful effects of such an approach.

AREAS COVERED

The present study delved into the latest pre-clinical research on utilizing MSCs to treat parasitic infections. As per investigations, the introduction of MSCs to patients grappling with parasitic diseases like schistosomiasis, malaria, cystic echinococcosis, toxoplasmosis, leishmaniasis, and trypanosomiasis has shown a reduction in parasite prevalence. This intervention also alters the levels of both pro- and anti-inflammatory cytokines. Furthermore, the combined administration of MSCs and antiparasitic drugs has demonstrated enhanced efficacy in combating parasites and modulating the immune response.

EXPERT OPINION

Mesenchymal stem cells are a potential solution for addressing parasitic drug resistance. This is mainly because of their remarkable immunomodulatory abilities, which can potentially help combat parasites' resistance to drugs.

Retrospective analysis of canine fecal flotation and coproantigen immunoassay hookworm positive results in Greyhounds and other dog breeds

Recent studies demonstrated that Greyhounds are commonly infected with Ancylostoma caninum and these infections have been shown to be resistant to anthelmintics. This study evaluated samples submitted to a commercial reference laboratory (IDEXX Laboratories) for canine fecal flotation zinc sulfate centrifugation and coproantigen immunoassay between January 1, 2019, and July 30, 2023 for evidence that Greyhounds were more often positive for Ancylostoma spp. (hookworms) compared to other breeds. The purpose of the study was to determine if Greyhounds were more likely to be hookworm-positive compared to other breeds, if Greyhounds on preventives with efficacy against hookworm infections are more likely to test positive than other breeds, if their infections take longer to resolve, to estimate how long this takes and to assess whether the proportion of hookworm positive tests for all breeds is increasing over time. Records of 25,440,055 fecal results were obtained representing 17,671,724 unique dogs. Of these, 49,795 (∼0.3%) were Greyhounds. The overall odds ratio (OR) of 15.3 (p < 0.001) suggests that Greyhounds are at significantly higher risk than other breeds for hookworm positive float findings, and the OR of 14.3 (p < 0.001) suggests significantly higher risk for hookworm antigen positive results. The median time to negative testing event from the Turnbull distribution estimate was in the interval of 1-2 days for other breeds and 71-72 days for Greyhounds. These results provide evidence that anthelmintic resistant A. caninum strains may be having population-level impacts on the frequency and duration of infections in Greyhounds. The findings have broader health implications beyond Greyhounds as MADR A. caninum strains could spread to other breeds and even pet owners.

Benzimidazole F167Y polymorphism in the canine hookworm, Ancylostoma caninum: Widespread geographic, seasonal, age, and breed distribution in United States and Canada dogs

Surveillance data for Ancylostoma spp. and the A. caninum benzimidazole treatment resistance associated F167Y polymorphism using molecular diagnostics was obtained in a large population of dogs from the United States and Canada. Real-time PCR (qPCR) for Ancylostoma spp. and allele-specific qPCR detecting a single nucleotide polymorphism (SNP) F167Y was used in 262,872 canine stool samples collected between March and December of 2022. Ancylostoma spp. was found at an overall prevalence of 2.5% (6538/262,872), with the highest prevalence in the Southern US, 4.4% (4490/103,095), and the lowest prevalence in Canada 0.6% (101/15,829). The A. caninum F167Y polymorphism was found with the highest prevalence (13.4%, n = 46/343) in the Western US and the lowest in Canada at 4.1% (4/97). The F167Y polymorphism was detected every month over the 10-month collection period. Seasonal distribution showed a peak in June for both Ancylostoma spp. (3.08%, 547/17,775) and A. caninum F167Y (12.25%, 67/547). However, the A. caninum F167Y polymorphism prevalence was highest in September (13.9%, 119/856). Age analysis indicates a higher prevalence of both hookworm infections and occurrence of resistant isolates in puppies. The breeds with the highest F167Y polymorphism prevalence in Ancylostoma spp. detected samples were poodles (28.9%), followed by Bernese Mountain dogs (25%), Cocker spaniels (23.1%), and greyhounds (22.4%). Our data set describes widespread geographic distribution of the A. caninum benzimidazole resistance associated F167Y polymorphism in the United States and Canada, with no clear seasonality compared to the Ancylostoma spp. prevalence patterns. The F167 polymorphism was present in all geographic areas with detected hookworms, including Canada. Our study highlights that the F167Y polymorphism is represented in many dog breeds, including greyhounds.

Diagnosis of canine intestinal parasites: Improved detection of Dipylidium caninum infection through coproantigen testing

Intestinal parasites, including cestodes like Dipylidium caninum, are common in dogs in the United States of America (USA), but fecal flotation consistently, and, at times, dramatically, fails to identify many of these infections. To determine the extent to which including coproantigen testing for D. caninum would improve the identification of dogs infected with this cestode, we evaluated fecal samples from 877 dogs (589 pet and 288 from municipal shelters) from six USA states using zinc sulfate (specific gravity 1.24) fecal flotation with centrifugation along with coproantigen detection for Giardia sp., hookworms, ascarids, and Trichuris vulpis. For D. caninum, PCR of perianal swabs was included. Intestinal parasite infections were identified, using centrifugal fecal flotation or coproantigen, in 265 dogs (13.2 % pet, 64.9 % shelter). Dipylidium caninum infection was detected in 5.6 % of dogs with the combination of coproantigen and centrifugal fecal flotation, and 7.3 % of dogs when perianal swab results were included; prevalence varied by diagnostic method, population, and geographic region. In pet dogs, D. caninum infection was identified by fecal flotation (0), coproantigen (2.2 %), or perianal swabs (1.2 %). The same methods revealed infection in 0.3 %, 12.5 %, and 11.1 % of shelter dogs, respectively. Frequent use of praziquantel in shelter dogs (116/288; 40.3 %) may have reduced prevalence. Positive and negative agreement of D. caninum coproantigen with perianal swab PCR in pet dogs was 85.7 % and 98.8 %, respectively. Multiple logistic regression analysis accounting for region, population, and age found D. caninum infection to be more common in shelter dogs relative to pet (adjusted OR 4.91 [2.48, 10.24]) and in the Southcentral and Southeast regions relative to North (adjusted OR 9.59 [1.92, 174.13] and 17.69 [3.67, 318.09] respectively). Coproantigen testing also enhanced the detection of other intestinal parasites over fecal flotation alone, including Giardia sp. (14.7 % vs 3.3 %), hookworms (13.8 % vs 8.4 %), ascarids (2.9 % vs 2.2 %), and T. vulpis (2.9 % vs 1.4 %). Together, these data indicate that the coproantigen assay employed increases detection of D. caninum infections several fold, supporting the use of this test in clinical practice, and add to a growing body of research documenting enhanced diagnosis through implementation of multiple laboratory-based methods.

Mapping resistance-associated anthelmintic interactions in the model nematode Caenorhabditis elegans

Parasitic nematodes infect billions of people and are mainly controlled by anthelmintic mass drug administration (MDA). While there are growing efforts to better understand mechanisms of anthelmintic resistance in human and animal populations, it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. Mutations that alter drug permeability across primary nematode barriers have been identified as potential resistance mechanisms using the model nematode Caenorhabditis elegans. We leveraged high-throughput assays in this model system to measure altered anthelmintic susceptibility in response to genetic perturbations of potential cuticular, amphidial, and alimentary routes of drug entry. Mutations in genes associated with these tissue barriers differentially altered susceptibility to the major anthelmintic classes (macrocyclic lactones, benzimidazoles, and nicotinic acetylcholine receptor agonists) as measured by animal development. We investigated two-way anthelmintic interactions across C. elegans genetic backgrounds that confer resistance or hypersensitivity to one or more drugs. We observe that genetic perturbations that alter susceptibility to a single drug can shift the drug interaction landscape and lead to the appearance of novel synergistic and antagonistic interactions. This work establishes a framework for investigating combinatorial therapies in model nematodes that can potentially be translated to amenable parasite species.