Isolation and characterization of a naturally occurring multidrug-resistant strain of the canine hookworm, Ancylostoma caninum

Smells Like Anthelmintic Resistance-Gastrointestinal Prevalence, Burden and Diversity in Dogs from Portugal

Anthelmintic resistance has been documented worldwide, but few cases have been reported in dogs. Shelter dogs are a great opportunity to study intestinal helminths and assess their potential resistance to anthelmintic compounds. With these two goals in mind, 361 faecal samples were collected from dogs in 18 municipalities in Portugal, from 19 shelters and 11 private tutors. These samples were analysed using the Mini-FLOTAC before and 13 days after deworming. The percentage of faecal egg count reduction was calculated. Parasitic forms were identified in 22.4% of the samples collected: Trichuris vulpis (10.5%), Toxocara canis (8.0%), members of the family Ancylostomatidae (6.4%), Toxascaris leonina (0.8%), Dipylidium caninum (0.6%) and members of the family Taeniidae (0.3%). The first three nematode parasites showed the highest intensity of infection (2900, 1325, and 1265 eggs per gram, respectively). In the second faecal collection, parasites were present in 20.8% of the samples. The anthelmintics febendazole + pyrantel embonate + praziquantel and praziquantel + fenbendazole were ineffective for T. vulpis and members of the family Ancylostomatidae in 16.2% and 6.9% of the samples, respectively. The parasites identified are all potentially zoonotic. This study is the first to suggest a potential resistance of T. vulpis to anthelmintics.

Quantitative tests of albendazole resistance in Caenorhabditis elegans beta-tubulin mutants

Benzimidazole (BZ) anthelmintics are among the most important treatments for parasitic nematode infections in the developing world. Widespread BZ resistance in veterinary parasites and emerging resistance in human parasites raise major concerns for the continued use of BZs. Knowledge of the mechanisms of resistance is necessary to make informed treatment decisions and circumvent resistance. Benzimidazole resistance has traditionally been associated with mutations and natural variants in the C. elegans beta-tubulin gene ben-1 and orthologs in parasitic species. However, variants in ben-1 alone do not explain the differences in BZ responses across parasite populations. Here, we examined the roles of five C. elegans beta-tubulin genes (tbb-1, mec-7, tbb-4, ben-1, and tbb-6) in the BZ response as well as to determine if another beta-tubulin acts redundantly with ben-1. We generated C. elegans strains with a loss of each beta-tubulin gene, as well as strains with a loss of tbb-1, mec-7, tbb-4, or tbb-6 in a genetic background that also lacks ben-1. We found that the loss of ben-1 conferred the maximum level of resistance following exposure to a single concentration of albendazole, and the loss of a second beta-tubulin gene did not alter the level of resistance. However, additional traits other than larval development could be affected by the loss of additional beta-tubulins, and the roles of other beta-tubulin genes might be revealed at different albendazole concentrations. Therefore, further work is needed to fully define the possible roles of other beta-tubulin genes in the BZ response.

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.

Assessing the applications and efficacy of using helminthophagous fungi to control canine gastrointestinal parasites

Helminths are a major challenge in dog breeding, particularly affecting young animals and posing a significant zoonotic risk. The widespread use of anthelmintics to treat gastrointestinal helminth infections in companion animals is common. However, these chemical products generate residues that can have adverse effects on animal, human and environmental health. In addition to the challenge of parasite resistance to treatment, there is an urgent need to explore and discuss complementary and sustainable methods of controlling helminthiases in these animals. In this context, nematophagous or helminthophagous fungi have emerged as a potential tool for the control of environmental forms of helminths. The purpose of this review is to emphasize the importance of these fungi in the control of free-living forms of helminth parasites in companion animals by highlighting the research that has been conducted for this purpose. In vitro experiments demonstrated the efficacy of fungi like Pochonia chlamydosporia, Arthrobotrys robusta, and Monacrosporium thaumasium in trapping and reducing helminth infective forms. These findings, along with soil contamination studies, suggest the feasibility of using helminthophagous fungi as a sustainable and effective strategy for environmental control. The current literature supports the potential of these fungi as an environmentally friendly solution for managing helminthiasis in dogs, benefiting both animal health and public welfare.

Quantitative tests of albendazole resistance in beta-tubulin mutants

Benzimidazole (BZ) anthelmintics are among the most important treatments for parasitic nematode infections in the developing world. Widespread BZ resistance in veterinary parasites and emerging resistance in human parasites raise major concerns for the continued use of BZs. Knowledge of the mechanisms of resistance is necessary to make informed treatment decisions and circumvent resistance. Benzimidazole resistance has traditionally been associated with mutations and natural variants in the C. elegans beta-tubulin gene ben-1 and orthologs in parasitic species. However, variants in ben-1 alone do not explain the differences in BZ responses across parasite populations. Here, we examine the roles of five C. elegans beta-tubulin genes (tbb-1, mec-7, tbb-4, ben-1, and tbb-6) to identify the role each gene plays in BZ response. We generated C. elegans strains with a loss of each beta-tubulin gene, as well as strains with a loss of tbb-1, mec-7, tbb-4, or tbb-6 in a genetic background that also lacks ben-1 to test beta-tubulin redundancy in BZ response. We found that only the individual loss of ben-1 conferred a substantial level of BZ resistance, although the loss of tbb-1 was found to confer a small benefit in the presence of albendazole (ABZ). The loss of ben-1 was found to confer an almost complete rescue of animal development in the presence of 30 μM ABZ, likely explaining why no additive effects caused by the loss of a second beta-tubulin were observed. We demonstrate that ben-1 is the only beta-tubulin gene in C. elegans where loss confers substantial BZ resistance.

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.

Nationwide USA re-analysis of amplicon metabarcoding targeting β-tubulin isoform-1 reveals absence of benzimidazole resistant SNPs in Ancylostoma braziliense, Ancylostoma tubaeforme and Uncinaria stenocephala

Nationwide sampling by Venkatesan and colleagues (2023) described the resistance status of the canine hookworm, Ancylostoma caninum, to benzimidazoles across the USA via β-tubulin isotype-1 amplicon metabarcoding. In this study, we aimed to use the existing public amplicon metabarcoding data and mine it for the presence of β-tubulin isotype-1 sequences that belong to hookworm species other than A. caninum. Through bioinformatics analysis we assigned species to A. caninum, Ancylostoma braziliense, Ancylostoma tubaeforme and Uncinaria stenocephala. All non-A. caninum sequences contained only the benzimidazole susceptible residues of β-tubulin isotype-1. Using two β-tubulin isotype-1 metabarcoding sequence data (assay targeting 134 and 167 codons, and assay targeting 198 and 200 codons), 2.0% (6/307) and 2.9% (9/310) individual samples had hookworms other than A. caninum (A. braziliense n = 5, A. tubaeforme n = 4 and U. stenocephala n = 2), respectively. We identified one sample containing A. braziliense in each of the Northeastern region and Midwestern region, and in three samples from the Southern region. Presence of A. tubaeforme in dog faeces is considered as pseudoparasitism. There were no statistically significant regional differences for the distribution of each species, for either of the two assays independently or combined (χ2 tests, P > 0.05). Our work demonstrates the utility of the amplicon metabarcoding for the identification of species through antemortem assays, thus resolving the dilemma of assigning hookworm species based on either post-mortem or egg sizes for the identification of hookworms.

Hookworm Anthelmintic Resistance: Novel Fecal Polymerase Chain Reaction Ancylostoma caninum Benzimidazole Resistance Marker Detection in a Dog

A 4 yr old castrated male greyhound presented with a history of chronic (>3 wk) intermittent diarrhea. Initial fecal analysis identified infection with Ancylostoma caninum. Despite treatment with routine anthelmintics, the dog remained persistently A caninum positive for several months. A novel fecal gastrointestinal real-time polymerase chain reaction (qPCR) parasite panel detected A caninum and the genetic benzimidazole (BZ) F167Y resistance marker in multiple samplings over 48 hr. This finding, together with the dog's clinical signs (diarrhea) and lack of response to routine anthelmintics, prompted treatment with cyclooctadepsipeptide emodepside, a drug currently not registered for dogs in the United States. The dog's clinical signs resolved and post-treatment fecal qPCR testing was negative. However, 5 mo later, retesting with fecal qPCR detected A caninum and concurrent BZ resistance marker, as well as Giardia. A presumptive diagnosis of re-infection was made and the emodepside treatment was continued. The dog again reverted to undetected (A caninum and the 167 resistance marker) on reassessment fecal qPCR. This case report describes the use of a novel fecal qPCR panel for gastrointestinal parasites, persistent hookworm and BZ F167Y resistance marker detection in a dog, and highlights the importance of a stepwise approach to clinical management, treatment, and retesting.

Altered larval activation response associated with multidrug resistance in the canine hookworm Ancylostoma caninum

Parasitic gastrointestinal nematodes pose significant health risks to humans, livestock, and companion animals, and their control relies heavily on the use of anthelmintic drugs. Overuse of these drugs has led to the emergence of resistant nematode populations. Herein, a naturally occurring isolate (referred to as BCR) of the dog hookworm, Ancylostoma caninum, that is resistant to 3 major classes of anthelmintics is characterized. Various drug assays were used to determine the resistance of BCR to thiabendazole, ivermectin, moxidectin and pyrantel pamoate. When compared to a drug-susceptible isolate of A. caninum, BCR was shown to be significantly resistant to all 4 of the drugs tested. Multiple single nucleotide polymorphisms have been shown to impart benzimidazole resistance, including the F167Y mutation in the β-tubulin isotype 1 gene, which was confirmed to be present in BCR through molecular analysis. The frequency of the resistant allele in BCR was 76.3% following its first passage in the lab, which represented an increase from approximately 50% in the founding hookworm population. A second, recently described mutation in codon 134 (Q134H) was also detected at lower frequency in the BCR population. Additionally, BCR exhibits an altered larval activation phenotype compared to the susceptible isolate, suggesting differences in the signalling pathways involved in the activation process which may be associated with resistance. Further characterization of this isolate will provide insights into the mechanisms of resistance to macrocyclic lactones and tetrahydropyrimidine anthelmintics.

Pyrantel resistance in canine hookworms in Queensland, Australia

Hookworms are the most common intestinal nematode parasites of dogs in Australia. The control of these parasites relies mostly on regular deworming with anthelmintics, with pyrantel-based dewormers being a relatively low cost and readily-available option for dog owners. Pyrantel resistance in canine hookworms in Australia was first reported in 2007, however pyrantel-based dewormers are still used against hookworm infection in dogs across Australia. The present study was conducted to evaluate the efficacy of pyrantel against hookworms infecting dogs housed in a shelter facility in Southeast Queensland which receives rescued or surrendered animals from greyhound rescue centres and dog shelters across this region. A total of 10 dogs were examined using the faecal egg count reduction test (FECRT). There was no reduction in FEC in any of the dogs following pyrantel treatment, with drug efficacies ranging from -0.9% to -283.3%. Given that these dogs originated from various sites across Southeast Queensland, the present study suggests that pyrantel resistance is widespread in this region, and hence this anthelmintic may not be a useful option for treatment of hookworm infections in dogs.

Occurrence of zoonotic enteric parasites in fecal samples from dogs in shelters, parks, squares and public roads, and the dog guardians' perception of zoonoses as for the risk to public health in the city of Guarapuava, Paraná, Brazil

The aim of this study was to determine the occurrence of zoonotic enteroparasites in the feces of dogs from public shelters, squares, parks, and public roads in the city of Guarapuava, Paraná, Brazil, and to evaluate the perception of dog guardians regarding zoonoses and their risk to public health. Fecal samples were collected, coproparasitological examinations were performed to detect zoonotic enteroparasites, and polymerase chain reaction (PCR) was used to identify Giardia spp. and Cryptosporidium spp. Questionnaires were given to guardians who walked their dogs in parks, squares, and public roads, as to assess their perception of zoonoses. A total of 333 samples were collected, of these 75, 123, and 135 of them were from public shelters, squares and parks, and public roads, respectively. One or more parasites were identified in 166 (50 %) samples, of which 58/75 (77 %) were from public shelters, 50/123 (41 %) from squares and parks, and 58/135 (43 %) from public roads. The parasites detected included Ancylostoma spp., Giardia spp., Trichuris spp., Toxocara spp., and Cystoisospora spp., with Ancylostoma spp. having the highest occurrence. PCR was performed on 161 samples for convenience due to financial limitations, because only a portion of the study was funded by the municipal government, of which 15.6 % were positive for Giardia spp., and all were negative for Cryptosporidium spp. In total, 246 guardians were interviewed, of which 36 % said they did not collect their animals' feces during walks, 20 % did not use anti-helminthics on their dogs, and 23 % did not know which diseases could be transmitted by feces. Therefore, we conclude that there is a high infection rate of parasites with zoonotic potential in public places, showing the need to raise awareness among guardians about the diseases transmitted by dog feces, correct vermifugation and the importance of collecting feces in public places.

Immunity mediates host specificity in the human hookworm Ancylostoma ceylanicum

Hookworm infection affects millions globally, leading to chronic conditions like malnutrition and anaemia. Among the hookworm species, Ancylostoma ceylanicum stands out as a generalist, capable of infecting various hosts, including humans, cats, dogs and hamsters. Surprisingly, it cannot establish in mice, despite their close phylogenetic relationship to hamsters. The present study investigated the development of A. ceylanicum in immunodeficient NSG mice to determine the contribution of the immune system to host restriction. The infections became patent on day 19 post-infection (PI) and exhibited elevated egg production which lasted for at least 160 days PI. Infective A. ceylanicum larvae reared from eggs released by infected NSG mice were infectious to hamsters and capable of reproduction, indicating that the adults in the NSG mice were producing viable offspring. In contrast, A. ceylanicum showed limited development in outbred Swiss Webster mice. Furthermore, the closely related canine hookworm Ancylostoma caninum was unable to infect and develop in NSG mice, indicating that different mechanisms may determine host specificity even in closely related species. This is the first report of any hookworm species completing its life cycle in a mouse and implicate the immune system in determining host specificity in A. ceylanicum.

Anthelmintic resistance in soil-transmitted helminths: One-Health considerations

The One-Health approach recognizes the intricate connection between human, animal, and environmental health, and that cooperative effort from various professionals provides comprehensive awareness and potential solutions for issues relating to the health of people, animals, and the environment. This approach has increasingly gained appeal as the standard strategy for tackling emerging infectious diseases, most of which are zoonoses. Treatment with anthelmintics (AHs) without a doubt minimizes the severe consequences of soil-transmitted helminths (STHs); however, evidence of anthelmintic resistance (AR) development to different helminths of practically every animal species and the distinct groups of AHs is overwhelming globally. In this regard, the correlation between the application of anthelmintic drugs in both human and animal populations and the consequent development of anthelmintic resistance in STHs within the context of a One-Health framework is explored. This review provides an overview of the major human and animal STHs, treatment of the STHs, AR development and drug-related factors contributing towards AR, One-Health and STHs, and an outline of some One-Health strategies that may be used in combating AR.

Biological implications of long-term anthelmintic treatment: what else besides resistance are we selecting for?

Long-term intensive use of anthelmintics for parasite control of livestock, companion animals, and humans has resulted in widespread anthelmintic resistance, a problem of great socioeconomic significance. But anthelmintic therapy may also select for other biological traits, which could have implications for anthelmintic performance. Here, we highlight recent examples of changing parasite dynamics following anthelmintic administration, which do not fit the definition of anthelmintic resistance. We also consider other possible examples in which anthelmintic resistance has clearly established, but where coselection for other biological traits may have also occurred. We offer suggestions for collecting more information and gaining a better understanding of these phenomena. Finally, we propose research questions that require further investigation and make suggestions to help address these knowledge gaps.

Unambiguous identification of Ancylostoma caninum and Uncinaria stenocephala in Australian and New Zealand dogs from faecal samples

Hookworms (Ancylostomatidae) are well-known parasites in dogs due to their health impacts and zoonotic potential. While faecal analysis is the traditional method for detection, improvements in husbandry and deworming have decreased their prevalence in urban owned dogs. Drug resistance in Ancylostoma caninum is becoming a discussion point in small animal practices across the region. This study aimed to identify hookworm species present in Australian and New Zealand dogs using molecular techniques. The ITS-2 and isotype-1 β-tubulin assays were used to identify and quantify hookworm species. Results showed absence of coinfection in Australian samples from Greater Sydney region belonging either to A. caninum or Uncinaria stenocephala, while New Zealand samples were a mixture of A. caninum and U. stenocephala. The amplified isotype-1 β-tubulin sequences exhibited susceptibility to benzimidazole drugs. Rare mutations were identified in A. caninum and U. stenocephala sequences, representing a small percentage of reads. This study highlights the importance of molecular techniques in accurately identifying and quantifying hookworm species in dog populations.

Multiple anthelmintic drug resistant Ancylostoma caninum in foxhounds

Ancylostoma caninum is the most common and important gastrointestinal nematode of dogs in the United States. Despite recent reports of A. caninum isolates resistant to all classes of anthelmintics, little is known about the frequency and extent of this anthelmintic resistance. The study aim was to evaluate the efficacy of three commercial anthelmintic products in the treatment of foxhound dogs with a history of persistent A. caninum infections. In the first phase of this study, 35 foxhounds were randomly divided into three treatment groups: moxidectin/imidacloprid (MI), pyrantel pamoate/febantel/praziquantel (PFP), and emodepside/praziquantel (EP). Fecal samples were collected on day 0, 11, and 33 post-treatment (PT), and hookworm eggs were quantified using the mini-FLOTAC technique with a multiplication factor of 5 eggs per gram (EPG). The fecal egg count reduction (FECR) on day 11 PT was 65% (95% CI: 62%-68%) for MI, 69% (95% CI: 66%-72%) for PFP, and 96% (95% CI: 94%-97%) for EP. On day 33 PT, the FEC in the MI and PFP groups returned to almost the same values as on day 0, while in the EP group, the FEC remained low. Since MI and PFP proved ineffective, 32 animals were randomly divided into two groups in the second phase. They were treated either with a combination of MI/PFP or EP. The FECR at day 13 PT for the combination MI/PFP was 89% (95% CI: 87%-91%) and 99% (95% CI: 98%-99%) for EP. These results suggest that this A. caninum population is resistant to multiple anthelmintics. Although the combination of MI/PFP improved the anthelmintic efficacy, the FECR remained below 90%. Future studies are indicated to evaluate further the epidemiology of persistent hookworm infections in dogs in the US and to identify more effective treatment protocols as they pose a significant health risk to canine and human health.

Present status with impacts and roles of miRNA on Soil Transmitted Helminthiosis control: A review

Soil-Transmitted Helminthiasis (STH) is one of the most widespread Neglected Tropical Diseases (NTDs), and almost 1.5 billion of the global population is affected, mostly in the indigent, countryside sectors of tropics/subtropics. STH, commonly caused by various nematodes, adversely affects the hosts' growth, cognatic development, and immunity. Albendazole is most commonly used against STH (Soil-Transmitted Helminths) but resistance has already been reported in different countries. To date, no effective vaccine is present against STH. miRNAs are a unique class of small non-coding RNA, regulating various biological activities indulging host immune responses in host-pathogen interaction of STH. Dysregulation of miRNAs are being considered as one of the most important aspect of host-parasite interactions. Thus, it is the prime importance to identify and characterize parasite-specific as well as host-derived miRNAs to understand the STH infection at the molecular level. Systematic bibliometric analysis reveals a huge knowledge gap in understanding the disease by using both host and parasitic miRNAs as a potential biomarker. In this study, we addressed the present status of the STH prevalence, and therapy under the light of miRNAs. This would further help in designing new inhibitors and therapeutic strategies to control STH.

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

Reports of anthelmintic resistance in Ancylostoma caninum are increasing in frequency in the United States of America (USA). In the last few years in vitro and in vivo studies characterized individual isolates, demonstrating multiple anthelmintic drug resistance (MADR). In 2021, the American Association of Veterinary Parasitologists initiated a hookworm task force to address this issue. The first report of drug resistant A. caninum occurred in 1987 in Australian racing Greyhounds. In the last five years multiple case reports and investigations show drug resistant A. caninum is becoming a much greater problem in the USA and now extends beyond racing Greyhounds into the general companion animal dog population. The literature, regarding drug resistance in livestock and equine nematodes, provides helpful guidance along with diagnostic methods to better understand the evolution and selection of canine MADR hookworms; however, there are limitations and caveats due to A. caninum's unique biology and zoonotic potential. Mass drug administration (MDA) of anthelminthic drugs to humans to reduce morbidity associated with human hookworms (Necator americanus) should consider the factors that contributed to the development of MADR A. caninum. Finally, as Greyhound racing undergoes termination in some regions and the retired dogs undergo subsequent rehoming, drug resistant parasites, if present, are carried with them. Drug resistant A. caninum requires greater recognition by the veterinary community, and small animal practitioners need to be aware of the spread into current pet dog populations. The current understanding of anthelmintic resistance, available treatments, and environmental mitigation for these drug resistant A. caninum isolates must be monitored for horizontal spread. A major goal in this emerging problem is to prevent continued dissemination.

Molecular evidence of widespread benzimidazole drug resistance in Ancylostoma caninum from domestic dogs throughout the USA and discovery of a novel β-tubulin benzimidazole resistance mutation

Ancylostoma caninum is an important zoonotic gastrointestinal nematode of dogs worldwide and a close relative of human hookworms. We recently reported that racing greyhound dogs in the USA are infected with A. caninum that are commonly resistant to multiple anthelmintics. Benzimidazole resistance in A. caninum in greyhounds was associated with a high frequency of the canonical F167Y(TTC>TAC) isotype-1 β-tubulin mutation. In this work, we show that benzimidazole resistance is remarkably widespread in A. caninum from domestic dogs across the USA. First, we identified and showed the functional significance of a novel benzimidazole isotype-1 β-tubulin resistance mutation, Q134H(CAA>CAT). Several benzimidazole resistant A. caninum isolates from greyhounds with a low frequency of the F167Y(TTC>TAC) mutation had a high frequency of a Q134H(CAA>CAT) mutation not previously reported from any eukaryotic pathogen in the field. Structural modeling predicted that the Q134 residue is directly involved in benzimidazole drug binding and that the 134H substitution would significantly reduce binding affinity. Introduction of the Q134H substitution into the C. elegans β-tubulin gene ben-1, by CRISPR-Cas9 editing, conferred similar levels of resistance as a ben-1 null allele. Deep amplicon sequencing on A. caninum eggs from 685 hookworm positive pet dog fecal samples revealed that both mutations were widespread across the USA, with prevalences of 49.7% (overall mean frequency 54.0%) and 31.1% (overall mean frequency 16.4%) for F167Y(TTC>TAC) and Q134H(CAA>CAT), respectively. Canonical codon 198 and 200 benzimidazole resistance mutations were absent. The F167Y(TTC>TAC) mutation had a significantly higher prevalence and frequency in Western USA than in other regions, which we hypothesize is due to differences in refugia. This work has important implications for companion animal parasite control and the potential emergence of drug resistance in human hookworms.

Molecular evidence of hookworms in public environment of Bangladesh

Accurate diagnosis by precise identification of causative agents is essential for the effectiveness of any control interventions. Despite high zoonotic potential, available literature on hookworms in Bangladesh is still scarce and nonspecific. The objective of this study was to determine the occurrence of hookworms in public locations across northeastern Bangladesh (Sylhet metropolitan area) using integrated parasitological and molecular assays. A total of 130 samples (80 soil and 50 environmental canine feces) were collected and examined using modified flotation technique and formalin-ether sedimentation methods. Modified plate culture was used to isolate larvae. The identification was made based on morphometric features and confirmed by amplifying the ITS region of the nuclear rDNA. Overall, 66.2% (86/130) of examined samples were positive for hookworms infection. Characteristic eggs (61-68 × 29-37 μm) and/or larvae of hookworms were observed in 73.8% (59/80) soils and 54.0% (27/50) environmental fecal samples. Rhabditiform larvae (0.48-0.54 × 0.04-0.07 mm) were observed in cultured samples. Genetic analysis of rDNA sequences revealed the presence of Ancylostoma caninum and Ancylostoma ceylanicum. In this study, hookworms' contamination of the public environment was substantial. To the best of our knowledge, this is the first molecular proof of A. caninum and A. ceylanicum observed in urban public environment in Bangladesh.

Lack of efficacy of fenbendazole against Giardia duodenalis in a naturally infected population of dogs in France

Giardiosis is a worldwide intestinal parasitosis, affecting both humans and animals. Treatment in dogs remains limited and the lack of efficacy of the few approved medications is a rising concern. In this study, 23 dogs raised by veterinary students and naturally infected with Giardia duodenalis were treated in home conditions with fenbendazole (50 mg/kg orally for 5 consecutive days). Fecal samples were collected immediately before treatment (FS1), 2-4 days after treatment (FS2) and 8-10 days after treatment (FS3). Giardia duodenalis cyst excretion was measured quantitatively by direct immunofluorescence assay (DFA) at FS1, FS2 and FS3. Molecular typing with a nested PCR targeting the SSU _rDNA locus was also performed at FS1 and FS2. Fecal consistency improved in 16/21 dogs (76%) and mean cyst shedding was reduced by 84% after treatment. However, only 8/23 dogs (35%) achieved therapeutic success (≥90% reduction of cysts) and only 4/23 dogs (17%) had complete elimination of G. duodenalis. Molecular typing showed that dogs harbored only canine-specific assemblages, with a high prevalence of assemblage C in analyzed samples (30/39). We also detected different assemblages after treatment and nucleotide substitutions in assemblage C sequences that have not been described previously. Eight to ten days after treatment, high Giardia cyst excretion was measured, suggesting possible reinfection despite hygiene measures and/or multiplication. These data suggest that fenbendazole treatment may improve fecal consistency but has limited therapeutic efficacy against giardiosis in this population of dogs. Further research is still needed to assess the efficacy of fenbendazole against canine giardiosis.

Phenotypic characterization and multiple resistance analysis in an experimentally selected albendazole-resistant hookworm isolate

For some nematodes, alterations that leads to a resistance genotype may be accompanied by other modifications, causing changes in the biology of the parasite, although the exact mechanisms of this relationship are still not very clear. These alterations can have deleterious effects on their survival or even potentiate their pathogenicity. In this study a phenotypic characterization was carried out to compare two Ancylostoma ceylanicum isolates, a wild type one, kept in the laboratory and an albendazole selected resistant isolate (AceyBZR2). Differences in some analyzed parameters, between the two strains, were registered, as patency period, number and size of the recovered worms, including differences in the body structures. The AceyBZR2 isolate showed to be less adapted to the host, leading to a smaller number of recovered worms. However, no difference on the female egg content was observed between the two isolates. Concerning blood evaluation, no differences were found between the wild type and AceyBZR2 isolates, related to hemoglobin and hematocrit levels. However, animals in the group infected with the wild type isolate had lower serum iron concentrations than animals in the AceyBZR2 group. The possibility that the AceyBZR2 isolate might be resistant to other drugs was evaluated and it was demonstrated that it does not present cross-resistance to ivermectin and nitazoxanide. However, when animals infected with the AceyBZR2 were treated with another drug from the benzimidazoles group (mebendazole), the cross-resistance effect was observed. Morphometric analyses were performed comparing female and male adult worms from the two isolates. The results presented here allow a better understanding of the parasite-host relationship and may constitute a useful basis for establishing future control strategies for soil-transmitted helminths.

Faecal prevalence, distribution and risk factors associated with canine soil-transmitted helminths contaminating urban parks across Australia

Dog parks provide an ideal urban space where dogs and their owners can exercise, play, and socialize in a safe environment. However, these parks can also increase the risk of exposure to a series of infectious agents including canine soil-transmitted helminths (cSTHs) such as hookworms, roundworms, Strongyloides stercoralis, and Trichuris vulpis, which are endemic to Australia. In this study, we collected 1581 canine faecal samples in 190 urban parks across Australia and subjected these to faecal floatation and multiplex real-time PCRs (qPCR) to detect a range of cSTHs. In total, 44.2% of the parks sampled were contaminated with at least one species of cSTH, with hookworms being the most prevalent parasites (10.2%) followed by Trichuris spp. (1.3%) and Strongyloides spp. (1.2%). This is the first large-scale study investigating the contamination of urban parks with cSTHs in Australia, and the first nation-wide study to demonstrate the occurrence of Strongyloides spp. in canine faecal samples from urban areas in the country. This study reveals a high rate of contamination with cSTHs in dog parks in urban Australia, most of which having proven zoonotic potential. Preventive measures, including awareness-raising educational programs promoting responsible pet ownership, should be encouraged to minimise the health risks associated with cSTHs for both dogs and humans.

Gastrointestinal helminths in dogs: occurrence, risk factors, and multiple antiparasitic drug resistance

Helminth infections are detrimental to the overall health of dogs; therefore, this study aimed to identify antiparasitic-resistant helminths and evaluate the infection rate and risk factors for parasitism in canines. For this purpose, a parasitological evaluation of 38 randomly selected animals was performed, followed by the evaluation of the anthelminthic efficacy of three drugs: pyrantel pamoate with praziquantel (Canex Composto®), fenbendazole (Fenzol Pet®), and milbemycin oxime with praziquantel (Milbemax C®). Among the evaluated animals, 22/38 (57.89%) tested negative and 16/38 (42.71%) tested positive for Ancylostoma caninum infection. Evaluation of the efficacy of antiparasitic drugs showed that 12/16 (75%) dogs were infected with helminths that were susceptible to pyrantel pamoate with praziquantel. Among those for which pyrantel pamoate with praziquantel was not effective, 3/4 (75%) were susceptible to fenbendazole, while the remaining case resistant to both pyrantel pamoate with praziquantel and fenbendazole was sensitive to milbemycin oxime with praziquantel (100%). The odds ratio of infection in dogs inhabiting environments containing soil or grass was 6.67 times higher than that in dogs inhabiting impermeable environments. Mixed-breed dogs (SRD) were 6.54 times more likely to be infected compared to purebred dogs. A. caninum resistant to pyrantel pamoate with praziquantel (4/16, 25%) and fenbendazole (1/4, 25%) were detected. The results of this study demonstrated the importance of coproparasitological monitoring by professionals before and after treatments to assess antiparasitic drug effectiveness, ensure animal health and welfare, and minimize animal exposure to risk factors.

MINI-BAERMANN FUNNEL, A SIMPLE DEVICE FOR CLEANING NEMATODE INFECTIVE LARVAE

The Baermann filter method is a long-standing, simple technique for recovering nematodes from soil and charcoal coprocultures. Material containing the nematodes is placed on a mesh screen lined with several layers of tissue paper or cheesecloth, and the screen is placed in the mouth of the funnel. Rubber tubing attached to the funnel stem is clamped, and water is added to submerge the material. The filtration material allows the nematodes to swim through while holding back the substrate. Over time the nematodes settle at the clamp in the tubing. After several hours, the clamp is opened and water containing the nematodes is collected. Although recovery of the nematodes is efficient, they are often contaminated with soil or charcoal debris, requiring a secondary cleaning by sedimentation or filtration. Described here is a small, simplified version of the Baermann apparatus that can be used as a secondary cleaning device. The "mini-Baermann" is constructed from materials commonly found in the laboratory. Experiments using infective larvae of 3 nematode species demonstrated that the majority of the larvae applied to the device are collected within 2 hr, and nearly all by 4 hr. Dead larvae fail to pass through the filter and do not significantly impact the passage of living larvae. In addition to removing debris from nematode suspensions, this device can rapidly and efficiently separate living, motile larvae from dead larvae.

Ancylostoma ceylanicum Infection in a Miniature Schnauzer Dog Breed

PURPOSE

Canine hookworm disease is a global zoonotic parasitic disease caused by a variety of nematodes in families Ancylostomatidae, including Ancylostoma spp., Necator spp., and Uncinaria spp., in the small intestine (mainly the duodenum) of dogs. The disease is widely distributed in China. The purpose of this study is to systematically diagnose and treat canine hookworm disease through the case of miniaturization Schnauzer dog feed infected with A. ceylanicum, so as to provide experimental basis for subsequent prevention and control of canine hookworm disease.

METHODS

In the current study, we isolated hookworm eggs from a diseased miniature schnauzer, then the polymerase chain reaction (PCR) was used to amplify the ITS1-5.8S-ITS2 gene sequence from genomic DNA extracted from hookworms. Phylogenetic analysis based on ITS1-5.8S-ITS2 gene sequence sequences was inferred using MEGA-X. After phylogenetic analysis, etiologic and symptomatic therapies were used to treat the canine hookworm disease.

RESULTS

The sequencing results showed that the length of the ITS1-5.8S-ITS2 gene sequence was approximately 960 bp, and ITS1 and ITS2 were extracted to analyze similarity with other hookworms to build a phylogenetic tree. After phylogenetic analysis, the results showed that the diseased miniature schnauzer was infected by A. ceylanicum. Using etiologic and symptomatic therapies, the sick dog with an A. ceylanicum infection was also treated for 5 days.

CONCLUSIONS

To our knowledge, this is the first report of diagnosis and treatment for canine hookworm disease in Guangzhou city. In addition, with the improvement of economic level, the scale of pet dog breeding is also increasing. The diagnostic methods and treatment schemes adopted in this report will help to standardize the prevention and control of canine hookworm disease.

Interactions of C. elegans β-tubulins with the microtubule inhibitor and anthelmintic drug albendazole

Parasitic nematodes are major human and agricultural pests, and benzimidazoles are amongst the most important broad spectrum anthelmintic drug class used for their control. Benzimidazole resistance is now widespread in many species of parasitic nematodes in livestock globally and an emerging concern for the sustainable control of human soil transmitted helminths. β-tubulin is the major benzimidazole target, although other genes may influence resistance. Among the six C. elegans β-tubulin genes, loss of ben-1 causes resistance without other apparent defects. Here, we explored the genetics of C. elegans β-tubulin genes in relation to the response to the benzimidazole derivative albendazole. The most highly expressed β-tubulin isotypes, encoded by tbb-1 and tbb-2, were known to be redundant with each other for viability, and their products are predicted not to bind benzimidazoles. We found that tbb-2 mutants, and to a lesser extent tbb-1 mutants, were hypersensitive to albendazole. The double mutant tbb-2 ben-1 is uncoordinated and short, resembling the wild type exposed to albendazole, but the tbb-1 ben-1 double mutant did not show the same phenotypes. These results suggest that tbb-2 is a modifier of ABZ sensitivity. To better understand how BEN-1 mutates to cause benzimidazole resistance, we isolated mutants resistant to albendazole and found that 15 of 16 mutations occurred in the ben-1 coding region. Mutations ranged from likely nulls to hypomorphs, and several corresponded to residues that cause resistance in other organisms. Null alleles of ben-1 are albendazole-resistant and BEN-1 shows high sequence identity with tubulins from other organisms, suggesting that many amino acid changes could cause resistance. However, our results suggest that missense mutations conferring resistance are not evenly distributed across all possible conserved sites. Independent of their roles in benzimidazole resistance, tbb-1 and tbb-2 may have specialized functions as null mutants of tbb-1 or tbb-2 were cold or heat sensitive, respectively.

In Silico Docking of Nematode β-Tubulins With Benzimidazoles Points to Gene Expression and Orthologue Variation as Factors in Anthelmintic Resistance

The efficacy of benzimidazole anthelmintics can vary depending on the target parasite, with Ascaris nematodes being highly responsive, and whipworms being less responsive. Anthelmintic resistance has become widespread, particularly in strongyle nematodes such as Haemonchus contortus in ruminants, and resistance has recently been detected in hookworms of humans and dogs. Past work has shown that there are multiple β-tubulin isotypes in helminths, yet only a few of these contribute to benzimidazole interactions and resistance. The β-tubulin isotypes of ascarids and soil-transmitted helminths were identified by mining available genome data, and phylogenetic analysis showed that the ascarids share a similar repertoire of seven β-tubulin isotypes. Strongyles also have a consistent pattern of four β-tubulin isotypes. In contrast, the whipworms only have two isotypes, with one of these clustering more basally and distinct from any other group. Key β-tubulin isotypes selected based on previous studies were the focus of in silico molecular docking simulations to look at the interactions with benzimidazoles. These showed that all β-tubulins had similar interactions with benzimidazoles and maintained the key bond with residue E198 in all species, indicating similar mechanisms of action. However, the interaction was stronger and more consistent in the strongyles and whipworms than it was in the ascarids. Alteration of β-tubulin isotypes with the common resistance-associated mutations originally identified in H. contortus resulted in similar interaction modeling for all species. In conclusion, ascarids, strongyles, and whipworms all have their own unique repertoire of β-tubulins, which could explain why benzimidazole resistance and susceptibility varies between these groups of parasites. These data complement recent work that has highlighted the roles of essential residues in benzimidazole drug binding and shows that there is a separation between strongyle parasites that frequently develop resistance and ascarid parasites, which have been much less prone to developing resistance.

Advances in our understanding of nematode ion channels as potential anthelmintic targets

Ion channels are specialized multimeric proteins that underlie cell excitability. These channels integrate with a variety of neuromuscular and biological functions. In nematodes, the physiological behaviors including locomotion, navigation, feeding and reproduction, are regulated by these protein entities. Majority of the antinematodal chemotherapeutics target the ion channels to disrupt essential biological functions. Here, we have summarized current advances in our understanding of nematode ion channel pharmacology. We review cys-loop ligand gated ion channels (LGICs), including nicotinic acetylcholine receptors (nAChRs), acetylcholine-chloride gated ion channels (ACCs), glutamate-gated chloride channels (GluCls), and GABA (γ-aminobutyric acid) receptors, and other ionotropic receptors (transient receptor potential (TRP) channels and potassium ion channels). We have provided an update on the pharmacological properties of these channels from various nematodes. This article catalogs the differences in ion channel composition and resulting pharmacology in the phylum Nematoda. This diversity in ion channel subunit repertoire and pharmacology emphasizes the importance of pursuing species-specific drug target research. In this review, we have provided an overview of recent advances in techniques and functional assays available for screening ion channel properties and their application.

ConVarT: a search engine for matching human genetic variants with variants from non-human species

The availability of genetic variants, together with phenotypic annotations from model organisms, facilitates comparing these variants with equivalent variants in humans. However, existing databases and search tools do not make it easy to scan for equivalent variants, namely 'matching variants' (MatchVars) between humans and other organisms. Therefore, we developed an integrated search engine called ConVarT (http://www.convart.org/) for matching variants between humans, mice, and Caenorhabditis elegans. ConVarT incorporates annotations (including phenotypic and pathogenic) into variants, and these previously unexploited phenotypic MatchVars from mice and C. elegans can give clues about the functional consequence of human genetic variants. Our analysis shows that many phenotypic variants in different genes from mice and C. elegans, so far, have no counterparts in humans, and thus, can be useful resources when evaluating a relationship between a new human mutation and a disease.

Risk factors and impact of COVID-19-related clinic closures on the detection of gastrointestinal parasites in dogs, a cross-sectional study

Infections with endoparasites, especially gastrointestinal helminths, are a common finding in client-owned dogs. The Community Practice section at the Ohio State University Veterinary Medical Center (OSU-VMC) follows Companion Animal Parasite Council, American Animal Hospital Association, and American Veterinary Medical Association guidelines for parasitology by recommending annual fecal analyses for dogs and prescribing year-round, broad-spectrum parasite preventatives. There is increasing interest in determining if parasite occurrence is changing in client-owned dogs. Therefore, a retrospective study was designed to examine risk factors associated with the detection of parasites in samples submitted to the OSU-VMC Clinical Veterinary Parasitology Diagnostic Laboratory. Of the 1198 canine fecal samples, 254 (21.2%) of these samples had a positive fecal analysis for gastrointestinal (GI) parasites. The age of the dog, time of year, reproductive status, purpose of fecal examination, GI signs, and type of parasite preventatives were assessed as potential risk factors for GI parasite infection in dogs. To determine if Coronavirus Disease 2019 (COVID-19)-associated hospital restrictions impacted the number of fecal examinations performed, data from January to December 2020, was compared to the same period in 2019. There was nearly a 50% reduction in canine fecal samples submitted to the OSU-VMC Clinical Veterinary Parasitology Diagnostic Laboratory in March 2020 compared to March 2019. At least one canine GI parasite was found in over 20% of all 1198 canine fecal samples (21.2%, 254/1198). The most commonly detected canine GI parasite in all the fecal samples was hookworm at 9.6% (115/1198), followed by Giardia sp. at 7.6% (91/1198). Age, use of parasite preventatives, breed, and reproductive status were found to be associated with parasite occurrence in the dog samples. Identifying such risk factors in dogs will guide veterinarians to advise annual fecal examinations more strongly to clients with high-risk dogs or when routine health visits are postponed for an extended period.

Prevalence of intestinal parasites in dogs in southern Ontario, Canada, based on fecal samples tested using sucrose double centrifugation and Fecal Dx® tests

In southern Ontario, Canada, there is a lack of information concerning the prevalence of intestinal parasites in dogs. As such, this study aimed to characterize the prevalence of intestinal parasites in dogs visiting off-leash parks in the region using sucrose double centrifugation and Fecal Dx® tests. Additionally, data obtained via the sucrose double centrifugation method were used to evaluate the performance of the Fecal Dx® tests. Fecal samples were collected from 466 dogs aged ≥6 months from May to November 2018 (mean age = 3.7 years). Overall, eleven intestinal parasites were identified using sucrose double centrifugation. Roundworm eggs (Toxocara canis and Baylisascaris procyonis), hookworm eggs (Ancylostoma caninum and Uncinaria stenocephala), and whipworm eggs (Trichuris vulpis) were identified in 1.07% (95% confidence interval [CI] 0.38-2.56%), 5.79% (95% CI 3.85-8.31%), and 5.15% (95% CI 3.33-7.57) of samples, respectively. Using the Fecal Dx® tests, 1.07% (95% CI 0.38-2.56%), 4.29% (95% CI 2.64-6.55%), and 2.15% (95% CI 1.03-3.91) of the samples tested positive for roundworm, hookworm, and whipworm antigen, respectively. To assess the level of agreement between the Fecal Dx® tests and sucrose double centrifugation, three methods were used. Cohen's kappa indicated a fair-to-moderate level of agreement between Fecal Dx® tests and sucrose double centrifugation. In contrast, the prevalence-adjusted bias-adjusted kappa and Gwet's first-order agreement coefficient indicated almost perfect agreement between these tests, ranging from 0.87 to 0.99 among the parasites examined. This study provides valuable information on the prevalence of intestinal parasites in mature dogs in southern Ontario that will help guide parasite control recommendations for dogs in this region.

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.

Newly identified parasitic nematode beta-tubulin alleles confer resistance to benzimidazoles

Infections by parasitic nematodes cause large health and economic burdens worldwide. We use anthelmintic drugs to reduce these infections. However, resistance to anthelmintic drugs is extremely common and increasing worldwide. It is essential to understand the mechanisms of resistance to slow its spread. Recently, four new parasitic nematode beta-tubulin alleles have been identified in benzimidazole (BZ) resistant parasite populations: E198I, E198K, E198T, and E198stop. These alleles have not been tested for the ability to confer resistance or for any effects that they might have on organismal fitness. We introduced these four new alleles into the sensitive C. elegans laboratory-adapted N2 strain and exposed these genome-edited strains to both albendazole and fenbendazole. We found that all four alleles conferred resistance to both BZ drugs. Additionally, we tested for fitness consequences in both control and albendazole conditions over seven generations in competitive fitness assays. We found that none of the edited alleles had deleterious effects on fitness in control conditions and that all four alleles conferred strong and equivalent fitness benefits in BZ drug conditions. Because it is unknown if previously validated alleles confer a dominant or recessive BZ resistance phenotype, we tested the phenotypes caused by five of these alleles and found that none of them conferred a dominant BZ resistance phenotype. Accurate measurements of resistance, fitness effects, and dominance caused by the resistance alleles allow for the generation of better models of population dynamics and facilitate control practices that maximize the efficacy of this critical anthelmintic drug class.

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Four newly identified parasitic nematode beta-tubulin alleles confer benzimidazole resistance.

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The four newly identified alleles do not confer deleterious fitness consequences.

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Five beta-tubulin alleles confer recessive benzimidazole resistance.

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.

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.

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.

Challenges and opportunities for the adoption of molecular diagnostics for anthelmintic resistance

Anthelmintic resistance is a significant threat to livestock production systems worldwide and is emerging as an important issue in companion animal parasite management. It is also an emerging concern for the control of human soil-transmitted helminths and filaria. An important aspect of managing anthelmintic resistance is the ability to utilise diagnostic tests to detect its emergence at an early stage. In host-parasite systems where resistance is already widespread, diagnostics have a potentially important role in determining those drugs that remain the most effective. The development of molecular diagnostics for anthelmintic resistance is one focus of the Consortium for Anthelmintic Resistance and Susceptibility (CARS) group. The present paper reflects discussions of this issue that occurred at the most recent meeting of the group in Wisconsin, USA, in July 2019. We compare molecular resistance diagnostics with in vivo and in vitro phenotypic methods, and highlight the advantages and disadvantages of each. We assess whether our knowledge on the identity of molecular markers for resistance towards the different drug classes is sufficient to provide some expectation that molecular tests for field use may be available in the short-to-medium term. We describe some practical aspects of such tests and how our current capabilities compare to the requirements of an 'ideal' test. Finally, we describe examples of drug class/parasite species interactions that provide the best opportunity for commercial use of molecular tests in the near future. We argue that while such prototype tests may not satisfy the requirements of an 'ideal' test, their potential to provide significant advances over currently-used phenotypic methods warrants their development as field diagnostics.

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.

Anthelmintic Activity of Extracts and Active Compounds From Diospyros anisandra on Ancylostoma caninum, Haemonchus placei and Cyathostomins

The present study aimed to evaluate the anthelmintic activity of leaf and bark extracts of Diospyros anisandra collected during different seasons and their major constituents on eggs of Ancylostoma caninum, Haemonchus placei, and cyathostomins. Specifically, the eclosion inhibition of the methanolic extracts of the leaves and bark of D. anisandra collected during the dry and rainy seasons (600–37.5 μg/ml) were evaluated in addition to the fractions, sub-fractions (300–37.5 μg/ml) and active major constituents (150–2.3 μg/ml). The rainy season bark extract had the highest percentage of eclosion inhibition (PEI) against the evaluated nematodes (≥ 90% at 75 μg/ml) along with high ovicidal activity (90.0 to 93.4% at 75 μg/ml). The purification of the rainy season bark extract showed that its biological activity came from the non-polar n-hexane fraction (≥ 93% at 75 μg/ml). The bioguided fractionation pointed to sub-fraction 5 as having the highest anthelmintic activity against the three evaluated genera of nematodes (PEI ≥ 93% at 37.5 μg/ml). Gas chromatography and mass spectrometry revealed that the major constituent in sub-fraction 5 was plumbagin. Upon evaluation, plumbagin was confirmed to be responsible for the anthelmintic activity of D. anisandra, with a PEI ≥ 90% at 2.3 μg/ml on the three evaluated nematodes. Additionally, the compounds betulin and lupeol in the bark of D. anisandra were evaluated but presented low anthelmintic activity (PEI ≤ 5.3% at 2.3 μg/ml). In conclusion, the rainy season bark extract of D. anisandra exerts a high ovicidal activity against the eggs of the three studied nematodes. Plumbagin is the active compound responsible for this activity and represents a potential alternative for the control of different genera of gastrointestinal nematodes given the current scenario of anthelmintic resistance.

Caenorhabditis elegans in anthelmintic research - Old model, new perspectives

For more than four decades, the free-living nematode Caenorhabditis elegans has been extensively used in anthelmintic research. Classic genetic screens and heterologous expression in the C. elegans model enormously contributed to the identification and characterization of molecular targets of all major anthelmintic drug classes. Although these findings provided substantial insights into common anthelmintic mechanisms, a breakthrough in the treatment and control of parasitic nematodes is still not in sight. Instead, we are facing increasing evidence that the enormous diversity within the phylum Nematoda cannot be recapitulated by any single free-living or parasitic species and the development of novel broad-spectrum anthelmintics is not be a simple goal. In the present review, we summarize certain milestones and challenges of the C. elegans model with focus on drug target identification, anthelmintic drug discovery and identification of resistance mechanisms. Furthermore, we present new perspectives and strategies on how current progress in C. elegans research will support future anthelmintic research.

Comparative H-gal-GP and H11 specific antibody binding in equine cyathostomins

The biological-based vaccine (Barbervax®) generates effective antibodies against the biologically essential H-gal-GP and H11 protein complex of the ruminant parasite Haemonchus contortus to target and kill the parasites after taking a blood meal. A comparative analysis of several parasite genera was performed to determine if a similar protein complex or one that is recognized by H-gal-GP and H11 specific antibodies was present. If so, it suggests the vaccine could be effective for other nematode parasites. Ancylostoma caninum, H. contortus, equine cyathostomins, bovine Bunostomum phlebotomum, Dracunculus lutrae, Parascaris sp., Ixodes scapularis, Amblyomma americanum, Dirofilaria immitis and Brugia malayi were evaluated for specific antibody binding using hyperimmunized antibodies against H-gal-GP and H11 native proteins. Of the parasites evaluated, specific and reproducible staining was observed in H. contortus and adult and encysted cyathostomins only. To further evaluate the similar reactivities between cyathostomins and H. contortus, cross-reactivity of equine serum with antibodies to cyathostomins on a H. contortus adult histology cross-section was observed using immunofluorescence. These findings pave the way for future studies on the safety and efficacy of H-gal-GP and H11 protein complex as a potential control for cyathostomins.

Nematicidal and ovicidal activity of Bacillus thuringiensis against the zoonotic nematode Ancylostoma caninum

Ancylostoma caninum is a gastrointestinal parasite that affect dogs and humans, considered a worldwide public health problem. The control of these parasitosis is increasingly difficult due to the development of multi-drug resistance. Bacillus thuringiensis is an insecticidal, spore forming bacterium, often species specific. The strain GP526 of B. thuringiensis has toxic effect on the cestode Dipylidium caninum and the trematode Centrocestus formosanus, both of them zoonotic parasites. The high degrees of specificity and environment safe make B. thuringiensis suitable for use against pathogen parasites, especially those resistant to synthetic chemical insecticides. The objective of the current work was to evaluate the in vitro effect of B. thuringiensis on Ancylostoma caninum. Spore-crystal mixture of the strains was co-incubated with 120 adult nematodes (males, non-pregnant females and pregnant females) or with 4800 eggs. GP526 showed a nematicidal effect with an LT₅₀ of 35.8 h and an LC₅₀ of 60 μg/ml. It also showed an ovicidal effect with an LC₅₀ of 94.9 μg/ml. Histological analyses showed detachment of the cuticle and of the uterus in adult females, and vacuolization with destruction of the eggs. The effects of GP526 strain were comparable to those of albendazole, allowing us to propose GP526 for A. caninum control, in both, the adult stage at a gastrointestinal level, and in egg stage in the environment. In addition, GP526 can be proposed as a potential broad spectrum antiparasitic drug.

Quantitative benzimidazole resistance and fitness effects of parasitic nematode beta-tubulin alleles

Infections by parasitic nematodes inflict a huge burden on the health of humans and livestock throughout the world. Anthelmintic drugs are the first line of defense against these infections. Unfortunately, resistance to these drugs is rampant and continues to spread. To improve treatment strategies, we must understand the genetics and molecular mechanisms that underlie resistance. Studies of the fungus Aspergillus nidulans and the free-living nematode Caenorhabditis elegans discovered that a beta-tubulin gene is mutated in benzimidazole (BZ) resistant strains. In parasitic nematode populations, three beta-tubulin alleles, F167Y, E198A, and F200Y, have long been correlated with resistance. Additionally, improvements in sequencing technologies have identified new alleles - E198V, E198L, E198K, E198I, and E198Stop - also correlated with BZ resistance. However, none of these alleles have been proven to cause resistance. To empirically demonstrate this point, we independently introduced the F167Y, E198A, and F200Y alleles as well as two of the newly identified alleles, E198V and E198L, into the BZ susceptible C. elegans N2 genetic background using the CRISPR-Cas9 system. These genome-edited strains were exposed to both albendazole and fenbendazole to quantitatively measure animal responses to BZs. We used a range of concentrations for each BZ compound to define response curves and found that all five of the alleles conferred resistance to BZ compounds equal to a loss of the entire beta-tubulin gene. These results prove that the parasite beta-tubulin alleles cause resistance. The E198V allele is found at low frequencies along with the E198L allele in natural parasite populations, suggesting that it could affect fitness. We performed competitive fitness assays and demonstrated that the E198V allele reduces animal health, supporting the hypothesis that this allele might be less fit in field populations. Overall, we present a powerful platform to quantitatively assess anthelmintic resistance and effects of specific resistance alleles on organismal fitness in the presence or absence of the drug.

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Beta-tubulin alleles from parasitic nematodes were introduced into drug-susceptible C. elegans using CRISPR-Cas9.

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Beta-tubulin variants are strongly selected in albendazole competitive fitness assays.

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The E198V allele confers a fitness cost in control conditions as compared to other alleles.

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.

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.

Assessing anthelmintic resistance risk in the post-genomic era: a proof-of-concept study assessing the potential for widespread benzimidazole-resistant gastrointestinal nematodes in North American cattle and bison

As genomic research continues to improve our understanding of the genetics of anthelmintic drug resistance, the revolution in DNA sequencing technologies will provide increasing opportunities for large-scale surveillance for the emergence of drug resistance. In most countries, parasite control in cattle and bison has mainly depended on pour-on macrocyclic lactone formulations resulting in widespread ivermectin resistance. Consequently, there is an increased interest in using benzimidazole drugs which have been used comparatively little in cattle and bison in recent years. This situation, together with our understanding of benzimidazole resistance genetics, provides a practical opportunity to use deep-amplicon sequencing to assess the risk of drug resistance emergence. In this paper, we use deep-amplicon sequencing to scan for those mutations in the isotype-1 β-tubulin gene previously associated with benzimidazole resistance in many trichostrongylid nematode species. We found that several of these mutations occur at low frequency in many cattle and bison parasite populations in North America, suggesting increased use of benzimidazole drugs in cattle has the potential to result in widespread emergence of resistance in multiple parasite species. This work illustrates a post-genomic approach to large-scale surveillance of early emergence of anthelmintic resistance in the field.

Schistosomiasis and hookworm infection in humans: Disease burden, pathobiology and anthelmintic vaccines

Helminth diseases are the ancient scourges of humans and their damages are 'silent and insidious'. Of the helminth infections, schistosomiasis and hookworm infection have a great impact. This review covers information regarding vaccine candidates against schistosomiasis and hookworms that reached at least up to the phase-1 trial and literatures regarding other vaccine candidates have been excluded. For clinical manifestations, all available literatures were included, and for epidemiology and global burden of the diseases (GBD), literatures only within 2000-2019 were included. Literatures were searched surfing various databases including PubMED, Google Scholar, and Science Direct and overall over 150 literatures were identified. Globally ~250 million people are suffering from schistosomiasis, resulting 1430 thousand DALY (disability adjusted life year) per year. On the other hand, about 1.3 billion people are infected with hookworm (HW), and according to WHO, ~878 million school-age children (SAC) are at risk. HW is estimated to cause 65,000 deaths annually, accounts for 845 thousand DALYs as well as to cause 6-35.3% loss in productivity. Despite tremendous efforts, very few anthelmintic vaccine candidates such as Na-GST-1, Na-APR-1 and Na-ASP-2 against HW, and Sm28GST/Sh28GST, Sm-p80, Sm14 and Sm-TSP-1/SmTSP-2 against schistosomiasis reached up to the clinical trials. More efforts are needed to achieve the WHO targets taken against the maladies.

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

Background

The canine hookworm, Ancylostoma caninum is the most prevalent and important intestinal nematode parasite of dogs in the USA. Hookworms are typically well controlled by treatment with all commonly used anthelmintics that are approved for this use in dogs. However, in the past few years, cases of recurrent/persistent canine hookworm infections appear to have dramatically increased, suggesting that anthelmintic resistance (AR) may have evolved in this parasite. These cases are highly overrepresented by greyhounds, but multiple other breeds are also represented. The aim of this study was to characterize several of these suspected resistant isolates using in vitro, genetic and clinical testing to determine if these cases represent true anthelmintic resistance in A. caninum.

Methods

Fecal samples containing hookworm eggs from three cases of persistent hookworm infections; one from a greyhound, one from a miniature schnauzer and one from a hound-mix, were received by our laboratory. These were then used to establish infections in laboratory dogs and to perform egg hatch assays (EHA) and larval development assays (LDA) for detecting resistance to benzimidazoles and macrocyclic lactones, respectively. Additional EHA and LDA were performed on eggs recovered from the laboratory-induced infections. Fecal egg count reduction tests were performed to detect resistance to pyrantel. Deep amplicon sequencing assays were developed to measure the frequency of non-synonymous single nucleotide polymorphisms (SNP) at codons 167, 198 and 200 of the A. caninum isotype-1 β-tubulin gene.

Results

Resistance ratios for the three A. caninum isolates tested ranged from 6.0 to > 100 and 5.5 to 69.8 for the EHA and LDA, respectively. Following treatment with pyrantel, reduction in faecal egg counts was negative or 0%. Deep amplicon sequencing of the isotype-1 β-tubulin gene identified a high frequency of resistance-associated SNPs at codon 167 in all three resistant isolates and in two additional clinical cases.

Conclusions

These data conclusively demonstrate multiple anthelmintic resistance in multiple independent isolates of A. caninum, strongly suggesting that this is an emerging problem in the USA. Furthermore, evidence suggest that these resistant hookworms originate from racing greyhound farms and kennels, though additional research is needed to confirm this.