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

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.

Unraveling the mechanisms of benzimidazole resistance in hookworms: A molecular docking and dynamics study

BACKGROUND

Benzimidazole resistance is an emerging challenge among parasitic helminths. It is caused by single nucleotide polymorphisms (SNPs) in specific loci in helminths' β-tubulin genes. Field studies and laboratory investigations reported resistance-associated SNPs in 4 codon locations with 7 allelic variations among hookworms. This study aimed to determine the effects of these mutations on the binding efficiency and behavior of the β-tubulin protein in four hookworm species against four benzimidazole drugs.

METHODS

β-tubulin gene coding sequences of Ancylostoma caninum, A. duodenale, A. ceylanicum, and Necator americanus were retrieved, assessed phylogenetically, and used to construct the 3D structure models of the proteins. The modeled protein structures were verified and edited to contain the reported SNPs: Q134H, F167Y, E198A, E198K, E198V, F200L, and F200Y. Benzimidazole drugs such as albendazole (ABZ), fenbendazole (FBZ), mebendazole (MBZ) and oxfendazole (OBZ) were used as ligands. Molecular docking experiments were performed with the wild-type and mutated proteins. Molecular dynamics simulation assessed the dynamic behavior of the β-tubulin-benzimidazole complex.

RESULTS

In silico docking assessments showed that various amino acid substitutions due to resistance-associated SNPs cause alterations in binding affinities and positions. E198K and Q134H in hookworm β-tubulins substantially weakened the binding affinities and altered the binding positions of benzimidazole drugs. Molecular dynamics analysis revealed that these mutations also caused marked reductions in the binding free energies owing to diminished hydrogen bond contacts with the benzimidazole ligands.

CONCLUSION

The evidence shown herein indicates that mutations at positions 198 and 134 are detrimental to conferring benzimidazole resistance among hookworms. The presence of these mutations may alter the efficacy of pharmacological interventions. Hence, further studies should be conducted to assess their emergence among hookworms in endemic areas with histories of chemotherapy.

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.

Benzimidazole Resistance-Associated Mutations in the β-tubulin Gene of Hookworms: A Systematic Review

There is a growing number of reports on the occurrence of benzimidazole resistance-associated single nucleotide polymorphisms (SNPs) in the β-tubulin isotype 1 gene of various helminths of veterinary, and public health concerns. However, a comprehensive analysis of their occurrence, and their contributions to conferring benzimidazole resistance among hookworms has yet to be done. The objectives of this systematic review are to summarize and synthesize peer-reviewed evidence on the occurrence of these resistance-associated mutations in hookworms, document their geographical distribution, and assess their contributions to conferring phenotypic resistance. Three databases were systematically searched using specific keywords. Research that assessed the occurrence of benzimidazole resistance-associated SNPs in hookworms, papers that reported the geographical distribution of these SNPs, and studies that investigated the SNPs' resistance-associated phenotypic effects were included in the review. Research that was not done in hookworms, papers not in the English language, and literature reviews and book chapters were excluded. Critical appraisal checklists were used to determine the risk of bias in the selected papers. Data were extracted from the selected studies and analyzed. PROSPERO Systematic Review Protocol Registration No.: CRD42024510924. A total of 29 studies were included and analyzed. Of these, four were conducted in a laboratory setting, eight described the development and validation of SNP detection methods, and the remaining 17 involved field research. Seven SNP-induced amino acid substitutions at four loci were reported among several hookworm species: Q134H, F167Y, E198A, E198K, E198V, F200Y, and F200L. SNPs have been reported in isolates occurring in the United States, Canada, Brazil, Haiti, Australia, New Zealand, Kenya, Ghana, Mozambique, and Tanzania. Resistance mutations have not been reported in Asia. E198A and F200L were reported in Ancylostoma ceylanicum with laboratory-induced resistance. F167Y and Q134H conferred resistance in A. caninum, as revealed by in vitro investigations and field assessments. There is insufficient peer-reviewed evidence to prove the association between SNP occurrence and resistance. Mutations in the β-tubulin isotype 1 gene confer benzimidazole resistance in A. caninum and A. ceylanicum, but similar evidence is lacking for other human hookworms. Understanding benzimidazole resistance through further research can better inform treatment, prevention, and control strategies.

Benzimidazole resistance-associated mutations improve the in silico dimerization of hookworm tubulin: An additional resistance mechanism

Background and Aim

Mutations in the β-tubulin genes of helminths confer benzimidazole (BZ) resistance by reducing the drug's binding efficiency to the expressed protein. However, the effects of these resistance-associated mutations on tubulin dimer formation in soil-transmitted helminths remain unknown. Therefore, this study aimed to investigate the impact of these mutations on the in silico dimerization of hookworm α- and β-tubulins using open-source bioinformatics tools.

Materials and Methods

Using AlphaFold 3, the α- and β-tubulin amino acid sequences of Ancylostoma ceylanicum were used to predict the structural fold of the hookworm tubulin heterodimer. The modeled complexes were subjected to several protein structure quality assurance checks. The binding free energies, overall binding affinity, dissociation constant, and interacting amino acids of the complex were determined. The dimer's structural flexibility and motion were simulated through molecular dynamics.

Results

BZ resistance-associated amino acid substitutions in the β-tubulin isotype 1 protein of hookworms altered tubulin dimerization. The E198K, E198V, and F200Y mutations conferred the strongest and most stable binding between the α and β subunits, surpassing that of the wild-type. In contrast, complexes with the Q134H and F200L mutations exhibited the opposite effect. Molecular dynamics simulations showed that wild-type and mutant tubulin dimers exhibited similar dynamic behavior, with slight deviations in those carrying the F200L and E198K mutations.

Conclusion

Resistance-associated mutations in hookworms impair BZ binding to β-tubulin and enhance tubulin dimer interactions, thereby increasing the parasite's ability to withstand treatment. Conversely, other mutations weaken these interactions, potentially compromising hookworm viability. These findings offer novel insights into helminth tubulin dimerization and provide a valuable foundation for developing anthelmintics targeting this crucial biological process.

Gastrointestinal Helminths in Wild Felids in the Cerrado and Pantanal: Zoonotic Bioindicators in Important Brazilian Biomes

Environmental changes in the Brazilian Pantanal and Cerrado facilitate the spread of parasitic diseases in wildlife, with significant implications for public health owing to their zoonotic potential. This study aimed to examine the occurrence and diversity of gastrointestinal parasites in wild felids within these regions to assess their ecological and health impacts. We collected and analyzed helminth-positive samples from 27 wild felids using specific taxonomic keys. Diverse parasitic taxa were detected, including zoonotic helminths, such as Ancylostoma braziliense, Ancylostoma caninum, Ancylostoma pluridentatum, Toxocara cati, Toxocara canis, Dipylidium caninum, Taenia spp., Echinococcus spp., and Spirometra spp. Other nematodes, such as Physaloptera praeputialis and Physaloptera anomala, were identified, along with acanthocephalans from the genus Oncicola and a trematode, Neodiplostomum spp. (potentially the first record of this parasite in wild felids in the Americas). Human encroachment into natural habitats has profound effects on wild populations, influencing parasitic infection rates and patterns. This study underscores the importance of continuous monitoring and research on parasitic infections as a means of safeguarding both wildlife and human populations and highlights the role of wild felids as bioindicators of environmental health.

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.